I continue to try to figure out how to work in this area of the interface between the electron beam and the photon beam. I see that there is a close parallel between my personal life story of trying to figure out how to live with both my mom's family and dad's family.
How to create space and build something substantial between two different things?
Perhaps the key is that secretly one gets help from a third thing. With my life in Santa Cruz, I think the key was to have good friends. It was within this context that I came closer to finding a common ground out of which I could exist in between both parents' houses and not feel like I was having to change myself so dramatically that there would be no continuity.
So, one claims a bit of ground somewhere in between this and that. Both this and that each think you belong to them. Or perhaps I myself think I belong to each of them, periodically. At one moment I am this. At the next, I am that. And while I am in the space that I am creating and building between the two, I try to make something that relates to the other two.
The title of this blog "adiabatic invariants", expressed a hope that I could find a space of more stability without the dramatic shifts. Perhaps I might also use a double well potential as a physics model for the kind of dynamics I am trying to deal with. And, for yet a third image, I have often thought of building a bridge between this and that. Building a bridge, however, is helpful for traveling in between, but does not in itself constitute a place of residency. One does not live on a bridge. And the imagery suggests a deep chasm. Perhaps it is not a chasm, but simply forest. And thus, instead of building a bridge, all that is needed is a path, and perhaps a map.
The task of life, then, is to inhabit the in-between territory, or if uninhabitable, to go elsewhere, but perhaps to keep the paths back alive. What are some topics where one must do this? Food is certainly one area. At my mom's house, we cooked and shopped ourselves. At my dad's, we were cooked for. Food meant something different. Meals had a different feel. So, today, I still do not have a way of shopping and eating that feels comfortable. Perhaps by continuing to think and write about this topic, I will make more progress. Creating a personal space which is comfortable is another area where I have a hard time. Choices feel political and charged, and what I actually create is often not very coherent. The same applies to how I dress and how I clean, and how I organize my projects and papers and other belongings. I have made progress, but the result is still not so coherent. I am trying to build in the center, between this and that. And the result is not always as satisfying as I might like.
Friday, February 03, 2012
Monday, August 29, 2011
Becoming comfortable with
Both of my parents have moved to remote places, with unique communities, and are rather isolated in some ways. Had I grown up in either of these places, I think I would have wanted to escape in some way. I might have longed for something different and looked at how to get out, geographically, socially, and regarding lifestyle and mentality.
At this point in my life, I am only a visitor in these places. But arriving in each one, I get the feeling of being pulled into a black hole, with little communication to the rest of my life, and not sure how to connect the experience to who I am. At the same time, I am adaptable, and arriving, and within the experience, it has an integrity and a quality to it that is quite nice. But the boundaries are difficult. I can't think my way into it from outside, or out of it from inside.
So I have slowly worked on the problem over the years by looking carefully at the boundaries. In the remote town in California where my father lives, for example, I look to see whether there are surrounding communities that might have some life to them. I try to find things in common to other places regarding environment and landscape. I plan trips there with an exit strategy, and friends and other family flanking it. Certainly this is also quite personal, and relates to my own experience of family and who I am there, and who I am seen as. I am starting to try the same strategy with my mother's house in Iowa. There, the boundaries are physical, but there is also a strong ideological barrier that is uncomfortable to me. Is there something within that I can relate to? I find pieces of interest to that community that I might interpret in a different way, but still find interesting.
Is such an elaborate process necessary? Maybe I will reach a point where it will seem smaller and less important, but somehow this work is necessary. The other option is to say that visiting my family is too difficult, and no common ground can be found, but I don't want to do that.
On the Petrolia side, there is the natural environment. The trees, the river, the ocean.
On the MUM/Fairfield side, there is the nearby Mississippi river. There are coffee shops in Fairfield. Ideologically, MUM is more challenging. The Maharishi is a figure that I just have a very hard time appreciating. And the closed mentality fosters an inside/outside split that is hard to overcome. One of the Maharishi's main texts he interpretted and based his power around has been the Baghavad Gita. I think this is something I could become interested in.
At this point in my life, I am only a visitor in these places. But arriving in each one, I get the feeling of being pulled into a black hole, with little communication to the rest of my life, and not sure how to connect the experience to who I am. At the same time, I am adaptable, and arriving, and within the experience, it has an integrity and a quality to it that is quite nice. But the boundaries are difficult. I can't think my way into it from outside, or out of it from inside.
So I have slowly worked on the problem over the years by looking carefully at the boundaries. In the remote town in California where my father lives, for example, I look to see whether there are surrounding communities that might have some life to them. I try to find things in common to other places regarding environment and landscape. I plan trips there with an exit strategy, and friends and other family flanking it. Certainly this is also quite personal, and relates to my own experience of family and who I am there, and who I am seen as. I am starting to try the same strategy with my mother's house in Iowa. There, the boundaries are physical, but there is also a strong ideological barrier that is uncomfortable to me. Is there something within that I can relate to? I find pieces of interest to that community that I might interpret in a different way, but still find interesting.
Is such an elaborate process necessary? Maybe I will reach a point where it will seem smaller and less important, but somehow this work is necessary. The other option is to say that visiting my family is too difficult, and no common ground can be found, but I don't want to do that.
On the Petrolia side, there is the natural environment. The trees, the river, the ocean.
On the MUM/Fairfield side, there is the nearby Mississippi river. There are coffee shops in Fairfield. Ideologically, MUM is more challenging. The Maharishi is a figure that I just have a very hard time appreciating. And the closed mentality fosters an inside/outside split that is hard to overcome. One of the Maharishi's main texts he interpretted and based his power around has been the Baghavad Gita. I think this is something I could become interested in.
Sunday, August 28, 2011
Back to the mess
I have to finish a paper for a conference by Wednesday night. It is on the measurements relating to Touschek lifetime and momentum acceptance. There's an analysis of data to be done, and general writing and preparation of the paper. I really don't want to work on it.
Why don't I want to do it? Its late, I know. A paper needs to be written, and doing an analysis at the last minute can derail me from the process of fixing figures, adding references, and putting a clear narrative together. But its also that I've gotten myself out of thinking of this topic, and am wary of going back. It was my compromise. I will not leave accelerator physics entirely. I will do some work in this field, but move outward at the same time. But the topic is a mess for me. It is a personal mess in that my own files and documents and the relevant equations are not in such clear order. And a general historical mess in that it relates to the topic of dynamic aperture and sextupole optimization which is an unsolved problem. That question of dynamic aperture and stability has been the piece that I have slowly worked on, and tried to lay out a personal groundwork, so I don't feel so lost working in that area. Maybe this is a reflection of the fact that I didn't really finish this process.
So, my own angle on Touschek lifetime and measurement that I would like to get across is that the measurements are a diagnostic for the various lattice optimizations. There is both vertical emittance reduction goals, and increase of momentum acceptance via sextupole optimization. Stating clearly what these mean, and having measurements to ground discussion and results puts this other more nebulous "accelerator physics" activity onto a ground that relates to the goal of the machine- production of stable, long lived synchrotron radiation.
Why don't I want to do it? Its late, I know. A paper needs to be written, and doing an analysis at the last minute can derail me from the process of fixing figures, adding references, and putting a clear narrative together. But its also that I've gotten myself out of thinking of this topic, and am wary of going back. It was my compromise. I will not leave accelerator physics entirely. I will do some work in this field, but move outward at the same time. But the topic is a mess for me. It is a personal mess in that my own files and documents and the relevant equations are not in such clear order. And a general historical mess in that it relates to the topic of dynamic aperture and sextupole optimization which is an unsolved problem. That question of dynamic aperture and stability has been the piece that I have slowly worked on, and tried to lay out a personal groundwork, so I don't feel so lost working in that area. Maybe this is a reflection of the fact that I didn't really finish this process.
So, my own angle on Touschek lifetime and measurement that I would like to get across is that the measurements are a diagnostic for the various lattice optimizations. There is both vertical emittance reduction goals, and increase of momentum acceptance via sextupole optimization. Stating clearly what these mean, and having measurements to ground discussion and results puts this other more nebulous "accelerator physics" activity onto a ground that relates to the goal of the machine- production of stable, long lived synchrotron radiation.
Thursday, August 18, 2011
online
Can we get beyond talking about people "living online"?
Along the lines of this post from Crooked Timber, I think the metaphor has gone too far.
Yes, the modes of communication have expanded, and there things that we do that are interacting directly with software (and perhaps with others in a delayed way, such as blogging!), rather than directly with people, but we are not living online.
What does the question "are you online?" mean these days? Yes, we may be available or not to communicate via a variety of channels, but no "we" are not online. I'm still here, in this room, breathing, as usual.
Perhaps "living online" is used in the sense of "living in one's head", which is generally not though of as such a good thing to do.
I guess, as a general topic, and as a source for personal time and space and energy management, I want to limit the extent to which one says "we" are online. Things like Facebook have an almost avatar like quality to them, where a certain amount of our information is packaged and available to others even when we are not available. It sort of represents us. How this fits in is something to continue to struggle with, but I just need to remind myself at times, that I am here, and these are modes of communication. We do say that google can be like extended memory, but I just don't want to go down that path. Perhaps people of the future will have some kind of choice like this to make, but for myself, I am who I am, not changed so much, but with a few more communication and knowledge access tools.
Along the lines of this post from Crooked Timber, I think the metaphor has gone too far.
Yes, the modes of communication have expanded, and there things that we do that are interacting directly with software (and perhaps with others in a delayed way, such as blogging!), rather than directly with people, but we are not living online.
What does the question "are you online?" mean these days? Yes, we may be available or not to communicate via a variety of channels, but no "we" are not online. I'm still here, in this room, breathing, as usual.
Perhaps "living online" is used in the sense of "living in one's head", which is generally not though of as such a good thing to do.
I guess, as a general topic, and as a source for personal time and space and energy management, I want to limit the extent to which one says "we" are online. Things like Facebook have an almost avatar like quality to them, where a certain amount of our information is packaged and available to others even when we are not available. It sort of represents us. How this fits in is something to continue to struggle with, but I just need to remind myself at times, that I am here, and these are modes of communication. We do say that google can be like extended memory, but I just don't want to go down that path. Perhaps people of the future will have some kind of choice like this to make, but for myself, I am who I am, not changed so much, but with a few more communication and knowledge access tools.
Wednesday, August 10, 2011
What Technology Wants
I recently read Kevin Kelly's "What Technology Wants". I think my biggest complaint is the lack of humility when it comes to the big ideas, particularly with respect to the ill-defined "technium". The claims are grand and vague on the one hand, and at the same time it is stated that it is expected that these concepts will go through a number of iterations and changes over time. Stephen Wolfram's "A New Kind of Science" had a similar grandiosity to it. It allows the author some maneuver room later to claim further developments under his/her rubric.
I think one can classify this book under the category of books where the author holds two divergent view points and tries to build some kind of narrative that encompasses the two. In this case, Kelly seems to have some kind of Christian God viewpoint that he is seeking to capture in the "Technium", and at the same time has the computer science and general science background that is perhaps less able to make statements about overall meaning or goal orientation in the universe. I think this dissonance can occur in scientists who also have religious commitments. John Hagelin's writings connecting Transcendental Meditation to Unified field theories is one example. Frank Tipler's "Physics of Immortality" is another. Fritjof Capra's "The Tau of Physics" is another example, but I think less difficult to swallow. (Actually these first two struck me as so strange that I doubted the honesty of the authors, whereas with Capra, and here with Kelly, one feels a fervency that doesn't seem so forced, even if the logic is flawed. Perhaps the real dishonesty simply comes in with the claiming that such an integration has been achieved, and this could indeed relate to high levels of self-deception.) In all of these works, it would be nice to see a section evaluating how well the author believes such a synthesis has worked. But perhaps the existence of such a section would have a rhetorical effect of diminishing the power of the hoped for unification.
I did really appreciate Kelly's discussion of the Amish, and in general about ways of thinking about adoption of technology and the imperative that one (individually and collectively) have the option of saying no sometimes. And his discussion of the "Technium" did make me want to seek out a more precise definition of some collection of human created artifacts and tools including some ideas, culture, and laws perhaps, that might usefully be viewed as having a sort of unity to it. The identification of this not well articulated entity with a biological entity did not seem to be so well founded. Clearly it is the recent widespread adoption and development of some internet communication technologies that provides the ground for such speculations and theorizing. In any case, it seems to be the same kind of thinking in conspiracy theories where agency is ascribed to some larger entity that may contain people as elements. Certainly one can find some truth out of this kind of thinking, but it seems to often lead to more errors and less clarity than it illuminates.
(Update... here is an interview of K.K. on his explicit religious views about the "technium")
Thinking a little further, I think that what we should celebrate (and engage with) in this book, is the fact that Kelly is articulating a system of values here. In particular, he is willing to say and argue as why technology is intrinsically "good". I'll have to track down the relevant quote, but the basic point he makes is that each technology has a possibility to be used in both positive and negative ways. However, the very existence of this choice is what tips it to the positive. Do I believe this? Its not obviously wrong. And in fact it may be part of what motivates me to contribute to the world of ideas and technology. Its hard to say that its always true, though. Can we stomach it for guns, say? A gun allows you the new choice to either defend yourself, or to injure/kill someone else. There are certainly some who would argue that this choice is not a net benefit for society. For the case of the Amish, Kelly wants to say that their choices to reject a given technology are appropriate for them, but not necessarily overall. So his encouragement of this practice doesn't invalidate his larger point. What about the bigger, more questionable technologies (genetic engineering, nanotechnology, and nuclear). I think he wants to say that even here, more choice is better, even if those choices seem pretty odd. (With nuclear weapons, one has the new choice to blow up this city, or that city. Ok, maybe one can conceive of positive options, but it seems likely that as a whole, the options created are not really a net gain.)
Anyway, it seems to be a somewhat slim blanket justification, but it is better than a complete lack of engagement in ethics, which is the norm for technologists.
Qualifying this somewhat... I guess, the main point (or guess, or suggestion) Kelly makes is that technology is slightly more "good" than "bad". So even if sometimes the creation of more options isn't "good", if the options produced by most technologies are on the whole "good", then it could still come out ahead. The question then might become, what is this unified thing that is slightly more good than bad? Is it really one thing, or have the good things just somehow been selected. Are repugnant political philosophies that yield great harm on humanity considered part of the technium? Or does he really just have something like the current manifestation of the internet and the associated technologies that are required to create a sort of closure surrounding that?
****
Update, Aug. 30, 2012. Here is an interesting article critiquing the book from the cybergology blog.
I think one can classify this book under the category of books where the author holds two divergent view points and tries to build some kind of narrative that encompasses the two. In this case, Kelly seems to have some kind of Christian God viewpoint that he is seeking to capture in the "Technium", and at the same time has the computer science and general science background that is perhaps less able to make statements about overall meaning or goal orientation in the universe. I think this dissonance can occur in scientists who also have religious commitments. John Hagelin's writings connecting Transcendental Meditation to Unified field theories is one example. Frank Tipler's "Physics of Immortality" is another. Fritjof Capra's "The Tau of Physics" is another example, but I think less difficult to swallow. (Actually these first two struck me as so strange that I doubted the honesty of the authors, whereas with Capra, and here with Kelly, one feels a fervency that doesn't seem so forced, even if the logic is flawed. Perhaps the real dishonesty simply comes in with the claiming that such an integration has been achieved, and this could indeed relate to high levels of self-deception.) In all of these works, it would be nice to see a section evaluating how well the author believes such a synthesis has worked. But perhaps the existence of such a section would have a rhetorical effect of diminishing the power of the hoped for unification.
I did really appreciate Kelly's discussion of the Amish, and in general about ways of thinking about adoption of technology and the imperative that one (individually and collectively) have the option of saying no sometimes. And his discussion of the "Technium" did make me want to seek out a more precise definition of some collection of human created artifacts and tools including some ideas, culture, and laws perhaps, that might usefully be viewed as having a sort of unity to it. The identification of this not well articulated entity with a biological entity did not seem to be so well founded. Clearly it is the recent widespread adoption and development of some internet communication technologies that provides the ground for such speculations and theorizing. In any case, it seems to be the same kind of thinking in conspiracy theories where agency is ascribed to some larger entity that may contain people as elements. Certainly one can find some truth out of this kind of thinking, but it seems to often lead to more errors and less clarity than it illuminates.
(Update... here is an interview of K.K. on his explicit religious views about the "technium")
Thinking a little further, I think that what we should celebrate (and engage with) in this book, is the fact that Kelly is articulating a system of values here. In particular, he is willing to say and argue as why technology is intrinsically "good". I'll have to track down the relevant quote, but the basic point he makes is that each technology has a possibility to be used in both positive and negative ways. However, the very existence of this choice is what tips it to the positive. Do I believe this? Its not obviously wrong. And in fact it may be part of what motivates me to contribute to the world of ideas and technology. Its hard to say that its always true, though. Can we stomach it for guns, say? A gun allows you the new choice to either defend yourself, or to injure/kill someone else. There are certainly some who would argue that this choice is not a net benefit for society. For the case of the Amish, Kelly wants to say that their choices to reject a given technology are appropriate for them, but not necessarily overall. So his encouragement of this practice doesn't invalidate his larger point. What about the bigger, more questionable technologies (genetic engineering, nanotechnology, and nuclear). I think he wants to say that even here, more choice is better, even if those choices seem pretty odd. (With nuclear weapons, one has the new choice to blow up this city, or that city. Ok, maybe one can conceive of positive options, but it seems likely that as a whole, the options created are not really a net gain.)
Anyway, it seems to be a somewhat slim blanket justification, but it is better than a complete lack of engagement in ethics, which is the norm for technologists.
Qualifying this somewhat... I guess, the main point (or guess, or suggestion) Kelly makes is that technology is slightly more "good" than "bad". So even if sometimes the creation of more options isn't "good", if the options produced by most technologies are on the whole "good", then it could still come out ahead. The question then might become, what is this unified thing that is slightly more good than bad? Is it really one thing, or have the good things just somehow been selected. Are repugnant political philosophies that yield great harm on humanity considered part of the technium? Or does he really just have something like the current manifestation of the internet and the associated technologies that are required to create a sort of closure surrounding that?
****
Update, Aug. 30, 2012. Here is an interesting article critiquing the book from the cybergology blog.
Thursday, April 14, 2011
time
There is a rhythm to my life in France that seems to involve patience in new ways than I have experienced previously. It seems to require that I put faith into systems and processes that move slower than I am accustomed to working with. And at the same time, these processes seem hidden, and my instinct is to doubt and wonder whether they are in fact real, even though time and again they show progress and stability. It is something like observing the process of growth of a plant from a seed. There is a logic and robustness to the process, and unless one has watched this particular kind of seed grow before, one can't really look at the current state and figure out where it will go. Instead, one just continues to water, continues to protect, and has faith that something with come of all this.
Monday, March 14, 2011
Back to Cartwright
I seem to keep coming back to reading "How the Laws of Physics Lie" and "The Dappled World".
I think the reason is that I don't usually get very far. I get bogged down, skip ahead, and feel annoyed. I get a little out of it, but its dense, and the meaning of an essay is often not what I thought it was going to be. I didn't realize that the examples such as the BCS theory of superconductivity, and some laser physics (Also the measurement problem and the relations between classical and quantum systems) were gone into in such detail. The exposition is actually pretty clear, but you don't often know so much detail is on its way.
Anyway, I've finally been getting to the end and actually understanding more of it. In the end, it is more inspirational for a practicing physicist than I thought. The essay on the Quantum measurement problem in HLPL ends with stating that one should take the formalism of quantum statistical mechanics seriously which treats mixtures and superpositions on the same footing. This leaves physicists with the job of figuring out which cases have unitary evolution and which don't. And I think this is in line with the way one analyzes a new phenomena. Take a look at it. Use what we already know. Make some guesses. Test them. Refine them. An approach to learning about new things that involves actually studying those things.
And the discussion about capacities, vs. laws, is not so radical in the end. Perhaps from a philosophy perspective it is. But thinking of electric charge and gravitational mass as imbuing capacities on electrons rather than laying out laws of motion is just the way one thinks about these things. We learn about certain aspects of things, and then we may try to isolate it such that just that one property comes into play. This is what fundamental experiments are about. And we do learn some real about these things. The question may arise as to whether the same effect occurs in different environments, or exactly how the forces or whatever other properties combine when acting in concert. And this way of looking at physical knowledge puts it in the same box as other knowledge we have. There still may be questions of reduction or relationships between different kinds of knowledge, but the starting point seems good.
I must say I'm still not sure I get what she means by nomological machine. She makes a "strong claim" in "The Dappled World" that behind every regularity in the world is a nomological machine. Let's say we are in Switzerland where trains are highly reliable. The matching of the trains to the schedule is a nomological machine? I suppose it is. And the fact that my car (usually) works is a nomological machine. And atoms are nomological machines. And proteins are nomological machines. And a market is a nomological machine. And a beam of light is a nomological machine.
Anyway, just to remind that getting into certain details can be demotivating if one gets stuck in them, but if a topic actually relates to the world and the way things really work, then understanding it will lead to more tools and more clarity in the end. Which is to say that previously, reading this made me shut down certain ways of thinking, but now I find it mainly adds.
Apparently Philip Anderson may have had some trouble following "Dappled World" as well.
I just read Anderson's review (see here). Wow, that's pretty intense. He refers a lot to the feeling he gets about it. "One gets the feeling" he states a lot, without actually quoting many passages, or covering arguments. I must admit, that I sometimes had these same "feelings". But reading more closely, I often found that Cartwright was saying something more precise and more interesting than I initially thought.
Here are other reviews of The Dappled World.
Finally, once one digests some of the seemingly right arguments, one would like to see engagement of other authors. Here's some essays doing this. In particular, I'd like to understand this one by Carl Hoefer in defense of "fundamentalism". He concludes with
Another way to get at the question is to take this fact about hydrogen seriously and see how much it says. Using the capacity language, we say that we know the capacities of hydrogen atoms, and also that we find hydrogen atoms all of the place. And less us take it a step further, and say we know the capacities of molecules, and that we also find these things all over the place. Is physics the domain that is responsible for such knowledge? Its certainly a good part of it, but I think its reasonable to say that the methods and ideas of chemistry are also involved in this knowledge. So I'd need to understand a little better what is meant by a law in the expression "fundamental law" to see if it captures the knowledge we have about the atomic and molecular basis of matter.
I think the reason is that I don't usually get very far. I get bogged down, skip ahead, and feel annoyed. I get a little out of it, but its dense, and the meaning of an essay is often not what I thought it was going to be. I didn't realize that the examples such as the BCS theory of superconductivity, and some laser physics (Also the measurement problem and the relations between classical and quantum systems) were gone into in such detail. The exposition is actually pretty clear, but you don't often know so much detail is on its way.
Anyway, I've finally been getting to the end and actually understanding more of it. In the end, it is more inspirational for a practicing physicist than I thought. The essay on the Quantum measurement problem in HLPL ends with stating that one should take the formalism of quantum statistical mechanics seriously which treats mixtures and superpositions on the same footing. This leaves physicists with the job of figuring out which cases have unitary evolution and which don't. And I think this is in line with the way one analyzes a new phenomena. Take a look at it. Use what we already know. Make some guesses. Test them. Refine them. An approach to learning about new things that involves actually studying those things.
And the discussion about capacities, vs. laws, is not so radical in the end. Perhaps from a philosophy perspective it is. But thinking of electric charge and gravitational mass as imbuing capacities on electrons rather than laying out laws of motion is just the way one thinks about these things. We learn about certain aspects of things, and then we may try to isolate it such that just that one property comes into play. This is what fundamental experiments are about. And we do learn some real about these things. The question may arise as to whether the same effect occurs in different environments, or exactly how the forces or whatever other properties combine when acting in concert. And this way of looking at physical knowledge puts it in the same box as other knowledge we have. There still may be questions of reduction or relationships between different kinds of knowledge, but the starting point seems good.
I must say I'm still not sure I get what she means by nomological machine. She makes a "strong claim" in "The Dappled World" that behind every regularity in the world is a nomological machine. Let's say we are in Switzerland where trains are highly reliable. The matching of the trains to the schedule is a nomological machine? I suppose it is. And the fact that my car (usually) works is a nomological machine. And atoms are nomological machines. And proteins are nomological machines. And a market is a nomological machine. And a beam of light is a nomological machine.
Anyway, just to remind that getting into certain details can be demotivating if one gets stuck in them, but if a topic actually relates to the world and the way things really work, then understanding it will lead to more tools and more clarity in the end. Which is to say that previously, reading this made me shut down certain ways of thinking, but now I find it mainly adds.
Apparently Philip Anderson may have had some trouble following "Dappled World" as well.
I just read Anderson's review (see here). Wow, that's pretty intense. He refers a lot to the feeling he gets about it. "One gets the feeling" he states a lot, without actually quoting many passages, or covering arguments. I must admit, that I sometimes had these same "feelings". But reading more closely, I often found that Cartwright was saying something more precise and more interesting than I initially thought.
Here are other reviews of The Dappled World.
Finally, once one digests some of the seemingly right arguments, one would like to see engagement of other authors. Here's some essays doing this. In particular, I'd like to understand this one by Carl Hoefer in defense of "fundamentalism". He concludes with
To engineers and experimentalists, I commend Cartwright’s philosophy of science wholeheartedly. But I hope to have made space for theoreticians and philosophers of physics to keep their faith in a world with fundamental physical laws.As a quick summary of Hoefer's article, he says that one can keep the fundamentalist approach but deny that some kinds of reductionism may be possible. What I wonder then is about the terminology of laws. Cartwright already says that we learn about capacities. I'd assume that the hydrogen atom in the dewar and the hydrogen atom in the hallway and the hydrogren atom in a distant galaxy all have the same capacities. (It does seem a bit odd to say that a hydrogen atom has the capacity to form the states specified by the Shroedinger equation with the central force potential term in its Hamiltonian, but maybe this is just what one must say.) I guess the question to address is how to relate such facts to programs in which we take electrodynamics, quantum mechanics, fluid mechanics, thermal physics, statistical mechanics, etc. and try to say that in some sense these theories "govern" matter.
Another way to get at the question is to take this fact about hydrogen seriously and see how much it says. Using the capacity language, we say that we know the capacities of hydrogen atoms, and also that we find hydrogen atoms all of the place. And less us take it a step further, and say we know the capacities of molecules, and that we also find these things all over the place. Is physics the domain that is responsible for such knowledge? Its certainly a good part of it, but I think its reasonable to say that the methods and ideas of chemistry are also involved in this knowledge. So I'd need to understand a little better what is meant by a law in the expression "fundamental law" to see if it captures the knowledge we have about the atomic and molecular basis of matter.
Tuesday, January 18, 2011
information vs. story/meaning
Ok, another post to motivate myself to get back to some work I should be doing.
First about information in general: I was just realizing that in some sense, I never really got my head around what this actually means. We are saying that information is key. And we develop information technologies, etc. But what is information? There is the physics definition in terms of entropy, but what is the more practical definition? I suppose it would have to do with a representation of something existing in the real world? So why are these representations so important? I guess because some things are set up such that once one has such a representation, one can impact the thing itself? A person has a set of information associated with them that is deemed important. And this information represents certain aspects of that person. And with this information, the person can be affected. If one has information about a country, then one may affect that country in certain ways.
On another end of this topic, I've been realizing that I've had this concept of work where I just need to collect together the appropriate information associated with some topic, and then I feel that my job is mostly done. Now I need to put together a report on beam lifetime, and I'm realizing that there's a lot to be done even though in some sense most of what I thought of as the work, is already done. I need to put the report together which means presenting the plots in certain ways, labelling stuff, etc. I think that other people would keep such a report, or a paper, or some other final product more in mind as they do the work of assembling the information. Then it gets put into the proper form along the way. I suppose there's a balance. Collecting stuff with such a clear final goal in mind may also skew the results and make them less robust. But it may also be more understandable, and have more impact. I could learn to direct my work a bit more towards goals, and would probably save myself some work, and get more done. Pure information is not so useful if you can't do something with it.
Do these two different queries/angles on information inform each other? I will have to think further on this.
(Incidentally, this question about the nature of information was partially prompted by reading stuff by Jared Lanier. I've been finding a lot of his writing a nice anecdote to some of what scares me online these days. Thinking more clearly about ideology and about our opinions on "information" seems useful. Perhaps more later.)
First about information in general: I was just realizing that in some sense, I never really got my head around what this actually means. We are saying that information is key. And we develop information technologies, etc. But what is information? There is the physics definition in terms of entropy, but what is the more practical definition? I suppose it would have to do with a representation of something existing in the real world? So why are these representations so important? I guess because some things are set up such that once one has such a representation, one can impact the thing itself? A person has a set of information associated with them that is deemed important. And this information represents certain aspects of that person. And with this information, the person can be affected. If one has information about a country, then one may affect that country in certain ways.
On another end of this topic, I've been realizing that I've had this concept of work where I just need to collect together the appropriate information associated with some topic, and then I feel that my job is mostly done. Now I need to put together a report on beam lifetime, and I'm realizing that there's a lot to be done even though in some sense most of what I thought of as the work, is already done. I need to put the report together which means presenting the plots in certain ways, labelling stuff, etc. I think that other people would keep such a report, or a paper, or some other final product more in mind as they do the work of assembling the information. Then it gets put into the proper form along the way. I suppose there's a balance. Collecting stuff with such a clear final goal in mind may also skew the results and make them less robust. But it may also be more understandable, and have more impact. I could learn to direct my work a bit more towards goals, and would probably save myself some work, and get more done. Pure information is not so useful if you can't do something with it.
Do these two different queries/angles on information inform each other? I will have to think further on this.
(Incidentally, this question about the nature of information was partially prompted by reading stuff by Jared Lanier. I've been finding a lot of his writing a nice anecdote to some of what scares me online these days. Thinking more clearly about ideology and about our opinions on "information" seems useful. Perhaps more later.)
Tuesday, January 11, 2011
optics and light representation
Well, in accordance with this blog title, I move slowly, and as I noted recently, have been moving into the radiation end of things. Its somewhat of a shock to go from such a specialized literature of accelerator physics and beam physics to the extremely vast literature of optics and light.
On the other hand, accelerator physics was never such a well defined concept. It is well defined from the sense that it is a collection of all the physics one may need in analyzing, building, designing or improving a particle accelerator. But its a rather mixed bag of classical mechanics, relativity, electricity and magnetism, and material science.
On to radiation, one has Maxwell's equations describing the evolution of electric and magnetic fields. However, one often represents light via a complex scalar field, or via a Wigner function, when coherence properties are required. Currently I'm trying to understand all this terminology related to Fourier Optics. One has a point spread function. One has an optical transfer function. One has an amplitude transfer function. Does one gain something new with these different representations? With the Wigner function, there's a partial interpretation in terms of the distribution of photons. But, being sometimes negative, its not such a clear interpretation. There are operator representations for quantum optics. One has the coherent states and the squeezed states. Is all of this unified, or in each domain of application does one in some sense use a different representation and mapping between the the real physical system and our calculational tools?
On the other hand, accelerator physics was never such a well defined concept. It is well defined from the sense that it is a collection of all the physics one may need in analyzing, building, designing or improving a particle accelerator. But its a rather mixed bag of classical mechanics, relativity, electricity and magnetism, and material science.
On to radiation, one has Maxwell's equations describing the evolution of electric and magnetic fields. However, one often represents light via a complex scalar field, or via a Wigner function, when coherence properties are required. Currently I'm trying to understand all this terminology related to Fourier Optics. One has a point spread function. One has an optical transfer function. One has an amplitude transfer function. Does one gain something new with these different representations? With the Wigner function, there's a partial interpretation in terms of the distribution of photons. But, being sometimes negative, its not such a clear interpretation. There are operator representations for quantum optics. One has the coherent states and the squeezed states. Is all of this unified, or in each domain of application does one in some sense use a different representation and mapping between the the real physical system and our calculational tools?
Sunday, December 19, 2010
light source physics
I've been writing about some frustration with the field of accelerator physics and where I fit into it recently. I came up with something of a tentative solution to this long standing problem, which I want to say a little about here. It may look like just words, but it does represent a change of orientation, and perhaps will lead to a better fit between what I am interested in and can do well, and what I am doing and asked to be doing for my job/career.
Outside of the question of how well research is supported, there has been an additional problem.
My thesis work was on electron storage rings and equilibrium electron distributions. But to actually continue on with that sort of topic is typically defined as accelerator physics, or beam physics, or even machine physics. The problem is that none of these really excites me that much. I was basically interested in the classical mechanics, or the non-linear dynamics, or the statistical mechanics. But not in making particles go as fast as possible. Beam physics is more interesting to me, but if it is defined so narrowly and with such little research support, its still not great. Machine physics also seems like a somewhat derogatory way of describing the topic. It doesn't describe what the physics is about, but only where it takes place. It is the stuff back there, beyond where the real science is happening, inside that big machine.
So I decided to define my own field of work/research as light source physics. This is meant to both exclude and include. One can say that light source physics (for synchrotron light sources, anyway) relies on accelerator physics and beam physics. But one could also say there is some overlap with accelerator physics and beam physics. First of all, one needs to get the beam there in the first place. That's the accelerator physics (but of course, its much more. Its engineering, its control systems, its infrastructure...) Then one needs to know about general behavior of relativistic beams of charged particles. This would be beam physics. Light source physics implies that the purpose of this electron beam is the radiation it produces. And furthermore, the dynamics of this beam is only half the story. The other half is the light that is produced. The electrons produce electromagnetic fields, or perhaps photons, or perhaps a distribution of light. I'd say that until this light exits the front end and heads down the beamline, we are in the realm of light source physics. The source of the light.
Thus both accelerator physics and other applications of beams are excluded. Colliding beams are used for particle physics. There are also medical purposes for beams. There is electron microscopy using electron beams.
Finally, whereas beam physics is shared between synchrotron light sources and colliders, on the radiation end, we could say its shared with xray optics particularly, and optics more generally. So flashlights and LED's and the sun, and fluorescent molecules are also light sources. And its within the realm of these topics that the definitions of brightness, brilliance, flux, and all that has been developed. So its not cheating to say that they are part of the field.
As for its need, one can look to a site such as Lightsources.org and one finds all about the applications, but not too much about synchrotron radiation and even less about the electron beam. So, though unorthodox, it seems to me a gap that could use development, but with different emphasis and theory than comes to mind with accelerator physics or beam physics or machine physics. In particular, both single pass and multipass is included. FEL's can be included... for now, just my own personal definition. But I think it makes sense. Talman's "Accelerator X-Ray Sources" is I think a good reference to orient some of this.
Just briefly, so, the picture is going from an electron beam to a photon beam. The electron beam may be described with Twiss parameters, and more general coupling formalism. I believe one can describe the photon beam in the same way.
Anyway, this blog has been somewhat a strange mix of personal and professional stuff. Since I hope to see how well I can do as a light source physicist, I decided to create a separate blog called Light Source Physics. The present blog will stay a bit more personal, and amateurish, venturing briefly into topics I know little about, but find interesting. Perhaps the other will develop more substantially. Or perhaps by splitting into two, I'll lose interest in blogging on either one... we shall see...
Another idea is to focus more on the philosophical aspects of things here, and more technical on the other one. Light may be described with a Wigner function for example. I'm curious what it means. Its supposed to be the closest to a representation of the distribution of photons. But it can go negative. Its interpretation is also difficult in quantum mechanics. So I'm curious about it with light. Is it a quantum mechanics issue? Is light transport a good context for thinking about basic non-relativisitic quantum mechanics? Is symplecticity an important concept in light transport?
The other thing to do with this blog is to continue with the mess I've been working on and describing related to accelerator physics, and beam physics. But hopefully continuing in a positive direction. Oriented towards getting a good code, and a reasonable set of references to help understand these things. It is a part of light source physics, after all.
Outside of the question of how well research is supported, there has been an additional problem.
My thesis work was on electron storage rings and equilibrium electron distributions. But to actually continue on with that sort of topic is typically defined as accelerator physics, or beam physics, or even machine physics. The problem is that none of these really excites me that much. I was basically interested in the classical mechanics, or the non-linear dynamics, or the statistical mechanics. But not in making particles go as fast as possible. Beam physics is more interesting to me, but if it is defined so narrowly and with such little research support, its still not great. Machine physics also seems like a somewhat derogatory way of describing the topic. It doesn't describe what the physics is about, but only where it takes place. It is the stuff back there, beyond where the real science is happening, inside that big machine.
So I decided to define my own field of work/research as light source physics. This is meant to both exclude and include. One can say that light source physics (for synchrotron light sources, anyway) relies on accelerator physics and beam physics. But one could also say there is some overlap with accelerator physics and beam physics. First of all, one needs to get the beam there in the first place. That's the accelerator physics (but of course, its much more. Its engineering, its control systems, its infrastructure...) Then one needs to know about general behavior of relativistic beams of charged particles. This would be beam physics. Light source physics implies that the purpose of this electron beam is the radiation it produces. And furthermore, the dynamics of this beam is only half the story. The other half is the light that is produced. The electrons produce electromagnetic fields, or perhaps photons, or perhaps a distribution of light. I'd say that until this light exits the front end and heads down the beamline, we are in the realm of light source physics. The source of the light.
Thus both accelerator physics and other applications of beams are excluded. Colliding beams are used for particle physics. There are also medical purposes for beams. There is electron microscopy using electron beams.
Finally, whereas beam physics is shared between synchrotron light sources and colliders, on the radiation end, we could say its shared with xray optics particularly, and optics more generally. So flashlights and LED's and the sun, and fluorescent molecules are also light sources. And its within the realm of these topics that the definitions of brightness, brilliance, flux, and all that has been developed. So its not cheating to say that they are part of the field.
As for its need, one can look to a site such as Lightsources.org and one finds all about the applications, but not too much about synchrotron radiation and even less about the electron beam. So, though unorthodox, it seems to me a gap that could use development, but with different emphasis and theory than comes to mind with accelerator physics or beam physics or machine physics. In particular, both single pass and multipass is included. FEL's can be included... for now, just my own personal definition. But I think it makes sense. Talman's "Accelerator X-Ray Sources" is I think a good reference to orient some of this.
Just briefly, so, the picture is going from an electron beam to a photon beam. The electron beam may be described with Twiss parameters, and more general coupling formalism. I believe one can describe the photon beam in the same way.
Anyway, this blog has been somewhat a strange mix of personal and professional stuff. Since I hope to see how well I can do as a light source physicist, I decided to create a separate blog called Light Source Physics. The present blog will stay a bit more personal, and amateurish, venturing briefly into topics I know little about, but find interesting. Perhaps the other will develop more substantially. Or perhaps by splitting into two, I'll lose interest in blogging on either one... we shall see...
Another idea is to focus more on the philosophical aspects of things here, and more technical on the other one. Light may be described with a Wigner function for example. I'm curious what it means. Its supposed to be the closest to a representation of the distribution of photons. But it can go negative. Its interpretation is also difficult in quantum mechanics. So I'm curious about it with light. Is it a quantum mechanics issue? Is light transport a good context for thinking about basic non-relativisitic quantum mechanics? Is symplecticity an important concept in light transport?
The other thing to do with this blog is to continue with the mess I've been working on and describing related to accelerator physics, and beam physics. But hopefully continuing in a positive direction. Oriented towards getting a good code, and a reasonable set of references to help understand these things. It is a part of light source physics, after all.
Thursday, November 18, 2010
slow
Today I feel frustrated. There's a sense of crystalization. Job splits into two parts- a work part and a research part. Not exactly, and its still a little vague, but it feels like its heading towards this.
You create something- a possibility?- and then you live with it. But in the process you don't pursue other options, and I find a heaviness in taking on the option that I've created. I was talking to my dad a few days ago, and describing some of my thoughts and efforts at cleaning up old messes and turning my field into something I can work with. He recommended a book he was reading about two brothers who can't throw anything away, that live in an apartment with everything they have ever collected.
Is this what I do? Just simply refuse to move on? Keep on working with an unworkable situation? In the language of the mess- is the mess simply too big? And even if its not, will there be anything interesting left after the mess is clean?
I feel like its all come to a stop. I reached a point of unstable equilibrium and just sit there, but its a very gradual slope away from this point. There are things I can work on; they are somewhat useful but not urgent. There are half-way interesting research-like questions. But this is my own internal process. Does it match expectations, and categorizations for achievement?
All this digital life continues to bother me (though I participate, such as with this blog). I continue to hear from the computer scientists about optimization and automated search and categorization. And one's activities on social networks become discrete. "So and so did this." "Now they did this." "Oh?" "Yes, they did do that." "Now so and so did this." "Really. That's great! So glad that you told me." Someone tells me about classification of human actions. They describe the "atoms" of action. Tom Waits smoking a cigarette and drinking coffee from a mug, the motion of hand away from mouth, "atomic".
You create something- a possibility?- and then you live with it. But in the process you don't pursue other options, and I find a heaviness in taking on the option that I've created. I was talking to my dad a few days ago, and describing some of my thoughts and efforts at cleaning up old messes and turning my field into something I can work with. He recommended a book he was reading about two brothers who can't throw anything away, that live in an apartment with everything they have ever collected.
Is this what I do? Just simply refuse to move on? Keep on working with an unworkable situation? In the language of the mess- is the mess simply too big? And even if its not, will there be anything interesting left after the mess is clean?
I feel like its all come to a stop. I reached a point of unstable equilibrium and just sit there, but its a very gradual slope away from this point. There are things I can work on; they are somewhat useful but not urgent. There are half-way interesting research-like questions. But this is my own internal process. Does it match expectations, and categorizations for achievement?
All this digital life continues to bother me (though I participate, such as with this blog). I continue to hear from the computer scientists about optimization and automated search and categorization. And one's activities on social networks become discrete. "So and so did this." "Now they did this." "Oh?" "Yes, they did do that." "Now so and so did this." "Really. That's great! So glad that you told me." Someone tells me about classification of human actions. They describe the "atoms" of action. Tom Waits smoking a cigarette and drinking coffee from a mug, the motion of hand away from mouth, "atomic".
Wednesday, November 10, 2010
work
Back to this theme of work vs. research, I guess I want to put a good word in for the difficulty of work. (Previously I said researchers may work harder.)
I'm trying to calculate something for a bunch of stored measurements. The formula is known, and its programmed into a matlab code. I really just have to get the parameters and plug them into the formula. What can be so hard about this?
Well, first, there is a fair amount of uncertainty in some of the parameters. It takes some work to cross check with various sources to get the parameter values reasonable. Then I need to learn how to access the data and to manage transfer of data and programs I write across a varied computing landscape. Finally, I need to choose which data to actually analyze such that the results will hopefully tell some kind of story out of which we can learn something.
A lot of these steps are the same in research. But, even though there is a lot of uncertainty, in some ways there is more certainty, because there is a research program. A set of questions to be answered. In the case of almost research, where the job is to understand something and keep it going and maybe make a few improvements, it may be even more open ended than research. Not to say I can't define some research projects within this, but there is a lot to be done that is really about gathering together data from disparate sources to understand and diagnose problems. And I wouldn't call this aspect research per se.
I'm trying to calculate something for a bunch of stored measurements. The formula is known, and its programmed into a matlab code. I really just have to get the parameters and plug them into the formula. What can be so hard about this?
Well, first, there is a fair amount of uncertainty in some of the parameters. It takes some work to cross check with various sources to get the parameter values reasonable. Then I need to learn how to access the data and to manage transfer of data and programs I write across a varied computing landscape. Finally, I need to choose which data to actually analyze such that the results will hopefully tell some kind of story out of which we can learn something.
A lot of these steps are the same in research. But, even though there is a lot of uncertainty, in some ways there is more certainty, because there is a research program. A set of questions to be answered. In the case of almost research, where the job is to understand something and keep it going and maybe make a few improvements, it may be even more open ended than research. Not to say I can't define some research projects within this, but there is a lot to be done that is really about gathering together data from disparate sources to understand and diagnose problems. And I wouldn't call this aspect research per se.
Tuesday, November 09, 2010
models
I enjoyed reading this paper today by Ronald Giere called "Representing with Physical Models".
Its an interesting thought that one can consider a graph or other representation of data like a 3-d image as a model in a similar sense that one has legos for a model car, or lincoln logs for a model house.
In the process of working through some problem, I often want feedback at an early stage, and so I produce some kind of plot that may partially get at what I want to say, or where I want to go, and I show it to a supervisor, or someone else. Its always an interesting process to have someone else look at your plot and take it as it is. For me, it is a termporary representation of some data I've been playing around with, but for someone else, it becomes an object contained within itself. They look at its boundary, ask about its imperfections, and describe the picture that it paints.
In the article, Giere describes representation via theoretical, physical, and computational models. His example of a theoretical model is a harmonic oscillator, his physical model example is Watson and Crick's colored balls representing DNA, and for a computational model, it is a 3-D image picture of a protein based on theoretical calculations and some protein data. He wants to say that these are all basically doing the same thing. That together with a person to do the interpreting, each of these can be acted on in various ways to learn something about the real system.
I guess this makes some sense to me. The nice thing about a toy model of something is you can play with it, get some feeling for it. You know harmonic oscillators have a fixed frequency, you can picture them oscillating in your mind, and you can even imagine the force they push against you as you try to compress the spring. Similarly with the real balls representing DNA and the 3-D image, you can play with them and relate them to things you know in the world. So with a plot you produce. Its limits and its potentialities may come alive in the viewers mind. It doesn't tell all, but it gives something concrete to hang on to to start building a picture of a given something or other you're trying to understand.
In my last post I said that physics gives us a bunch of models which have been used to describe electron storage rings (the example I focus on because I work on this, and want to clarify certain messy aspects of it). I think maybe some of the difficulty in this field is that computational approaches were developed, but somehow the last step of using them to make models didn't happen so well. One has a picture of a map with a resonance, but there's no good software to really turn this into a model where one can play with it and get a feel for it. (I suppose frequency map analysis software may qualify in this sense. One gets colorful pictures in which the resonances show up in the tune diagrams.) The concepts are there, and the software has been written (e.g. FPP) but not many people know how to use it, or how it relates to the phenomena of storage ring maps. In this context, model has usually meant the elements going into the computer code, and I suppose that's the theoretical model. But with the incoming model being very complex (so its hard to play around with in one's mind), and the software not being easy to use and visualize and relate to familiar things, one is left without good conceptual tools to understand some of these phenomena.
Its an interesting thought that one can consider a graph or other representation of data like a 3-d image as a model in a similar sense that one has legos for a model car, or lincoln logs for a model house.
In the process of working through some problem, I often want feedback at an early stage, and so I produce some kind of plot that may partially get at what I want to say, or where I want to go, and I show it to a supervisor, or someone else. Its always an interesting process to have someone else look at your plot and take it as it is. For me, it is a termporary representation of some data I've been playing around with, but for someone else, it becomes an object contained within itself. They look at its boundary, ask about its imperfections, and describe the picture that it paints.
In the article, Giere describes representation via theoretical, physical, and computational models. His example of a theoretical model is a harmonic oscillator, his physical model example is Watson and Crick's colored balls representing DNA, and for a computational model, it is a 3-D image picture of a protein based on theoretical calculations and some protein data. He wants to say that these are all basically doing the same thing. That together with a person to do the interpreting, each of these can be acted on in various ways to learn something about the real system.
I guess this makes some sense to me. The nice thing about a toy model of something is you can play with it, get some feeling for it. You know harmonic oscillators have a fixed frequency, you can picture them oscillating in your mind, and you can even imagine the force they push against you as you try to compress the spring. Similarly with the real balls representing DNA and the 3-D image, you can play with them and relate them to things you know in the world. So with a plot you produce. Its limits and its potentialities may come alive in the viewers mind. It doesn't tell all, but it gives something concrete to hang on to to start building a picture of a given something or other you're trying to understand.
In my last post I said that physics gives us a bunch of models which have been used to describe electron storage rings (the example I focus on because I work on this, and want to clarify certain messy aspects of it). I think maybe some of the difficulty in this field is that computational approaches were developed, but somehow the last step of using them to make models didn't happen so well. One has a picture of a map with a resonance, but there's no good software to really turn this into a model where one can play with it and get a feel for it. (I suppose frequency map analysis software may qualify in this sense. One gets colorful pictures in which the resonances show up in the tune diagrams.) The concepts are there, and the software has been written (e.g. FPP) but not many people know how to use it, or how it relates to the phenomena of storage ring maps. In this context, model has usually meant the elements going into the computer code, and I suppose that's the theoretical model. But with the incoming model being very complex (so its hard to play around with in one's mind), and the software not being easy to use and visualize and relate to familiar things, one is left without good conceptual tools to understand some of these phenomena.
Monday, November 08, 2010
system, environment
So physics provides us with interpretive models. We have ways of translating things into mathematical structures. Let's take this example of the electron storage ring.
We have magnets. These are big, heavy metallic objects with current running through them, shaped in ways to produce magnetic fields. So we line these up and put them in some configuration. Now, there's a certain region of space that maps out a doughnut-type shape inside all these magnets. Physics gives us the model of a magnetic field at all places inside this doughnut.
We have devices that mesh well with this picture. They measure the field and we basically assume that at a given time, the field has some value everywhere, and one can repeat measurements and get the same value. Then, to this, we throw some matter in there. We interpret that matter in terms of point charges with various masses and charges, such as electrons or air molecules.
The magnets and magnetic field is the environment or the background. The charges now move in this background. Now, depending on the needs, one can use different descriptions of the dynamics of the electrons. One can use classical electrodynamics to describe the motion of the charges, and the electric and magnetic fields they produce that may then also act back on those charges. I'm not entirely sure the status of the self-force and consistency within classical E&M. But I think its basically understood how to deal with it.
But actually, we need a little more than classical E&M. We need a bit of quantum mechanics. The radiation the electrons give off comes in lumps, and the lumpiness actually has an important effect that we can't ignore. Without the quantum lumpiness, for an appropriately set-up storage ring, the electrons would all end up at the center of the potential. Classical E&M says there is a damping mechanism that causes this to happen. Now, the interaction between electrons would limit the size of the resulting beam to a very small, finite size. But it turns out that the quantum lumpiness causes the beam to be much larger, and together with the damping mechanism, sets the size of the electron beam.
How do we treat the lumpiness? We use quantum mechanics (is it really full-blown QED? Or some semiclassical approximation given the emission spectrum of the electron?) to provide the diffusion coefficient. This turns the Lorentz equation into a stochastic differential equation. In the case of linear dynamics and constant damping and diffusion, the result is a Gaussian probability distribution, which when considered for an ensemble of electrons results in an actual Gaussian charge distribution.
Once the magnetic field has been set, and one is considering charged particles, there are other formulations for describing the classical dynamics besides the Lorentz force law. In particular one can use Lagrangian or Hamiltonian mechanics. Let us take the lead of Michelotti in describing this framework. He begins with the pendulum to introduce model systems that have the properties we need that the maps around the storage ring will have. He emphasizes with the pendulum that the phase space may not be R^n, but is a manifold. In chapter two he introduces linear and nonlinear models. He discusses the Hopf map and the Henon map, and gives the ideas of ergodicity and some other probability concepts such as partitions. So in general, we are actually in the realm of dynamical systems. And where does Michelotti end up? By chapter 5, he is discussing perturabtion theories for Hamiltonian dynamics and tries to give description of the Forest, Berz, Irwin normal form algorithm, which may contain isolated resonances.
So this is a long path stretching away from the magnets we see and the measured fields. It provides tools. A path to walk on. But there has to be a pulling from the other end. We have to know where we want to go. I would say that one usually wants to go to questions of stability. One wants to know whether a given bunch of electrons moving through this doughnut will last very long or not. And unfortunately, the elaborate normal form perturbation theories don't tell us this. And the same goes for the numerical implementation of these perturbation theories. One can compute resonance strengths and tune shift with amplitude to arbitrary order, for a machine with all the appropriate misallignments and field errors, and the full Hamiltonian, and one still doesn't answer the stability question by the perturbation theories.
But these are nice paths. And the tools are good tools. But without some pulling from the other side, the use of these tools gets lost. One doesn't know that sometimes one needs to develop new tools, or maybe give up on full understanding and just track the particles and see what happens.
Between the end point of injection efficiency and Touschek lifetime (momentum aperture), and the beginning or magnets leading to particular paths through classical mechanics with brief borrowings/harvestings from the quantum, one will simply get lost on these paths.
We have magnets. These are big, heavy metallic objects with current running through them, shaped in ways to produce magnetic fields. So we line these up and put them in some configuration. Now, there's a certain region of space that maps out a doughnut-type shape inside all these magnets. Physics gives us the model of a magnetic field at all places inside this doughnut.
We have devices that mesh well with this picture. They measure the field and we basically assume that at a given time, the field has some value everywhere, and one can repeat measurements and get the same value. Then, to this, we throw some matter in there. We interpret that matter in terms of point charges with various masses and charges, such as electrons or air molecules.
The magnets and magnetic field is the environment or the background. The charges now move in this background. Now, depending on the needs, one can use different descriptions of the dynamics of the electrons. One can use classical electrodynamics to describe the motion of the charges, and the electric and magnetic fields they produce that may then also act back on those charges. I'm not entirely sure the status of the self-force and consistency within classical E&M. But I think its basically understood how to deal with it.
But actually, we need a little more than classical E&M. We need a bit of quantum mechanics. The radiation the electrons give off comes in lumps, and the lumpiness actually has an important effect that we can't ignore. Without the quantum lumpiness, for an appropriately set-up storage ring, the electrons would all end up at the center of the potential. Classical E&M says there is a damping mechanism that causes this to happen. Now, the interaction between electrons would limit the size of the resulting beam to a very small, finite size. But it turns out that the quantum lumpiness causes the beam to be much larger, and together with the damping mechanism, sets the size of the electron beam.
How do we treat the lumpiness? We use quantum mechanics (is it really full-blown QED? Or some semiclassical approximation given the emission spectrum of the electron?) to provide the diffusion coefficient. This turns the Lorentz equation into a stochastic differential equation. In the case of linear dynamics and constant damping and diffusion, the result is a Gaussian probability distribution, which when considered for an ensemble of electrons results in an actual Gaussian charge distribution.
Once the magnetic field has been set, and one is considering charged particles, there are other formulations for describing the classical dynamics besides the Lorentz force law. In particular one can use Lagrangian or Hamiltonian mechanics. Let us take the lead of Michelotti in describing this framework. He begins with the pendulum to introduce model systems that have the properties we need that the maps around the storage ring will have. He emphasizes with the pendulum that the phase space may not be R^n, but is a manifold. In chapter two he introduces linear and nonlinear models. He discusses the Hopf map and the Henon map, and gives the ideas of ergodicity and some other probability concepts such as partitions. So in general, we are actually in the realm of dynamical systems. And where does Michelotti end up? By chapter 5, he is discussing perturabtion theories for Hamiltonian dynamics and tries to give description of the Forest, Berz, Irwin normal form algorithm, which may contain isolated resonances.
So this is a long path stretching away from the magnets we see and the measured fields. It provides tools. A path to walk on. But there has to be a pulling from the other end. We have to know where we want to go. I would say that one usually wants to go to questions of stability. One wants to know whether a given bunch of electrons moving through this doughnut will last very long or not. And unfortunately, the elaborate normal form perturbation theories don't tell us this. And the same goes for the numerical implementation of these perturbation theories. One can compute resonance strengths and tune shift with amplitude to arbitrary order, for a machine with all the appropriate misallignments and field errors, and the full Hamiltonian, and one still doesn't answer the stability question by the perturbation theories.
But these are nice paths. And the tools are good tools. But without some pulling from the other side, the use of these tools gets lost. One doesn't know that sometimes one needs to develop new tools, or maybe give up on full understanding and just track the particles and see what happens.
Between the end point of injection efficiency and Touschek lifetime (momentum aperture), and the beginning or magnets leading to particular paths through classical mechanics with brief borrowings/harvestings from the quantum, one will simply get lost on these paths.
Friday, November 05, 2010
hot topics
I commented again (29) at Cosmic Variance on a post about "Physicalist Anti-Reductionism" which included a debate between John Dupré and Alex Rosenberg. Sean seems to minimize the importance of the topic, finding it "the most boring argument in all of philosophy of science."
To me, it gets back to this kind of split I experienced when reading Nancy Cartwright. I found it hard to do physics when I didn't have this grand picture of it in mind, and instead having a skeptical approach. Can one be critical of something and excited about it at the same time?
But actually, to me, reading more skeptical philosophy of science is kind of like finding an honest way back to appreciating some of the stuff that originally excited me.
Maybe I'm just trying to justify choosing a not so "hot" topic in physics. Condensed matter theory, or particle theory or cosmology might have been sexier in some ways. Maybe I chose a purposefully boring topic because I thought it would be more honest.
Anyway, I was just realizing that this sense that a kind of reductionism is wrong has made me just not think very much about the components of things. Yes, there's a real sense in which we're made of molecules. And they are pretty cool. And there's a lot of them. And people make pretty pictures of them. And understanding a mechanism is pretty exciting.
The basic problem I have with accelerator physics is that try as I may, I can't put it in the same bag of exciting stuff as I've seen a lot of other topics before. Thinking about protein structure, or photosynthesis, or quantum mechanics is fun for me. But thinking about dispersion functions and chromaticity and tune shift with amplitude and momentum compaction factors... is just hard to get excited about. There were topics that originally seemed exciting. There's basically a new approach to classical mechanics that is developed in the early accelerator theory- a Lie algebra approach. Then there's the stuff with power series, whose early advocate describes in terms of differential algebras with connection to non-standard analysis. But in some sense, these mathematical abstractions are a bit overblown (particularly the latter). The reason I say they are overblown is that the problem has not even been solved. The real non-linear dynamics problem is that of the dynamic aperture (the stable region of a non-linear map) and as far as I know, this isn't really a solved problem. So going out so far into a given formalism when that formalism doesn't even solve the main problem seems a little too much.
Anyway, I'm not giving up. I like the classical mechanics. Synchrotron radiation is something I can put in the bag of exciting stuff. And the awful messy code situation may be able to slowly improve. So that's sort of the package. We've got some kind of nice classical mechanics. A bunch of somewhat useful definitions of things that are measured. A bit of a computer code and sociological infrastructure difficulty, and then some cool stuff with synchrotron radiation. Its a topic. It may be more fun to think about ecology or species of mosses, or the definition and validity of reductionism. But at least the topic is becoming less awful. Less ugly. Back away from all the extremists with their unfinished pyramids to build, and one has a topic in need of some sprucing up and simplification, but honorable nonetheless.
To me, it gets back to this kind of split I experienced when reading Nancy Cartwright. I found it hard to do physics when I didn't have this grand picture of it in mind, and instead having a skeptical approach. Can one be critical of something and excited about it at the same time?
But actually, to me, reading more skeptical philosophy of science is kind of like finding an honest way back to appreciating some of the stuff that originally excited me.
Maybe I'm just trying to justify choosing a not so "hot" topic in physics. Condensed matter theory, or particle theory or cosmology might have been sexier in some ways. Maybe I chose a purposefully boring topic because I thought it would be more honest.
Anyway, I was just realizing that this sense that a kind of reductionism is wrong has made me just not think very much about the components of things. Yes, there's a real sense in which we're made of molecules. And they are pretty cool. And there's a lot of them. And people make pretty pictures of them. And understanding a mechanism is pretty exciting.
The basic problem I have with accelerator physics is that try as I may, I can't put it in the same bag of exciting stuff as I've seen a lot of other topics before. Thinking about protein structure, or photosynthesis, or quantum mechanics is fun for me. But thinking about dispersion functions and chromaticity and tune shift with amplitude and momentum compaction factors... is just hard to get excited about. There were topics that originally seemed exciting. There's basically a new approach to classical mechanics that is developed in the early accelerator theory- a Lie algebra approach. Then there's the stuff with power series, whose early advocate describes in terms of differential algebras with connection to non-standard analysis. But in some sense, these mathematical abstractions are a bit overblown (particularly the latter). The reason I say they are overblown is that the problem has not even been solved. The real non-linear dynamics problem is that of the dynamic aperture (the stable region of a non-linear map) and as far as I know, this isn't really a solved problem. So going out so far into a given formalism when that formalism doesn't even solve the main problem seems a little too much.
Anyway, I'm not giving up. I like the classical mechanics. Synchrotron radiation is something I can put in the bag of exciting stuff. And the awful messy code situation may be able to slowly improve. So that's sort of the package. We've got some kind of nice classical mechanics. A bunch of somewhat useful definitions of things that are measured. A bit of a computer code and sociological infrastructure difficulty, and then some cool stuff with synchrotron radiation. Its a topic. It may be more fun to think about ecology or species of mosses, or the definition and validity of reductionism. But at least the topic is becoming less awful. Less ugly. Back away from all the extremists with their unfinished pyramids to build, and one has a topic in need of some sprucing up and simplification, but honorable nonetheless.
Wednesday, November 03, 2010
advanced light sensing
A funny quote from p. 5 of the book "Elements of Synchrotron Light" by G. Margaritondo:
As new-born babies, we begin to learn by 'seeing' things with light, which consists of electromagnetic waves. As we grow up and become more sophisticated, we can use different types of electromagnetic waves to explore different properties of the world around us: for example infrared light to study atomic-level vibrations or X-rays to study the atomic structure of molecules.Now, I'm always looking for how to "tell the story" of synchrotron light sources. But this is an odd angle! We start our lives by seeing with visible light, and then after we become more mature (as a synchrotron light experimenter), then we add infrared and X-rays to the spectra of usable light to learn about the world!!
Saturday, October 30, 2010
some generality of science
I've been on a critical direction for awhile, and looking to find a more constructive direction.
I'd like to get back to some of the excitement I've had for science. And it really covers a lot of good stuff.
So what are some of the important things we know? I think Feynman said that he thought the most astonishing and important knowledge was about atoms. Here is something like a universal knowledge. We can take anything we find, anywhere, and if we break it down in a variety of ways, we find that there are atoms that made it up. Maybe often you get molecules instead of atoms. But this idea of breaking material apart and always getting something of a fixed set of elements. This does seem to be pretty significant knowledge, and to always be true. Does this mean that atoms are the "underlying story" of everything? Maybe.
So this seems to be a kind of reductionism defined operationally. Stuff can always be broken down into atoms. (How to make it more precise? Step 1. Find something. Step 2. break off a little piece. Step 3. break off a little piece of that. Step 4. heat it up? explode it? ...)
What else do we have? We have light. There are radio waves, and visible light, and ultraviolet waves, and xrays. You can't really talk about light in the same way you talk about matter. You don't break stuff apart and find light at the bottom. Stuff goes through some transitions, and light is emitted- it makes other stuff go through transitions.
I really don't want to end up with a network here, with nodes and messages being passed between the nodes. Yuck. I'm sick of networks.
Anyway, yeah, there's stuff, and there's light.
What about a beautiful forest- an intricate ecosystem? Stuff and light? Does that get us very far in understanding and appreciating it? More work for another day.
I'd like to get back to some of the excitement I've had for science. And it really covers a lot of good stuff.
So what are some of the important things we know? I think Feynman said that he thought the most astonishing and important knowledge was about atoms. Here is something like a universal knowledge. We can take anything we find, anywhere, and if we break it down in a variety of ways, we find that there are atoms that made it up. Maybe often you get molecules instead of atoms. But this idea of breaking material apart and always getting something of a fixed set of elements. This does seem to be pretty significant knowledge, and to always be true. Does this mean that atoms are the "underlying story" of everything? Maybe.
So this seems to be a kind of reductionism defined operationally. Stuff can always be broken down into atoms. (How to make it more precise? Step 1. Find something. Step 2. break off a little piece. Step 3. break off a little piece of that. Step 4. heat it up? explode it? ...)
What else do we have? We have light. There are radio waves, and visible light, and ultraviolet waves, and xrays. You can't really talk about light in the same way you talk about matter. You don't break stuff apart and find light at the bottom. Stuff goes through some transitions, and light is emitted- it makes other stuff go through transitions.
I really don't want to end up with a network here, with nodes and messages being passed between the nodes. Yuck. I'm sick of networks.
Anyway, yeah, there's stuff, and there's light.
What about a beautiful forest- an intricate ecosystem? Stuff and light? Does that get us very far in understanding and appreciating it? More work for another day.
Wednesday, October 27, 2010
research infrastructrure
In some ways, people doing research may do more work than others. You take the problem with you all the time, and you really put a lot of yourself into solving it. The benefit to this may be that you have freedom to pursue something that really interests you, and your work and passion may be aligned.
There's a danger when a field does not have a strong research culture, but still has a research component. If most of the work to be done really isn't research, then what is and isn't research may be confused. A person programming for a company doesn't think of themself as doing research, but rather as problem solving. The difference is that much of the framework is predetermined.
In a field without a strong research infrastructure, one is expected to make the framework oneself, but one will never really do something new, because the information is just badly managed. The problems have already been solved long before. If one is supposed to be doing research, but is really just catching up to where others have already been, or cleaning up old messes, this is not very healthy. Instead, this component should simply be called work, a set of objectives should be set up, and the work divided amongst those doing it.
(added...)
Summary: if its work and not research, then there need to be very clear goals and it should be finished, even if imperfectly. Depth and creativity and perfection is not well spent on something that cannot support real innovation. Real innovation will look bad at first, and will take awhile to get somewhere and perhaps other people to finish things at a later time. I need to learn to separate research from work. I seem to never quite learn this lesson, and it gets me again and again.
There's a danger when a field does not have a strong research culture, but still has a research component. If most of the work to be done really isn't research, then what is and isn't research may be confused. A person programming for a company doesn't think of themself as doing research, but rather as problem solving. The difference is that much of the framework is predetermined.
In a field without a strong research infrastructure, one is expected to make the framework oneself, but one will never really do something new, because the information is just badly managed. The problems have already been solved long before. If one is supposed to be doing research, but is really just catching up to where others have already been, or cleaning up old messes, this is not very healthy. Instead, this component should simply be called work, a set of objectives should be set up, and the work divided amongst those doing it.
(added...)
Summary: if its work and not research, then there need to be very clear goals and it should be finished, even if imperfectly. Depth and creativity and perfection is not well spent on something that cannot support real innovation. Real innovation will look bad at first, and will take awhile to get somewhere and perhaps other people to finish things at a later time. I need to learn to separate research from work. I seem to never quite learn this lesson, and it gets me again and again.
Sunday, October 10, 2010
beam distribution, lifetime, synchrotron radiation
Ok, closer to what I should actually be working on...
We have an electron beam with a variety of interactions. At high energy in a storage ring, mainly you get a Gaussian due to damping and diffusion processes from synchrotron radiation. The self interaction mainly manifests as a beam lifetime- scattered particles are lost in what's known as the Touschek lifetime. Also, if there's an aperture close enough to this Gaussian, then particles are lost through this diffusion process in what's known as the Quantum lifetime.
Suppose we have a non-Gaussian beam. How did it get this way? What does this say about the lifetime?
We can treat the synchrotron radiation effect on the distribution via the Fokker-Planck equation. Can other noise processes on the beam also be treated via the FP equation? What would a non-Gaussian distribution do to the emitted synchrotron radiation?
Finally, does anyone care? We use this radiation for all sorts of experiments. Which experiments care about lifetime? Which care about beam size? Which care about the coherence of the radiation?
We have an electron beam with a variety of interactions. At high energy in a storage ring, mainly you get a Gaussian due to damping and diffusion processes from synchrotron radiation. The self interaction mainly manifests as a beam lifetime- scattered particles are lost in what's known as the Touschek lifetime. Also, if there's an aperture close enough to this Gaussian, then particles are lost through this diffusion process in what's known as the Quantum lifetime.
Suppose we have a non-Gaussian beam. How did it get this way? What does this say about the lifetime?
We can treat the synchrotron radiation effect on the distribution via the Fokker-Planck equation. Can other noise processes on the beam also be treated via the FP equation? What would a non-Gaussian distribution do to the emitted synchrotron radiation?
Finally, does anyone care? We use this radiation for all sorts of experiments. Which experiments care about lifetime? Which care about beam size? Which care about the coherence of the radiation?
phil sci, dirac
From Taking up Spacetime is a link to the philosophy of science preprint server, here.
I've been browsing a bit and enjoying reading some papers. I found this paper on interpretations of the Dirac equation here (M. Valenti, 2008) which I've skimmed a bit. He talks about using QED to describe the Hydrogen atom, which I'd be interested to understand better. It does seem that mostly QFT calculates S-matrix type stuff, and bound states are more foreign. If NR QM and the Dirac equation really come out of QED, then it should be able to deal with bound states. I vaguely remember something about "resonances" (related to the complex poles) of the S-matrix being the bound states...
Maybe too hard to understand right now, but interesting stuff anyway.
(added... Ok, here's an interesting quote related to this reductionism, model building stuff:
I've been browsing a bit and enjoying reading some papers. I found this paper on interpretations of the Dirac equation here (M. Valenti, 2008) which I've skimmed a bit. He talks about using QED to describe the Hydrogen atom, which I'd be interested to understand better. It does seem that mostly QFT calculates S-matrix type stuff, and bound states are more foreign. If NR QM and the Dirac equation really come out of QED, then it should be able to deal with bound states. I vaguely remember something about "resonances" (related to the complex poles) of the S-matrix being the bound states...
Maybe too hard to understand right now, but interesting stuff anyway.
(added... Ok, here's an interesting quote related to this reductionism, model building stuff:
In this way we are not restricted by Haag’s theorem – and so we can retain the concept of quanta in the description of interactions – because, from a physical point of view, the Lagrangian of quantum electrodynamics does not provide us (contrary to what from a mathematical abstract point of view might appear) with the possibility of describing a system of (undifferentiated) interacting Dirac and Maxwell fields, but with a way of developing models that describe in a limited way the interaction between the fields.Valenti, p. 14)
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