Talks

The presence of an instability in the Standard Model Higgs potential may have important implications for inflation and the viability of our Universe. In particular, if the Hubble scale during inflation is comparable to (or larger than) the instability scale of the potential, quantum fluctuations in the Higgs field will lead to the Higgs sampling the unstable part of the potential during inflation. However, to correctly study transitions to the unstable regime and determine the significance for the resulting universe requires addressing a number of subtleties. I will discuss these subtleties and a variety of possible approaches to studying Higgs evolution during inflation. By considering both (1) the evolution of Higgs fluctuations in the Gaussian approximation and (2) a perturbative calculation of the fluctuation two-point correlation function, I aim to elucidate how to address these issues in a consistent, physical way. The insight provided by these approaches will set the scene for studying Higgs fluctuations via the Fokker-Planck (FP) approach, which captures the non-Gaussian nature of the field. As such, it provides information about the rare—but, in terms of the fate of our Universe, potentially extremely important—patches that experience particularly large fluctuations.

For isolated quantum systems fluctuation theorems are commonly derived within the two-time energy measurement approach. In this talk we will discuss recent developments and studies on generalizations of this approach. We will show that concept of fluctuation theorems is not only of thermodynamic relevance, but that it is also of interest in quantum information theory. In a second part we will show that the quantum fluctuation theorem generalizes to PT-symmetric quantum mechanics with unbroken PT-symmetry. In the regime of broken PT-symmetry the Jarzynski equality does not hold as also the CPT-norm is not preserved during the dynamics. These findings will be illustrated for an experimentally relevant system ? two coupled optical waveguides. It turns out that for these systems the phase transition between the regimes of unbroken and broken PT-symmetry is thermodynamically inhibited as the irreversible work diverges at the critical point. The discussion will be concluded with an alternative approach to fluctuation theorems and quantum entropy production in quantum phase space.

Galileons are higher-derivative effective field theories with curious properties which have attracted much recent interest among cosmologists.  I will review their origins, their properties, their generalizations, and some recent developments.