Tres físicos no hispanohablantes

Can't you see the dark matter? This is about how much we know about what dark matter is.

As you may or may not know, there is a problem in the field of cosmology which is that the mass in the universe that we can observe does not add up to what we would expect based on other observations. To explain how galaxies clump and stars move around in their galaxies, additional mass, called ‘dark matter’ is required.  It is called ‘dark’ because it doesn’t give off light.  The only problem is that because we can only observe it indirectly, no one really knows what this stuff is.  Consequently, we don’t know how to write down the necessary equations that explain it’s gravity.

Well, there is a possible solution to this problem that Martin and I have been looking at for the last couple weeks. There is a newly proposed theory of gravity by Petr Horava, which includes non-relativistic properties, such as faster than light travel for incredibly short distances.  In this theory, time and space, are treated unequally, which leads to an extra term that appears in our solutions.  This term acts like cold dark matter (cold because it’s not self-interacting). Here is the paper that explains the theory if you would like to read it: arxiv.org/abs/0905.3563. The whole situation is very exciting and we hope to find out more about it.

Pretty picture of the origin of the universe

We just got back from a conference at Penn State on Classical and Quantum Gravity.  The conference was being held in honor of the 60th birthday of Abhay Ashtekar, one of the founders of loop quantum gravity and the Director of the Institute for Gravitational Physics and Geometry at Pennsylvania State University.  Dr. Ashtekar was one of Dr. Alexander’s first mentors at Penn State.

At the conference we heard a wide variety of exciting talks ranging on topics from classical general relativity, to schemes for quantizing gravity, to black hole horizons, to numerical treatments of classical GR, to quantum field theory in curved-spacetimes.

igc.psu.edu/events/abhayfest/program.shtml

While we can’t claim to have understood all the talks, it was very exciting to be in the same room with many of the ‘big names’ in the field, such as Sir Roger Penrose, Abhay Ashtekar, Robert Wald, John Collins, and James Hartle.  We ate lunch with Deepak Vaid, Andy Randono, and Ted Jacobson and discussed composite fermions, black holes, and the experience of being a theoretical physicist.  Thursday night we attended a public lecture by Sir Roger Penrose called “Fashion, Faith, and Fantasy: How Big is Infinity.”  He presented a broad look at fundamental questions related to quantum mechanics, string theory, and inflation while maintaining a great deal of lay-person accessibility.

The Alexander Group is traveling to Santander, Spain to collaborate with researchers at the Instituto de Fisica de Cantabria (IFCA). While we are there we will be collaborating with professional astronomers, cosmologists, and nonlinear physicists on two projects. Collaborating with Dr. Jose Diego, Dr. Alexander and Garrett are exploring parity properties of the cosmic microwave background data. Under Dr. Alexander, Martin and Alex will be exploring the properties of fermionic fields in alternative formulations of general relativity. We will used this blog to report on our adventures leading up to and during the trip.