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Nuclear Theory·nucl-th

Wednesday·January 7, 2026

5 papers—2 primary·3 cross-listed

All5Primary2Cross-lists3
  1. 03

    [Submitted on 5 Jan 2026] (cross-list from hep-ph)

    Helicity Dependent Distribution Functions of the Proton and and Baryons

    Yang Yu🇨🇳 · Peng Cheng🇨🇳 · Hui-Yu Xing🇨🇳 · Daniele Binosi🇮🇹 · Craig D. Roberts🇨🇳

    Using continuum Schwinger function methods, a coherent set of predictions for proton, and distribution functions (DFs) has been made available -- both helicity dependent and unpolarised. The results and comparisons between them reveal impacts of diquark correlations and SU-flavour symmetry breaking, some of which are highlighted in this contribution. For instance: in-proton ratios of helicity-dependent/unpolarised valence-quark DFs are presented; it is highlighted that, were it not for the presence of axialvector diquarks in the , the valence strange quark would carry none of the spin; and the sign and size of polarised gluon DFs is discussed -- at a scale typical of modern measurements, gluon partons carry roughly 40% of each octet baryon's spin.

    Comments:
    9 pages, 1 figure. Contribution to the proceedings of the 26th International Symposium on Spin Physics (SPIN25) -- A Century of Spin, 2025 September 22-26, Qingdao Haitian Hotel, Qingdao, Shandong Province, China
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2601.02587 [pdf]
    0 citations
  2. 04

    [Submitted on 6 Jan 2026] (cross-list from gr-qc)

    How Lorentz boosts reshape relaxation spectra

    Lorenzo Gavassino🇬🇧

    In relativity, relaxation processes are often assumed to undergo time dilation under Lorentz boosts. We show that this intuition fails generically. Due to relativity of simultaneity, Lorentz boosts can split a single relaxation mode into a continuum of excitations, with a width set by the maximal signal propagation speed. Focusing on linearized relativistic (kinetic or rheological) theories with an Onsager-type symmetry, we derive rigorous bounds on relaxation spectra in arbitrary inertial frames, expressed solely in terms of rest-frame spectral data at zero wavenumber. As a consequence, non-hydrodynamic gaps, maximal relaxation rates, and the convergence radii of hydrodynamic modes obey nontrivial Lorentz-covariant constraints. These results provide a unified framework for understanding how relativity constrains relaxation dynamics in many-body systems.

    Comments:
    6 pages and 2 figures (main text) + 6 pages and 3 figures (supplementary material), published in PRL (see https://journals.aps.org/prl/abstract/10.1103/d2xr-rj7g)
    Subjects:
    General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2601.03081 [pdf]
    PRL(2026)·11 citations
  3. 05

    [Submitted on 6 Jan 2026] (cross-list from hep-ph)

    Anatomy of Roper Resonance

    Igor Strakovsky (GWU)🇺🇸

    Sixty years ago, the first excited state of a proton/neutron was ``born.'' During this time, we learned a lot about it, specifically - how unique this case is: a single resonance with two pole positions on different Riemann sheets. Let me present a brief history to remind readers how development progressed. Sure, history is sometimes something that never happened, described by those who were never there...

    Comments:
    6 pages, 3 figures, 1 table; It is a great pleasure to dedicate this article to Dave Roper on his ninetieth birthday
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2601.03102 [pdf]
    Acta Phys.Polon.B(2026)·0 citations

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first authorsco-authorsvia INSPIRE