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Nuclear Theory·nucl-th

Thursday·March 26, 2026

17 papers—6 primary·11 cross-listed

All17Primary6Cross-lists11
  1. 01

    [Submitted on 24 Mar 2026]

    Equation of state and cumulants of proton multiplicity in equilibrium near critical point from Pade estimates

    Gokce Basar🇺🇸 · Maneesha Pradeep🇮🇳 · Mikhail Stephanov🇺🇸

    The fluctuations of proton multiplicity in heavy-ion collisions are the key observables in the search for the QCD critical point. In this work we present an approach to constraining the cumulants of proton number based on the analytical properties of the QCD equation of state in the vicinity of the critical point. We show that, under the assumption of local equilibrium, the features of the collision energy dependence, such as the peaks and the dips of the cumulants, are significantly constrained by the data on the Lee-Yang singularity structure available via Pade resummation of the lattice QCD data. Furthermore, we identify four topologically distinct scenarios, all within the uncertainty range of the Pade estimates for the non-universal mapping parameters, classified based on the location of the critical point and the slope of the chiral crossover curve with respect to the freeze-out curve. These different scenarios result in qualitatively different critical signatures, especially for the third factorial cumulant and thus could be potentially discriminated using the experimental data.

    Comments:
    23 pages, 13 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2603.23635 [pdf]
    5 citations
  2. 02

    [Submitted on 25 Mar 2026]

    The Effects of Multi- Hyperons on Collective Modes in Nuclei

    Bahruz Suleymanli🇹🇷 · Kutsal Bozkurt🇹🇷 · Elias Khan🇫🇷 · Haşim Güven🇫🇷 · Jerome Margueron🇺🇸

    The dynamical influence of hyperons on the excited-state properties of closed-shell multi- Ca, Ni, Sn and Pb hypernuclei is investigated using the self-consistent Hartree-Fock + Random Phase Approximation in coordinate space. The strength distributions for the isoscalar monopole, isovector dipole, and isoscalar quadrupole modes are calculated, revealing a systematic upward energy shift with increasing hyperon number . The scaling behavior of the computed centroid energies with respect to both the mass and hyperon number is determined. The nuclear incompressibility modulus is found to increase monotonically with . The largest value is found in the Pb hypernucleus, reaching MeV. Calculations in uniform hypernuclear matter confirm that this stiffening is a bulk effect driven by both the and interactions. Analysis of the transition densities for states with maximal collective coherence indicates that the dynamical effect of hyperons is predominantly in phase with the protons, especially in the case of the isovector E1 modes.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2603.23992 [pdf]
    PRC(2026)·0 citations
  3. 03

    [Submitted on 25 Mar 2026]

    Deep learning approaches to extract nuclear deformation parameters from initial-state information in heavy-ion collisions

    Jun-Qi Tao🇨🇳 · Yang Liu🇨🇳 · Yu Sha🇨🇳 · Xiang Fan🇨🇳 · Yan-Sheng Tu🇨🇳 · Kai Zhou🇨🇳 · Hua Zheng🇨🇳 · Ben-Wei Zhang🇨🇳

    The deformation of heavy nuclei leaves characteristic imprints on the initial conditions of relativistic heavy-ion collisions. However, event-by-event fluctuations make the quantitative extraction of this information challenging. This study examines the identifiability of the quadrupole () and hexadecapole () deformation parameters from nucleon configurations sampled from a deformed Woods-Saxon distribution commonly used in initial-state modeling of heavy-ion collisions. As a baseline, we first establish an upper bound on the "intrinsic identifiability" of deformation information at the most microscopic level by constructing permutation-invariant point-cloud networks under controlled multi-event grouping. We then extend the analysis to the more realistic initial entropy-density profiles generated by the TRENTo model, where both standard regression and simulation-based inference (SBI) with conditional normalizing flows are employed to reconstruct the deformation parameters from ensembles of event images supplemented with global attributes. Multi-event averaging is found to be essential in this setting for suppressing stochastic fluctuations and revealing the underlying deformation information. While standard regression efficiently captures the central trends of deformation through point estimates, SBI provides calibrated posterior distributions, offering a more complete and robust characterization of uncertainty. Collectively, our results demonstrate that deformation information is effectively encoded in the initial state and becomes increasingly identifiable with sufficient ensemble averaging, laying a solid foundation for future extensions toward more complete dynamical modeling and final-state observables.

    Comments:
    23 pages, 25 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2603.24088 [pdf]
    0 citations
  4. 04

    [Submitted on 25 Mar 2026]

    Assessing continuum channel importance in continuum-discretized coupled-channels via dynamic polarization potential decomposition

    Jin Lei · Hao Liu

    A recurring question in continuum-discretized coupled-channels (CDCC) calculations is which continuum channels carry the breakup coupling, both to interpret the reaction and to decide which channels a model space can safely omit. The standard answer is bin deletion: remove a channel, re-solve the coupled equations, and read the change in the elastic -matrix. We show that this cannot isolate an individual channel's contribution. Deleting a channel forces the surviving model space to reorganize, the neighboring bins rerouting through the off-diagonal Green's function, so the recorded change mixes the channel's own effect with the readjustment of all the others. Working instead from the channel-resolved Feshbach dynamic polarization potential (DPP), whose full-coupling Green's function is a fixed reference shared by every channel, we define an exclusion that removes one channel while holding that reference fixed, returning its contribution to the intact system. The two operations disagree on which continuum bins matter most, for +Ni at 21.6~MeV even reversing their order of importance. The DPP further separates each channel's action into a direct path, virtual excitation and return, and a bridge path, relayed through neighboring bins, a split deletion cannot make; it shows the bins act on the elastic channel mainly as bridges, robustly across angular momentum, and that it is this bridge coupling that reorganizes under deletion. A deletion-based channel importance is therefore best read as the truncated calculation's sensitivity to a channel's removal, not as the channel's intrinsic coupling strength.

    Subjects:
    Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    2603.24253 [pdf]
    PRC(2026)·0 citations
  5. 05

    [Submitted on 25 Mar 2026]

    Qcombo: A Python Package for Automated Commutator Calculations of Quantum Many-Body Operators

    L. H. Chen · Y. Li · H. Hergert · J. M. Yao

    qcombo is a Python package for the symbolic evaluation of commutators between general quantum many-body operators expressed in normal-ordered form using the generalized Wick theorem. The package provides an automated and systematic framework for generating the corresponding algebraic expressions, significantly reducing the risk of human error in lengthy and complex analytical derivations. It is designed to assist the development and implementation of modern many-body methods in nuclear physics, quantum chemistry, and related fields. The functionality and workflow of the package are demonstrated through an application to the in-medium similarity renormalization group (IMSRG) method, which has been widely used for nuclear ab initio calculations. As a representative example, qcombo is employed to automatically generate the complete set of multi-reference IMSRG flow equations with operators truncated at the normal-ordered three-body level.

    Comments:
    17 pages with 1 figure
    Subjects:
    Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el)
    arXiv:
    2603.24399 [pdf]
    2 citations
  6. 06

    [Submitted on 25 Mar 2026]

    Many-body perturbation theory for the nuclear equation of state up to fifth order

    C. Drischler🇺🇸 · K. S. McElvain🇺🇸 · P. Arthuis🇫🇷

    We present an automated, GPU-accelerated framework for many-body perturbation theory (MBPT) calculations of the zero-temperature nuclear equation of state (EOS) based on chiral nucleon-nucleon (NN) and three-nucleon (3N) interactions. Automated diagram generation and evaluation enable the computation of all diagrams up to fifth order in the MBPT expansion at the normal-ordered two-body level in infinite matter, with residual three-body contributions explicitly included up to third order. Multi-GPU acceleration of 3N normal ordering, a novel Monte Carlo integrator (called PVegas), and further advances in high-performance computing enable us to evaluate all 840 fifth-order diagrams with controlled numerical uncertainties. We investigate the MBPT convergence up to fifth order in pure neutron matter (PNM) and symmetric nuclear matter (SNM) for two sets of chiral interactions, study neutron star matter, and present fourth-order results for asymmetric matter including normal-ordered 3N forces. The framework enables systematic MBPT studies with harder interactions and benchmarks against nonperturbative methods. It can be further extended to finite-temperature EOS calculations and to improved uncertainty quantification using emulation and resummation techniques.

    Comments:
    28 pages, 14 figures, 5 tables
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2603.24532 [pdf]
    6 citations

Affiliations

first authorsco-authorsvia INSPIRE