Search Talks

I will discuss the phenomenologically interesting scenario of matter inflation in supersymmetric hybrid inflation models. The inflaton resides in a gauge non-singlet matter multiplet and the eta-problem is solved by a "Heisenberg" symmetry. This symmetry relates the inflaton with a modulus field and we stabilize this modulus via corrections to the Kähler potential. The Heisenberg symmetry arises naturally for the untwisted matter fields in heterotic orbifolds. A way to embed matter inflation into heterotic orbifold compactifications is suggested and moduli stabilization in the extended setup is discussed. I argue that the corrections from moduli stabilization may not spoil the flatness of the inflaton potential at large radius.

I'll discuss my recent results (1108.2255) showing that, once gravity and some technical confusions are taken care of, two classes of potentials one expects to be generic in a landscape, namely ones resulting in thin-wall instantons or with small relative differences in potentials, result in instantons which typically decay rapidly, including exponentially enhanced rates for thin-wall instantons. I'll explain why this is true both generally and in detail and why the previous treatments have gone astray. This meeting will be designed to be a highly informal and interactive session to present these results in detail and address questions, confusions, and challenges of those, esp. cosmologists, with some level of background in tunnelling. I'll give a broader presentation of this material for a more general audience in the strings group meeting (Friday 11am, space room).

Cosmic strings are predicted to arise in both inflationary and non-inflationary cosmological models. The signatures of such strings will stand out particularly well at higher redshifts. I will discuss how to look for these signatures in CMB redshift and polarization maps and in 21cm redshift surveys.

Assuming that you are really (really) strong, what are the biggest objects in the Universe that hold together enough that you could throw them? What are they made of and why are they so big? In this talk, I will show how studies of the large scale structure of the Universe enable us to reconstruct the initial conditions at the Big-Bang and test the fundamental laws of physics. Among other things, scientist are trying to test one of the most provocative idea of modern physics: the possibility that these huge "things" actually originated from quantum fluctuations smaller than anything we have ever detected!

If we imagine that the universe is truly eternal, special challenges arise for attempts to solve cosmological fine-tuning problems, especially the low entropy of the early universe. If the space of states is finite, the universe should spend most of its time near equilibrium. If the space of states is infinite, it becomes difficult to understand why our universe was in a particular low-entropy state. I will discuss approaches to addressing this problem in a model-independent fashion.