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Nuclear Theory·nucl-th

Wednesday·August 6, 2025

10 papers—5 primary·5 cross-listed

All10Primary5Cross-lists5
  1. 06

    Second-order renormalized Hamiltonian of Yukawa theory

    Kamil Serafin🇺🇸 · Carter M. Gustin🇺🇸 · Peter J. Love🇨🇦

    Using the renormalization group procedure for effective particles (RGPEP) we calculate the effective Hamiltonians in the theory of a fermion field coupled to a scalar field via the Yukawa interaction. The theory is renormalized by the addition of counterterms. Necessary counterterms are determined by computing matrix elements of the effective Hamiltonian. All calculations are performed up to the second order in the expansion in powers of the coupling constant. Renormalized effective Hamiltonians are well-defined symmetric forms acting in the Fock space as opposed to the renormalized bare Hamiltonian, which is not well-defined without regularization. We introduce computational techniques that should streamline higher-order calculations and may be of independent interest.

    ↳ hep-phnucl-thPRD(2025)·3 citations
  2. 07

    Lattice results for the equation of state in dense QCD-like theories

    Etsuko Itou🇯🇵

    We review recent progress in Monte Carlo simulations of dense two-color QCD (QCD), focusing on the phase diagram, the equation of state, and the sound velocity in the low-temperature regime. In three-color QCD at finite density, especially at low temperatures, the notorious sign problem makes lattice Monte Carlo simulations intractable. In contrast, QCD is free from this issue due to the pseudoreality of the quark representation. Recent independent lattice studies have revealed unexpected phenomena through first-principles calculations of the phase structure and thermodynamics. A particularly notable finding is that the sound velocity exceeds the so-called conformal (holography) bound, \( c_s^2/c^2 \le 1/3 \), which had not been observed in QCD-like theories at finite temperature. In this review, we focus primarily on results from a series of works by our group~\cite{Iida:2019rah, Iida:2020emi,Iida:2022hyy, Ishiguro:2021yxr, Iida:2024irv}, along with related studies in dense QCD and three-color QCD with isospin chemical potential. We discuss the possibility and physical implications of conformal bound violation even for three-color dense QCD, together with insights from effective model analyses and recent observations of neutron stars.

    ↳ hep-lathep-phhep-thnucl-thUniverse(2025)·11 citations
  3. 08

    Probing non-perturbative QCD aspects on particle production in pp collisions with forward-backward correlations using \texttt{PYTHIA8}

    Rohit Agarwala🇮🇳 · Kalyan Dey🇮🇳

    We employ PYTHIA8 simulations to study forward-backward (FB) correlations in pp collisions at LHC energies, probing non-perturbative QCD dynamics via color reconnection (CR) and QCD radiation (ISR/FSR). Using \texttt{PYTHIA8} (v8.311) under ALICE/ATLAS kinematics, we analyze: extensive: FB multiplicity () and summed () correlations; intensive: FB mean () correlations; and \textit{strongly intensive:} quantity in symmetric pseudorapidity intervals, validated against available experimental data. Systematic studies of as functions of , , and - sectors show MPI-based CR (ranges 3.6, 5.4) and QCD Color Rope significantly improve agreement with data. ISR/FSR critically influence and , with ISR dominant than FSR. Disabling ISR/FSR fails to replicate -dependent trends. Further, shows minimal CR-range sensitivity but the correlation strength increases when CR is disabled. Intensive quantity, , exhibit the opposite behavior to extensive observables i.e. the magnitude of increases with the increase of CR strength, highlighting the distinct influence of CR on intensive versus extensive observables. Its azimuthal dependence indicates that parton showers drive short-range correlations. The analysis of the strongly intensive quantity as a function of pseudorapidity gap indicates that FSR plays a dominant role at larger gaps, in contrast to the behavior observed in FB multiplicity correlations.

    ↳ hep-phnucl-th0 citations
  4. 09

    New computational methods in lattice gauge theory -- quantum computation and tensor networks

    Etsuko Itou🇯🇵

    Lattice QCD calculations have been conducted using large-scale classical computers based on the Lagrangian formalism of field theory for the past 40 years. On the other hand, the advent of quantum computers has brought increasing attention to first-principles computational methods based on the Hamiltonian formalism compatible with these machines. In this talk, we discuss recent results on how to calculate hadronic properties using the Hamiltonian formalism.

    ↳ hep-lathep-phnucl-thquant-phPoS(2026)·2 citations
  5. 10

    Hyperon spin correlation in high-energy heavy-ion collisions

    Xin-Li Sheng🇮🇹 · Xiang-Yu Wu🇨🇦 · Dirk H. Rischke🇩🇪 · Xin-Nian Wang🇨🇳

    Recent experimental data show an unexpectedly large spin alignment of mesons in high-energy heavy-ion collisions, which can be explained by short-distance fluctuations of strong-force fields (vector fields) within the constituent-quark model. We calculate the hyperon spin correlations within the same model, taking into account hydrodynamic effects and a field fluctuating in space-time according to a Gaussian distribution. The spin correlation induced by the field is shown to be negative as opposed to that of or . We thus propose a new net spin-correlation observable as a sensitive probe to separate strong-force effects from hydrodynamic ones. With the strength of the field fluctuations extracted from the observed spin alignment, we predict the collision-energy dependence of the hyperon spin correlations and also investigate the dependence of the net spin correlation on azimuthal-angle and rapidity difference.

    ↳ hep-phnucl-thPRL(2026)·12 citations

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first authorsco-authorsvia INSPIRE