# 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 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
• 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.

• 16 September 2015, Anna Zsigmond (MTA-Wigner)

Studies of nuclear parton distribution functions in proton-lead collisions with the CMS experiment slides

The purpose of the study of nuclear parton distribution functions (nPDFs) is two-fold. On one hand, it provides a handle on the initial state cold nuclear effects that can be separated from the final state effects of the hot and dense medium produced in nucleus-nucleus collisions at the LHC and RHIC. On the other hand, precise knowledge of nPDFs is required for understanding the mechanisms associated with nuclear binding from a QCD improved parton model perspective. The proton-lead collision data recorded by CMS in 2013 provides the best sample to constrain nuclear parton distribution functions in the previously unexplored high Q^2 and low Bjorken x region. Results from the CMS experiment on electroweak boson, charged hadron and jet production in proton-lead collisions will be presented.

• 30 September 2015, Andras Laszlo (MTA-Wigner)

A natural extension of the conformal Lorentz group in a field theory context slides

In this talk a finite dimensional unital associative algebra is presented, and its group of algebra automorphisms is detailed. The studied algebra can physically be understood as the creation operator algebra in a formal quantum field theory at fixed momentum for a spin 1/2 particle along with its antiparticle. It shall be shown that the essential part of the corresponding automorphism group can naturally be related to the conformal Lorentz group. In addition, the non-semisimple part of the automorphism group can be understood as dressing'' of the pure one-particle states. The studied mathematical structure may help in constructing quantum field theories in a non-perturbative manner. In addition, it provides a simple example of circumventing Coleman-Mandula theorem using non-semisimple groups, without SUSY. preprint

• 7 October 2015, Zoltan Bajnok (MTA-Wigner)

Form factor approach to the string vertex slides

• 14 October 2015, Andrey Slavnov (Steklov Mathematical Institute, Moscow)

Soliton solutions of classical equations of motion in the modified Yang-Mills theory slides

It is shown that classical solutions with finite enery exist in the modified formulation of Yang-Mills theory.

• 21 October 2015, Yoichi Kazama

AdS/CFT and integrability: Cognate structure at weak and strong coupling for three-point functions

• 4 November 2015, Sona Pochybova (MTA-Wigner)

High Momentum Particle identification with the HMPID detector at the CERN's ALICE Experiment slides

The High Momentum Particle IDentification (HMPID) detector is a Ring Imaging CHerenkov (RICH) radiation detector within the ALICE experiment used to identify pions, Kaons and protons between 1.0 < pT < 5.0 GeV/c. It is used by the collaboration in several physics analyses as a supporting tool for the tracking detectors in the ALICE central barrel. In the first part of my talk I will show how the track-by-track particle identification is utilized to extend the pion identification range by 1 GeV/c in momentum. Further, I will show how this extension helps in the spectra and correlation analyses to cross-check the results. Such and independent cross-check not only strengthens the robustness of the experimental claims, moreover, it has the potential of decreasing the systematic errors connected to these analyses. In the second part of my talk I will discuss the physics implications of the results I obtained in the analysis of p/pi ratio, where protons and pions are identified using the HMPID. This ratio is extracted from the spectra analysis and the origins of it's value are studied in the correlation analysis.

• 11 November 2015, Tamas Gombor (ELTE)

Algebraic Bethe Ansatz for O(2N) sigma models with integrable diagonal boundaries slides

The finite volume problem of the O(2N) sigma models with integrable diagonal boundaries on a finite interval is investigated. The double row transfer matrix is diagonalized by Algebraic Bethe Ansatz. The boundary Bethe Yang equations for the particle rapidities and the accompanying Bethe Ansatz equations are derived.

• 18 November 2015, Robert Vertesi (MTA-Wigner)

Recent results from the STAR experiment slides

In ultrarelativistic heavy ion collisions, a phase transition occurs from hadronic matter into a state of deconfined quarks and gluons. Properties of this latter state of matter, dubbed as the strongly interacting Quark Gluon Plasma (sQGP) has been a subject of extensive measurements at the Relativistic Heavy Ion Collider (RHIC), which collides several types of heavy nuclei (eg. d+Au, Cu+Cu, Au+Au, U+U) with collision energies that range from \sqrt{s_{NN}}=7.7 to 200 GeV. The Solenoidal Tracker at RHIC (STAR) identifies particles and measures their properties in the full azimuth angle and in a wide rapidity range. STAR's beam energy scan (BES) program aims to understand the QCD phase diagram and search for the critical point, and includes a new fixed target program that extends the lower energy limit down to \sqrt{s_{NN}}=3.3 GeV. Heavy and light flavor probes, on the other hand, are used to understand the thermal and dynamical properties of the sQGP. Some of the most interesting recent heavy-ion results from STAR will be overviewed in this talk.

• 25 November 2015, Miklos Horvath (MTA-Wigner)

Liquid-gas crossover within a quasi-particles picture slides

We consider an effective field theory description of quasi-particle excitations aiming to associate the transport properties of the system with the spectral density of states. Tuning various properties of the many-particle correlations, we investigate how robust microscopic features are translated into the macroscopic observables like shear viscosity and entropy density. The liquid-gas crossover is discussed using several counterexamples. We sketch the adaptability of the present examination to much more intricate questions, like transport in (continuum extrapolated) lattice QCD or in correlated solid state systems with condensate.

• 2 December 2015, Gabor Sarosi (BME)

Warped Weyl fermion partition functions

Warped conformal field theories (WCFTs) are a novel class of non-relativistic theories. A simple, yet non-trivial, example of such theory is a massive Weyl fermion in (1+1)-dimensions, which we study in detail. We derive general properties of the spectrum and modular properties of partition functions of WCFTs. The periodic (Ramond) sector of this fermionic system is non-trivial, and we build two novel partition functions for this sector which have no counterpart in a two dimensional CFT. The thermodynamical properties of WCFTs are revisited in the canonical and micro-canonical ensemble.

• 9 December 2015, Judit Kovacs (Eotvos)

Doublet-singlet model and unitarity

Simplified models are useful tools to study the low energy extensions of the Standard Model. Here, we study a doublet-singlet fermionic extension, where new vector-like fermions couple to the weak gauge bosons and the Higgs via new Yukawa couplings. These allow for nontrivial mixing in the new sector, providing a stable, neutral dark matter candidate. We calculate the two particle scattering amplitudes in the model, impose the perturbative unitarity constraints and establish bounds on the Yukawa couplings.

• 16 December 2015, Istvan Kaposvari (Eotvos)

Scalar mass stability bound in a simple Yukawa-theory from renormalisation group equations

Functional Renormalisation Group equations are constructed for a simple fermion-scalar Yukawa-model with discrete chiral symmetry, including also the effect of a nonzero composite fermion background beyond the conventional scalar condensate. Two approximate versions consistent with the scale dependent equations of motion are solved, taking into account also field renormalisation. The lower bound for the mass of the scalar field is determined requiring the stability of effective potential in the full momentum range, from the cutoff down to vanishing momentum. Close agreement is demonstrated with the results of previous studies done exclusively in presence of scalar condensate. A semiquantitative explanation is provided both for the negligible effect of the wave-function renormalisation and the narrow dispersion in the scalar mass bounds found from different approximation schemes.

# For students

Our group offers TDK, diploma and PhD topics in Lattice Field Theory.

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

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

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

Attila Pasztor

PhD student

2010 - Eotvos University, Hungary

apasztor {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

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

# 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

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

# 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: