Tue·Dec 13, 2022Tuesday·December 13, 2022

1. 01*

   Dynamical solution of the strong CP problem within QCD ?

   Gerrit Schierholz🇩🇪

   The strong CP problem is inseparably connected with the topology of gauge fields and the mechanism of color confinement, which requires nonperturbative tools to solve it. In this talk I present results of a recent lattice investigation of QCD with the $\theta$ term in collaboration with Yoshifumi Nakamura. The tool we are using to address the nonperturbative properties of the theory is the gradient flow, which is a particular realization of momentum space RG transformations. The novel result is that within QCD the vacuum angle $\theta$ is renormalized, together with the strong coupling constant, and flows to $\theta =0$ in the infrared limit. This means that CP is conserved by the strong interactions.

   hep-lathep-phhep-thnucl-thEPJ Web Conf.(2022)·8 citations
2. 02*

   Estimation of the photon production rate using imaginary momentum correlators

   Csaba Török🇩🇪 · Marco Cè🇨🇭 · Tim Harris🇬🇧 · Ardit Krasniqi🇩🇪 · Harvey B. Meyer🇩🇪 · Samuel Ruhl🇩🇪

   The thermal photon emission rate is determined by the spatially transverse, in-medium spectral function of the electromagnetic current. Accessing the spectral function using Euclidean data is, however, a challenging problem due to the ill-posed nature of inverting the Laplace transform. In this contribution, we present the first results on implementing the proposal of directly computing the analytic continuation of the retarded correlator at fixed, vanishing virtuality of the photon via the calculation of the appropriate Euclidean correlator at imaginary spatial momentum. We employ two dynamical O(a)-improved Wilson fermions at a temperature of 250 MeV.

   hep-latPoS(2023)·6 citations
3. 03*

   Inhomogeneous phases in the 3+1-dimensional Nambu-Jona-Lasinio model and their dependence on the regularization scheme

   Laurin Pannullo🇩🇪 · Marc Wagner🇩🇪 · Marc Winstel🇩🇪

   In this work we study the $3+1$-dimensional Nambu-Jona-Lasinio (NJL) model in the mean field-approximation. We carry out calculations using five different regularization schemes (two continuum and three lattice regularization schemes) with particular focus on inhomogeneous phases and condensates. The regularization schemes lead to drastically different inhomogeneous regions. We provide evidence that inhomogeneous condensates appear for all regularization schemes almost exclusively at values of the chemical potential and with wave numbers, which are of the order of or even larger than the corresponding regulators. This can be interpreted as indication that inhomogeneous phases in the $3+1$-dimensional NJL model are rather artifacts of the regularization and not a consequence of the NJL Lagrangian and its symmetries.

   hep-lathep-phPoS(2023)·20 citations
4. 04*

   Topology and the Dirac Spectrum in Hot QCD

   Tamas G. Kovacs (Eotvos U. and Debrecen, Inst. Nucl. Res.)🇭🇺

   It is known that contrary to expectations, the order parameter of chiral symmetry breaking, the Dirac spectral density at zero virtuality does not vanish above the critical temperature of QCD. Instead, the spectral density develops a pronounced peak at zero. We show that the spectral density in the peak has large violations of the expected volume scaling. This anomalous scaling and the statistics of these eigenmodes is consistent with them being produced by mixing instanton and antiinstanton zero modes. Consequently, we show that a nonvanishing topological usceptibility implies a finite density of eigenvalues around zero, which can have implications on the restoration of chiral symmetry above the critical temperature.

   hep-lathep-thPoS(2023)·1 citation
5. 05*

   Applying NOX Error Mitigation Protocols to Calculate Real-time Quantum Field Theory Scattering Phase Shifts

   Zachary Parks🇺🇸 · Arnaud Carignan-Dugas🇨🇦 · Erik Gustafson🇺🇸 · Yannick Meurice🇺🇸 · Patrick Dreher🇺🇸

   Real-time scattering calculations on a Noisy Intermediate Scale Quantum (NISQ) quantum computer are disrupted by errors that accumulate throughout the circuits. To improve the accuracy of such physics simulations, one can supplement the application circuits with a recent error mitigation strategy known as Noisy Output eXtrapolation (NOX). We tested these error mitigation protocols on a Transverse Field Ising model and improved upon previous calculations of the phase shift. Our proof-of-concept 4-qubit application circuits were run on several IBM quantum computing hardware architectures. Metrics were introduced that show between 21\% and 74\% error reduction for circuit depths ranging from 14 to 37 hard cycles, confirming that the NOX technique applies to circuits with a broad range of failure rates. This observation on different cloud-accessible devices further confirms that NOX provides performance improvements even in the advent where circuits are executed in substantially time-separated batches. Finally, we provide a heuristic method to obtain systematic error bars on the mitigated results, compare them with empirical errors and discuss their effects on phase shift estimates.

   ↳ quant-phhep-lathep-thPRD(2024)·3 citations
6. 06*

   Dirac gauge theory for topological spinors in 3+1 dimensional networks

   Ginestra Bianconi🇬🇧

   Gauge theories on graphs and networks are attracting increasing attention not only as approaches to quantum gravity but also as models for performing quantum computation. Here we propose a Dirac gauge theory for topological spinors in $3+1$ dimensional networks associated to an arbitrary metric. Topological spinors are the direct sum of $0$-cochains and $1$-cochains defined on a network and describe a matter field defined on both nodes and links of a network. Recently in Ref. \cite{bianconi2021topological} it has been shown that topological spinors obey the topological Dirac equation driven by the discrete Dirac operator. In this work we extend these results by formulating the Dirac equation on weighted and directed $3+1$ dimensional networks which allow for the treatment of a local theory. The commutators and anti-commutators of the Dirac operators are non vanishing an they define the curvature tensor and magnetic field of our theory respectively. This interpretation is confirmed by the non-relativistic limit of the proposed Dirac equation. In the non-relativistic limit of the proposed Dirac equation the sector of the spinor defined on links follows the Schrödinger equation with the correct giromagnetic moment, while the sector of the spinor defined on nodes follows the Klein-Gordon equation and is not negligible. The action associated to the proposed field theory comprises of a Dirac action and a metric action. We describe the gauge invariance of the action under both Abelian and non-Abelian transformations and we propose the equation of motion of the field theory of both Dirac and metric fields. This theory can be interpreted as a limiting case of a more general gauge theory valid on any arbitrary network in the limit of almost flat spaces.

   ↳ cond-mat.dis-nncond-mat.stat-mechgr-qchep-lat+1J.Phys.A(2023)·11 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.