[phys4phys] Group for Gravitation, Particles and Fields seminars, Friday, 20th of March, 2026

[prlina]

Dear colleagues,

This Friday, March 20, the Group for Gravitation, Particles and Fields 
will host two seminars, which you are cordially invited to. The first 
talk will be given by Nikola Paunković at 11:00. The second talk will be 
given by Thomas Basile at 13:00. Both seminars will be held at the 
Institute of Physics Belgrade, lecture hall 360.

The talk entitled:

Quantum information geometry and applications to phase transitions of 
many-body systems

will be given by Nikola Paunković (Institute of Physics Belgrade) at 
11:00.

Abstract: As an introduction, I will briefly overview the main research 
directions throughout my career: (i) quantum information theory, (ii) 
quantum cryptography, (with the emphasis on security protocols beyond 
key distribution), (iii) interface between quantum mechanics and quantum 
gravity, and (iv) information geometry and applications, which will be 
the focus of this talk.

I will present an overview of information geometry of quantum states and 
its application to the study of phase transitions in many-body systems, 
with a special focus on the results I was involved in during the past 20 
years of research. On the example of classical physics and probability 
distributions, I will first briefly introduce how the notions of 
information and geometry fit in the description of this line of 
research. Then, I will analyse in more detail three particular 
geometries of quantum states: a pure-state U(1) Berry gauge geometry, 
and two distinct mixed state geometries, one equipped with U(N) gauge 
group (Uhlmann), as well as the so-called interferometric geometry 
obtained from a symmetry broken Uhlmann gauge group [U(N) --> \otimes_i 
U(N_i), with \sum_i N_i = N]. I will then move to describe the so-called 
fidelity approach to the study of phase transitions. Being based on an 
abstract notion of state distinguishability (the notion that gives rise 
to information geometry), it is intended to present a general approach 
to the study of phase transitions that goes beyond Landau Ginzburg and 
other partial approaches. I will introduce the so-called fidelity 
susceptibility (a metric field over the space of states) and discuss it 
on a few examples of many-body systems, showing its explicit connection 
to dynamical susceptibilities of both zero-temperature quantum and 
finite-temperature equilibrium phase transitions. If time permits, I 
will also briefly discuss recently introduced non-equilibrium dynamical 
phase transitions and their connection to the geometry of channels and 
processes.

The talk entitled:

Introduction to (multisymplectic) AKSZ sigma models

will be given by Thomas Basile (Mons University, Mons, Belgium) at 
13:00.

Abstract: The Alexandrov–Kontsevich–Schwarz–Zaboronsky (AKSZ) 
construction provides a way to build topological sigma models starting 
from certain graded manifolds equipped with geometric structures (namely 
a symplectic form and a compatible nilpotent vector field of degree 1). 
In this talk, I will begin with an introduction to AKSZ sigma models and 
review how these structures on the target space graded manifold allow 
one to define gauge-invariant field theories formulated in a covariant, 
multidimensional, analogue of the first-order Hamiltonian formalism.

I will then present a generalisation which gives rise to 
higher-derivative extensions of AKSZ-type actions, using a version of 
the Chern–Weil morphism adapted to graded manifolds. As an illustration, 
I will discuss how several familiar gauge theories such as 
higher-dimensional Chern–Simons theory, MacDowell–Mansouri–Stelle–West 
gravity, and self-dual gravity with its higher-spin extensions, fit 
naturally into this framework.

Based on [2601.16785] with Maxim Grigoriev and Evgeny Skvortsov.


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Time: March 20, 2026 11:00/13:00 Belgrade

Institute of Physics Belgrade, lecture hall 360, 2nd floor

BigBlueButton platform link: 
https://gravityserver.ipb.ac.rs/b/mar-ae0-f4q-qww

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Best regards,
Igor Prlina