Lattice Gauge Theory group
We are the lattice gauge theory group at the Eotvos University in Budapest, part of the Department of Theoretical Physics at the Faculty of Science.
Currently there are nine members and we are seeking new ones. Positions are available for PhD students and postdocs for 2  4 years appointments. If you are interested please email Sandor Katz at katz@bodri.elte.hu or Daniel Nogradi at nogradi@bodri.elte.hu.
Our activities are and were funded by various funding agencies for which we are grateful, these include the Lendulet grant of the Hungarian Academy of Sciences, the OTKANF104034 grant of OTKA and the EU Framework Programme 7 grant (FP7/20072013)/ERC No 208740.
Research
Our primary interests are:
 Chiral symmetry restoration and deconfinement in QCD with Wilson fermions
 Finite chemical potential
 QCD hadron spectrum
 Eigenvalue distributions of the overlap Dirac operator
 Strongly interacting Higgs sector  strong dynamics
 Conformal gauge theories
Seminar
Weekly ELFT seminars at the Department of Theoretical Physics
Location: 2nd floor, 2.54, Novobatzky room, 1117 Budapest, Pazmany Peter setany 1/a
If you'd like to receive seminar email announcements please write to nogradi@bodri.elte.hu
Time: Tuesdays at 14:15
See the archive for seminars since 2014.

7 March 2023, Gyozo Kovacs (Wigner) slides
Fate of the critical endpoint at large Nc
The phase diagram of QCD is investigated by varying number of colors Nc within a Polyakov loop quarkmeson chiral model. In particular, our attention is focused on the critical point(s); the critical point present for Nc=3 moves toward the mu_qaxis and disappears as soon as the number of color is increased. Yet, a distinct critical point emerges along the temperature axis for Nc=53 and moves toward finite density when increasing Nc further. Thus, the phase diagram at large Nc looks specular with respect to the Nc=3 results, with the firstorder transition in the upperleft and crossover in the lowerright regions of the (mu_q,T)plane. The pressure is also evaluated in dependence of Nc, showing a scaling with Nc^0 in the confined and chirally broken phase and with Nc^2 in the deconfined one. Moreover, the presence of a chirally symmetric but confined "quarkyonic phase" at large density and moderate temperature with a pressure proportional to Nc is confirmed.

14 March 2023, Balazs Pozsgay (Eotvos)
Exotic symmetries and breakdown of ergodicity from hard rod deformations
We treat a new mechanism for ergodicity breaking in one dimensional quantum many body systems. We treat spin chains with local Hamiltonians, which have a special fine tuned form: there is interaction in the system, nevertheless the models have a large noncommutative symmetry algebra, generated by Matrix Product Operators (MPO). Meanwhile, the models are NOT integrable, and not exactly solvable. The exotic symmetries cause exact degeneracies in the finite volume spectrum, leading to a breakdown of thermalization. The mechanism we treat is a special type of ,,Hilbert space fragmentation''. It appears that our models are the first ones, where noncommutative MPO symmetries are found, such that the models are not integrable.

21 March 2023, Mate Lencses (Wigner) slides
Multicriticality in YangLee edge singularity
The YangLee edge singularity is related to the anomalous behaviour of zeroes of the partition function in the twodimensional Ising model. It was shown by Cardy, that this behaviour is described by the M(2,5) nonunitary minimal model of conformal field theory, known as the YangLee model. This model can be realised as the Ising model above the critical temperature in an imaginary external magnetic field, as the point where the PT symmetry becomes spontaneously broken. In this talk, I will consider the analogue of this scenario in the tricritical Ising model, where a threeparameter family of nonunitary PTsymmetric flows exists. I will present our findings regarding massless flows ending in the YangLee model and in a nonunitary "tricritical" point identified as M(2,7). Finally, I will discuss our conjecture on higher nonunitary multicritical points, connected by PTsymmetric nonunitary flows.

28 March 2023, Arthur Hutsalyuk (Eotvos)
Finite temperature spin diffusion in the Hubbard model in the strong coupling limit
We investigate finite temperature spin transport in one spatial dimension by considering the spinspin correlation function of the Hubbard model in the limiting case of infinitely strong repulsion. We find that in the absence of bias the transport is diffusive, and derive the spin diffusion constant. Our approach is based on asymptotic analysis of a Fredholm determinant representation, which is entirely analytic and free of phenomenological assumptions of Generalized Hydrodynamics.
Based on arXiv:2301.13840, O. Gamayun et. al.

4 April 2023, Zoltan Bajnok (Wigner)
The full analytic transseries in integrable field theories
We analyze a family of generalized energy densities in integrable quantum field theories in the presence of an external field coupled to a conserved charge. By using the WienerHopf technique to solve the linear thermodynamic Bethe ansatz equations we derive the full analytic transseries for these observables in terms of a perturbatively defined basis. We show how to calculate these basis elements to high orders analytically and reveal their complete resurgence structure. We demonstrate that the physical value of the generalized energy densities is obtained by the median resummation of their ambiguityfree transseries.

11 April 2023, David Pesznyak (ELTE)
TBA

9 May 2023, Janos Takatsy (Wigner)
TBA
For students
Our group offers BSc/MSc diploma, PhD and TDK topics in Lattice Field Theory.
Please contact Sandor: katz@bodri.elte.hu or Daniel: nogradi@bodri.elte.hu in case you are interested.
Current topics include:
 QCD thermodynamics
 2 and 4 dimensional CFT
 Beyond Standard Model
People
assistant professor
2009 PhD  University of Pisa, Italy
20102010 postdoc  IPhT/CEASaclay, France
20102012 postdoc  University of Zaragoza, Spain
20122015 postdoc  ATOMKI, Debrecen, Hungary
20152018 postdoc  Eotvos University, Budapest, Hungary
PhD student
2018 Eotvos University, Hungary
professor
2001 PhD  Eotvos University, Hungary
20012003 postdoc  DESY, Hamburg, Germany
20032005 postdoc  University of Wuppertal, Germany
20062012 assistant professor  Eotvos University, Hungary
2012 professor  Eotvos University, Hungary
professor
1996 PhD  UCLA, USA
19961998 postdoc  University of Colorado, Boulder, USA
19982000 postdoc  University of Leiden, the Netherlands
20002002 postdoc  DESY, Zeuthen, Germany
20022011 professor  University of Pecs, Hungary
2011 senior researcher  ATOMKI, Debrecen, Hungary
2020 professor, Eotvos University, Hungary
professor
2005 PhD  University of Leiden, the Netherlands
20052007 postdoc  University of Wuppertal, Germany
20072009 postdoc  UCSD, USA
20092011 senior research fellow  Eotvos University, Budapest
2012  2020 assistant professor  Eotvos University, Budapest
2020 professor  Eotvos University, Budapest
postdoc
2015 PhD  Eotvos University, Hungary
20162018 postdoc  Wuppertal University, Germany
2018 postdoc  Eotvos University, Hungary
PhD student
2016 Eotvos University, Hungary
postdoc
2020 PhD  University of Debrecen, Hungary
2020  postdoc  Eotvos University, Hungary
Former members
2009 PhD  Eotvos University, Hungary
20102015 postdoc  University of Regensburg, Germany
2016 Emmy Noether group leader  University of Frankfurt, Germany
2020 professor  University of Bielefeld, Germany
2013 PhD  University of Calcutta, India
20132016 postdoc  Eotvos University, Hungary
20162018 postdoc  National Chiao Tung University, Taiwan
2018 postdoc  Los Alamos National Laboratory, USA
2013 PhD  University of Pecs, Hungary
20132016 postdoc  Eotvos University, Budapest
2017 postdoc  Bonn University, Germany
2017 PhD  Eotvos University, Hungary
2017 postdoc  Wuppertal University, Germany
20052006 research assistant  University of Wuppertal, Germany
2007 assistant lecturer  University of Pecs, Hungary
2010 PhD  Eotvos University, Hungary
2010 postdoc  University of Wuppertal, Germany
PhD student
2015 PhD  Eotvos University, Hungary
PhD student
2018 Eotvos University, Hungary
Publications
Computing
Our group has access to a number of high performance computer installations in Europe and also maintains several PC and GPU clusters on site in Budapest.
For visitors
Our department is on the Buda side of the Danube very close to the Petofi Bridge, the address is Budapest 1117, Pazmany Peter setany 1/A:
The Department of Theoretical Physics is on the sixth floor opposite the Danube facing side of the building: