PaperPanorama
FAQ

Nuclear Theory·nucl-th

Thursday·December 14, 2023

13 papers—8 primary·5 cross-listed

All13Primary8Cross-lists5
  1. 09

    [Submitted on 12 Dec 2023] (cross-list from hep-lat)

    Continuum extrapolated high order baryon fluctuations

    Szabolcs Borsányi🇩🇪 · Zoltán Fodor🇩🇪 · Jana N. Guenther🇩🇪 · Sándor D. Katz🇭🇺 · Paolo Parotto🇺🇸 · Attila Pásztor🇭🇺 · Dávid Pesznyák🇭🇺 · Kálmán K. Szabó🇩🇪 · Chik Him Wong🇩🇪

    Fluctuations play a key role in the study of QCD phases. Lattice QCD is a valuable tool to calculate them, but going to high orders is challenging. Up to the fourth order, continuum results are available since 2015. We present the first continuum results for sixth order baryon fluctuations for temperatures between MeV, and eighth order at MeV in a fixed volume. We show that for MeV, relevant for criticality search, finite volume effects are under control. Our results are in sharp contrast with well known results in the literature obtained at finite lattice spacing.

    Comments:
    5 pages, 2 figures (main text) + 5 pages, 7 figures (supplemental material)
    Subjects:
    High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2312.07528 [pdf]
    PRD(2024)·34 citations
  2. 10

    [Submitted on 13 Dec 2023] (cross-list from hep-lat)

    Leveraging neural control variates for enhanced precision in lattice field theory

    Paulo F. Bedaque🇺🇸 · Hyunwoo Oh🇺🇸

    Results obtained with stochastic methods have an inherent uncertainty due to the finite number of samples that can be achieved in practice. In lattice QCD this problem is particularly salient in some observables like, for instance, observables involving one or more baryons and it is the main problem preventing the calculation of nuclear forces from first principles. The method of control variables has been used extensively in statistics and it amounts to computing the expectation value of the difference between the observable of interest and another observable whose average is known to be zero but is correlated with the observable of interest. Recently, control variates methods emerged as a promising solution in the context of lattice field theories. In our current study, instead of relying on an educated guess to determine the control variate, we utilize a neural network to parametrize this function. Using 1+1 dimensional scalar field theory as a testbed, we demonstrate that this neural network approach yields substantial improvements. Notably, our findings indicate that the neural network ansatz is particularly effective in the strong coupling regime.

    Comments:
    6 pages, 3 figures
    Subjects:
    High Energy Physics — Lattice (hep-lat); Machine Learning (cs.LG); Nuclear Theory (nucl-th)
    arXiv:
    2312.08228 [pdf]
    PRD(2024)·14 citations
  3. 11

    [Submitted on 13 Dec 2023] (cross-list from cond-mat.quant-gas)

    Complex-valued in-medium potential between heavy impurities in ultracold atoms

    Yukinao Akamatsu · Shimpei Endo · Keisuke Fujii · Masaru Hongo

    We formulate the induced potential in a finite temperature cold atomic medium between two heavy impurities, or polarons, which is shown to be \textit{complex-valued} in general. The imaginary part of the complex-valued potential describes a decoherence effect, and thus, the resulting Schrödinger equation for the two polarons acquires a non-Hermitian term. We apply the developed formulation to two representative cases of polarons interacting with medium particles through the -wave contact interaction: (i) the normal phase of single-component (i.e., spin-polarized) fermions using the fermionic field theory, and (ii) a superfluid phase using the superfluid effective field theory, which is valid either for a Bose-Einstein condensate (BEC) of a single-component Bose gas or for the BEC-BCS crossover in two-component fermions at a low-energy regime. Computing the leading-order term, the imaginary part of the potential in both cases is found to show a universal behavior at long distance. We propose three experimental ways to observe the effects of the universal imaginary potential in cold atoms.

    Comments:
    16 pages, version accepted for publication in Phys. Rev. A
    Subjects:
    Quantum Gases (cond-mat.quant-gas); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2312.08241 [pdf]
    PRA(2024)·1 citation
  4. 12

    [Submitted on 13 Dec 2023] (cross-list from hep-ph)

    Spin relaxation rate for baryons in thermal pion gas

    Yoshimasa Hidaka🇯🇵 · Masaru Hongo🇯🇵 · Mikhail Stephanov🇺🇸 · Ho-Ung Yee🇺🇸

    We study the relaxation dynamics of the spin polarization of baryons (nucleon and -baryon), in a thermal pion gas as a simple model of the hadronic phase of the QCD plasma produced in relativistic heavy-ion collisions. For this purpose, we formulate the quantum kinetic theory for the spin density matrix of baryons in the leading order of the gradient expansion. Considering the baryon-pion elastic scattering processes as the dominant interaction between baryons and thermal pions, we compute the spin relaxation rate of nucleons and -baryons in a pion gas up to temperature 200 MeV. In the case of nucleons, we evaluate the spin relaxation rate in the -channel resonance approximation, based on the known experimental data on -resonances. We also estimate the spin relaxation rate for -baryons, based on experimental inputs and theoretical models for the low-energy scattering, including the chiral perturbation theory.

    Comments:
    16 pages, 8 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2312.08266 [pdf]
    PRC(2024)·25 citations
  5. 13

    [Submitted on 13 Dec 2023] (cross-list from hep-ph)

    Nonrelativistic nuclear reduction for tensor couplings in dark matter direct detection and conversion

    Ayala Glick-Magid🇺🇸

    The nonrelativistic effective field theory (NRET) is widely used in dark matter direct detection and charged-lepton flavor violation studies through conversion. However, existing literature has not fully considered tensor couplings. This study fills this gap by utilizing an innovative tensor decomposition method, extending NRET to incorporate previously overlooked tensor interactions. This development is expected to have a significant impact on ongoing experiments seeking physics beyond the Standard Model and on our understanding of the new-physics interactions. Notably, we identify additional operators in conversion that are absent in scalar and vector couplings. To support further research and experimental analyses, comprehensive tables featuring tensor matrix elements and their corresponding operators are provided.

    Comments:
    9 pages, 3 tables, accepted version by PRD
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2312.08339 [pdf]
    PRD(2024)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE