PaperPanorama
FAQ

Nuclear Theory·nucl-th

Friday·August 8, 2025

17 papers—13 primary·4 cross-listed

All17Primary13Cross-lists4
  1. 14

    [Submitted on 6 Aug 2025] (cross-list from hep-ph)

    Anisotropic modifications to the transport phenomena and observables in a hot QCD medium at finite baryon asymmetry

    Shubhalaxmi Rath🇨🇱

    We have studied how the transport of charge and heat as well as associated observables become influenced by a weak-momentum anisotropy arising due to the asymptotic expansion of baryon asymmetric matter in the initial stages of heavy ion collisions. This study facilitates the understanding of the local equilibrium property of the medium through the Knudsen number, and explores the correlation between the heat flow and the charge flow through the Lorenz number in the Wiedemann-Franz law for an anisotropic hot QCD medium at finite baryon asymmetry. We have determined the electrical and the thermal conductivities by solving the relativistic Boltzmann transport equation in the relaxation time approximation within the kinetic theory approach. The interactions among partons are appended through their distribution functions within the quasiparticle model of the hot QCD medium at finite temperature, anisotropy and baryon asymmetry. We have observed a decrease in both electrical and thermal conductivities in the presence of expansion-induced anisotropy for baryonless scenario as well as for baryon asymmetric scenario. Conversely, these conductivities are found to be larger in the baryon asymmetric matter as compared to their counterparts in the baryonless matter. The impact of anisotropy on the baryon asymmetric matter is as conspicuous as on the baryonless matter. The above results are attributed to the squeezing of the distribution function due to the momentum anisotropy generated by the asymptotic expansion of baryon asymmetric matter and the dispersion relations of partons in the presence of anisotropy. Additionally, the aforesaid observables are also modulated by the expansion-induced anisotropy in the baryon asymmetric medium, indicating new predictions for the equilibrium characteristic and the relative behavior between the heat and charge flow for the said medium.

    Comments:
    29 pages, 8 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2508.04934 [pdf]
    EPJA(2026)·3 citations
  2. 15

    [Submitted on 7 Aug 2025] (cross-list from quant-ph)

    Optimal Qubit Purification and Unitary Schur Sampling via Random SWAP Tests

    Shrigyan Brahmachari🇺🇸 · Austin Hulse🇺🇸 · Henry D. Pfister🇺🇸 · Iman Marvian🇺🇸

    The goal of qubit purification is to combine multiple noisy copies of an unknown pure quantum state to obtain one or more copies that are closer to the pure state. We show that a simple protocol based solely on random SWAP tests achieves the same fidelity as the Schur transform, which is optimal. This protocol relies only on elementary two-qubit SWAP tests, which project a pair of qubits onto the singlet or triplet subspaces, to identify and isolate singlet pairs, and then proceeds with the remaining qubits. For a system of qubits, we show that after approximately random SWAP tests, a sharp transition occurs: the probability of detecting any new singlet decreases exponentially with . Similarly, the fidelity of each remaining qubit approaches the optimal value given by the Schur transform, up to an error that is exponentially small in . More broadly, this protocol achieves what is known as weak Schur sampling and unitary Schur sampling with error , after only SWAP tests. That is, it provides a lossless method for extracting any information invariant under permutations of qubits, making it a powerful subroutine for tasks such as quantum state tomography and metrology.

    Comments:
    9 pages + 17 pages of Appendices; 5 figures; V2: A reference is added, typos corrected. Comments Welcome!
    Subjects:
    Quantum Physics (quant-ph); cond-mat.dis-nn (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
    arXiv:
    2508.05046 [pdf]
    5 citations
  3. 16

    [Submitted on 7 Aug 2025] (cross-list from hep-ph)

    On the origin of the scaling in the confined but chirally symmetric phase at high T

    L. Ya. Glozman🇦🇹

    There is lattice evidence that the QCD matter above the chiral restoration temperature Tch and below the deconfinement temperature Td, called stringy fluid, is characterized by an approximate chiral spin symmetry, which is a symmetry of confinement in QCD with light quarks. The energy density, pressure and entropy density in the stringy fluid scale as Nc^1, which is in contrast to the Nc^0 scaling in the hadron gas and to the Nc^2 scaling in the quark-gluon plasma. Here we clarify the origin of the Nc^1 scaling. We employ a solvable field-theoretical large chirally symmetric and confining model. In vacuum the confining potential induces a spontaneous breaking of chiral symmetry. The mesons are spatially localized states of quarks and antiquarks. Still in the confining regime the system undergoes the chiral restoration phase transition at because of Paili blocking of the quark levels required for the existence of the quark condensate, by the thermal excitation of quarks and antiquarks. The same Paili blocking leads to a delocalization of the color singlet low-spin meson-like states that become infinitely large in the chiral limit. Consequently the stringy fluid represents a very dense medium of the overlapping huge color-singlet low-spin quark-antiquark systems. The Bethe-Salpeter equation that determines the rest-frame excitation energies of the color-singlet quark-antiquark system is Nc-independent both in vacuum and in the medium in the confining regime. The excitation energy of the quark-antiquark color-singlet systems scales as Nc^0, i.e. as meson mass in vacuum. The Nc^1 scaling of the energy density in the stringy fluid is provided by the fluctuations of the color-singlet quark-antiquark systems.

    Comments:
    8 pages, final version accepted by EPJC
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2508.05277 [pdf]
    EPJC(2025)·4 citations
  4. 17

    [Submitted on 7 Aug 2025] (cross-list from hep-ph)

    Vertex corrections and wavefunction renormalization for atoms, nuclei, and other heavy composite particles

    Ryan Plestid🇺🇸 · Mark B. Wise🇺🇸

    We study QED corrections to operator matrix elements involving heavy composite particles (e.g., heavy-mesons, nuclei, and atoms). We define a new notion of reducible and irreducible graphs which is useful for systems with many discrete excited states. The equivalence of the LSZ reduction formula and old fashioned perturbation theory is explicitly demonstrated. The self energy and vertex corrections are defined (to all orders), and the one-loop corrections are reduced to operator matrix elements which may be evaluated by hadronic, nuclear, or atomic theorists. The gauge dependence of the various pieces are studied in detail at one loop, and cancellation of spurious contributions are demonstrated in a class of covariant gauges; Coulomb gauge is also discussed. The formalism is applied to superallowed beta decay where the one-loop structure is connected to existing literature based on current algebra techniques. We further identify the well known isospin breaking correction from the intranuclear Coulomb field as arising from two-loop diagrams. We comment on future applications of our results to the radiative corrections necessary in extractions of , in particular for corrections that required beyond one-loop order.

    Comments:
    Results unchanged, but discussion has been modified to reflect proper mapping to existing literature. Thanks to Chien-Yeah Seng for helping us understand mapping to existing results
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2508.05540 [pdf]
    PRD(2026)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE