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.

• 28 January 2015, Chaiho Rim (Sogang University, South Korea)

Some applications of random matrix models slides

Random matrix models are used to describe (1) statistical variance of multivariables using Gaussian pontential (2) 2d quantum gravity using polynomial potential (3) regular and irregular conformal block using Penner-type (logarithmic) potential.

• 11 February 2015, Fidel I Schaposnik Massolo (La Plata, Argentina)

D5-brane boundary reflection factors slides

a We compute the strong coupling limit of the boundary reflection factor for excitations on open strings attached to various kinds of D5-branes that probe AdS(5)xS(5). We study the crossing equation, which constrains the boundary reflection factor, and propose that some solutions will give the boundary reflection factors for all values of the coupling. Our proposal passes various checks in the strong coupling limit by comparison with diverse explicit string theory computations. In some of the cases we consider, the D5-branes correspond to Wilson loops in the k-th rank antisymmetric representation of the dual field theory. In the other cases they correspond in the dual field theory to the addition of a fundamental hypermultiplet in a defect.

• 18 February 2015, Yunfeng Jiang (Saclay, France)

Integrability in AdS/CFT : Three-Point Functions in N=4 SYM theory

The discovery of integrability in the planar N=4 Super-Yang-Mills theory and its AdS dual has triggered a lot of progress in recent years. Equipped with powerful integrability based techniques, it is now possible to compute many interesting quantities such as the spectrum, Wilson loop and scattering amplitudes of the theory at any value of the coupling constant. In this talk, I will explain how to compute three-point functions in the planar N=4 SYM theory at tree level and one loop in perturbation theory using Bethe ansatz. I will also discuss the semi-classical limit and the comparison with the computation at strong coupling.

• 25 February 2015, Robert Wald (Enrico Fermi Institute, Chicago)

Dynamic and Thermodynamic Stability of Black Holes and Black Branes slides

I describe work with with Stefan Hollands that establishes a new criterion for the dynamical stability of black holes in $D \geq 4$ spacetime dimensions in general relativity with respect to axisymmetric perturbations: Positivity of the canonical energy, $\mathcal E$, on a subspace of linearized solutions that have vanishing linearized ADM mass, momentum, and angular momentum at infinity and satisfy certain gauge conditions at the horizon implies mode stability. Conversely, failure of positivity of $\mathcal E$ on this subspace implies the existence of perturbations that cannot asymptotically approach a stationary perturbation. We further show that $\mathcal E$ is related to the second order variations of mass, angular momentum, and horizon area by $\mathcal E = \delta^2 M - \sum_i \Omega_i \delta^2 J_i - (\kappa/8\pi) \delta^2 A$. This establishes that dynamic stability of a black hole is equivalent to its thermodynamic stability (i.e., its area, $A$, being a maximum at fixed state parameters'' $M$, $J_i$). For a black brane, we prove that a sufficient condition for instability is the failure of the Hessian of $A$ with respect to $M$, $J_i$ to be negative, thus proving the Gubser-Mitra conjecture. We also prove that positivity of $\mathcal E$ is equivalent to the satisfaction of a local Penrose inequality,'' thus showing that satisfaction of this local Penrose inequality is necessary and sufficient for dynamical stability.

• 25 February 2015, George Sparling (Pittsburgh)

Searching for structure: A tribute to Doctor Zoltan Perjes - the universe, large and small.

One hundred years after the final formulation of general relativity by Albert Einstein, the quest to comprehend his theory continues. Doctor Zoltan Perjes was a master of the theory, constantly stretching its boundaries. He would work in cosmology, the study of the whole universe, always being concerned with relating the abstract theory to measurable quantities, such as the Sachs-Wolfe effect. He would also work locally dealing with isolated bodies, such as stars, testing their stability and trying to construct realistic models. He had his own speciality the theory of space times with a timelike symmetry, for which he developed his beautiful triad formalism and the sub-theory of conformastat space-times.

In this talk I will present two recent results of mine and my colleague Jonathan Holland, which I believe would have been dear to Zoltan's heart: First an analysis of Bach flat metrics of a split form: in particular it is proved that all such have a symmetry. Second a discussion of the new approach to cosmology that we have initiated in the last two years: in our basic model a key role is played by a timelike conformal symmetry. This new theory leads to a remarkable new picture of the relationship between local and global cosmology and brings to bear for the first time major modern mathematical tools: the theory of Fano manifolds.

• 4 March 2015, Gabor Takacs (BME, Hungary)

Form faktorok a lepcsohazbol slides

Alyosha Zamolodchikov a sinh-Gordon modell termodinamikai Bethe Ansatz egyenletenek analitikus elfolytatasaval lepcsos renormalasi csoport folyamot konstrualt, amivel sikerult alternativ leirast adnia a konform minimalis modellek (multikritikus Ising modellek) kozotti cross-over folyamokra. Otletet a c-tetelen keresztul megfogalmazva eljarast adunk a cross-overt leiro terelmeletek egzakt form faktorainak konstrukciojara. A feltarulo struktura felveti annak lehetoseget, hogy szamos integralhato terelmelet egzakt form faktorait a bootstrap jelentette igen bonyolult matrix Riemann-Hilbert problema helyett egy, a TBA univerzalis megfogalmazasabol kapcsolodo diagrammatikus konstrukciobol megkonstrualjuk.

• 11 March 2015, Tamas Kovacs (ATOMKI, Debrecen, Hungary)

The chiral and the Anderson transition in QCD slides

Recently we have been studying an Anderson-type localization-delocalization transition in the spectrum of the Dirac operator describing quarks in the quark-gluon plasma. In the talk I summarize the latest results about the properties of this transition and its possible implications on the thermodynamics of QCD and other QCD-like theories.

• 18 March 2015, Peter Mati (BME, Hungary)

The Vanishing Beta Function Curves from the Functional Renormalisation Group

We will discuss the derivation of the so called Vanishing Beta Function curves which can be used to explore the fixed point structure of the theory under consideration. This can be applied to the O(N) symmetric theories essentially for arbitrary dimensions (D) and field component (N). We will show the restoration of the Mermin-Wagner theorem for theories defined in D <= 2 and the presence of the Wilson Fisher fixed point in 2<D<4. Triviality is found in D>4. Interestingly, one needs to make an excursion to the complex plane to see the triviality of the four dimensional O(N) theories. The large N analysis shows a new fixed point candidate in 4<D<6 dimensions which turns out to define an unbounded fixed point potential supporting the recent results by R. Percacci and G. P. Vacca. Corresponding paper: http://arxiv.org/abs/1501.00211

• 1 April 2015, Peter Gnadig (Eotvos)

Alkalmazhato-e a Biot--Savart-torveny nem zarodo "aramkorokre"?

• 8 April 2015, Richard Szabo (Heriot-Watt University, UK)

Nonassociative Quantum Mechanics slides

We briefly review recent developments from string theory which suggest that non-geometric string backgrounds experience a nonassociative deformation of spacetime geometry. A geometrisation of this frame leads to a sigma-model for closed strings propagating in an effective target space that is the phase space of the original compactification manifold. Quantization of the sigma-model produces an explicit nonassociative star-product algebra on functions on phase space, which is related to the quantization of Nambu-Poisson structures. We use this formalism to develop a phase space formulation of nonassociative quantum mechanics, and demonstrate that, against all odds, a consistent formulation seems indeed possible. Our approach is completely quantitative and adds to previous qualitative discussions of nonassociativity in quantum mechanics, and it moreover avoids previous no-go theorems.

• 22 April 2015, Peter Bantay (Eotvos)

Replication identities in 2D Conformal Field Theory slides

We discuss an approach to replication identities satisfied by conformal characters of a 2D CFT that links them with symmetries of symmetric products, providing a physics interpretation of the Hauptmodul property of Monstruous Moonshine.

• 29 April 2015, Marietta Homor (Eotvos)

Transport Coefficients and Thermalisation in Classical Field Theories slides

Our first objective is to show a practical method for the determination of viscosity in classical, relativistic field theories. We will discuss the relevant physical quantities in thermalised systems by the example of Phi^4 theory. Furthermore, we recently observed that the thermalisation in itself has interesting properties e.g. the distributions thermalize in a much shorter scale than the temperature. Inspired by this, our second objective is to examine the thermalisation properties of Phi^4 theory from various initial conditions. We propose, that the first correction to the Maxwell-Boltzmann distribution is the Tsallis distribution.

• 20 May 2015, Andreas Ringwald (DESY Hamburg)

Ultralight Axion-Like Particles from Strings slides

There are various puzzling observations in sastrophysics which may be explained by the existence of light axion-like particles (ALPs) with a tiny coupling to the known particles of the Standard Model. In this talk, we will discuss how such ALPs and their couplings to the Standard Model may arise naturally from ultraviolet extensions inspired by string theory.

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: