Thema:

Phases of QCD: a lattice perspective

Datum:

01.02.21

Uhrzeit:

16:15

Ort:

cyberspace

Vortragender:

JProf. Francesca Cuteri

Goethe-Universität Frankfurt

Inhalt:

Quantum chromodynamics (QCD) is established as the fundamental underlying theory of the strong interaction, yet there are only few firmly established aspects when it comes to its rich phase diagram. There are, though, systems which did/may happen to wander around in the QCD phase diagram within environments that are so extreme, in terms of temperature and/or density, as to accommodate other QCD phases than the hadronic one that we are more familiar with. These systems are our Universe, in the first microseconds after the “Big Bang”, Neutron Stars (even more so in their mergers), heavy ions in their collisions and, theoretically rather than practically speaking, a large part of modern supercomputers around the globe. We can, indeed, use supercomputers to simulate strong interaction matter under extreme conditions thanks to an almost 50-years-old numerical framework for describing non perturbative phenomena in QCD via Monte Carlo simulations: lattice QCD. In this talk we will discuss how lattice QCD simulations allow us to explore, from a theoretical perspective, some rather interesting portions of the QCD phase diagram (in temperature and nonzero net isospin density directions). We will also discuss how we try to learn about interesting regimes, like that of nonzero net baryon densities, that lattice QCD fails accessing, by extending our parameter space even further (varying i.e. the microscopic parameters of the theory away from their physical value) and then exploiting the universal features of continuous phase transitions.

Ansprechpartner:

F. Karsch/TR211

Thema:

05/02/2021 - TBC

Datum:

05.02.21

Uhrzeit:

16:15

Ort:

ZOOM/Konferenzschaltung

Vortragender:

Tamara Grava

University of Bristol

Inhalt:

TBC

Ansprechpartner:

G. Akemann

Thema:

Machine learning as a physical observable: Renormalization, symmetry breaking and histogram reweighting

Datum:

12.01.21

Uhrzeit:

14:15

Ort:

cyberspace

Vortragender:

Dimitrios Bachtis

Swansea University

Inhalt:

A physical interpretation of machine learning functions is presented that enables efficient studies of phase transitions. In particular, the predictive function of a neural network, designed for phase classification, is treated as a physical observable with an associated Boltzmann weight. This allows its extrapolation in parameter space with histogram reweighting techniques. We further include the predictive function in the Hamiltonian as a conjugate variable coupled to an external field to control properties of the statistical system, specifically to induce symmetry breaking or symmetry restoration. Accurate calculations of the critical exponents and the critical temperature of the two-dimensional Ising model are presented using finite size scaling and the renormalization group on quantities derived entirely from the neural network.

Ansprechpartner:

Ch. Schmidt

Thema:

Quantum computing and quantum annealing in a nutshell

Datum:

04.02.21

Uhrzeit:

14:15

Ort:

ZOOM / Konferenzschaltung

Vortragender:

Madita Willsch

FZ Jülich

Inhalt:

In this talk I will give a broad introduction to quantum computing and quantum annealing, starting with the definition of a quantum bit (qubit). I will explain the working principles of quantum annealing as well as gate-based quantum computers and describe the programming of such devices. Additionally, I will present some of our work at JSC regarding simulations of quantum computers and applications on the D-Wave quantum annealer.

Ansprechpartner:

Jürgen Schnack

Thema:

The Character Expansion in effective Theories for chiral Symmetry Breaking

Datum:

03.12.20

Uhrzeit:

16:30

Ort:

ZOOM / Konferenzschaltung

Vortragender:

Noah Aygün

Universität Bielefeld

Inhalt:

Ansprechpartner:

Gernot Akemann

Thema:

On the distribution of the maximum of the Airy process with wanderers

Datum:

27.01.21

Uhrzeit:

09:00

Ort:

ZOOM / Konferenzschaltung

Vortragender:

Gia Bao Nguyen

KTH Stockholm

Inhalt:

Consider a system of $N$ non-intersecting Brownian bridges on the time interval $[-1,1]$ such that the first $N-m$ paths start and end at the origin and the $m$ remaining top paths go between arbitrary positions. The Airy process with $m$ wanderers is defined as the motion of these Brownian particles near the edge curve $\mathcal{C}:=\{(t,\sqrt{2N(1-t^2)}):t\in[-1,1]\}$ in the large $N$ limit. In this talk, we focus on the distribution of the maximum of the Airy process with wanderers minus a parabola, which provides a $2m$-parameter deformation of the Tracy-Widom GOE distribution. We provide a Fredholm determinant formula for this distribution function. We also discuss the connection with KPZ fluctuations, as well as some results on relations with Painlev\'e II and other PDEs. This is based on joint work with Daniel Remenik and Karl Liechty.

Ansprechpartner:

Thorsten Neuschel