Fri·Oct 22, 2021Friday·October 22, 2021

1. 01*

   Electromagnetic conductivity of quark-gluon plasma at non-zero baryon density

   N. Astrakhantsev🇨🇭 · V.V. Braguta🇷🇺 · M. Cardinali🇮🇹 · M. D'Elia🇮🇹 · L. Maio🇮🇹 · F. Sanfilippo🇮🇹 · A. Trunin🇷🇺 · A. Vasiliev🇷🇺

   In this preprint we present our results on the study of the electromagnetic conductivity in dense quark-gluon plasma obtained within lattice simulations with $N_f=2+1$ dynamical quarks. We employ stout improved rooted staggered quarks at the physical point and the tree-level Symanzik improved gauge action. The simulations are performed at imaginary baryon chemical potential, and the Tikhonov regularisation method is used to extract the conductivity from current-current correlators. Our results indicate an increase of QGP electromagnetic conductivity with real baryon density, and this dependence is quite strong.

   hep-lathep-phhep-thPoS(2022)·8 citations
2. 02*

   Latent heat and pressure gap at the first-order deconfining phase transition of SU(3) Yang-Mills theory using the small flow-time expansion method

   Kazuyuki Kanaya🇯🇵 · Mizuki Shirogane🇯🇵 · Shinji Ejiri🇯🇵 · Ryo Iwami🇯🇵 · Masakiyo Kitazawa🇯🇵 · Hiroshi Suzuki🇯🇵 · Yusuke Taniguchi🇯🇵 · Takashi Umeda🇯🇵

   We study the latent heat and the pressure gap between the hot and cold phases at the first-order transition temperature $T=T_c$ of SU(3) Yang-Mills theory, using the small flow-time expansion (SF$t$X) method based on the gradient flow. We first examine alternative procedures in the SFtX method -- the order of the continuum and vanishing flow-time extrapolations. We confirm that the final results adopting the two orders, as well as other alternatives in which the perturbative order of the matching coefficients and the renormalization scale of the flow scheme are varied, are all consistent with each other. We also confirm $\Delta p$ is consistent with zero, as expected from the dynamical balance of two phases at $T_c$. For the latent heat in the continuum limit, we find $\Delta ϵ/T^4=1.117(40)$ for the spatial volume $L^3$ corresponding to the aspect ratio $N_s/N_t=T_{c}L=8$ and $1.349(38)$ for $N_s/N_t=6$. From hysteresis curves, we show that the entropy density in the hot phase is sensitive to the spatial volume, while that in the confined phase is insensitive.

   hep-latPoS(2022)·1 citation
3. 03*

   Evaluation of $SU(3)$ smearing on FPGA accelerator cards

   Salvatore Calì🇺🇸 · Grzegorz Korcyl · Piotr Korcyl

   Recent FPGA accelerator cards promise large acceleration factors for some specific computational tasks. In the context of Lattice QCD calculations, we investigate the possible gain of moving the $SU(3)$ gauge field smearing routine to such accelerators. We study Xilinx Alveo U280 cards and use the associated Vitis high-level synthesis framework. We discuss the possible pros and cons of such a solution based on the gathered benchmarks.

   hep-latPoS(2022)·0 citations
4. 04*

   Entanglement Structures in Quantum Field Theories: Negativity Cores and Bound Entanglement in the Vacuum

   Natalie Klco🇺🇸 · D. H. Beck🇺🇸 · Martin J. Savage🇺🇸

   The many-body entanglement between two finite (size-$d$) disjoint vacuum regions of non-interacting lattice scalar field theory in one spatial dimension -- a $(d_A\times d_B{)}_{\mathrm{mixed}}$ Gaussian continuous variable system -- is locally transformed into a tensor-product "core" of $(1_A\times 1_B{)}_{\mathrm{mixed}}$ entangled pairs. Accessible entanglement within these core pairs exhibits an exponential hierarchy, and as such identifies the structure of dominant region modes from which vacuum entanglement could be extracted into a spatially separated pair of quantum detectors. Beyond the core, remaining modes of the "halo" are determined to be AB-separable in isolation, as well as separable from the core. However, state preparation protocols that distribute entanglement in the form of $(1_A\times 1_B{)}_{\mathrm{mixed}}$ core pairs are found to require additional entanglement in the halo that is obscured by classical correlations. This inaccessible (bound) halo entanglement is found to mirror the accessible entanglement, but with a step behavior as the continuum is approached. It remains possible that alternate initialization protocols that do not utilize the exponential hierarchy of core-pair entanglement may require less inaccessible entanglement. Entanglement consolidation is expected to persist in higher dimensions and may aid classical and quantum simulations of asymptotically free gauge field theories, such as quantum chromodynamics.

   ↳ quant-phhep-lathep-phhep-th+1PRA(2023)·35 citations
5. 05*

   Quantum field theories, Markov random fields and machine learning

   Dimitrios Bachtis🇬🇧 · Gert Aarts🇬🇧 · Biagio Lucini🇬🇧

   The transition to Euclidean space and the discretization of quantum field theories on spatial or space-time lattices opens up the opportunity to investigate probabilistic machine learning within quantum field theory. Here, we will discuss how discretized Euclidean field theories, such as the ${\varphi }^4$ lattice field theory on a square lattice, are mathematically equivalent to Markov fields, a notable class of probabilistic graphical models with applications in a variety of research areas, including machine learning. The results are established based on the Hammersley-Clifford theorem. We will then derive neural networks from quantum field theories and discuss applications pertinent to the minimization of the Kullback-Leibler divergence for the probability distribution of the ${\varphi }^4$ machine learning algorithms and other probability distributions.

   ↳ cs.LGcond-mat.dis-nncond-mat.stat-mechhep-latJ.Phys.Conf.Ser.(2022)·8 citations
6. 06*

   Quantum Flatness in Two-Dimensional CDT Quantum Gravity

   J. Brunekreef🇳🇱 · R. Loll🇳🇱

   Flatness -- the absence of spacetime curvature -- is a well-understood property of macroscopic, classical spacetimes in general relativity. The same cannot be said about the concepts of curvature and flatness in nonperturbative quantum gravity, where the microscopic structure of spacetime is not describable in terms of small fluctuations around a fixed background geometry. An interesting case are two-dimensional models of quantum gravity, which lack a classical limit and therefore are maximally "quantum". We investigate the recently introduced quantum Ricci curvature in CDT quantum gravity on a two-dimensional torus, whose quantum geometry could be expected to behave like a flat space on suitably coarse-grained scales. On the basis of Monte Carlo simulations we have performed, with system sizes of up to 600.000 building blocks, this does not seem to be the case. Instead, we find a scale-independent "quantum flatness", without an obvious classical analogue. As part of our study, we develop a criterion that allows us to distinguish between local and global, topological properties of the toroidal quantum system.

   ↳ hep-thgr-qchep-latPRD(2021)·12 citations
7. 07*

   The emergence of gapless quantum spin liquid from deconfined quantum critical point

   Wen-Yuan Liu🇨🇳 · Juraj Hasik🇫🇷 · Shou-Shu Gong🇨🇳 · Didier Poilblanc🇫🇷 · Wei-Qiang Chen🇨🇳 · Zheng-Cheng Gu🇨🇳

   A quantum spin liquid (QSL) is a novel phase of matter with long-range entanglement where localized spins are highly correlated with the vanishing of magnetic order. Such exotic quantum states provide the opportunities to develop new theoretical frameworks for many-body physics and have the potential application in realizing robust quantum computations. Here we show that a gapless QSL can naturally emerge from a deconfined quantum critical point (DQCP), which is originally proposed to describe Landau forbidden continuous phase transition between antiferromagnetic (AFM) and valence-bond solid (VBS) phases. Via large-scale tensor network simulations of a square-lattice spin-1/2 frustrated Heisenberg model, both QSL state and DQCP-type AFM-VBS transition are observed. With tuning coupling constants, the AFM-VBS transition vanishes and instead, a gapless QSL phase gradually develops in between. Remarkably, along the phase boundaries of AFM-QSL and QSL-VBS transitions, we always observe the same correlation length exponents $\nu \approx 1.0$, which is intrinsically different from the one of the DQCP-type transition, indicating new types of universality classes. Our results explicitly demonstrate a new scenario for understanding the emergence of gapless QSL from an underlying DQCP. The discovered QSL phase survives in a large region of tuning parameters and we expect its experimental realizations in solid state materials or quantum simulators.

   ↳ cond-mat.str-elhep-lathep-thPRX(2022)·52 citations
8. 08*

   Super-Universality in Anderson Localization

   Ivan Horváth🇨🇿 · Peter Markoš🇸🇰

   We calculate the effective spatial dimension $d_{\text{IR}}$ of electron modes at critical points of 3D Anderson models in various universality classes (O,U,S,AIII). The results are equal within errors, and suggest the super-universal value $d_{\text{IR}}=2.665(3)\approx 8/3$. The existence of such a unique marker may help identify natural processes driven by Anderson localization, and provide new insight into the spatial geometry of Anderson transitions. The recently introduced $d_{\text{IR}}$ is a measure-based dimension of Minkowski/Hausdorff type, designed to characterize probability-induced effective subsets.

   ↳ cond-mat.dis-nnhep-lathep-thPRL(2022)·7 citations
9. 09*

   The $\gamma \pi \to \pi \pi$ anomaly from lattice QCD and dispersion relations

   Malwin Niehus🇩🇪 · Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪

   We propose a formalism to extract the $\gamma \pi \to \pi \pi$ chiral anomaly $F_{3\pi }$ from calculations in lattice QCD performed at larger-than-physical pion masses. To this end, we start from a dispersive representation of the ${\gamma }^{(\ast )}\pi \to \pi \pi$ amplitude, whose main quark-mass dependence arises from the $\pi \pi$ scattering phase shift and can be derived from chiral perturbation theory via the inverse-amplitude method. With parameters constrained by lattice calculations of the $P$-wave phase shift, we use this combination of dispersion relations and effective field theory to extrapolate two recent ${\gamma }^{(\ast )}\pi \to \pi \pi$ calculations in lattice QCD to the physical point. Our formalism allows us to extract the radiative coupling of the $\rho (770)$ meson and, for the first time, the chiral anomaly $F_{3\pi }=38(16)(11){\text{GeV}}^{-3}$. The result is consistent with the chiral prediction albeit within large uncertainties, which will improve in accordance with progress in future lattice-QCD computations.

   ↳ hep-phhep-exhep-latnucl-thJHEP(2021)·35 citations

* 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.