|Friday 22 January 2021|
|Events for day: Wednesday 20 January 2021|
| 11:00 - 12:00 Wednesday Weekly Seminar-google meet|
Mass corrections to the DGLAP evolution equations
PARTICLES AND ACCELERATORS
Abstract: We propose a mass-dependent MOM scheme to renormalize UV divergence of unpolarized PDFs at one-loop order. This approach which is based on a once subtracted dispersion relation does not need any regulator. The overall counterterms are obtained from the imaginary part of large transverse momentum region in loop integrals.
The mass-dependent characteristic of the scheme yields to mass-dependent splitting functions for the DGLAP evolution equations. While the flavor number is fixed at any renormalization scale, the decoupling theorem is automatically imposed by the mass-dependent splitting functions. The required symmetries are ...
13:30 - 15:00 Weekly Seminar (Online)
Markovian dynamics in de Sitter
The equilibrium state of fields in the causal wedge of a dS observer is thermal, though realistic observers have only partial access to the state. To them, out-of-equilibrium states of a light scalar field appear to thermalize in a Markovian fashion. We show this by formulating a systematic expansion for tracing out the environment. As an example, we calculate the O(lambda) correction to the result of Starobinsky and Yokoyama for the relaxation exponents of $lambdaphi^4$ theory. ...
14:00 - 15:00 Weekly Seminar
Condensed Matter and Statistical Physics Group
Many-body theory of nonlinear optics in two dimensional materials
Because of the many-body interactions, the standard concepts of nonlinear response to electromagnetic fields break down in two dimensional Dirac systems, like graphene, in the quantum regime close to the Dirac point. I this talk, I will first discuss the dramatic impact of long-range Coulomb interaction on the nonlinear optical responses owing to the plasmonic and screening effects . Then, I will present how using a conserving Baym-Kadanoff approach, we can provide a fully compelling theory of nonlinear optical and transport response of a Dirac system to electric fields in the presence of disorder scattering. We s ...
16:30 - 18:00 Mathematics Colloquium
What is Geometry ? Elements of Answer from a Grothendieckian Perspective
The ancient Greek word "geometry" is, with its etymological meaning of "measurement of the earth", one of the oldest of mathematics. The discovery of non-euclidean geometries in the 19th century dramatically increased the scope of geometry. This scope was further extended in the 20th century by dividing geometry into branches differing in their objects of study and their methods: topology, differential geometry, Riemannian geometry, symplectic geometry, complex geometry, algebraic geometry, ... Grothendieck is known primarily for having re-founded algebraic geometry on entirely new bases. But he himself considered himself to be ...