Nuclear Theory·nucl-th

Thu·Sep 10, 2026Thursday·September 10, 2026

10 papers—4 primary·6 cross-listed

01
MUSES workflows for pQCD constraints on dense matter with finite quark masses
Isabella Danhoni🇺🇸 · Mateus Reinke Pelicer🇺🇸 · Débora Mroczek🇺🇸 · Yumu Yang🇺🇸 · Mauricio Hippert🇧🇷 · Jacquelyn Noronha-Hostler🇺🇸
We present a modular implementation of next-to-leading order (NLO) perturbative QCD (pQCD) thermodynamics with finite strange quark mass in the MUSES Calculation Engine, enabling reproducible connections between high-density QCD calculations and neutron star observables. Using this implementation, we investigate the interplay between flavor symmetry and physically motivated renormalization-scale prescriptions in cold, $β$ -equilibrated quark matter. We compare prescriptions associated with the conserved-charge $B QS$ , isospin $B I_{3} S$ , and $S U (3)$ Cartan $B I_{3} Y$ bases, and show that their different symmetry properties at finite perturbative order can significantly affect the predicted flavor composition. In particular, while the $B QS$ and $B I_{3} Y$ prescriptions yield the same reduced $β$ -equilibrated \eos{} for $μ_{S} = 0$ , they can predict different flavor compositions, whereas the $B I_{3} S$ prescription generates additional contributions to the charge-neutrality condition and develops strong scale dependence at low chemical potentials. We then apply stability and causality constraints to investigate the effect of the strange quark mass on the neutron star \eos{}. In an exploratory benchmark at $μ_{B} = 2.4$ ~GeV and fixed fiducial renormalization scale, increasing the fixed strange quark mass from $m_{s} = 0$ to $m_{s} = 300$ ~MeV reduces the fraction of \eos{} in our prior that is incompatible with the pQCD constraint from 51\% to 36\% and qualitatively changes the region of \eos{} space that is selected, retaining greater support for stiffer behavior. These results motivate systematic studies of strange quark mass and renormalization-scale uncertainties in pQCD constraints. The MUSES implementation provides a modular framework for such extensions and for future higher-order calculations.
nucl-thastro-ph.HEhep-ph0 citations
02
BRST quantization for the restoration of broken symmetries: a pedagogical example
Pranav Sharma🇺🇸 · R.J. Furnstahl🇺🇸
We present a pedagogical showcase of BRST quantization for restoring symmetries in nuclear many-body systems as a reformulation and potential alternative to conventional projection methods. The formalism is illustrated using translational invariance for a simple system of two interacting masses in one dimension, but with an eye toward generalizing to more particles, higher dimensions, and other symmetries. We explain the considerations underlying particular choices within the BRST construction, and develop both Hamiltonian and path integral formulations to provide guidance for the variety of many-body and effective field theory contexts where gauge fixing for symmetry restoration might be useful. For the demonstration system we show how to diagonalize within the extended BRST phase space, how variation after projection is recovered for product reference states, how the corresponding gauge-fixed functional integral is constructed, and how collective zero modes are isolated and controlled. Throughout, we keep in mind extensions of BRST symmetry to various approximation schemes as a guide for consistent symmetry restoration.
nucl-thhep-phquant-ph0 citations
03
Development of the {\gamma} strength function with the neutron number
Stefan Frauendorf · Ronald Schwengner🇩🇪 · Gowhar Bhat🇮🇳 · Javid Sheikh
The M1 and E2 {\gamma} strength functions ({\gamma}sf) have been calculated for extended series of the Mo, Fe, Sn, Ge and Gd isotopes using the conventional spherical shell model (SSM) and, as a new tool, the triaxial projected shell model (TPSM). For almost all cases the strong enhancement of the M1 {\gamma}sf (low energy magnetic radiation-LEMAR) is found. In the mid-shell region, a bimodal structure of the LEMAR spike and a bump around 3 MeV, interpreted as the scissors resonance (SR), develops. The combination of LEMAR and the SR is generated by the splitting of the spherical single particle multiplets of given j caused by deformation and their fragmentation over nearby quasiparticle configurations.
nucl-thnucl-ex0 citations
04
Systematic study of E2 matrix elements in the framework of the Triaxial Projected Shell Model
Stefan Frauendorf · Syed Rouoof · Gowhar Bhat🇮🇳 · Sheikh Jehangir🇮🇳 · Nazira Nazir · Kouser Qureshie · Niyaz Rather · Javid Sheikh
Nuclides for which extended sets of E2 matrix elements have been measured by means of COULEX experiments are studied in the framework of the triaxial projected shell model (TPSM). The studies encompass: 70,72,74,76Ge, 76,78,80,82Se, 100Mo, 104Ru, 110Pd, 168Er, 186,188,190Os, 184Pt. The experimental energies of the ground band, of the quasi gamma band and of some excited 0+ bands as well as their individual intra and inter band matrix E2 matrix elements are systematically accounted for by the microscopic TPSM calculations.
nucl-thnucl-ex0 citations
05
Decoding the Imprints of Energy-Momentum Squared Gravity in Neutron Stars with Machine Learning Analysis
Sayantan Ghosh🇮🇳 · Premachand Mahapatra🇮🇳 · Dipti Deb🇮🇳
Neutron stars (NSs) provide a unique laboratory for testing gravity in the strong-field regime and for searching for deviations from General Relativity (GR). In this work, we investigate the effects of Energy-Momentum Squared Gravity (EMSG) on NS structure and examine whether its signatures can be identified from observable stellar properties using supervised machine learning (ML). We solve the modified Tolman-Oppenheimer-Volkoff equations for approximately $1 0^{4}$ nuclear equations of state (EOSs) for EMSG coupling parameters $α = {- 5.01, - 2.50, 0, + 2.50, + 5.01} \times 1 0^{- 38} erg^{- 1} cm^{3}$ , and calculate the gravitational mass $M$ , radius $R$ , dimensionless tidal deformability $Λ$ , and fundamental $f$ -mode oscillation frequency for each stellar configuration. Imposing observational constraints on $M$ , $R$ , and $Λ$ , we split our datasets into train and test sets, and we employ Random Forest (RF), K-Nearest Neighbors (KNN), Support Vector Machine (SVM), Logistic Regression (LR), and Gaussian Naive Bayes (GNB) to classify the representative sectors $α = {- 5.01, 0, + 5.01} \times 1 0^{- 38} erg^{- 1} cm^{3}$ using $(M, R, Λ, f)$ . The RF classifier performs best, achieving an accuracy of approximately $99.85%$ with precision, recall, and F1-scores exceeding $99.8%$ , while KNN also achieves accuracy above $99%$ . The nearly diagonal confusion matrices demonstrate that the observationally viable NS configurations associated with different EMSG sectors remain highly separable in the multidimensional observable space. Our results show that NS observables retain robust signatures of EMSG even after observational filtering, establishing ML-assisted NS observations as a promising complementary approach for probing modified gravity with current and future multi-messenger observations.
↳ astro-ph.HEgr-qchep-phnucl-th0 citations
06
Universal Entanglement Dynamics of Unitary Operators
Ian Low🇺🇸 · Navin McGinnis🇺🇸
The entangling power of a unitary operator acting on a bipartite Hilbert space measures the entanglement it generates from product states, averaged over the inputs. A finite-dimensional unitary has a spectral decomposition $U = \sum_{a = 1}^{n} e^{i θ_{a}} P_{a}$ , where $e^{i θ_{a}}$ are the eigenvalues, $P_{a}$ the corresponding eigen-projectors, and $n$ is the number of distinct eigenvalues. After removing an overall phase, the entangling power is a function on the $(n - 1)$ -torus of relative eigenphases at fixed spectral projectors. We prove that this function is stationary at all $2^{n - 1}$ points on the torus where every relative phase is $0$ or $π$ , which we define as \textit{corners}. Up to an overall phase, $U$ at each corner is a generalized reflection $R = I - 2 Q$ satisfying $R^{2} = I$ , where $Q$ is the sum of spectral projectors whose relative phase is $π$ . At the corner the entangling power is expressed in terms of seven local-unitary invariants of $Q$ . A unitary gate $U$ can be realized as a corner of some projector family if and only if $U^{2} \propto I$ , a condition satisfied by many Clifford and non-Clifford gates. We illustrate the theorem with two-qubit gates, $S U (N)$ channel decompositions, and two-site spin chains, obtaining examples of minima, maxima, and saddle points. In addition, a corner that is a saddle point on the full phase torus can appear as a local maximum or minimum along different time-evolution trajectories.
↳ quant-phhep-phhep-thnucl-th0 citations
07
Bounds on scattering amplitudes of non-identical scalar particles in 4d
Gabriele Ferretti🇸🇪 · Denis Karateev🇨🇭 · Alessandro Piazza🇮🇹 · Marco Serone🇮🇹
We initiate the study of two-to-two scattering amplitudes involving two distinct scalar particles in $d = 4$ spacetime dimensions using the primal S-matrix bootstrap. We impose a $Z_{2} \times Z_{2}$ global symmetry under which the two particles are the lightest ones carrying charges $(-, +)$ and $(+, -)$ , guaranteeing their absolute stability and absence of triangular anomalous thresholds. For unequal masses, the presence of a pseudo-physical cut whose discontinuity is not directly constrained by physical unitarity qualitatively changes the bootstrap problem. We find several observables to be unbounded, while others obey non-trivial one-sided bounds or become bounded once another observable is fixed. In the equal-mass limit, where the pseudo-physical region disappears, two-sided bounds are recovered. As a proof of concept, we show that supplying information about the pseudo-physical discontinuity through an Omnès parametrisation also restores boundedness. Our results provide a starting point for future studies of physical processes such as pion-kaon and pion-nucleon scattering.
↳ hep-thhep-phnucl-th0 citations
08
Detailed experimental study of excited states in $^{50}$ Ti via the $(d, p)$ and $(d, p γ)$ reactions
B. Kelly🇺🇸 · M. Spieker🇺🇸 · L. T. Baby🇺🇸 · S. Baker🇺🇸 · A. L. Conley🇺🇸 · D. Houlihan · K. W. Kemper🇺🇸 · E. Litvinova🇺🇸 · N. Tsoneva · A. Volya🇺🇸
Excited states of semi-magic $^{50}$ Ti were studied up to the neutron-separation energy via the $(d, p)$ and $(d, p γ)$ reactions. In total, 82 excited states were identified based on the measurement of angular distributions with the Super-Enge Split-Pole Spectrograph (SE-SPS) at Florida State University. From the experimental data, sum rules related to vacancies were calculated for the $2 p_{3/2}$ , $2 p_{1/2}$ , $1 f_{5/2}$ , $1 g_{9/2}$ , and $2 d_{5/2}$ neutron single-particle orbitals and compared to predictions obtained with the time-dependent continuum shell model (TDCSM), the quasiparticle-phonon model (QPM), and the relativistic equation of motion theory (REOM $^{3}$ ). A comparison for the $(d, p)$ data obtained for $^{51}$ Ti and $^{50}$ Ti is also presented, focusing on differences of the single-particle strength fragmentation in even- $A$ and odd- $A$ nuclei.
↳ nucl-exnucl-th0 citations
09
Zero-locus diagnostic of the direct contact term in $ϕ \to π^{+} π^{-} π^{0}$
Seung-il Nam🇰🇷 · Jung Keun Ahn🇰🇷
We formulate, within a fixed FSI-improved amplitude convention, a zero-locus diagnostic for the direct contact term in $ϕ \to π^{+} π^{-} π^{0}$ . The resonant $ρ π$ contribution is dressed channel by channel with the complex Omnès function, the direct term is multiplied by the averaged Omnès factor, and a real constant background is retained as a smooth residual amplitude. In this convention, $F^{FSI} = R + c e^{i δ_{dir}} D$ with $c = g_{ϕ 3 π}^{eff}$ , and the difference of two constrained invariant-mass gradients of the reduced Dalitz density gives a local quadratic identity for $c$ on the zero-contour. The construction provides a closure and stability diagnostic complementary to a global Dalitz-plot fit. For the benchmark input $g_{ϕ 3 π}^{eff} = - 24.0 GeV^{- 3}$ , we identify a numerically stable zero-contour branch around $M_{+ 0} = 0.460 \pm 0.025 GeV$ and $M_{+-} \leq 0.560 GeV$ , where the tight-contour median estimator reproduces $g_{ϕ 3 π}^{est} ≃ - 24.0 GeV^{- 3}$ , a closure recovery of the injected coupling within the chosen FSI-improved convention rather than an independent extraction. We further vary the mass-window selection of the branch. The median remains close to the injected value under shifts of the $M_{+ 0}$ window and moderate changes of its width, while the mean and standard deviation are more sensitive to outlier points near unstable quadratic branches. The method therefore identifies Dalitz-plane regions where the direct-term interference is locally well-conditioned and provides useful guidance for control-region choices and systematic variations in future global fits.
↳ hep-phnucl-th0 citations
10
An improved partial-wave projection of the one-particle exchange in relativistic three-body scattering
Nicholas C. Chambers🇺🇸 · Andrew W. Jackura🇺🇸
A critical component of relativistic three-body scattering amplitudes is the one-particle exchange (OPE) process, wherein a single particle is exchanged between incoming and outgoing two-body subsystems. We present an improved, finite-sum expression for the partial-wave OPE that is valid for three massive, spinless particles in arbitrary angular momentum configurations. A collection of analytic and numerical checks demonstrate that our finite-sum expression reproduces the known properties of the partial-wave OPE, including its threshold scaling behavior and singularity structure. Compared with previous work, this result more efficiently handles the rapid proliferation of partial waves contributing to any total angular momentum $J$ , enabling the construction of robust wavesets for three-body amplitude analyses.
↳ hep-phhep-lathep-thnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE