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Nuclear Theory·nucl-th

Wednesday·June 24, 2026

11 papers—3 primary·8 cross-listed

All11Primary3Cross-lists8
  1. 01

    [Submitted on 22 Jun 2026]

    As above, so below: assessing extremeness of the neutron-star equation of state based on the unstable branch

    Tyler Gorda · Oleg Komoltsev · Aleksi Kurkela · Jürgen Schaffner-Bielich

    Microscopic models of neutron-star matter have been widely used in astrophysical applications. The focus of attention has been on densities up to the maximal densities reached in stable neutron stars. The possibility that the underlying model assumptions may have important implications at higher densities has not been addressed. Here, we show that the behaviour at higher densities is strongly constrained by requiring a causal, stable, and thermodynamically consistent extension to the perturbative-QCD regime. We explicitly reveal what that behaviour must be and provide a tool for constructing and visualizing such extensions. We find that purely hadronic models trusted up to the maximal central density often require radically different behaviour at higher densities from that assumed in the original model, while models with additional degrees of freedom fare better. Our analysis disfavors purely nucleonic models for describing all stable neutron stars and supports the appearance of some type of additional degrees of freedom in stable massive neutron stars.

    Comments:
    9 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Theory (hep-th)
    arXiv:
    2606.23929 [pdf]
    2 citations
  2. 02

    [Submitted on 23 Jun 2026]

    Understanding the Intermittency Signal in RHIC-STAR Data through Modeling

    Jin Wu🇨🇳 · Zhiming Li🇨🇳 · Mingmei Xu🇨🇳 · Shuyun Yang🇨🇳 · Ranran Guo🇨🇳 · Yuanfang Wu🇨🇳

    Intermittency analysis provides a promising probe of scale-invariant density fluctuations near the QCD critical point. The intermittency measurements reported in the STAR BES-I data call for a quantitative assessment of the signal strength and a clearer physical understanding of its collision-energy dependence. In this work, we perform such a study for the STAR measurements using an improved hybrid UrQMD+CMC model, in which critical-like fluctuations are embedded into a realistic non-critical background through event-level, particle-level, and combined replacement schemes. By directly comparing the second-order factorial moment between model calculations and experimental data on a point-by-point basis, we constrain the effective critical-like contribution compatible with the STAR measurements without relying on scaling exponents. The STAR data at -- used for model comparison can be consistently described only by small and nearly energy-independent effective critical-like fractions. These results indicate that the current BES-I intermittency signal is weak and exhibits little collision-energy dependence, thereby favoring only a limited critical-like contribution rather than a strong critical-point-induced enhancement localized near a specific collision energy.

    Comments:
    10 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2606.24436 [pdf]
    0 citations
  3. 03

    [Submitted on 23 Jun 2026]

    Mass-Dependent Non-Extensivity in Tsallis Blast-Wave Fits to Identified Hadron Spectra at RHIC and LHC

    C.Y. Tsang🇺🇸 · Z. Xu🇺🇸

    We analyze identified-hadron transverse-momentum spectra from STAR Au+Au and ALICE Pb+Pb collisions over ~GeV--~TeV using an extended Tsallis Blast-Wave (TBW) framework, which includes a non-extensivity parameter to quantify the degree of incomplete thermal equilibrium. Conventionally, either a common value of , or two separate values, one for mesons and one for baryons, are used to describe particle spectra in the TBW framework, with the latter being referred to as TBW4 in Ref.~\cite{Chen:2020zuw}. This work extends the TBW framework by studying the dependence of on different kinds of particles in detail. Fits allowing independent non-extensivity parameters for each species reveal a systematic correlation between and particle mass, except for quarkonia. Motivated by this trend, we introduce two new parameterizations: TBW5, which posits that depends linearly on particle mass, and TBW6, which allows the intercepts for mesons and baryons to differ. Across all energies and centralities considered in this study, TBW5 improves relative to the TBW4 fit in 71\% of the datasets, while TBW6 shows improvement in 94\% of the datasets. They perform especially well in central collisions. These results demonstrate a robust mass ordering in non-equilibrium behavior at kinetic freeze-out and provide a more accurate description of hadron spectra from RHIC to LHC energies.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2606.24777 [pdf]
    0 citations

Affiliations

first authorsco-authorsvia INSPIRE