Perturbative construction of QED using ERG
Kobe University Physics Dept.
13.09-2012 Thursday / Perşembe 15:00
Özet / Abstract : I would like to explain how to use the exact renormalization group (Wilson-Polchinski differential equation) to construct QED perturbatively. I first introduce the necessary tools using a real scalar theory as a concrete example. I then explain how to construct QED by imposing the Ward-Takahashi identity to the solution of the ERG differential equation. I end the talk by deriving the Khalatnikov-Landau equation for the gauge parameter dependence of the correlation functions.
Place/Yer : MSGSÜ Bomonti Binası, Fizik Bölümü.
Cosmology in nonlinear massive gravity
A. Emir Gümrükçüoğlu
Kavli IPMU, University of Tokyo
06-09-2012 Perşembe/Thursday 15:00
Özet/Abstract : General theory of relativity, in which the interactions have an infinite range, is in agreement with current experimental and observational data. On the other hand, from a theorist’s point of view, it is an interesting question whether the range of gravity can be consistently made to be finite, or equivalently, whether graviton can have a non-zero mass. This has been one of the most persistent challenges in classical field theory for the last 70 years. Recently, de Rham, Gabadadze and Tolley constructed a nonlinear theory of massive gravity, which successfully avoids the complications encountered before. Moreover, the theory has also phenomenological relevance, since the graviton mass may account for the accelerated expansion of the present universe, providing an alternative to dark energy. I will present self-accelerating cosmological solutions in the framework of this theory. The cosmological perturbations around these background have an interesting behaviour: instead of the 5 degrees of freedom expected from a massive spin-2 field, only the 2 gravity wave polarizations are dynamical, at linear level. However, nonlinear analysis of the extra modes reveal the existence of ghost instabilities. This implies that a consistent universe solution in this theory should be inhomogeneous and/or anisotropic.
Yer : MSGSÜ Bomonti Binası, Fizik Bölümü.
Tarih : 6 Eylül 2012 Perşembe, 15:00