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.)

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?