HEP Lattice·hep-lat
10 papers—6 primary·4 cross-listed·reconstructed*
G. Aarts🇬🇧 · C. Allton🇬🇧 · S. Hands🇬🇧 · B. Jäger🇩🇰 · S. Kim🇰🇷 · M.P. Lombardo🇮🇹 · A.A. Nikolaev🇬🇧 · S.M. Ryan🇮🇪 · J.-I. Skullerud🇮🇪
We discuss some selected recent developments in the field of lattice QCD at nonzero temperature and density, describing in particular the transition from the hadronic gas to the quark-gluon plasma, as seen in simulations using Wilson fermions.
Exotic states have been predicted before and after the advent of QCD. In the last decades they have been observed at accelerator experiments in the sector with two heavy quarks, at or above the quarkonium strong decay threshold and called X Y Z states. These states offer a unique possibility for investigating the dynamical properties of strongly correlated systems in QCD. I will show how an alliance of nonrelativistic effective field theories and lattice can allow us to address these states in QCD. In particular I will explain what are the opportunities and challenges of lattice QCD in this respect and which new tools should be developed.
Massimo D'Elia🇮🇹 · Lorenzo Maio🇮🇹 · Francesco Sanfilippo🇮🇹 · Alfredo Stanzione🇮🇹
We provide numerical evidence that the thermal QCD crossover turns into a first order transition in the presence of large enough magnetic background fields. The critical endpoint is found to be located between GeV (where the pseudocritical temperature is MeV) and GeV (where the critical temperature is MeV). Results are based on the analysis of quark condensates and number susceptibilities, determined by lattice simulations of QCD at the physical point, discretized with three different lattice spacings, and fm, via rooted stout staggered fermions and a Symanzik tree level improved pure gauge action. We also present preliminary results regarding the confining properties of the thermal theory, suggesting that they could change drastically going across the phase transition
Peter Boyle🇺🇸 · Luigi Del Debbio🇬🇧 · Felix Erben🇬🇧 · Andreas Jüttner🇬🇧 · Takashi Kaneko🇯🇵 · Michael Marshall🇬🇧 · Antonin Portelli🇬🇧 · J Tobias Tsang🇩🇰 · Oliver Witzel🇩🇪
We are presenting our ongoing Lattice QCD study on mixing on several RBC/UKQCD and JLQCD ensembles with 2+1 dynamical-flavour domain-wall fermions, including physical-pion-mass ensembles. We are extracting bag parameters and using the full 5-mixing-operator basis to study both Standard-Model mixing as well as Beyond the Standard Model mixing, using a fully correlated combined fit to two-point functions and ratios of three-point and two-point functions. Using 15 different lattice ensembles we are simulating a range of heavy-quark masses from below the charm-quark mass to just below the bottom-quark mass.
Kim A. Nicoli🇩🇪 · Christopher Anders🇩🇪 · Lena Funcke🇺🇸 · Tobias Hartung🇬🇧 · Karl Jansen🇩🇪 · Pan Kessel🇩🇪 · Shinichi Nakajima🇯🇵 · Paolo Stornati🇩🇪
Estimating the free energy, as well as other thermodynamic observables, is a key task in lattice field theories. Recently, it has been pointed out that deep generative models can be used in this context [1]. Crucially, these models allow for the direct estimation of the free energy at a given point in parameter space. This is in contrast to existing methods based on Markov chains which generically require integration through parameter space. In this contribution, we will review this novel machine-learning-based estimation method. We will in detail discuss the issue of mode collapse and outline mitigation techniques which are particularly suited for applications at finite temperature.
Emanuele Mereghetti🇺🇸 · Christopher J. Monahan🇺🇸 · Matthew D. Rizik🇺🇸 · Andrea Shindler🇺🇸 · Peter Stoffer🇨🇭
The quark chromoelectric dipole (qCEDM) operator is a CP-violating operator describing, at hadronic energies, beyond-the-standard-model contributions to the electric dipole moment of particles with nonzero spin. In this paper we define renormalized dipole operators in a regularization-independent scheme using the gradient flow, and we perform the matching at one loop in perturbation theory to renormalized operators of the same and lower dimension in the more familiar MS scheme. We also determine the matching coefficients for the quark chromomagnetic dipole operator (qCMDM), which contributes, for example, to matrix elements relevant to CP-violating and CP-conserving kaon decays. The calculation provides a basis for future lattice QCD computations of hadronic matrix elements of the qCEDM and qCMDM operators.
This is a pedagogical introduction to the physics of confinement on , using Yang-Mills with massive or massless adjoint fermions as the prime example; at the end, we also add fundamental flavours. The small- limit is remarkable, allowing for controlled semiclassical determination of the nonperturbative physics in these, mostly non-supersymmetric, theories. We begin by reviewing the Polyakov confinement mechanism on . Moving on to , we show how introducing adjoint fermions stabilizes center symmetry, leading to abelianization and semiclassical calculability. We explain how monopole-instantons and twisted monopole-instantons arise. We describe the role of various novel topological excitations in extending Polyakov's confinement to the locally four-dimensional case, discuss the nature of the confining string, and the -angle dependence.~We study the global symmetry realization and, when available, present evidence for the absence of phase transitions as a function of the size. As our aim is not to cover all work on the subject, but to prepare the interested reader for its study, we also include brief descriptions of topics not covered in detail: the necessity for analytic continuation of path integrals, the study of more general theories, and the 't Hooft anomalies involving higher-form symmetries.
Guido Martinelli🇮🇹 · Silvano Simula🇮🇹 · Ludovico Vittorio🇮🇹
We show how to extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element from exclusive semileptonic decays by using the Dispersive Matrix (DM) method. It is a new approach which allows to determine in a full non-perturbative way the hadronic form factors (FFs) in the whole kinematical range, without making any assumption on their dependence on the momentum transfer. We investigate also the issue of Lepton Flavor Universality (LFU) by computing a pure theoretical estimate of the ratio . Our approach is applied to the preliminary LQCD computations of the FFs, published by the FNAL/MILC [1] and the JLQCD [2] Collaborations, for the decays and to the final ones, computed by FNAL/MILC [3], for the transitions . Since the FNAL/MILC Collaborations have recently published the final results of their LQCD computations of the FFs [4] for the case, we present also the results of our procedure after its application on these data. We find and from and decays, respectively. These estimates are consistent within with the most recent inclusive determination [5]. Furthermore, we obtain and , which are both compatible with the latest experimental averages [6] at the 1.6 level.
Hidenori Fukaya🇯🇵 · Mikio Furuta🇯🇵 · Yoshiyuki Matsuki🇯🇵 · Shinichiroh Matsuo🇯🇵 · Tetsuya Onogi🇯🇵 · Satoshi Yamaguchi🇯🇵 · Mayuko Yamashita🇯🇵
Gauge anomaly in 4-dimensions can be viewed as a current inflow into an extra-dimension, where the total phase of the fermion partition function is given in a gauge invariant way by the Atiyah- Patodi-Singer(APS) eta-invariant of a 5-dimensional Dirac operator. However, this formalism requires a non-local boundary condition, with which the physical roles of edge/bulk modes are unclear and how the causality of the theory is maintained is not obvious. In this work, we consider a special case where the Dirac operator is in a real representation and its eta invariant becomes the mod-two type APS index. We propose a physicist-friendly reformulation of the mod-two index using domain-wall fermion formalism, which naturally describes how the global anomaly is canceled between edge and bulk.
Zijian Xiong🇨🇳 · Yining Xu🇨🇳 · Xue-Feng Zhang🇨🇳
The quantum phase transition between plaquette valence bound solid (PVBS) and superfluid (SF) phases on the planar pyrochlore lattice (square ice) is under debate, because the conventional deconfined theory does not support continuous one, but the numerical evidence is still not solid. Here, we propose the system can be effectively described by a 2+1 dimensional Abelian-Higgs model which may host the mixed 't Hooft anomaly, so that the deconfinement can exist on the domain walls at the transition point. To verify it, we study the spin excitation spectra by combining stochastic analytic continuation and quantum Monte Carlo simulation. In both PVBS and SF phases, a flat band with bow-tie structure is observed and can be explained by group theoretic analysis. At the transition point, the spectra turn to be continuous and gapless, which indicates the topological excitations. From the snapshot of the spin configuration in real space, we found the existence of the domain wall in which the symmetries satisfy the anomaly. Meanwhile, a Luttinger liquid like continuum implies additional domain walls (point-defect) can emerge in the domain walls (line-defect) and take the role of deconfinement at transition point, as prediction of mixed 't Hooft anomaly. Our work can build a new bridge between the topological gauge field theory and a strongly correlated system.
* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.