Nuclear Theory·nucl-th

Fri·Oct 2, 2026Friday·October 2, 2026

17 papers—8 primary·9 cross-listed

01
Coexistence of strange quark stars and neutron stars: metastability and nucleation in proto-neutron stars
Mirco Guerrini · Giuseppe Pagliara · Luca Passarella · Alessandro Drago
If strange quark matter (SQM) is absolutely stable, hadronic neutron stars (NSs) and strange quark stars (QSs) may coexist in the so-called two-families scenario. A key issue is explaining how hadronic NSs can survive as long-lived metastable objects, rather than promptly converting into stable QSs. Since all NSs are born as hot proto-neutron stars (PNSs), a necessary condition for their existence is that the conditions for conversion, triggered by the nucleation of the first critical SQM droplet, are not reached in every PNS. We investigate the thermal nucleation of critical SQM droplets under representative PNS conditions, accounting for flavor-composition fluctuations and finite-size effects on color superconductivity by suppressing pairing in droplets smaller than the diquark coherence length. We define the nucleation conditions as the thermodynamic state at which a critical SQM droplet is expected to nucleate statistically within the characteristic dynamical timescale of the system. Under these conditions, the reduced nucleation barrier is nearly universal, with $W_{*} / T ≃ 167$ to within a few units. Exploring the SQM parameter space, we show that requiring a canonical $1.4 M_{⊙}$ NS to survive the PNS stage sets a lower bound on the hadron-quark surface tension $σ ≳ 67$ MeVfm $^{- 2}$ .
nucl-thastro-ph.HE
02
A Two-Component Exciton Model for $β$ -Delayed Neutron Emission
Nico Braukman · Toshihiko Kawano · Robert Grzywacz · Zhengyu Xu
A model for $β$ -delayed neutron emission is presented in which the emission of neutrons is allowed to occur before states populated in $β^{-}$ decay have reached equilibrium in the so-called "compound nucleus" picture. The pre-equilibrium neutron spectra are computed using a two-component exciton model, where neutron and proton, particle and hole degrees of freedom are treated independently. This model is implemented in the code BeoH to supplement the existing Hauser-Feshbach model for statistical decay of compound-nucleus states. The effect of a pre-equilibrium component in the total neutron spectrum on the single- and multi-neutron emission probabilities $P_{x n}$ is investigated for $β$ -decay precursor nuclei in the regions $47 \leq Z \leq 49, 83 \leq N \leq 86$ and $54 \leq Z \leq 58, N = 125, 126$ . An absolute change in the $P_{x n}$ values of up to 5-10% is observed in the $N = 126$ region when including pre-equilibrium emission compared to the values predicted by the Hauser-Feshbach model alone.
nucl-th
03
Dispersive optical model description of the CaFe experiment
R. A. Ramon · M. C. Atkinson · W. H. Dickhoff
High-momentum ratios measured in the CaFe experiment using high-energy electron scattering off the CaFe nuclei $(i . e .^{40} Ca,^{48} Ca,^{54} Fe)$ have revealed a surprising correlation between the nuclear shell structure and the high-momentum components generated by short-range and tensor correlations (SRC). The non-local dispersive optical model (DOM) successfully describes the experimentally measured high-momentum ratios while simultaneously describing the nuclear bound-state properties and scattering observables for these CaFe nuclei. The experimentally measured average high-momentum ratio of $^{48} Ca$ / $^{40} Ca$ and $^{54} Fe$ / $^{48} Ca$ are $1.10 \pm 0.02$ and $1.49 \pm 0.03$ , respectively. The corresponding DOM results are $1.05 \pm 0.05$ and $1.52 \pm 0.08$ , which is the first successful description of these experimental results. The present DOM analysis of CaFe nuclei relied on an extended version of the DOM incorporating a shrinkable geometry to provide a more localized and stronger volume absorption at higher missing energies to correctly represent the SRC physics. The success of the DOM can be attributed to its simultaneous treatment of structure and reaction data, the latter requiring a depletion of the mean-field accompanied by the proper admixture of high-momentum components in the respective ground states.
nucl-th
04
Microscopic Insights into the Quarkyonic Hadron--Quark Crossover: Lessons from Ultracold Fermi Gases
Hiroyuki Tajima
In neutron-star and dense quantum chromodynamics (QCD) physics, it is important to understand how baryonic matter evolves into quark matter at high density. A continuous hadron--quark crossover is one of the most attractive candidates because it can reconcile the comparatively soft equation of state around nuclear density with the rapid stiffening required to support massive neutron stars. Recent neutron-star observations motivate equations of state that stiffen rapidly across the intermediate-density regime, while quarkyonic-matter descriptions feature a shell-like baryon momentum distribution there. In this paper, we review our recent work on the microscopic description and interpretation of these phenomena by drawing an analogy with the Bose--Einstein condensate (BEC) to Bardeen--Cooper--Schrieffer (BCS) crossover in ultracold Fermi gases and two-color QCD. As pairing fluctuations play a crucial role in the BEC--BCS crossover, we discuss the role of its three-body counterpart, that is, tripling fluctuations associated with baryon formation in the hadron--quark crossover. In terms of a phase-shift representation of tripling fluctuations, the interplay between a three-body bound-state pole and the scattering continuum suppresses low-momentum baryonic occupation, generates a baryonic momentum shell, and reduces the density susceptibility, thereby producing a peak in the speed of sound. We review the demonstration of this mechanism in a one-dimensional three-component Fermi gas, its relativistic extension, and its connection to phenomenological quarkyonic equations of state.
nucl-thcond-mat.quant-gashep-ph
05
Hadronization into Nuclei: Does Size Matter?
Anton Andronic · Peter Braun-Munzinger · Hjalmar Brunßen · Johanna Stachel
We investigate an extension of the statistical hadronization model (SHM) that takes (hyper)nucleus sizes into account. The spatial extent of nuclear wave functions relative to the fireball volume is used to calculate a size correction, which describes the suppression with respect to a point-like treatment of the (hyper)nucleus at hadronization. For several species of light nuclei (d, $^{3} H$ , $^{3} He$ ) and for the hypernucleus $_{Λ}^{3} H$ , the predicted effects of the size correction on SHM yields are compared to yield measurements in pp, p-Pb, and Pb-Pb collisions in the ALICE experiment. The experimental data suggest that this size correction, based on applying final-state wave functions at chemical freeze-out, does not give a consistent description of (hyper)nucleus production in nuclear and hadronic collisions. By contrast, the SHM without a nuclear-size correction provides a substantially better description of the data. This result lends further support to the interpretation that such nuclear states are formed from initially compact (multi-quark) configurations which after hadronization expand to their final-state wave functions.
nucl-thhep-ph
06
Properties of rapidly rotating hot neutron stars within Brueckner theory
Hong-Ming Liu · Bo-Xiu Zhou · Zeng-Hua Li · Jin-Biao Wei · H.-J. Schulze
We study the properties of hot rapidly rotating neutron stars using various equations of state based on the Brueckner-Hartree-Fock approach at finite temperature. The temperature dependence of gravitational mass, equatorial radius, Kepler frequency, moment of inertia are analysed in detail and universal relations are examined.
nucl-thEur. Phys. J. C 86 (2026) 770
07
Thermodynamic signatures do not uniquely identify deconfinement in neutron stars
Yong-Liang Ma · Jia-Ying Xiong
The smallness of polytropic index $Γ_{ε} ≲ 1.75$ and near conformality of sound velocity $c_{s}^{2} \approx 1/3$ in neutron star matter are usually referred to as signals of the emergence of quark matter. We construct a density-resolved nucleonic reference domain in the $(P/P_{\rm free},\Gamma_\varepsilon)$ plane using nucleonic EoSs jointly constrained by nuclear matter properties and neutron star mass, radius and tidal data, and found that the domain extends unambiguously below $\Gamma_\varepsilon=1.75$. Crucially, the nucleonic domain becomes stable against the truncation order only after $Z_0$ and $Z_{sym}$ are included, showing that the higher-order density dependence controls the extrapolation from finite nuclei to neutron-star matter. These findings therefore provide concrete targets for finite-nucleus and heavy-ion experiments, while linking terrestrial nuclear physics directly to multimessenger observations. We compare the domain with smooth equations of state generated by neural networks without phase labels and represented by symbolic regression. Among these reconstructions, $35.29\%$ have complete trajectories inside the nucleonic domain over $0.5\leq n/n_0\leq8$. Within the EoS sample obtained after minimizing the multimessenger loss, the smallest value of $\max_n c_s^2(n)$ is 0.38, above the conformal value $1/3$ . In conclusion, we convert microscopic interpretation into a falsifiable, density-resolved null-hypothesis test and show quantitatively that current observations do not reject the nucleonic null over much of the admissible space of equation of state.
nucl-th
08
Trace-anomaly decomposition and universal dark matter scaling in compact stars
Adamu Issifu · Constança Providência · Tobias Frederico
We investigate how dark matter (DM) admixture modifies the conformal properties and phase structure of dense neutron-star matter within a self-consistent single-fluid framework, with the global DM fraction $F_{χ} = N_{χ} / N_{B}$ fixing the local relation $n_{χ} = F_{χ} n_{B}$ . We derive an exact decomposition of the total trace anomaly, $Δ_{tot}$ , into microscopic contributions. For collider-motivated Higgs-portal benchmarks, explicit Higgs, vector-mediator, and contact-interaction contributions are negligible, while heavy nonrelativistic DM has an intrinsic trace anomaly close to the nonrelativistic limit, $Δ_{χ} ≃ 1/3$ . Consequently, the DM rest-mass energy fraction dominates the DM-induced modification of $Δ_{tot}$ , producing a smooth upward shift of up to $\sim 0.1$ for $F_{χ} \sim 0.2%$ . In the pressureless, comoving heavy-WIMP regime, we further identify a universal dark-sector scaling governed by the mass-loading parameter $λ = F_{χ} m_{χ} / m_{N}$ : numerical calculations with different $(F_{χ}, m_{χ})$ pairs at fixed $λ$ exhibit overlapping trace-anomaly, sound-speed, and mass--radius responses for a given baryonic equation of state. In hybrid stars, DM leaves the coexistence pressure and chemical potential essentially unchanged, whereas first-order hadron--quark deconfinement produces sharp discontinuities in the squared sound speed $c_{s}^{2}$ , $Δ_{tot}$ , and $Δ_{tot} - Δ_{B}$ . The combined softening substantially reduces the maximum stellar mass, placing $F_{χ} \sim 0.2%$ in tension with the observed $2 M_{⊙}$ neutron stars. These results show that the trace anomaly and its density evolution provide a sensitive diagnostic for distinguishing smooth DM-induced modifications of dense matter from genuine first-order deconfinement.
nucl-thastro-ph.HEhep-ph
09
Full-event anomaly detection for new physics searches at the Electron-Ion Collider
Dimitrios Athanasakos · Sebastian Grieninger · Hongkai Liu · Tymothy Mangan · Felix Ringer · Robert Szafron
The future Electron-Ion Collider (EIC) will offer new opportunities to search for physics beyond the Standard Model. We study resonant anomaly detection using machine learning and the full particle content of an event. We consider a new neutral gauge boson and a heavy neutral lepton as illustrative signals with different electron-jet topologies. Weakly supervised learning uses this event information to enhance the sensitivity of an invariant-mass search without identifying individual signal events during training. Comparisons with high-level observables show that the electron kinematics account for an important part of the separation, while correlations among the particles provide further sensitivity. We also construct a conditional full-event generator by adapting a model pretrained on LHC jets to produce EIC background events. A scan over signal fractions demonstrates substantial signal enhancement using the learned background reference, providing a proof of concept for this approach at the EIC. Finally, we consider a fully unsupervised graph autoencoder that provides modest signal enhancement but retains sensitivity at signal fractions too small for effective weak supervision. Our results motivate full-event anomaly detection as part of the EIC physics program and identify directions for developing methods suited to its distinct kinematics.
↳ hep-phhep-exnucl-exnucl-th+1
10
Fractional anomalous determinants and the chiral phase transition
Robert D. Pisarski
At high temperature instantons form a dilute gas, so in QCD-like theories the breaking of the anomalous $U (1)_{A}$ symmetry is given by integral powers of the anomalous determinant, $\sim (det Φ)^{Q}$ , where $Φ \sim q_{L} q_{R}$ is bilinear in the quark fields, and with untwisted boundary conditions, the topological charge, $Q$ , is an integer. A syncretic model is constructed, which is manifestly "beyond Landau". In the chiral limit, at temperatures above the chiral phase transition, $T > T_{χ}$ , only integral powers of the anomalous determinant appear. Below $T_{χ}$ , following 't Hooft et al. I assume that the topological charge $Q$ is fractional, as an integer times $1/ N_{c}$ , where $N_{c}$ is the number of colors. I suggest that consequently, fractional powers of the anomalous determinant appear in the chiral effective Lagrangian. For $N_{f}$ degenerate flavors, this generalizes the Witten-Veneziano term, valid for small $N_{f} / N_{c}$ , to arbitrary $N_{f} / N_{c}$ . In this model the chiral phase transition is generically of second order. The two exceptions are for one flavor, where it is probably crossover, and three flavors, where it could well be weakly first order. This can be tested in lattice QCD with $2 + 1$ flavors by comparing the (known) temperature dependence of the difference of the $π^{a}$ and $a_{0}^{a}$ propagators, to the chiral condensate of the strange quark, between $T_{χ}$ and $\sim 2 T_{χ}$ . Analogous measurements are possible for one to four degenerate flavors about $T_{χ}$ . Lastly, I propose an operator for baryon number in the symmetric phase.
↳ hep-phcond-mat.str-elhep-lathep-th+1
11
Glueballs and fractional anomalous determinants at nonzero $θ$ , and the decays of the X(2370)
Francesco Giacosa · Shahriyar Jafarzade · Győző Kovács · Péter Kovács · Robert D. Pisarski · Fabian Rennecke
Using fractional anomalous determinants, we construct a model of the trace and axial anomalies of a $S U (3)$ gauge theory at nonzero $θ$ angle through the couplings to scalar and pseudoscalar glueballs. In the pure gauge theory, we reproduce the $θ$ dependence of the vacuum energy and the scalar-glueball mass from the lattice, and estimate the jump in the topological charge density for the first-order transition at $θ = π$ . In QCD, the coupling of a pseudoscalar glueball to fractional anomalous determinants describes all of the four three-pseudoscalar decay channels of the $0^{-+}$ glueball candidate $X (2370)$ measured by the BESIII collaboration. Measuring the decay rates for $η η η$ and $η η η^{'}$ can provide a stringent test of the model.
↳ hep-phhep-lathep-thnucl-th
12
Unified description of longitudinal and transverse parton dynamics in cold nuclear matter
Weiyao Ke
We present a unified description of longitudinal momentum evolution and transverse-momentum broadening in cold nuclear matter using soft collinear effective theory with Glauber gluon interactions (SCET $_{G}$ ). In a finite nucleus, Landau--Pomeranchuk--Migdal interference couples medium-induced energy loss to the transverse scale resolved by the observable. Our framework combines RG evolution of impact-parameter-dependent energy loss with BFKL-type rapidity evolution of the collision kernel, improved by kinematical constraints and running coupling. With a common set of cold-nuclear-matter parameters, it accounts for the main nuclear modification patterns in semi-inclusive DIS and Drell--Yan production and provides predictions for TMD hadron multiplicities at the EIC. We also discuss the one-point energy correlator in DIS, whose energy weighting suppresses the leading final-state energy-loss contribution. In the EIC kinematics studied, the residual dynamical corrections are small, leaving the nuclear modification dominated by the initial-state nuclear parton distributions.
↳ hep-phnucl-th
13
Late-Time Power Laws in Fluorescence Decays: Quantum Decay or Alternative Mechanisms?
Francesco Giacosa · Anna Kolbus · Krzysztof Kyziol · Magdalena Plodowska · Milena Piotrowska · Karol Szary · Arthur Vereijken
In quantum mechanics, the properties of an unstable system are closely related to its corresponding energy distribution. One of the predictions of the theory is the emergence of a late-time power law in the survival probability $P (t)$ of the unstable state. However, in complex systems, similar effects may emerge due to other phenomena. This is the case for nonextensive statistical models, for some continuous lifetime distribution models, and also for certain energy-migration models applied to fluorescence. In this work, these alternative interpretations are confronted with data from time-resolved fluorescence spectroscopy experiments with erythrosine B and eosine Y as fluorophores. It turns out that some of the features expected within the quantum-mechanical description, such as the sharp transition from the exponential to the power-law regime, cannot be reproduced by the specific statistical and energy-migration parametrizations fitted in the analysis.
↳ quant-phnucl-th
14
Gravitational D-form factors of the nucleon and pion with mixing between two-quark and four-quark states
Mamiya Kawaguchi · Yao Ma · Yong-Liang Ma
We investigate the gravitational $D$ -form factors of the nucleon and pion within an extended linear sigma model (eLSM) that incorporates both two-quark and four-quark states, as well as nucleon fields. Within the scalar-meson-dominance picture, we find that meson mixing between two-quark and four-quark states suppresses the nucleon $D$ -form factor and leads to agreement with the lattice-QCD results. Interestingly, a quantitatively similar suppression was previously found in the parity doublet model (PDM) as a consequence of a nonzero chiral invariant component of the nucleon mass. This suggests that the effects of meson mixing and the chiral invariant mass are difficult to distinguish from the nucleon $D$ -form factor alone. We therefore examine the pion $D$ -form factor in the chiral limit. While its value in the forward limit remains fixed at $- 1$ in both the eLSM and the PDM, meson mixing modifies its momentum-transfer dependence. In contrast, the chiral invariant mass does not directly affect the pion $D$ -form factor. These results suggest that a combined analysis of the nucleon and pion $D$ -form factors can provide further insight into the mass decomposition of the nucleon and the quark composition of mesons.
↳ hep-phhep-latnucl-th
15
Generalized fluctuation-dissipation theorem and Einstein relation in rotating equilibrium
Shuo Fang · Shi Pu
We derive a generalized fluctuation-dissipation theorem (FDT) for vector fields in rotating thermal equilibrium from an exact phase-space Kubo-Martin-Schwinger (KMS) relation. The resulting FDT contains rotation-induced tensorial contributions beyond a scalar thermal factor. In the local transport limit, we obtain a model-independent generalized Einstein relation with rotation in which, through second order in thermal vorticity, symmetric momentum diffusion depends on low-frequency spectral information beyond that encoded in the rotation-dependent dissipative drag. Remarkably, we find a new Einstein-type relation linking zero modes in the spectral function to the nonrotating drag coefficient. These zero modes underlie a new mechanism for the orbital polarization of heavy quarkonium. The same FDT constraint yields a modified detailed-balance relation whose first-order vortical correction is governed by transition polarization, without explicit dependence on the bath model. Our findings establish microscopic equilibrium constraints for studying rotating quantum matter in various fields.
↳ hep-phcond-mat.stat-mechhep-thnucl-th
16
Confronting $K^{-} d$ dynamics with kaonic atom measurements within a novel unitary framework
Albert Feijoo · Àngels Ramos · Juan Torres-Rincon
We study the low-energy interaction of negative kaons with deuterons using chiral $K ˉ N$ interaction models (OR and BCN) as input. The three-body $K^{-} d$ amplitude is constructed within the Fixed-Center Approximation to the Faddeev equations, where the unitary constraints missing in the conventional approach are formally implemented with the incorporation of coherent multiple-scattering processes. The unitary procedure is extended to coupled channels including charge-exchange processes, as well as isospin-breaking effects through the use of physical particle masses. This provides a consistent description of the low-energy $K^{-} d$ amplitude and allows for the determination of the scattering length and the effective range. The resulting framework is then used to assess the compatibility of the BCN $K ˉ N$ interaction model with the recent SIDDHARTA-2 measurements of kaonic hydrogen and kaonic deuterium through a bootstrap analysis. The procedure leads to a readjustment of the BCN parameterization which produces visible effects in several isospin-sensitive $K ˉ N$ scattering observables, hence highlighting the additional information provided by the new kaonic-atom measurements to better constrain the poorly known isovector component of the $K ˉ N$ interaction.
↳ hep-phhep-exnucl-exnucl-th
17
Unitary Schur Sampling of Qudits via Random SWAP Tests: Hunt for Antisymmetry
Shrigyan Brahmachari · David Jakab · Henry D. Pfister · Iman Marvian
Schur sampling is a fundamental primitive for extracting permutation-invariant information from many-body quantum systems and has broad applications in quantum information science. Circuit-based implementations typically rely on coherent representation-theoretic operations such as Clebsch-Gordan transforms, generalized phase estimation, or quantum Fourier transforms over the symmetric group. We show that unitary Schur sampling of arbitrary permutation-invariant mixed states on $n$ $d$ -dimensional qudits can instead be implemented using only pairwise SWAP tests, namely, two-qudit projective measurements onto the symmetric and antisymmetric subspaces. Our protocol achieves error $ϵ$ in diamond distance using $O (n min {n, d}^{3} lo g^{2} (n / ϵ))$ random SWAP tests. The central idea is to repeatedly identify and extract the largest antisymmetric subsystem. This turns unitary Schur sampling into a search for antisymmetry and gives the algorithm a natural interpretation as a stochastic traversal of a Young diagram. The protocol preserves the $SU (d)$ -irrep state while preparing a canonical pure state in the multiplicity subsystem. As an application, we consider quantum purity amplification (QPA), in which multiple noisy copies of a pure quantum state are combined to produce a state of higher purity. We show that the optimal purified state can be obtained by retaining a single designated output qudit and discarding the rest.
↳ quant-phcond-mat.stat-mechhep-thmath-ph+2