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 and were funded by various funding agencies for which we are grateful, these include the Lendulet grant of the Hungarian Academy of Sciences, the OTKA-NF-104034 grant of OTKA and 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 ELFT seminars at the Department of Theoretical Physics

Location: 2nd floor, 2.54, Novobatzky room, 1117 Budapest, Pazmany Peter setany 1/a

Due to the covid-19 pandemic the seminar is currently held in the Ortvay lecture hall allowing for social distancing. Please bring a mask with you.

Time: Wednesdays at 14:15

See the archive for seminars since 2014.

• 23 September 2020, Tamas Kovacs (Eotvos) slides

  Prediction of chaotic time series -- a machine learning approach

  Recently, it turned out that recurrent neural network (RNN) is an extremely successful concept to forecast nonlinear dynamical systems. However, it is computationally expensive to train all the parameters in a nonlinear optimization problem. In this talk I am going to review a special case of RNNs, the reservoir computing (RC), that fits also perfectly to the task of forecasting. In RC only the output layer must be trained with many few parameters and a cheap linear least square operation. The method will be introduced step by step through practical examples.

• 30 September 2020, Zoltan Peli (Debrecen) slides

  Derivative expansion for computing critical exponents of O(N) symmetric models at NNLO accuracy

  We apply the derivative expansion of the effective action in the exact renormalization group (ERG) equation up to fourth order (\partial^4-order, NNLO) on the Z_2 and O(N) symmetric scalar models in d=3 Euclidean dimensions. We compute the critical exponents nu, eta and omega using polynomial expansion in the field. We obtain our predictions for the exponents employing two regulators widely used in ERG computations. We find that both regulators produce results in agreement with predictions obtained by the available Monte-Carlo and conformal bootstrap methods, but requiring significantly less computational time than those do.

• 7 October 2020, Gergely Fejos (Eotvos) slides

  Order of the color superconducting phase transition

  I will present recent results on the finite temperature phase transition of color superconductivity, predicted to exist in dense quark matter. By reviewing renormalization group analyses of ordinary superconductivity, I will generalize its Ginzburg-Landau functional to QCD and calculate the flow of the free energy in three spatial dimensions via the functional renormalization group technique. The findings show that unlike ordinary superconductivity, the color superconducting phase transition can only be of first order.

• 14 October 2020, Peter Bantay (Eotvos) slides

  Gauge Lattice Theory

  We give an overview of some recent advances in the field, with special emphasis on computational issues.

• 21 October 2020, Sven Moch (Hamburg)

  QCD evolution at 1% precision

  We review the status and precision of evolution equations in perturbative QCD. We give an overview on the current theoretical status and the calculational techniques used in perturbation theory. We discuss the application of QCD evolution equations in the determination of parton distribution functions in the proton, the strong coupling constant alpha_s and the quark masses m_c, m_b and m_t in global fits. We give an overview of current results and compare to available information from other approaches like lattice QCD.

• 28 October 2020, Balazs Pozsgay (Eotvos)

  TBA

• 4 November 2020, Josu Hernandez-Garcia (Eotvos)

  GeV-scale neutrinos: interactions with mesons and DUNE sensitivity

  The simplest extension of the SM to account for the observed neutrino masses and mixings is the addition of at least two singlet fermions (or right-handed neutrinos). If their masses lie at or below the GeV scale, such new fermions would be produced in meson decays. Similarly, provided they are sufficiently heavy, their decay channels may involve mesons in the final state. Although the couplings between mesons and heavy neutrinos have been computed previously, significant discrepancies can be found in the literature. The aim of this talk is to clarify such discrepancies and provide consistent expressions for all relevant effective operators involving mesons with masses up to 2 GeV. As an application, we numerically compute the expected sensitivity of the DUNE near detector to these heavy neutral leptons.

• 11 November 2020, Gyula Bene (Eotvos)

  TBA

• 18 November 2020, Daniel Nogradi (Eotvos)

  Revisiting the semi-classical approximation at high temperature

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

Since it is tricky to locate all papers by a large number of people whose names are not unique on inspire, you can try various search queries:

• Papers by Sandor Katz and Zoltan Fodor
• Papers by Sandor Katz and Gergely Endrodi
• Papers by Sandor Katz and Matteo Giordano
• Papers by Daniel Nogradi

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.

Our department is on the Buda side of the Danube very close to the Petofi Bridge:

The Department of Theoretical Physics is on the first floor on the Danube facing side of the building: