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Nuclear Theory·nucl-th

Friday·August 30, 2024

10 papers—7 primary·3 cross-listed

All10Primary7Cross-lists3
  1. 08

    [Submitted on 29 Aug 2024] (cross-list from quant-ph)

    Quantum decoherence from complex saddle points

    Jun Nishimura · Hiromasa Watanabe

    Quantum decoherence is the effect that bridges quantum physics to well-understood classical physics. As such, it plays a crucial role in understanding the mysterious nature of quantum physics. Quantum decoherence is also a source of quantum noise that has to be well under control in quantum computing and in various experiments based on quantum technologies. Here we point out that quantum decoherence can be captured by saddle points in the Feynman path integral in much the same way as quantum tunneling can be captured by instantons. In particular, we present some first-principle calculations in the Caldeira-Leggett model, which reproduce the predicted scaling behavior of quantum decoherence with respect to the parameters of the environment, such as the temperature and the coupling to the system of interest. We also discuss how to extend our approach to general models by Monte Carlo calculations using a recently developed method to overcome the sign problem.

    Comments:
    6 pages, 3 figures; v2: the version accepted for publication in Physical Review Letters
    Subjects:
    Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2408.16627 [pdf]
    PRL(2025)·3 citations
  2. 09

    [Submitted on 29 Aug 2024] (cross-list from nucl-ex)

    Flavor Dependence of Charged Pion Fragmentation Functions

    H. Bhatt🇺🇸 · P. Bosted🇺🇸 · S. Jia🇺🇸 · W. Armstrong🇺🇸 · D. Dutta🇺🇸 · R. Ent🇺🇸 · D. Gaskell🇺🇸 · E. Kinney🇺🇸 · H. Mkrtchyan🇦🇲 · S. Ali🇺🇸 · R. Ambrose🇨🇦 · D. Androic🇭🇷 and 58 other authors

    We have measured the flavor dependence of multiplicities for pi^+ and pi^- production in semi-inclusive deep-inelastic scattering (SIDIS) on proton and deuteron targets to explore a possible charge symmetry violation in fragmentation functions. The experiment used an electron beam with energies of 10.2 and 10.6 GeV at Jefferson Lab and the Hall-C spectrometers. The electron kinematics spanned the range 0.3<x<0.6, 2<Q^2<5.5 GeV^2, and 4<W^2<11 GeV^2. The pion fractional momentum range was 0.3< z <0.7, and the transverse momentum range was 0<p_T<0.25 GeV/c. Assuming factorization at low p_T and allowing for isospin breaking, we find that the results can be described by two "favored" and two "un-favored" effective low fragmentation functions that are flavor-dependent. However, they converge to a common flavor-independent value at the lowest x or highest W of this experiment.

    Comments:
    6 pages, 3 figures with 11 pages of supplementary material which has 9 figures
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2408.16640 [pdf]
    PLB(2025)·7 citations
  3. 10

    [Submitted on 29 Aug 2024] (cross-list from cond-mat.quant-gas)

    Pseudogap regime of the unitary Fermi gas with lattice auxiliary-field quantum Monte Carlo in the continuum limit

    S. Jensen · C. N. Gilbreth · Y. Alhassid

    The unitary Fermi gas (UFG) is a strongly correlated system of two-species (spin-1/2) fermions with a short-range attractive interaction modeled by a contact interaction and has attracted much interest across different disciplines. The UFG is considered a paradigm for strongly correlated superfluids and has been investigated extensively, with generally good agreement found between theory and experiment. However, the extent of a pseudogap regime above the critical temperature for superfluidity is still debated both theoretically and experimentally. Here we study thermodynamic properties of the UFG across the superfluid phase transition using finite-temperature lattice auxiliary-field quantum Monte Carlo (AFMC) methods in the canonical ensemble of fixed particle numbers. We extrapolate our lattice AFMC results to the continuous time and continuum limits, thus removing the systematic error associated with the finite filling factor of previous AFMC studies. We determine the critical temperature to be . For the largest particle number studied , the energy-staggering pairing gap is suppressed above a pairing scale temperature of . The spin susceptibility displays moderate suppression above with a spin gap temperature of . We also calculate a free energy-staggering pairing gap, which shows substantially reduced statistical errors when compared with the energy-staggering gap, allowing for a clear signature of pairing correlations in the finite-size system. All results indicate that the pseudogap regime is narrow, with pseudogap signatures emerging at temperatures below . The reduced statistical errors of the free energy gap enable an extrapolation at low temperatures, allowing an estimate of the zero-temperature pairing gap .

    Comments:
    18 pages, 7 figures
    Subjects:
    Quantum Gases (cond-mat.quant-gas); Superconductivity (cond-mat.supr-con); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2408.16676 [pdf]
    1 citation

Affiliations

first authorsco-authorsvia INSPIRE