Lattice Gauge Theory group

GPU Research Center 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.

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.


  • 10 February 2016, Diego Correa (La Plata, Argentina)

    1-loop exponentiation for large rank Wilson loops slides

    In this talk I will describe Wilson loops in N=4 super Yang-Mills, for external particles in k-rank totally symmetric representations. I will argue that for large k the perturbative resummation of diagrams is dominated by ladder diagrams and simply given by the exponential of the 1-loop result. This will be verified -for a generic family of Wilson loops- in the strong coupling limit performing a classical D-brane computation and using the AdS/CFT correspondence.

  • 17 February 2016, Attila Pasztor (Wuppertal)

    QCD at small chemical potentials: the equation of state and fluctuations

    I will present some recent continuum extrapolated lattice results on QCD in the grand canonical ensemble. The chemical potentials and temperatures considered are relevant for the RHIC beam energy scan. The methods used are Taylor expansion near zero chemical potential and analytic continuation from an imaginary chemical potential. I will present comparisons with the hadron resonance gas model at low and with resummed perturbation theory at high temperatures.

  • 24 February 2016, Marton Lajer (Eotvos)

    Truncated Hilbert Space Approach for the 1+1D phi^4 Theory slides

    We used the massive analogue of the truncated conformal space approach to study the broken phase of the 1+1 dimensional scalar phi^4 model in finite volume, similarly to the work by S. Rychkov and L. Vitale. In our work, the finite size spectrum was determined numerically using an effective eigensolver routine, which was followed by a simple extrapolation in the cutoff energy. We analyzed both the periodic and antiperiodic sectors. The results were compared with semiclassical and Bethe-Yang results as well as perturbation theory. We obtained the coupling dependence of the infinite volume breather and kink masses for moderate couplings. The results fit well with semiclassics and perturbative estimations, and confirm the conjecture of Mussardo that at most two neutral excitations can exist in the spectrum. We believe that improving our method with the renormalization procedure of Rychkov et al. enables to measure further interesting quantities such as decay rates and the inelastic part of scattering matrices.

  • 2 March 2016, Gabor Cynolter MTA-ELTE)

    Diphoton excess, gauge invariance and perturbative unitarity

    I discuss some aspects of the recently reported excess in the diphoton resonance search by ATLAS and CMS. Assuming that the resonance is due to a new singlet (pseudo)scalar, 5-dimensional effective interactions are postulated. SU(2)xU(1) gauge invariance implies additional dim-5 interactions with the weak bosons leading to nontrivial constraints on the validity of the effective theory. The effective interactions can be generated at 1-loop by additional coloured and charged vector-like quarks, these favour narrow-width and are further constrained.

  • 9 March 2016, Gabor Takacs (BME)

    Particle Formation and Ordering in Strongly Correlated Fermionic Systems: Solving a Model of Quantum Chromodynamics slides

    We study a (1+1)-dimensional version of the famous Nambu-Jona-Lasinio model of Quantum Chromodynamics (QCD2) both at zero and finite matter density using non-perturbative techniques (non-Abelian bosonization and Truncated Conformal Space Approach). At zero density we describe a formation of fermion three-quark (nucleons and Delta-baryons) and boson (two-quark mesons, six-quark deuterons) bound states and also a formation of a topologically nontrivial phase. At finite matter density, the model has a rich phase diagram which includes phases with density wave and superfluid quasi-long-range (QLR) order and also a phase of a baryon Tomonaga-Luttinger liquid (strange metal). The QLR order results as a condensation of scalar mesons (the density wave) or six-quark bound states (deuterons).

  • 16 March 2016, Laszlo Hollo (Ecole Normale Superieure)

    On form factors of boundary changing operators slides

    We develop a form factor bootstrap program to determine the matrix elements of local, boundary condition changing operators. We propose axioms for these form factors and determine their solutions in the free boson and Lee-Yang models. The sudden change in the boundary condition, caused by an operator insertion, can be interpreted as a local quench and the form factors provide the overlap of any state before the quench with any outgoing state after the quench. http://arxiv.org/abs/1510.08232

  • 23 March 2016, Gabriella Pasztor (MTA-ELTE)

    Search for a New Heavy Boson in the di-photon channel (and elsewhere) at the LHC slides

    The ATLAS and CMS experiments observe a moderate excess of events in their search for new heavy bosons in the di-photon final state in the 2015 LHC data collected at a centre-of-mass energy of 13 TeV corresponding to about 3 fb^{-1} integrated luminosity per experiment. Is this a statistical fluctuation in the limited amount of 2015 data or maybe the first sign of New Physics? I will review the updated results on the di-photon search as well as the newly emerging results from other final states such a new particle could decay into.

