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.
Timetable of department common room.
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.

20 February 2024, Gyorgy Baranka (Eotvos) slides
Localization of Dirac modes in the SU(2)Higgs model at finite temperature
The lowlying Dirac modes become localized at the finitetemperature transition in QCD and in other gauge theories, suggesting a general connection between their localization and deconfinement. This connection can be understood in terms of the "sea/islands'' picture of localization: in the deconfined phase, modes get "trapped" on "islands'' of Polyakovloop fluctuations, and other gauge field fluctuations that decrease correlations in the temporal direction, within the "sea'' of ordered Polyakov loops.
As a test of the universality of the "sea/islands" mechanism, one can investigate whether a change in the localization properties of low modes takes place across other thermal transitions where the Polyakov loop gets ordered, besides the usual deconfinement transition. Additionally, one can investigate this phenomenon by changing the type of dynamical matter from fermionic to scalar. A model allowing one to carry out both these tests at once is the lattice fixedlength SU(2)Higgs model. After mapping out the phase diagram of the model at finite temperature, we study the localization properties of the lowlying modes of the staggered Dirac operator, and how these properties change across the various transitions. We find localized low modes in the deconfined and in the Higgs phase, where the Polyakov loop is strongly ordered, but in both cases they disappear as one crosses over to the confined phase. Our findings confirm the general expectations of the "sea/islands" picture.

5 March 2024, Timea Vitos (Uppsala) slides
Precision Standard Model tools: electroweak Sudakovs and multijet processes
It is evident that the present state of particle physics requires some additional extension to the current Standard Model in order to capture phenomena which are not covered by this theory. For this task, two very important ingredients are needed, on both the theory and experiment side: on the one hand, developing new models and on the other hand, discriminating in a precise way from the Standard Model background. In this phenomenologybased seminar, I will target the latter aspect in two topics. Firstly, I will present the combination of the leading Sudakov effects in the oneloop electroweak corrections and QCD parton showers, implemented in the widelyused matrixelement generator MadGraph5_aMC@NLO. Secondly, I will discuss a project which aims to improve the simulation of multijet events (more than 56 QCD jets in the final state) in particle collisions. These processes are present in almost any new physics searches at hadron colliders and hence their efficient simulation is crucial for the possible detection of any signals beyond our current established model.

12 March 2024, Ramon Miravitllas Mas (Wigner) slides
Transseries from condensates
Perturbation theory fails to describe the lowenergy phenomenology of QCD, like confinement, the mass gap, and the masses of hadrons. Invoking the Wilson's operator expansion, one can extend perturbative expansions to transseries, which contain some nonperturbative information encoded in the vacuum condensates. Motivated by this, we will discuss the GrossNeveu model, a toy QFT of N fermions in 1+1 dimensions which shares some of the nonperturbative properties of QCD. This toy model is amenable to some exact results when the number of fermions N is large. In particular, the twopoint function of the fermions can be computed exactly at the first nontrivial order in 1/N. We then compare this result with a direct computation of the first coefficients of the Wilson's operator expansion, also at large N, and find a perfect match. This provides a precise test for the validity of the operator expansion and the methods used to compute its coefficients.

19 March 2024, Maria Vittoria Garzelli (DESY) slides
Prompt neutrinos in the atmosphere vs. LHC: where do we stand?
We describe the main mechanisms of production of prompt neutrinos in the atmosphere, where they are a background for the detection of astronomical neutrinos from far sources, and at the Large Hadron Collider. These involve the production and decay of heavyflavoured hadrons in hadronic collisions. We show the differences in the kinematics relevant for the two cases, also depending on the detail of the experiments capable of detecting these neutrinos. We stress the importance of reducing the present large uncertainties, coming from different sources, ranging from the still too low accuracy of calculation of the partonic crosssections for charm production, to the quite uncertain charm pole mass value and parton distribution functions of protons and nuclei, to the still quite debated ultrahighenergy cosmicray mass composition.

26 March 2024, Claudio Bonati (INFN Pisa)  cancelled
Some peculiar transitions in Abelian gauge systems
In this talk we will introduce some problematics related to the so called "beyond the LandauGinzburgWilson" critical phenomena, i.e. those critical phenomena which requires gauge fields to be explicitly used in their effective description. In particular we will analyze the case of some three dimensional scalar Abelian lattice systems: the phase diagrams of these models present several lines of phase transitions, whose critical properties are described by the continuum Abelian Higgs model or by more standard universality classes.

9 April 2024, Dennis le Plat (Wigner) slides
Integrability for higherpoint functions in N=4 SYM
Higherpoint functions in N=4 super YangMills theory became accessible by methods from integrability through the introduction of hexagon form factor. Originally proposed for threepoint functions, it can also be used to calculate more general higherpoint functions. In this talk, I will give an overview of the formalism and present recent results about its application to higherrank sectors, importing only a minimum of information from the nested Bethe ansatz. Further, I will introduce the Lagrangian insertion technique in this framework, allowing to calculate perturbative corrections without having to resort to the gluing prescription.

16 April 2024, Matteo Giordano (Eotvos) slides
Constraints on the Dirac spectrum from chiral symmetry restoration in hightemperature QCD
The nature of the symmetryrestoring transition in finitetemperature QCD in the chiral limit is still an open question, in particular for what concerns the fate of the anomalous U(1)_A symmetry. In this talk I discuss this problem from the point of view of the Dirac spectrum, focussing on the case of two massless fermion flavours. Using only general properties of correlation functions of scalar and pseudoscalar fermion bilinears, I prove that in the limit of vanishing quark mass m all the corresponding susceptibilities must be power series in m^2 with finite coefficients. This is then used to derive constraints on the Dirac spectrum in the chirally symmetric phase. Exploiting these constraints, I then show that for the anomalous U(1)_A symmetry to remain effectively broken in the symmetric phase (i) the spectral density must develop a singular peak near the origin as m goes to zero; (ii) the twopoint eigenvalue correlator of nearzero modes must also be singular, and nearzero modes cannot be localised; (iii) the topological charge distribution must be indistinguishable from that of a free gas of instantons and antiinstantons of vanishing density.

23 April 2024, Sam van Thurenhout (Wigner) slides
Renormalization of composite operators in QCD
We give an overview of the computation and renormalization of operator matrix elements in QCD. This allows one to extract the corresponding operator anomalous dimensions, which determine the scale dependence of nonperturbative parton distributions. The latter provide important information about hadronic structure and are accessible experimentally in hard scattering processes such as deepinelastic scattering and deeplyvirtual Compton scattering. The extraction of the anomalous dimensions from the renormalization process is nontrivial for exclusive processes because of mixing with totalderivative operators. During the talk we discuss how one can nevertheless reconstruct the functional form of the anomalous dimensions. Particular emphasis will be put on a recently developed method that exploits a consistency relation for the anomalous dimensions which follows from the renormalization structure of the operators.

30 April 2024, David Pesznyak (Eotvos) slides
Continuum extrapolated highorder baryon fluctuations
Cumulants of conserved charges of QCD (i.e. baryon number, electric charge and strangeness) play a key role in the study of QCD phases both theoretically and experimentally. Lattice QCD is a valuable tool to calculate them, but going to higher orders remains challenging. During my seminar talk, I will introduce the methodology of computing such cumulants on the lattice at vanishing strangeness chemical potential, and on the socalled strangeness neutral line, relevant for phenomenological studies. Up to the fourth order in baryochemical potential, continuum results are available since 2015. I will present the first continuum results for sixth order baryon fluctuations for temperatures between T = 130200 MeV, and eighth order at T = 145 MeV in a fixed volume. Our results are in sharp contrast with well known results in the literature obtained at finite lattice spacing. I will also discuss to what extent fluctuations can be used to constraint the position of the coveted critical endpoint of QCD using Pade resummation.

7 May 2024, Gergely Fejos (Eotvos) slides
Order of the chiral phase transition for N_f flavors
Based on the epsilon expansion of the renormalization group flows of the GinzburgLandau potential for the chiral phase transition of QCD, it has been widely accepted that it is of first order in the zero quark mass limit for N_f > 2, with the possibility of a second order transition for N_f = 2, given the axial anomaly remains strong enough at the critical point. Recently, several lattice QCD studies hint that the transition can be of second order in the whole range of flavor numbers, after all. In this talk, I reanalyze the renormalization group flows of the GinzburgLandau potential using the functional renormalization group technique. Instead of employing the epsilon expansion around d = 4, with the inclusion of all (perturbatively) relevant and marginal interactions directly in d = 3, the method predicts that there exist new fixed points in the whole flavor number range potentially belonging to conformal systems going through a finitetemperature chiral transition. The results indicate that the chiral transition can be of second order for N_f >= 5, while its nature depends on the strength of the U_A(1) anomaly for N_f = 2,3,4.

14 May 2024, Claudio Bonanno (IFT Madrid) slides
Aspects of topology and confinement in largeN gauge theories
Although the strong interaction observed in Nature is described within the Standard Model by an SU(3) gauge theory, where N=3 is the number of quark "colors", studying the behavior of YangMills theories in the ideal limit N > infinity provides a unique tool to gain a deeper understanding of the nonperturbative properties of gauge theories, and their connecton with phenomenological aspects of the Standard Model and Beyond.
In this talk, I will review some of the main predictions obtained for SU(N) gauge theories in the largeN limit using very general theoretical arguments, highlighting the tight connection among topological features of gauge theories and confinement, and discussing several recent novel nonperturbative results confirming the predicted largeN scenario.

21 May 2024, Tamas Kovacs (Eotvos) slides
The fate of chiral symmetry in the quarkgluon plasma
I present a new way of understanding how chiral symmetry is realized in the high temperature phase of QCD. I show that a simple instantonbased random matrix model provides an excellent description of the lowest part of the spectrum of the Dirac operator, the part that dominates physical quantities related to chiral symmetry. Remarkably in a strongly interacting theory, this part of the spectrum can be understood in terms of a gas of noninteracting instantons, even in the chiral limit. The model I present does not only provide an intuitive physical picture of how light quarks interact with gluons at high temperature, but also has nontrivial quantitative predictions. In particular it indicates a possible resolution of the longstanding debate about the fate of the anomalous U(1)_A symmetry above the critical temperature.
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
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
postdoc
2020 PhD  University of Debrecen, Hungary
2020  postdoc  Eotvos University, Hungary
PhD student
2021 Eotvos University, Hungary
PhD student
2021 Eotvos University, Hungary
Former members
PhD student
2023 postdoc, Technical University, Hungary
20182023 Eotvos University, Hungary
PhD student
2016  2023 Eotvos University, Hungary
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: