Mon·Nov 1, 2021Monday·November 1, 2021

1. 01*

   CP-violating Dashen phase transition in the two-flavor Schwinger model: a study with matrix product states

   Lena Funcke🇺🇸 · Karl Jansen🇩🇪 · Stefan Kühn🇨🇾

   We numerically study the Hamiltonian lattice formulation of the two-flavor Schwinger model using matrix product states. Keeping the mass of the first flavor at a fixed positive value, we tune the mass of the second flavor through a range of negative values, thus exploring a regime where conventional Monte Carlo methods suffer from the sign problem and may run into instabilities due to zero modes. Our results indicate a phase transition at the point where the absolute value of the second flavor mass approaches the first flavor mass. The phase transition is accompanied by the formation of a fermion condensate, a steep drop of the average electric field, and a peak in the bipartite entanglement entropy. Our data hints at a second order transition, which is the 1+1D analog of the CP-violating Dashen phase transition in QCD.

   hep-latcond-mat.str-elquant-phPoS(2022)·6 citations
2. 02*

   Exploring SU(3)-Higgs theories

   Elizabeth Dobson🇦🇹 · Axel Maas🇦🇹 · Bernd Riederer🇦🇹

   The requirement of manifest gauge invariance leads to a conflict between perturbative and non-perturbative predictions for the low-energy spectra of grand-unified theories. These conflicts already emerge in simplified prototype models of SU(3) gauge theories with Higgs fields in different representations. We expand earlier lattice investigations on this subject and provide further support for the predicted deviations. These can be understood in terms of the Froehlich-Morchio-Strocchi mechanism.

   hep-latPoS(2022)·5 citations
3. 03*

   $\pi \pi$ scattering at Large $N_{\text{c}}$

   Jorge Baeza-Ballesteros🇪🇸 · Pilar Hernández🇪🇸 · Fernando Romero-López🇺🇸

   We study the Large $N_{\text{c}}$ scaling of pion-pion scattering amplitudes for $N_{\text{f}}=4$ degenerate quark flavors. We focus on the standard isospin-2 channel and the adjoint-antisymmetric (AA) representation. The latter only exists for $N_{\text{f}}\ge 4$ and a representative state is $\frac{1}{\sqrt{2}}(|D_s^{+}{\pi }^{+}⟩-|D^{+}{K}^{+}⟩)$. We compare the results obtained for two regularizations (Wilson and twisted-mass fermions) and three values of the lattice spacing, and observe significant discretization effects in the AA channel. Finally, we match our results to NLO SU(4) and NNLO U(4) Chiral Perturbation Theory and constrain the $N_{\text{c}}$ scaling of the relevant low-energy couplings.

   hep-latPoS(2022)·2 citations
4. 04*

   The electroweak Hamiltonian in the gradient flow formalism

   Robert Harlander🇩🇪 · Fabian Lange🇩🇪

   Over the last decade the gradient flow formalism has become an important tool for lattice simulations of Quantum Chromodynamics. It offers remarkable renormalization properties which pave the way for cross-fertilization between perturbative and lattice calculations. In this contribution we report on the construction of the flowed operator product expansion for the current-current operators of the electroweak Hamiltonian at NNLO QCD. This allows for simpler transformations between lattice and perturbative schemes and might reduce the uncertainties of theoretical predictions for low-energy flavor observables.

   hep-lathep-phPoS(2022)·1 citation
5. 05*

   Structure-Dependent Electromagnetic Finite-Size Effects

   Matteo Di Carlo🇬🇧 · Maxwell T. Hansen🇬🇧 · Nils Hermansson-Truedsson🇨🇭 · Antonin Portelli🇬🇧

   We present a model-independent and relativistic approach to analytically derive electromagnetic finite-size effects beyond the point-like approximation. The key element is the use of electromagnetic Ward identities to constrain vertex functions, and structure-dependence appears via physical form-factors and their derivatives. We apply our general method to study the leading finite-size structure-dependence in the pseudoscalar mass (at order $1/L^3$) as well as in the leptonic decay amplitudes of pions and kaons (at order $1/L^2$). Knowledge of the latter is essential for Standard Model precision tests in the flavour physics sector from lattice simulations.

   hep-lathep-phhep-thPoS(2024)·0 citations
6. 06*

   Contribution to understanding the phase structure of strong interaction matter: Lee-Yang edge singularities from lattice QCD

   P. Dimopoulos🇮🇹 · L. Dini🇩🇪 · F. Di Renzo🇮🇹 · J. Goswami🇩🇪 · G. Nicotra🇩🇪 · C. Schmidt🇩🇪 · S. Singh🇮🇹 · K. Zambello🇮🇹 · F. Ziesché🇩🇪

   We present a calculation of the net baryon number density as a function of imaginary baryon number chemical potential, obtained with highly improved staggered quarks (HISQ) at temporal lattice extent of $N_{\tau }=4,6$. We construct various rational function approximations of the lattice data and discuss how poles in the complex plane can be determined from them. We compare our results of the singularities in the chemical potential plane to the theoretically expected positions of the Lee-Yang edge singularity in the vicinity of the Roberge-Weiss and chiral phase transitions. We find a temperature scaling that is in accordance with the expected power law behavior.

   hep-latPRD(2022)·81 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.