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Thursday, 3 December 2009, 14:00 in P8445B
Dr. Adam Moss (UBC)
Dark energy: Violations of isotropy and homogeneity
Dark energy is one of the biggest mysteries in cosmology. In this talk I discuss two alternatives, each with very different physical origins, which have the unusual properties that they break fundamental cosmological principles of isotropy and homogeneity. In the first model, I extend the fluid approximation used to model stress-energy components in cosmology, and treat dark energy as a stiff fluid. Such models are stable, even when the pressure is negative, making them natural candidates to describe the dark energy. I show how this model can be extended to the anisotropic case, in an attempt to explain usual features in the CMB maps. In the second, I discuss whether we can remove the need for dark energy altogether. In this case, we have to sacrifice the Copernican principle and live near a large, non-linear, and close to spherical underdense region of the Universe.
Thursday, 3 December 2009, 16:00 in P8445?
Dr. Neil Barnaby (CITA)
Nonlocal inflation
The inflationary paradigm has been extremely successful in accounting for cosmological observations, however, it still lacks a firm motivation from fundamental theory. Attempts to embed inflation into theories of physics beyond the standard model, such as string theory, have been stymied by the difficulty of constructing flat scalar field potentials. I will discuss how this difficulty can be evaded by taking advantage of the higher derivative structure of string field theory. I will show that these nonlocal inflation models are predictive, they generically lead to nongaussian signatures in the CMB. At the formal level these theories have a rich mathematical structure. After discussing the complications that can arise when working with high derivative theories, I will describe recent progress in understanding the initial value problem for infinite order differential equations.
Seminars in 2009:
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Modified by Andrei Frolov <frolov@sfu.ca> on 2023-11-01