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January 29, 2011
Center for Gravitation and Cosmology hosts Gravitational-wave Physics and Astronomy Workshop
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Seminars
February 10, 2012
Non-Gaussian features of primordial magnetic fields
Leonardo Motta
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Seminars
The Center holds frequent seminars on a broad range of ongoing cosmology and gravitation research topics. Unless otherwise noted, seminars are on Friday afternoons at 1 PM in Room 481; there is a gathering for a brown bag lunch at 12:30.
February 10, 2012
Non-Gaussian features of primordial magnetic fields
Leonardo Motta, Dartmouth College
Abstract: Little is known about the Lagrangian of inflation. Information about that epoch can be obtained from the non-gaussian corrections to cosmological correlations which have been explored extensively for the gravitational field. However, other cosmological observables may also be probed for this purpose. For instance, if new physics during inflation breaks the conformal invariance of electrodynamics, a relic cosmic magnetic field can be produced. We explored the non-gaussian correction that arises under this assumption in two models of inflation. In power-law inflation it is possible to produce a nG relic magnetic field at Mpc scales at the present time with a cross-correlation amplitude of 10-5 with matter fluctuations. This cross-correlation signal might be accessible by the SKA telescope, which would provide new information about the physics of the early universe.
March 2, 2012
Evidence for Neutron Superfluidity in Neutron Star Cores
Craig Heinke, University of Alberta
Abstract: Massive stars explode as supernovae at the end of their lives, leaving neutron stars, dense balls of matter at super-nuclear density. The behavior of matter at such high density is not well understood. X-ray observations of hot young neutron stars are one method of probing the physics of neutron stars. I will discuss X-ray observations of some young neutron stars, focusing on the youngest known neutron star, in Cassiopeia A. Our team proposed that its unusual X-ray properties are naturally explained by a carbon atmosphere, and discovered that its surface is measurably cooling with time. The observed rate of cooling, and its current temperature, require a rapid, short-lived transition in the neutron star's interior. Our proposed explanation is that the neutrons in the core are undergoing a transition to a superfluid state, radiating away their heat via neutrinos as the neutrons pair up.