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

Time: Wednesdays at 14:15

See the archive for seminars in past years.

• 13 February 2019, Andras Laszlo (Wigner-MTA)

  General Relativity experiment with spin polarized particle beams slides

  In experimental proposals published in the last two decades, a so called frozen spin storage ring concept emerged, for setting upper experimental bounds to electric dipole moment (EDM) of charged elementary particles with spin. In a recent paper of ours (Class.Quant.Grav.35(2018)175003), a fully covariant general relativistic (GR) calculation was presented on the Earth's gravitational modification effect on the spin transport inside such a frozen spin storage ring. It turns out that in certain configurations, Earth's gravity is expected to produce a similar order of magnitude effect as the aimed EDM sensitivity, and thus it becomes kind of realistic to experimentally see this GR effect. If such an experiment could be conducted, it could provide a novel test of GR: with microscopic particles, at relativistic speeds, along non-geodesic (forced) trajectories, and the tensorial nature of GR would be at test, not merely the gravitational drag. In more technical terms: the GR correction to the so called Thomas precession could be tested in lab. For details on the experimental idea, we refer to: arXiv:1901.06217 (Proceedings of Spin2018 Conference).

• 20 February 2019, Ferenc Pittler (Bonn)

  A novel mechanism for dynamical generation of elementary fermion masses slides

  The Standard Model (SM) is very successful in describing a plethora of low energy phenomena, however it is unable to explain the electro-weak scale naturalness and the fermion mass hierarchy problem. In this talk we numerically verify an intrinsically non-perturbative mechanism for elementary fermion mass generation advocated in 1402.0389 using lattice QCD techniques. This mechanism takes place in non-Abelian gauge models if fermionic chiral symmetries are explicitly broken at the UV cutoff scale and an exact invariance acting on both fermions and scalars forbids power divergent fermion mass corrections. We argue that a complete, composite Higgs-like beyond SM (BSM) scenario can be built using this mass generation mechanism. We also discuss differences-similarities with respect to the current BSM models studied with lattice simulations.

• 27 February 2019, Mate Csanad (Eotvos)

  The RHIC(+SPS+FAIR+NICA+JPARC) Beam Energy Scan Program slides

  The RHIC beam energy scan program, complemented by similar programmes at other accelerators, allows for the investigation of the phase diagram of QCD matter by varying the beam energy in the region where the change from crossover to first order phase transition is suggested to occur. The nature of the quark-hadron transition can be studied through analyzing the space-time structure of the hadron emission source. Many measurements were performed in the recent years, from spectra and yields through fluctuations and anisotropies to intermittency and quantumstatistical correlations. These as of now show a controversial picture, and in this talk, we will go through the plethora of results, with special focus on Bose-Einstein correlations.

• 6 March 2019, Koushik Mandal (Eotvos)

  Fully Hadronic SUSY Search in CMS slides

  Supersymmetry (SUSY) is one of the best motivated and most compelling theories going beyond Standard Model (SM) physics. In the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC), SUSY searches have been extensively carried out exploring the possibility of the existence of the supersymmetric partners of SM particles in a wide mass range studying diverse experimental signatures. Given the naturalness theory, the scalar top quarks and the gluino are of particular interest. Depending on the final state of the scalar top and gluino decays, search channel could be leptonic, hadronic or mixed. Because of the higher expected rate at the LHC, we studied the fully hadronic final state containing missing transverse momenta and multiple jets. A comprehensive study of stop and gluino searches will be presented, underlining the method to tag top quark decays and to estimate from the LHC data the SM background rate.

• 13 March 2019, Ruchi Chudasama (Eotvos)

  Physics of ultra-peripheral collisions with CMS experiment slides

  Moving highly-charged ions carry strong electromagnetic fields that act as a beam of photons. In collisions at large impact parameters, hadronic interactions are not possible, and the ions interact through photon-photon and photon-ion collisions known as ultra-peripheral collisions (UPCs). Photon-photon interactions provide a wide range of opportunities from the test of Quantum Electro-Dynamic (QED) to search for physics beyond Standard Model (SM). We provide the evidence for light by light scattering and search for axion-like particles using high photon fluxes from PbPb collisions. On the other hand, photon-ion processes can probe the gluon distribution in proton and heavy-ions down to Bjorken -x values 10^{-6}, far smaller than can be otherwise studied. In this low-x regime, non-linear QCD effects (gluon recombination) may become important, possibly leading to the saturation of the parton distribution functions. We probe the parton distribution inside proton by studying the exclusive upsilon photoproduction in pPb collisions.

• 20 March 2019, Antal Jakovac (Eotvos)

  Bound states in quantum field theory: an FRG study

  In the talk we review the traditional approaches to define bound states in quantum theories. In the example of QED with two oppositely charged fermionic fields, we demonstrate the construction of an effective model that contains bound states, and which reproduces the fermionic observables of the original model. Using numerical analysis in the nonrelativistic limit, we argue that considerable simplifications can be made, still maintaining a reasonable accuracy in the computation of the ground state energy.

• 27 March 2019, Gergely Marko (Eotvos)

  Magnetic field dependence of the NJL coupling from lattice QCD slides

  Chiral effective models of strong interactions struggle to capture the inverse magnetic catalysis observed in continuum extrapolated lattice results. One recent trend is to incorporate absent degrees of freedom by making effective model parameters depend on B. We try to improve on this approach by deducing the magnetic field dependence of the Nf=2 (P)NJL coupling directly from lattice observables. We carried out full lattice QCD simulations for the baryon octet masses as a function of the magnetic field using staggered fermions. A continuum extrapolated result is obtained in the eB < 0.6 GeV^2 region. Using a simple non-relativistic quark model we infer constituent quark masses from the baryons which in turn serve as inputs to obtain the B-dependent coupling. We then solve the (P)NJL model to assess the effect of the B-dependent coupling on the pseudo-critical temperature of the chiral phase transition.

• 12 April 2019, Slava Rychkov (IHES, Ecole Normale Superieure Paris)

  Walking, weakly first-order phase transitions, and complex CFTs

  Most people have heard that the 2d Potts model with Q=5 states has a first order phase transition, but not everyone knows that the correlation length at this phase transition is 2500 lattice spacings. We will review "walking RG" behavior in gauge theories and connect it to Type II weak first-order phase transitions in statistical physics. Despite appearing in very different systems (QCD below the conformal window, the Potts model, deconfined criticality) these two phenomena both imply approximate scale invariance in a range of energies and have the same RG interpretation: a flow passing between pairs of fixed point at complex coupling, dubbed "complex CFTs". Observables of the real walking theory are approximately computable by perturbing the complex CFTs. The general mechanism will be illustrated by a specific and computable example: the two-dimensional Q-state Potts model with Q > 4. Based on 1807.11512 and 1808.04380.

• 24 April 2019, Laurent Lellouch (CNRS, Aix-Marseille U)

  Hadronic vacuum polarization contribution to the muon magnetic moment from lattice QCD slides

  In the early 2000s, the anomalous magnetic moment of the muon, a_mu=(g_mu-2)/2, was measured with a remarkable precision of 0.54ppm. Since those results were published, a discrepancy of more than 3 standard deviations has persisted between the standard model (SM) prediction and experiment. At present theoretical and experimental uncertainties are close in size. However, a new experiment underway at Fermilab is aiming to reduce the experimental uncertainty on a_mu by 4. To leverage this future measurement and possibly claim the presence of new fundamental physics, it is imperative to reduce and fully control the uncertainties in the SM prediction. After an introduction to the role that anomalous magnetic moments play in testing the SM and a discussion of the current experimental and theoretical status of a_mu, I will present a lattice QCD calculation of the contribution to this quantity that most limits the precision of its SM prediction.

• 8 May 2019, Mordehai Milgrom (Weizmann Institute, Israel)

  Scale invariance at low accelerations as an alternative to dark matter slides

  Galactic systems, and the Universe at large, exhibit much larger accelerations than are predicted by Newtonian dynamics and general relativity, if only the matter we actually observe is responsible for gravity. The mainstream comes to the rescue of these revered paradigms by invoking large quantities of `dark matter' -- which purportedly supplies the needed extra accelerations -- and also of `dark energy', to account for the unexplained accelerated expansion of the Universe. The MOND paradigm offers a different solution: a breakdown of standard dynamics (gravity and/or inertia) in the limit of low accelerations -- below some acceleration a_0. In this limit, dynamics become space-time scale invariant, and is controlled by a gravitational constant A_0 ~ G a_0, which replaces Newton's G. With the new dynamics, the various detailed manifestations of the anomalies in galaxies are predicted with no need for dark matter. An intriguing aspect of MOND is that the MOND constant turns out to carry cosmological connotations: a_0 ~ c^2/R_U, R_U being `the radius of the Universe'. There are MOND theories in which this `coincidence' is natural. I draw on enlightening historical and conceptual analogies to limelight aspects of MOND.

• 15 May 2019, Robert Harlander (Aachen)

  Gradient flow at higher orders in perturbation theory slides

  The implementation of a systematic approach to the perturbative calculation of Green's functions in the gradient-flow formalism is described. Results for the conversion of the gradient-flow coupling to the MSbar scheme, and an analogous relation for the quark mass are presented through next-to-next-to-leading order (NNLO) QCD. As a second application, the gradient-flow definition of the energy-momentum tensor through NNLO QCD will be considered. The relevance of the higher-order effects will be highlighted by studying their impact on the theoretical uncertainty estimate.

• 29 May 2019, Sho Iwamoto (Padova)

  SUSY status at the LHC, focusing on the muon g-2 anomaly and dark matter slides

  The Run-2 LHC provided sufficient data to search for "non-colored" TeV-scale new particles. Before the Run 2, I expected that we would discover such "non-colored" particles that are predicted by TeV-scale SUSY, because they may solve an anomaly of the muon g-2 and also can explain the origin of the dark matter.

  Unfortunately, it seems that my expectations do not fulfill. One piece of good news is that we have a new measurement of the muon g-2, which will publish their results later this year. If it confirms the anomaly, then it may tell us that the non-colored SUSY particles are hidden somewhere in the parameter space and evading from our search strategy. In this talk, we review the LHC status of TeV-scale SUSY, focusing on the muon g-2 anomaly and the dark matter, and discuss possibilities of this hide-and-seek.

  In addition, I will be talking briefly on two other recent works of mine: leptogenesis on "neutrino option" models, and dark matter models with new confining gauge group, as an introduction of myself to the ELTE people.

• 12 June 2019, Laszlo Csernai (University of Bergen)

  Laser driven ignition for inertial confinement fusion slides

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: