Sunday, April 13, 2008

Black Hole Sun Won't You Come...

Welcome to day two of my attendance at the APS meeting in St. Louis. This time, I remembered to bring my laptop with me. I am currently sitting in on a session entitled "Neutron Stars, Pulsars, and Black Holes. Earlier today, I stumbled into a wonderful story-telling session about the Manhattan Project which included some wonderful little anecdotes about life at Los Alamos. One of the speakers was a British physicist who had worked there at the time. I would repeat some here but I would get the details wrong. Looks like the first talk is starting. I'd better listen up.

First up is Dr. J. R. Stone of Oxford discussing the equation of state for high density matter. The main question discussed is whether or not observational or experimental data can be used to place constraints on the equation of state of neutron star matter. One of the major pieces of data necessary for these constraints is a good measurement of gravitational mass v. radius for neutron stars. According to to Dr. Stone, "That would do it for me." Sadly, technical problems have cut this talk sort of it's ten minute allowed time. My estimate is that Dr. Jones was able to present about a third of her planned talk. I think I might have had a chance of understanding her neutron-neutron scattering data if she were given a few more minutes. If is the neutron-neutron interaction that must be fully understood in order to come up with the desired equation of state.

Talk number two is also on the equation of state for neutron starts. Dr. John Friedman is talking on astronomical constraints to the equation of state. Dr. Friedman tout that neutron stars might be strange quark stars. I'll have to look into that later. So the required astronomical include mass, moment of inertia, and spin frequency. From this talk, I have learned that if you know little about the field, the 10 minute talk format is probably not to go. Yesterday, while I was in the dark matter talks, I loved the 10 minute format because I absorbed a lot of information in little time. Knowing little about determining the equation of state of neutron stars, this talk is hard to follow, but I will talk about it anyway. Overall, I have learned that determining either the mass and moment of inertial or the mass and the gravitational wave characteristics both place good constraints on the shape of the equation of state.

On to the third talk! Guess what it is about. Come on, guess. That's right, it's another talk on the parameterization of the equation of state for a neutron star. This speaker is giving the second half of the second talk. Turns out they are testing 31 different equations of state some including all kinds of exotic matter including hyperons, mesons and quarks. One of the parameters most often used to parameterize these equations of state is the maximum allowed mass of the neutron star. Also used it causality which considers the speed of sound in the star. Redshift and rotation rate are also used in this manner. Currently, measuring the mass and radius of neutron stars is quite difficult. The four parameters mentioned above can be used to determine bulk properties of nuclear matter through the determination of the equation of state and therefore would have application beyond neutron stars. As you might be able to tell, this talk cleared up the previous one a little.

I'm going to sign off now to save some battery power for the dark matter talks.
Edit: I've decided to take pen and paper notes for the Dark Matter talks. I'll tell y'all about them later.