  • 30 March 2016, Gyula Bencedi (MTA-Wigner)

    Multiplicity dependence of charged pion, kaon, and (anti)proton production at large transverse momentum in p-Pb collisions at 5.02 ATeV

    The discovery of fluid-like behaviour in small collision systems (like pp, pA) is one of the recent discoveries at the Large Hadron Collider (LHC). To understand the origin of the phenomenon several observables are being studied as a function of the event multiplicity. In particular, the measurement of identified particle production in a broad transverse momentum (pT) range provides valuable information since it is sensitive to flow-like effects and new hadronization mechanisms like recombination and jet quenching. In this talk I am going to present the recent results, arXiv:1601.03658v1 [nucl-ex], on the multiplicity dependence of charged pion, kaon and (anti)proton production in p-Pb collisions at 5.02 ATeV measured by the ALICE Collaboration at the LHC. The detailed discussion of the analysis to measure the pT spectra will be covered. Comparisons among pp, p-Pb and Pb-Pb collisions will be shown, in addition the nuclear modification factor for identified particles in non-single diffractive p--Pb collisions will be discussed as well.

  • 6 April 2016, Janos Balog (MTA-Wigner)

    Mass-coupling relation in quantum integrable models slides

    We determine exactly the mass-coupling relation in the simplest multi-scale quantum integrable model, the homogenous sine-Gordon model with two independent mass scales. We find a generalization of the ? sum rule Ward identity which enables one to derive a differential equation for the mass-coupling relation. The solution can be expressed in terms of hypergeometric functions.

  • 13 April 2016, Falk Bruckmann (Regensburg)

    Phase diagram of an asymptotically free sigma model through lattice dualization

    The 2d O(3) sigma model shares asymptotic freedom, mass generation and other nonperturbative features with 4d QCD. Likewise, a sign problem at nonzero chemical potential hampers numerical simulations of its thermodynamics. I demonstrate how mapping the corresponding lattice fields to dual degrees of freedom solves the sign problem. At finite volume and low temperatures this can be used to extract the phase shifts governing the particles' interaction. Moreover, I discuss the phase diagram of this model including a quantum phase transition and a comparison to an integrable model.

  • 20 April 2016, Zoltan Keresztes (Szeged)

    Gravitational, shear and matter waves in Kantowski-Sachs cosmologies

    A general treatment of vorticity-free, perfect fluid perturbations of Kantowski-Sachs models with a positive cosmological constant are considered within the framework of the 1+1+2 covariant decomposition of spacetime. The dynamics is encompassed in six evolution equations for six harmonic coefficients, describing gravito-magnetic, kinematic and matter perturbations, while a set of algebraic expressions determine the rest of the variables. The six equations further decouple into a set of four equations sourced by the perfect fluid, representing forced oscillations and two uncoupled damped oscillator equations. The two gravitational degrees of freedom are represented by pairs of gravito-magnetic perturbations. In contrast with the Friedmann case one of them is coupled to the matter density perturbations, becoming decoupled only in the geometrical optics limit. In this approximation, the even and odd tensorial perturbations of the Weyl tensor evolve as gravitational waves on the anisotropic Kantowski-Sachs background, while the modes describing the shear and the matter density gradient are out of phase dephased by Pi/2 and share the same speed of sound.

  • 27 April 2016, Nicolas Filipovic (Eotvos)

    Latest results on Quarkonium production in nuclear matter at the LHC

    In this talk I will review the latest experimental results on quarkonium production and nuclear modification at the LHC. I will introduce the basics of quarkonium modification in the Quark-Gluon Plasma (QGP), and present the current state-of-the-art measurements on charmonia and bottomonia. The emphasis will be put on the pp, pPb and PbPb data recorded by the CMS Collaboration during Run 1, with a look at the results from other experiments at LHC and RHIC.

  • 4 May 2016, Denes Sexty (Wuppertal)

    The complex Langevin equation and the sign problem in lattice QCD

    The Complex Langevin method is a proposal to solve sign problems by generating a positive measure ensemble on the complexified field manifold using analytical continuation. I report on recent developments such as gauge cooling and show simulation results in full QCD, and point out open questions and pitfalls of the method.

  • 11 May 2016, Antal Jakovac (Eotvos)

    Functional Renormalization Group at finite chemical potential

    In the talk I give a short overview about the Functional Renormalization Group (FRG) technique, the usually applied approximations and solution methods. Then I will discuss our recently developed approach to treat fermionic systems at small (zero) temperature and finite chemical potential on the example of a simple Yukawa-model. We determine the phase diagram on the coupling constant space, and discuss the role of the different approximation schemes (mean field, one-loop, FRG LPA). Finally I will mention some possible applications.

  • 18 May 2016, Szilveszter Harangozo (MTA-Wigner)

    TBA

    TBA

  • 25 May 2016, Walter Winter (DESY)

    High-energetic cosmic neutrinos and the test of fundamental physics

    The very recent discovery of a diffuse flux of cosmic neutrinos has introduced a new messenger of the high-energy universe in addition to photons at multiple wavelengths, cosmic rays, and now also gravitational waves. We discuss the possible origin of these neutrinos, and we illustrate how they could be used for tests of fundamental particle physics.

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

People

Matteo Giordano

postdoc

2009 PhD - University of Pisa, Italy

2010-2010 postdoc - IPhT/CEA-Saclay, France

2010-2012 postdoc - University of Zaragoza, Spain

2012-2015 postdoc - ATOMKI, Debrecen, Hungary

giordano {at} bodri {dot} elte {dot} hu

Sandor Katz

professor

2001 PhD - Eotvos University, Hungary

2001-2003 postdoc - DESY, Hamburg, Germany

2003-2005 postdoc - University of Wuppertal, Germany

2006-2012 assistant professor - Eotvos University, Hungary

2012- professor - Eotvos University, Hungary

katz {at} bodri {dot} elte {dot} hu

Santanu Mondal

postdoc

2013 PhD - University of Calcutta, India

2013 postdoc - Eotvos University, Hungary

santanu {at} bodri {dot} elte {dot} hu

 

 

 

 

 

 

Daniel Nogradi

assistant professor

2005 PhD - University of Leiden, the Netherlands

2005-2007 postdoc - University of Wuppertal, Germany

2007-2009 postdoc - UCSD, USA

2009-2011 senior research fellow - Eotvos University, Budapest

2011 assistant professor - Eotvos University, Budapest

nogradi {at} bodri {dot} elte {dot} hu

Ferenc Pittler

postdoc

2013 PhD - University of Pecs, Hungary

2013- postdoc - Eotvos University, Budapest

pittler {at} bodri {dot} elte {dot} hu

Andras Saradi

MSc student

2014 - Eotvos University, Hungary

 

 

 

 

 

 

Csaba Torok

MSc student

2014 - Eotvos University, Hungary

 

Norbert Trombitas

PhD student

2010 - Eotvos University, Hungary

trombitas {at} ludens {dot} elte {dot} hu

 

 

Lorinc Szikszai

BSc student

2014 - Eotvos University, Hungary

 

 

Zoltan Varga

BSc and MSc student

2014 - Eotvos University, Hungary

 

 

Former members

Gergely Endrodi

2009 PhD - Eotvos University, Hungary

2010 postdoc - University of Regensburg, Germany

endrodi {at} general {dot} elte {dot} hu

Tamas Kovacs

1996 PhD - UCLA, USA

1996-1998 postdoc - University of Colorado, Boulder, USA

1998-2000 postdoc - University of Leiden, the Netherlands

2000-2002 postdoc - DESY, Zeuthen, Germany

2002-2011 professor - University of Pecs, Hungary

2011- senior researcher - ATOMKI, Debrecen, Hungary

kgt {at} fizika {dot} ttk {dot} pte {dot} hu

Attila Pasztor

PhD student

2010 - Eotvos University, Hungary

apasztor {at} bodri {dot} elte {dot} hu

 

 

 

 

 

 

 

Balint Toth

2005-2006 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

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 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: