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.

• 12 September 2018, Zsolt Frei (Eotvos)

  The road to the detection of gravitational waves, and ELTE's contribution to the quest

  I will briefly summarise what we all know by now about gravitational waves (GW) as a prediction of general relativity, the history of searching for the waves, and some technical details of the Laser Interferometer Gravitational-wave Observatory (LIGO), where the group I formed participated since 2007.

  I will tell you about our contribution to the data search: we have been an active member of the so-called "burst" group, where we are searching for transient-type signals in the noisy data stream of the detector. We have came up with two new search methods, the "Locust" and "Hough" algorithms. We also contributed to the experiment by developing, making and installing infrasound detectors at both the Hanford and Livingston sites. These detectors are increasingly important to measure the srength of gravity gradient noise, so I will spend some time to elaborate on this topic. Lately, we are also contributing to the identification of possible electromagnetic (EM) counterparts of the newly detected GW sources: binary neutron stars. We have developed a new galaxy catalog for LIGO, containing 2.5 million galaxies (compared to the 50.000 galaxies in the catalog LIGO used before). Some of our partners actually found the EM counterparts of the 2018 August event using our data.

  I will conclude with our current work and plans for the future: launching 9 small satellites to low-Earth orbit within the next 5 years to detect gamma-rays originating from binary neutron star merges and using these detections to precisely and promptly locate (triangulate) the position of the sources of the emerging GWs on the sky for subsequent EM observations.

• 19 September 2018, Ankita Mehta (Eotvos)

  Study of double-parton scattering processes using same-sign WW events at the CMS experiment slides

  Double-parton scattering (DPS) processes include the simultaneous occurrence of two distinct hard parton-parton interactions within in a single proton-proton collision. These interesting physics processes could provide valuable information on the distribution of partons inside the proton in the transverse direction and act as a background for SM and new physics searches at the LHC. This presentation is based on the results obtained from the first search for same-sign WW production via DPS processes, based on proton-proton collision data at a center-of-mass energy of 8 TeV. The decay of two W bosons is considered in dimuon and electron-muon final states. A multivariate analysis is used to discriminate the single from different background processes. Obtained results on the production cross section for same-sign WW via DPS and effective cross section parameter for DPS processes are compared with existing measurements and predictions from MC event generators.

• 26 September 2018, Attila Pasztor (Eotvos)

  QCD thermodynamics at finite density from imaginary chemical potential slides

  I will present a mini-review of some recent lattice QCD results on the bulk thermodynamic properties of QCD matter at finite temperature and small nonzero chemical potential. I will mostly focus on observables relevant for the RHIC Beam Energy Scan.

• 3 October 2018, Keming Shen (Wigner-MTA)

  Hadronization within Non-Extensive Approaches slides

  However Tsallis-like distributions describe well the momentum spectra measured in high-energy nuclear collisions, to find the microscopical origin of the non-extensive behavior is not straightforward. Our aim is to explore source of this distribution from the first principles.

  We investigated the transverse momentum distributions of various identified charged particles in high energy relativistic heavy ion collisions. I studies the interpretations of these spectra within the non-extensive approaches in details. Results on best-fits show that the mass scaling behaves more explicit with heavier produced hadrons in both pp and heavy ion collisions. In this talk I'll present my recent investigations and new results on mass-scaling and on specific distribution-types.

• 10 October 2018, Zoltan Kokenyesi (Eotvos)

  Topological string theory and generalized geometry slides

  Generalized geometry is a natural framework for describing geometric and non-geometric flux backgrounds in string compactifications. We study the A- and B-models of topological string theory and construct a membrane sigma-model based on a generalized complex structure, which reduces to the A- or B-models on the boundary in different gauges. Our construction allows the introduction of geometric and non-geometric fluxes as well as an S-duality at the level of the membrane sigma-model based on the generalized complex structure, and we interpret it as topological S-duality, which exchanges the A- and B-models. As an outlook we also discuss the relation of membrane sigma-models in topological M-theory to generalized geometry of M-theory.

• 17 October 2018, Zoltan Trocsanyi (Eotvos)

  On the origin of neutrino masses

  We consider an anomaly free extension of the standard model gauge group G_SM by an abelian group to G_SM x U(1)_Z. The condition of anomaly cancellation is known to fix the Z-charges of the particles, but two. We fix one remaining charge by requiring that the masses of the left handed neutrinos are generated by a mixing with right-handed neutrinos that obtain their masses through interaction with a new scalar field whose vacuum is broken spontaneously. We discuss some of the possible consequences of the model and ways of constraining the parameter space.

• 24 October 2018, Zoltan Kunszt (ETH Zurich)

  Feynman 100, Neutrino '72 Balatonfured slides

  The talk will shortly overview Feynman's unique, ingenious, inspiring scientific achievements as well as his teaching and popular lectures. Feynman's talk at Balatonfuered will be put in historic perspective in conjunction with the discovery of the QCD improved parton model.

• 25 October 2018, Akio Tomiya (RIKEN)

  Phase structure of three flavor QCD in external magnetic fields using HISQ actions slides

  We study the phase structure of QCD with three degenerate flavors in external magnetic fields using HISQ actions. The simulations are performed on 16^3. In order to investigate the quark mass dependence of the QCD transition we vary the values of pion masses from m=320 MeV to 80 MeV in the continuum limit. We found no indication of a first order phase transition in the current window of quark masses and external magnetic fields. Unlike to the case with standard staggered fermions inverse magnetic catalysis is always observed above the critical temperature. The microscopic origin of this phenomena as well as the volume effects are further discussed by looking into the Dirac eigenvalue spectrum.

• 31 October 2018, Dezso Horvath (Wigner-MTA, Atomki Debrecen)

  Recent results in Higgs studies and BSM searches at the LHC slides

  The almost half-century old theory of particle physics, the standard model (SM) seems to describe most of the experimental data very well. All of its elementary particles were identified and studied, and the discovery of the Higgs boson by ATLAS and CMS at the LHC with the mass m(H) = 125.09 +/- 0.21 (stat.) +/- 0.11 (syst.) GeV proved the validity of the Brout-Englert-Higgs mechanism of spontaneous symmetry breaking. In spite of the general quantitative agreement of its predictions with experiment the SM has serious theoretical shortcomings. It cannot account for neutrino oscillations, cannot solve the hierarchy problem (the unnaturally high corrections to the mass of the Higgs boson), there is no place in it for the particles of dark matter, and it cannot explain the lack of antimatter galaxies in the universe. Its gauge couplings are converging but not to the same point at high energies and it cannot include gravity as a gauge interaction. Most of these problems are solved within the frameworks of SM extensions, the most popular of them being supersymmetry. The latter predicts several deviations from the SM, especially in the Higgs sector, where it expects 5 Higgs bosons, three neutral and two charged ones.

  Studying the observed Higgs boson may uncover new physics beyond the SM, and thus it is one of the most important programs for the experiments of the Large Hadron Collider. We summarize the activity of CMS and also ATLAS to measure the mass and couplings of the 125 GeV Higgs boson, its decay properties as compared to the SM predictions, and also attempts to check for other Higgs bosons at different masses. Thus far all data collected by ATLAS and CMS agree with the SM, no deviation is found. Great effort is invested by both experiments to study extensions of the standard model and possibly uncover physics beyond it. We shall describe the history of an aborted discovery: a new boson at 750 GeV. Thus the question what new physics is beyond the SM is open yet.

  The talk is based on a plenary given on behalf of CMS at the QCD at LHC 2018 Workshop, 27-31 August 2018, Dresden (Germany).

• 7 November 2018, Vladimir Korobov (Dubna)

  Precision theory for hydrogen molecular ions

  At present theoretical prediction for the spin-averaged frequency of ro-vibrational transitions in the hydrogen molecular ions (HMI) has reached a relative precision of ~ 7.5 x 10^(-12) . On the other hand, recent experiment on pure rotational transition in HD+ has demonstrated the power of the Lamb-Dicke regime for precision spectroscopy of the HMI with strong potentiality in the nearest future to achieve a ppt level of spectroscopic accuracy.

  The Rydberg constant as it is determined in the CODATA14 adjustment of the fundamental constants has the relative uncertainty 5.9 x 10^(-12). At the same time the two new experiments on spectroscopy of hydrogen atom performed at LKB, Paris, and MPQ, Munich, disagree in measuring the Rydberg constant by more than 3-sigma!

  In our presentation we want to outline the way how the high precision results for the hydrogen molecular ions may be achieved with the help of the effective field theory --- the Nonrelativistic QED. At the very end of our talk we intend to discuss the problems, which are to be solved in order to improve (at least threefold) theoretical predictions. That will bring our theory to the level of accuracy which is better than for the present CODATA14 value of the Rydberg constant. And, we hope, that this will help to resolve the discrepancy between the LKB and MPQ experiments as well as to find answers to many other questions related to the fundamental constants.

• 14 November 2018

  No seminar because of CERN25 event of the Academy

• 21 November 2018, Stefan Teufel (Tubingen)

  Non-equilibrium almost-stationary states and linear response for gapped quantum systems slides

  I report on recent mathematical results concerning the validity of linear response theory at zero temperature for perturbations of gapped Hamiltonians describing interacting fermions on a lattice, e.g. quantum Hall systems. The challenge here is to prove Kubo's formula uniformly in the volume and also for perturbations (like a small constant electric field) that close the spectral gap. Our justification of linear response theory is based on a novel extension of the adiabatic theorem to situations where a time-dependent perturbation closes the gap. According to the standard version of the adiabatic theorem, when the perturbation is switched on adiabatically and as long as the gap does not close, the initial ground state evolves into the ground state of the perturbed operator. The new adiabatic theorem states that for perturbations that are either slowly varying potentials or small quasi-local operators, once the perturbation closes the gap, the adiabatic evolution follows non-equilibrium almost-stationary states (NEASS) that we construct explicitly.

• 28 November 2018, Peter Posfay (Wigner-MTA)

  Estimating the variation of neutron star observables by dense nuclear matter properties slides

  Description of extreme dense nuclear matter is an active research field, however Lattice QCD calcualtions are challenging for the case of cold dense matter. One needs effective theories to describe this region of the QCD matter and the consistency of these models can be constrained by studying compact astrophysical objects.

  Parameters corresponding to effective models of cold nuclear matter (interactions, coupling, mass) affect the observable parameters (mass and radius) of neutron stars. Moreover, detailed studies of QCD phase diagram shows the importance of bosonic quantum fluctuations. In this work we use the Functional Renormalization Group (FRG) method to take into account bosonic quantum fluctuations at fininte chemical potential at zero temperature. We did our caclulations in a system consisting of one fermionic and one bosonic degree of freedom, where the fermions and bosons are coupled together by a Yukawa coupling and the bosons have self interaction terms. We studied the effect of different interaction terms in the Lagrangian on the properties of nuclear matter.

• 5 December 2018

  No seminar because of Zimanyi School

• 12 December 2018, Gabor Biro (Wigner-MTA)

  Monte Carlo event generators in heavy-ion physics: a review slides

  In the recent decades the rapid technological advancement resulted in larger than ever collision energies, huge, complex detector systems, sophisticated readout systems with immense amount of experimental data, and therefore in the Golden Age of high-energy physics. Along with the experiments also the underlying theories went through a huge development. Nowadays the theoretical calculations are becoming more and more challenging, therefore numerical calculations are getting key importance, with special emphasis not just on the precision but on performance as well.

  In this talk I give a review on the Monte Carlo event generators used by the high-energy physics community. Through a historical perspective I introduce today's most widely used frameworks and I highlight the important aspects that emerged during their development and lead to their present state. I give also an outlook to the future's event generators, focusing on our HIJING++ project.

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.

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: