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 OTKA-NF-104034 grant of OTKA and the EU Framework Programme 7 grant (FP7/2007-2013)/ERC No 208740.

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

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 quark-meson chiral model. In particular, our attention is focused on the critical point(s); the critical point present for Nc=3 moves toward the mu_q-axis 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 first-order transition in the upper-left and crossover in the lower-right 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 non-commutative 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 non-commutative MPO symmetries are found, such that the models are not integrable.

• 21 March 2023, Mate Lencses (Wigner) slides

  Multicriticality in Yang--Lee edge singularity

  The Yang--Lee edge singularity is related to the anomalous behaviour of zeroes of the partition function in the two-dimensional 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 Yang--Lee 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 three-parameter family of nonunitary PT-symmetric flows exists. I will present our findings regarding massless flows ending in the Yang--Lee 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 PT-symmetric 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 spin-spin 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 trans-series 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 Wiener-Hopf technique to solve the linear thermodynamic Bethe ansatz equations we derive the full analytic trans-series 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 ambiguity-free trans-series.

• 11 April 2023, David Pesznyak (ELTE)

  TBA

• 9 May 2023, Janos Takatsy (Wigner)

  TBA

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

Since it is tricky to locate all papers by a large number of people whose names are not unique on inspire, you can try various search queries:

• Papers by Sandor Katz and Zoltan Fodor
• Papers by Sandor Katz and Gergely Endrodi
• Papers by Sandor Katz and Matteo Giordano
• Papers by Tamas Kovacs
• Papers by Daniel Nogradi

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.

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: