Altas Energías
New Methods and Results for the Topological Susceptibility
by Dr. Wolfgang Bietenholz (ICN, UNAM)
Wednesday, 6 February 2019
from
to
(Mexico/General)
at IF-UNAM ( Sandoval Vallarta )
at IF-UNAM ( Sandoval Vallarta )
Instituto de Física,
UNAM
Description |
There are important models of quantum field theory, where the configurations are divided into topological sectors. In these models the topological susceptibility is a prominent, fully non-perturbative observable. We first discuss its definition, and its meaning in QCD and in axion physics. Then we address the difficulty in its numerical measurement. In this regard, we describe a new method - the "slab method" - which is applicable even when the Monte Carlo history is confined to a single topological sector. We present results for the quantum rotor, the 2d Heisenberg model and 2-flavor QCD. In the latter case, a modern smoothing procedure is involved, the Gradient Flow. In the second part we focus on the Heisenberg model and the millennium question whether or not its topological susceptibility scales to a finite continuum limit. According to the paradigm of the late 20th century this is not the case, which implies that this famous model suffers from a conceptual disease. We have revisited this issue by involving for the first time the Gradient Flow, along with a powerful cluster algorithm. |
Support | Email: epeinado@fisica.unam.mx |