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 OTKA-NF-104034 grant of OTKA.

We are also grateful to our past funding agencies, 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 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.

• 21 February 2018, Andras Laszlo (Wigner-MTA)

  Quantification of the GR contribution to the muon g-2 measurement slides

  Recently, Morishima, Futamase and Shimizu published a series of manuscripts, putting forward arguments, based on a post-Newtonian approximative calculation, that there can be a sizable general relativistic (GR) correction in the experimental determination of the muon magnetic moment, i.e., in muon g-2 experiments. In response, other authors argued that the effect must be much smaller than claimed. Further authors argued that the effect exactly cancels. All this indicates that it is difficult to estimate from first principles the influence of GR corrections in the problem of spin propagation. Therefore, in this paper we present a full general relativistic calculation in order to quantify this effect. The used methodology is the purely differential geometrical tool of Fermi-Walker transport over a Schwarzschild background. This is compared to the Minkowski limit in order to quantify the GR corrections. The correction turns out to be of first order in terms of the Schwarzschild radius, and is increasing with particle velocity, and thus is sizable for ultrarelativistic particles. The calculated effect can be basically attributed to the contribution of general relativity to the Thomas precession, which appears since the muons are forced to move on a non-geodesic trajectory. Our calculation, however, does not include the Larmor precession, which is present in the real experiment, only the Thomas precession of the gyroscopic motion which is of purely kinematic origin. Taking this into account, the presented calculation, showing a 1ppm relative systematic error, can only be regarded as a preliminary estimate. Preprint: 1803.01395.

• 28 February 2018, Tamas Gombor (ELTE)

  New boundary transfer matrices for classical sigma models slides

  The 2d principal models without boundaries have symmetry group GxG. The possible classical symmetries with integrable boundaries found so far are HxH or G_D where H is a subgroup of G for which G/H is symmetric space and G_D is the diagonal subgroup of GxG. A common property of these known boundary conditions is that they do not contain any free parameters. We have found new integrable boundary conditions for which the remaining symmetry groups are either GxH or HxG and they contain one free parameter. The related boundary transfer matrices are also described.

• 7 March 2018, Miklos Werner (BME)

  TEBD simulation of quantum quenches in the S=1 Heisenberg chain: numerical test of the semiclassical approximation slides

  We investigate quantum quenches in the antiferromagnetic S=1 Heisenberg chain. Due to the gap in the excitation spectrum, after a small quench, the initial state is supposed to be a dilute gas of magnons (with spin S=1). An effective approach is then the so called semi-classical description, where we describe the system as a classical gas of quasiparticles that collide totally reflectively with each other. In our work we make an attempt to test the predictions of the semi-classical description, by comparing them with large scale TEBD simulations. In our calculations we exploit the SU(2) symmetry of the model, that radically speeds up the calculations and provides an easy way to extract the total spin of the states. We find that the half-chain spin fluctuations at short times are accurately described by semi-classics. However, at longer times the effect of fast (non reflected) quasiparticles make the semi-classical description untenable.

• 14 March 2018, Daniel Berenyi (Wigner-MTA)

  Chiral Magnetic Effect with Wigner Functions slides

  The Chiral Magnetic Effect is a chiral anomaly effect that manifests in an electric current parallel to an external magnetic field. It is expected to form in non-central heavy ion collisions, where the moving highly charged nuclei induce the external magnetic field orthogonal to the reaction plane. During the collision left and right handed quarks interact with the QCD gauge fields resulting in chirality changes, charge separation and finally, electric current. Usually, the effect is calculated on the lattice, but here we describe an alternate formulation with relativistic Wigner functions. With suitable transformations, the external magnetic and QCD fields can be transcribed into a QED formulation and the equation of motion for the Wigner function can be solved. In this talk I summarize the Wigner function formalism, the formation of the anomalous current and the results obtained by inspecting the time evolution of the system. https://arxiv.org/abs/1707.03621

• 28 March 2018, Rajan Gupta (Los Alamos National Lab, USA)

  Precision calculations of nucleon structure using lattice QCD

  I will provide high precision results on matrix elements of quark bilinear operators between nucleon states using lattice QCD. From these, we extract a number of exciting quantities, at the intersection of nuclear and particle physics. We show that the axial charge g_A, a fundamental parameter encapsulating the weak interaction of nucleons, is calculated with a few percent accuracy. Results for the scalar and tensor charges, g_S and g_T, which combined with precision neutron decay distribution probe novel scalar and tensor interactions at the TeV scale. Vector form factors are probed in electron scattering, while axial vector form factors are used in the calculation of the cross-section of neutrinos on nuclear targets. These energy dependent cross-sections are needed to determine the neutrino flux, an important systematic in neutrino oscillation experiments.

• 4 April 2018, Dezso Horvath (Wigner-MTA)

  Anomalous magnetic moment of the muon slides

  The muon is 200 times heavier brother of the electron. As it is a heavy lepton with relatively long (2.2 microsec) lifetime it is the most penetrative charged particle and so the favourite messenger of new physical phenomena of particle physics. The present lecture will be devoted to the anomalous magnetic moment of the muon: its measurement and the deviation between the measured and calculated values which could be a sign of physics beyond the standard model.

• 11 April 2018, Marton Lajer (Eotvos-Wigner-MTA)

  Luscher corrections for non-diagonal form factors in integrable QFTs slides

  I will outline a framework that provides direct access both to the excited states' finite volume energy levels and non-diagonal form factors in integrable QFTs. The idea is to expand and analytically continue the Euclidean torus two-point function in the limit when the major radius is sent to infinity. We obtained the first Luscher correction for a one-particle form factor of local operators in any integrable theory involving only a single massive excitation. We then applied the result to the Sinh-Gordon model and the form factor of the field operator, and expanded the same quantity in the coupling constant using Hamiltonian perturbation theory. Comparing the results in the regime where the two expansions overlap, we found complete agreement.

• 13 June 2018, Alessandro Sfondrini (ETH Zurich)

  Integrable spin chain for stringy Wess-Zumino-Witten models

  For the first time we reveal the integrable structure of the CFT2 describing superstrings on AdS3xS3xT4 with pure NS-NS background fluxes. The Wess-Zumino-Witten spectrum is reproduced by a remarkably simple integrable spin chain with exactly solvable Bethe equations. This paves the way to establishing a firm contact between integrability and CFT2 techniques. Based on arXiv:1806.00422, arXiv:1804.01998.

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) non-linear sigma model with topological term
• Beyond Standard Model - technicolor

• 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.
  
  
• Freeze-out 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 [hep-lat]].
  
  
• Freeze-out parameters: lattice QCD meets heavy-ion experiments.
  By Sz. Borsanyi, Z. Fodor, S.D. Katz, S. Krieg, C. Ratti, K. Szabo.
  PoS QCD-TNT-III (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 [hep-lat]].
  
  
• 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 [hep-lat]].
  10.1007/JHEP04(2014)132.
  JHEP 1404 (2014) 132.
  
  
• Local CP-violation 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 [hep-lat]].
  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 [hep-lat]].
  
  
• 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 [hep-lat]].
  10.1016/j.physletb.2014.01.007.
  Phys.Lett. B730 (2014) 99-104.
  
  

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.

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 30-35 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 seven-story building on the right. The Department of Theoretical Physics is on the first floor on the Danube facing side of the building: