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. Since 2011 we are an NVIDIA GPU Research Center.
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 {at} bodri {dot} elte {dot} hu or Daniel Nogradi at nogradi {at} bodri {dot} elte {dot} hu.
Our activities are funded by the Lendulet grant of the Hungarian Academy of Sciences and by the OTKANF104034 grant of OTKA.
We are also grateful to our past funding agencies, 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 seminars of the Department of Theoretical Physics
Location: 2nd floor, 2.54, Novobatzky room
Time: Wednesdays at 14:15
See the archive for seminars in past years.

11 October 2017, Matteo Giordano (Eotvos)
Quantum gravity on the lattice: a new look at an old problem slides
The formulation of general relativity as a (kind of) gauge theory has been the starting point of several nonperturbative approaches to quantum gravity. In this talk I will briefly introduce the gauge formulation of gravity and discuss related attempts at quantisation on the lattice, focussing on the difficulties of this approach. I will then show some preliminary results of our numerical studies, and discuss a few yet unexplored directions.

18 October 2017, Haryanto Siahaan (MTAWigner)
Some aspects of magnetized black holes slides
In the last couple of years, there has been a growing interest in the studies of black holes interacting with external magnetic fields. One of the reasons is that astronomers found some evidence of strong magnetic fields in the centers of galaxies, where normally supermassive black holes sit. When the external magnetic field cannot be treated as some perturbations, the exact solutions by Ernst in EinsteinMaxwell theory can be employed to model a magnetized black hole. The solution is obtained by applying a Harrisonlike transformation to a known unmagnetized one, which is also in the EinsteinMaxwell theory. However, the resulting magnetized spacetime has no asymptotic flatness anymore. Nevertheless, some interesting questions can still be addressed to the magnetized black holes in EinsteinMaxwell theory, which will be discussed in this talk. One of the questions is whether the conjectured Kerr/CFT correspondence still holds in the case of rotating black holes immersed in a strong magnetic field. The Kerr/CFT correspondence states that the physics of four dimensional rotating black holes is dual to a two dimensional conformal field theory (2d CFT). Some evidences in supporting this conjecture are the ability of entropy and scattering formulas in 2d CFT to recover the BekensteinHawking entropy and scattering process calculation in the black hole background. Another question is about the possibility of destroying a magnetized black hole by using a test particle. It can be shown that a near extremal black hole can be turned into a naked singularity if the black hole captures a classical test particle released from far away. One may wonder how the presence of external magnetic field may contribute to the possibility of destroying a black hole immersed in this field.

25 October 2017, Adam Kardos (Debrecen)
NNLO QCD calculations at work: determining the strong coupling in electronpositron annihilation slides
The strong coupling is one fundamental parameter of the standard model. Its most precise determination is demanded. One way to obtain it is from physical observables defined in electronpositron collisions. The strong coupling is extracted using a fitting procedure over a range of the observable. In order to minimize theoretical uncertainties the most precise fixedorder calculation has to be used in perturbation theory which is matched to another one where contributions coming from all orders are summed up. In my talk I present the determination of strong coupling in electronpositron annihilation using twoparticle correlations as the physical observable.

2 November 2017, Janos Polonyi (Strasbourg)
Electrodynamics near the classical electron radius slides
The absence of nonperturbative, relativistic regulators in quantum field theory has troubled me since a long time. This problem is discussed within the context of the last open chapter of classical electrodynamics, the radiation reaction force of a point charge. The mysterious conflict with causality and stability turns out to be the result on the one hand of the lack of relativistic regulator and the other hand of a naive, prerenormalization group way of arguing. A more careful calculation reproduces the AbrahamLorentz force without instability as a saddle point effect of QED. There are two interesting lessons to be learned here: One is that we have no general argument about the stability of a relativistic field theory of point particles, in particular the stability of electrodynamics can be established numerically only. The other is that the perturbative classical effective theories contain loop diagrams making regularization and renormalization necessary already at the level of the classical saddle point physics.

8 November 2017, Lorinc Szikszai (Eotvos)
Lattice gauge theory with a topological action slides
We investigate a topological lattice action in SU(2) gauge theory. This action only contains a sharp cutoff in field space and does not give rise to classical field equations. These kinds of actions were investigated in sigma models before and shown to lead to the correct quantum continuum limit. We investigate both finite and zero temperature observables and the running coupling. In all cases we find the same continuum result as with the usual lattice actions. Our study shows the robustness of universality.

22 November 2017, Zoltan Zimboras (MTAWigner)
Quantum information theory concepts in high energy physics

29 November 2017, Tamas Biro (MTAWigner)
Entropy Production During Hadronization of a QuarkGluon Plasma slides
We revisit some physical pictures for the hadronization of quarkgluon plasma, concentrating on the problem of entropy production during processes where the number of degrees of freedom is seemingly reduced due to color confinement. Based on observations on Regge trajectories we propose not having an infinite tower of hadronic resonances. We discuss possible entropy production mechanisms far from equilibrium in terms of stochastic dynamics.

13 December 2017, Antal Jakovac (Eotvos)
Quantum Measurement Theory from the Functional Renormalization Group Perspective slides
In the talk the quantum measurement problem is discussed from a novel point of view. An effective model is proposed for the measurement devices, concentrating only its relevant degrees of freedom. As it will be argued, the most simple measurement device is realized by spontaneous symmetry breaking (SSB), and so the effective model of quantum measurements can be thought as a generalization of SSB. In the talk the SSB is treated in a purely quantum way with the help of functional renormalization group, which reveals how the fixed point structure is connected to the quantumclassical crossover. At the end well known experiments and paradoxes (SternGerlach experiment, uranium decay, SchrÃ¶dinger's cat) are discussed from the point of view of this new interpretation.
For students
Our group offers TDK, diploma and PhD topics in Lattice Field Theory.
Please contact Sandor: katz {at} bodri {dot} elte {dot} hu
or Daniel: nogradi {at} bodri {dot} elte {dot} hu
in case you are interested.
Current topics include:
 QCD thermodynamics
 SU(N) gauge theory with topological lattice action
 O(3) nonlinear sigma model with topological term
 Beyond Standard Model  technicolor
People
postdoc
2009 PhD  University of Pisa, Italy
20102010 postdoc  IPhT/CEASaclay, France
20102012 postdoc  University of Zaragoza, Spain
20122015 postdoc  ATOMKI, Debrecen, Hungary
giordano {at} bodri {dot} elte {dot} hu
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
katz {at} bodri {dot} elte {dot} hu
postdoc
2013 PhD  University of Calcutta, India
2013 postdoc  Eotvos University, Hungary
santanu {at} bodri {dot} elte {dot} hu
assistant 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
2011 assistant professor  Eotvos University, Budapest
nogradi {at} bodri {dot} elte {dot} hu
postdoc
2013 PhD  University of Pecs, Hungary
2013 postdoc  Eotvos University, Budapest
pittler {at} bodri {dot} elte {dot} hu
MSc student
2014  Eotvos University, Hungary
MSc student
2014  Eotvos University, Hungary
PhD student
2010  Eotvos University, Hungary
trombitas {at} ludens {dot} elte {dot} hu
PhD student
2016  Eotvos University, Hungary
BSc and MSc student
2014  Eotvos University, Hungary
Former members
2009 PhD  Eotvos University, Hungary
2010 postdoc  University of Regensburg, Germany
endrodi {at} general {dot} elte {dot} hu
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
kgt {at} fizika {dot} ttk {dot} pte {dot} hu
PhD student
2010  Eotvos University, Hungary
apasztor {at} bodri {dot} elte {dot} hu
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
tothbalint {at} szofi {dot} elte {dot} hu
Recent papers

Can the Higgs Impostor Hide Near the Conformal Window?.
By Zoltan Fodor, Kieran Holland, Julius Kuti, Daniel Nogradi, Christopher Schroeder, Chik Him Wong.
10.1142/9789814566254_0002.

Freezeout parameters from electric charge and baryon number fluctuations: is there consistency?.
By S. Borsanyi, Z. Fodor, S.D. Katz, S. Krieg, C. Ratti, K.K. Szabo.
[arXiv:1403.4576 [heplat]].

Freezeout parameters: lattice QCD meets heavyion experiments.
By Sz. Borsanyi, Z. Fodor, S.D. Katz, S. Krieg, C. Ratti, K. Szabo.
PoS QCDTNTIII (2014) 033.

The chiral condensate from the Dirac spectrum in BSM gauge theories.
By Zoltan Fodor, Kieran Holland, Julius Kuti, Daniel Nogradi, Chik Him Wong.
[arXiv:1402.6029 [heplat]].

Charmonium spectral functions from 2+1 flavour lattice QCD.
By Szabolcs Borsanyi, Stephan Durr, Zoltan Fodor, Christian Hoelbling, Sandor D. Katz, Stefan Krieg, Simon Mages, Daniel Nogradi et al..
[arXiv:1401.5940 [heplat]].
10.1007/JHEP04(2014)132.
JHEP 1404 (2014) 132.

Local CPviolation and electric charge separation by magnetic fields from lattice QCD.
By G.S. Bali, F. Bruckmann, G. Endrodi, Z. Fodor, S.D. Katz, A. Schafer.
[arXiv:1401.4141 [heplat]].
10.1007/JHEP04(2014)129.
JHEP 1404 (2014) 129.

Can a light Higgs impostor hide in composite gauge models?.
By Zoltan Fodor, Kieran Holland, Julius Kuti, Daniel Nogradi, Chik Him Wong.
[arXiv:1401.2176 [heplat]].

Full result for the QCD equation of state with 2+1 flavors.
By Szabocls Borsanyi, Zoltan Fodor, Christian Hoelbling, Sandor D. Katz, Stefan Krieg, Kalman K. Szabo.
[arXiv:1309.5258 [heplat]].
10.1016/j.physletb.2014.01.007.
Phys.Lett. B730 (2014) 99104.
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.
Our primary resource is a 128 node cluster with two NVIDIA GTX 275 cards in each node, hosted in Budapest. There is also a 60 node cluster with one NVIDIA GTX 8800 card per node.
In addition we also have access to the Juropa cluster and the BlueGene/P installation in Forschungszentrum Juelich, Germany.
Our collaboriation with the University of Wuppertal, Germany also allows us to use several PC and GPU clusters there.
In case you are interested you can see a map of GPU cluster installations throughout the world dedicated to Lattice Gauge Theory.
For visitors
You will most likely stay at the Peregrinus hotel in the downtown area of Pest.
The simplest way to get to/from your hotel from/to the airport is by taxi. The fare should be around 30 euros. Uber also works in Budapest :)
Our department is on the Buda side of the Danube very close to the Petofi Bridge and it is about a 3035 minutes walk from the hotel:
You exit your hotel, walk past the Great Market Hall (definitely worth a closer look if you have about half an hour or an hour!) and the Corvinus University, cross the Danube on the Szabadsag Bridge and walk South. You will pass the Budapest University of Technology and the Petofi Bridge and our building will be a redish sevenstory building on the right. The Department of Theoretical Physics is on the first floor on the Danube facing side of the building: