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.

7 September 2016, Daniel Barna (Wigner)
Magyar reszvetel a jovo 5050 TeVes gyorsitojanak fejleszteseben
Az eloadasban szo lesz az FCCrol (Future Circular Collider), a CERN kovetkezo generacios gyorsito terverol; arrol, hogy hogyan lehet megszabadulni az egyenkent 8.4 GJ energiat tarolo nyalaboktol (ami 23 darab 200 m hosszu, 150 km/h sebessegu TGV vonat mozgasi energiajanak felel meg); az LHC es az FCC nyalabtemetojerol; szupravezetokrol, szupravezeto magnesekrol es szupravezeto arnyekolasrol; specialis kicsatolo magnesekrol. Minderrol annak a BudapestCERN kozos projektnek a kereteben fogok beszelni, ami iden indult, es a fenti problemakra keres megoldast, es fejleszt prototipusokat.

21 September 2016, Matteo Giordano (Eotvos)
Landau levels in QCD in an external magnetic field slides
The effect of an external magnetic field on strongly interacting matter is relevant for important problems in particle physics and cosmology, such as heavy ion collisions, neutron stars, and the evolution of the early universe. In this talk I will first briefly review the current knowledge on this topic, as obtained by means of firstprinciples lattice numerical calculations. I will then discuss in detail the issue of Landau levels in QCD, showing preliminary numerical results obtained on the lattice. In particular, I will show that, after turning on the strong interactions, only the lowest Landau level remains of the whole Landau level structure. I will then discuss how much of the observed effects of a magnetic field can be explained in terms of the lowest Landau level. Our results can be used to test the validity of lowenergy models of QCD that make use of the lowestLandaulevel approximation.

28 September 2016, Gergely Fejos (Osaka University)
Thermal properties and evolution of the axial anomaly for 2+1 flavors slides
I will be talking about the thermal evolution of the axial anomaly of QCD in terms of effective theories with 2+1 flavors. It will be shown that mesonic fluctuations are of great importance from the point of view of the thermal behavior of the 't Hooft determinant term. Results indicate that fluctuations strengthen the axial anomaly at finite temperature and it does not vanish at the critical point. The phenomenon has been found to have significance in the thermal properties of the mesonic spectrum, especially concerning the eta  eta' system. Analysis of the spectrum and the anomaly in nuclear medium will also be discussed.

5 October 2016, Sandor Katz (Eotvos)
Axion cosmology from lattice QCD slides
The strong CP problem of QCD can be solved via the PecceiQuinn mechanism. The resulting pseudoGoldstone boson, the axion is a natural candidate for dark matter. In order to quantitatively understand axion dark matter production two important QCD inputs are required: the equation of state and the topological susceptibility at high temperatures. We determine these quantities and use them to constrain the axion mass in different axion production scenarios.

12 October 2016, Zoltan Kokenyesi (Eotvos)
Chiral expansion and Macdonald deformation of twodimensional YangMills theory slides
There is a conjecture that relates the partition function of a fourdimensional BPS black hole in Type IIA string theory compactified on a CalabiYau threefold with the Amodel topological string amplitudes on the CalabiYau. The topological string amplitudes on special geometries reduce to a qdeformed version of twodimensional U(N) YangMills theory. We study the refined version of this duality which leads to a refinement of the twodimensional YangMills theory.
We derive the analog of the large N GrossTaylor holomorphic string expansion for the refinement ofqdeformed U(N) YangMills theory on a compact oriented Riemann surface.The derivation combines SchurWeyl duality for quantum groups with the EtingofKirillov theory of generalized quantum characters which are related to Macdonald polynomials. In the unrefined limit we reproduce the chiral expansion of qdeformed YangMills theory derived by de Haro, Ramgoolam and Torrielli. In the classical limit q=1, the expansion defines a new betadeformation of Hurwitz theory wherein the refined partition function is a generating function for certain parameterized Euler characters, which reduce in the unrefined limit to the orbifold Euler characteristics of Hurwitz spaces of holomorphic maps. We discuss the geometrical meaning of our expansions in relation to quantum spectral curves and betaensembles of matrix models arising in refined topological string theory.

26 October 2016, Janos Polonyi (Strasbourg)
Time scales of diffusion and decoherence slides
A disszipativ es a dekoherenciahoz vezeto folyamatokat altalaban az utkozesek kovetesevel irjuk le (E. Joos, H. Zeh, Z. Phys. 59 223 (1985), B. Vacchini, K. Hornberg Phs. Rep. 478 71 (2009)). Ennel megbizhatobb, egy szisztematikus kozelitesen alapulo modszerrol, a tesztreszecske SchwingerKeldysh effektiv Lagrangefuggvenyenek kiszamolasarol lesz szo az eloadasban (Polonyi, arxiv.org/abs/1605.00834). Harom kis parameterben valo kifejtesre alapul a levezetes, melyek a kovetkezoek: a tesztreszecskegaz kolcsonhatas erossege, a kolcsonhatas altal indukalt koordinata megvaltozas nagysaga es annak sebessege. Az utkozesi modell alapjan a dekoherenciat sok nagysagrenddel gyorsabbnak kepzelik mint a disszipacios folyamatokat. Ugyan ennek az elvarasnak az alapjaul szolgalo egyenletekhez hasonlora vezet az uj modszer, azonban az is kiderul, hogy az emlitett kovetkezmenyre az egyenleteknek alkalmazhatosagi tartomanyan kivuli hasznalata vezet el. Ez az utkozesi modellben a tobbszoros utkozesek tartomanyanak felel meg. Az egyenletek figyelmesebb hasznalata alapjan a dekoherencia nem adodik gyorsabbnak a disszipacional, inkabb egymashoz kozel marad a ket idoskala. Harom kulonbozo dekoherencia fogalmat lehet az uj levezetes gondolatmenete alapjan megkulonboztetni es az egzaktul megoldhato harmonikus rendszerekben a "valodi" dekoherencia az ido dupla exponencialis fuggese alapjan all be. Ez a SchwingerKeldyshleiras egy figyelmre melto tulajdonsaganak egyszeru kovetkezmenye, nevezetesen annak, hogy nyilt, disszipativ rendszerekben az ido ellentetes iranyban folyik a megfigyelheto mennyisegekben mint a kvantum fluktuaciokban. Tehat vegul is nagyon gyorsan all be a dekoherencia, sokkal gyorsabban mint barmely mas fizikai folyamat csak epp nem vilagos az aszimptotikus allapot eleresenek a modja a kolcsonhato rendszerekben, mert annak leirasara az alkalmazott kifejtesek kereten belul egyenlore nem latszik lehetoseg.

2 November 2016, Istvan Szecsenyi (Durham, BME)
TTbardeformed 2D Quantum Field Theories slides
It was noticed many years ago, in the framework of massless RG flows, that the irrelevant composite operator TTbar, built with the components of the energymomentum tensor, enjoys very special properties in 2D quantum field theories, and can be regarded as a peculiar kind of integrable perturbation. Novel interesting features of this operator have recently emerged from the study of effective string theory models. In this talk, we focus on further properties of this distinguished perturbation. We discuss how it affects the energy levels and onepoint functions of a general 2D QFT in finite volume through a surprising relation with a simple hydrodynamic equation. We argue that, at the classical level, the deformation naturally maps the action of N massless free bosons into the NambuGoto action in static gauge, in N+2 target space dimensions, and we briefly discuss a possible interpretation of this result in the context of effective string models.

16 November 2016, Arpad Hegedus (Wigner)
Numerical solution and strong coupling results in the spectral problem of planar AdS/CFT correspondence slides
Maldacena's famous AdS/CFT correspondence states that type IIB string theory on AdS5 x S5 background is equivalent to maximally supersymmetric YangMills theory with SU(N) gauge group. In the large N (planar) limit integrability was discovered on both sides of the correspondence, which makes it possible to get exact results in the planar limit. In this talk we use integrability to compute numerically the anomalous dimensions for twist2 operators in the superYangMills theory. Numerical data allowed us to get the coefficients of the strong coupling series expansion of the anomalous dimensions with high precision and to compare them with earlier proposals.

23 November 2016, Monika Kofarago (Wigner)
Characterization of the nearside jetpeak in Pb Pb collisions at sqrt(s_NN) = 2.76 TeV at ALICE slides
By studying jets which propagate through the medium produced in heavyion collisions, one can get insight to the properties of the quarkgluon plasma. At low p_T the reconstruction of jets is difficult over the large fluctuating background, and instead twoparticle angular correlation measurements can be used to study the interplay of jets with the produced medium. In these measurements jets manifest themselves as a nearside peak, and the interactions would result in a centrality dependent modification of this peak. I will present the results obtained by the ALICE detector in pp and PbPb collisions at 2.76 TeV, which show an asymmetric broadening of the nearside peak in PbPb collisions towards central events at low p_T. The broadening is more pronounced in the Delta eta direction, and a novel feature is also observed at low p_T in central collisions: the peak shape depart from a Gaussian and a depletion around (Delta phi,Delta eta) = (0,0) develops. The data is compared to AMPT simulations to study the influence of longitudinal, radial and elliptic flow, and the studies suggest that the interplay of jets with radial and longitudinal flow play a key role in the development of the observed effects.

30 November 2016, Bence Kocsis (Eotvos)
The dynamical origin of black hole mergers
With the detections of the gravitational waves emitted during black hole mergers, LIGO has recently opened the field of gravitational wave astrophysics. In this talk I will discuss some of the astrophysical processes that may be responsible for the observed events. Although less than 0.5% of the stellar mass is in dense stellar systems, I will argue that a large fraction of the black hole mergers may originate in these environments due to gravitational bremsstrahlung and multibody interactions. Accretion disks in active galactic nuclei may also facilitate black hole mergers. Finally, if primordial black holes constitute a fraction of dark matter, gravitational waves may shed light on its composition. I will discuss predictions on the event rate distribution that may be used to disentangle these astrophysical processes to understand the origin of the observed gravitational wave events.

7 December 2016, Kentaroh Yoshida (Kyoto University)
Recent progress on YangBaxter deformations of type IIB superstring
TBA

14 December 2016, Csaba Torok (Eotvos)
The sign problem in the O(3) nonlinear sigma model at finite chemical potential
TBA
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
BSc student
2014  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: