Nuclear Theory·nucl-th

Monday·July 13, 2026

18 papers—11 primary·7 cross-listed

01
[Submitted on 9 Jul 2026]
Stochastic Similarity Renormalization Group
Rongzhe Hu · Xin Zhen · Furong Xu · Junchen Pei
By integrating the quantum Monte Carlo technique into the similarity renormalization group (SRG), we have developed a stochastic SRG framework (SRGQMC) capable of both free-space two-body and in-medium many-body evolutions. This approach circumvents the combinatorial tensor-space explosion of many-body flow equations by mapping continuous unitary transformations onto an ensemble of signed random walkers. We benchmark the SRGQMC against deterministic free-space SRG evolutions of realistic nucleon-nucleon (NN) interactions, as well as against in-medium SRG (IMSRG) many-body calculations with the Richardson pairing model at two- and three-body levels [IMSRG(2)/(3)]. While a deterministic extension to the four-body level [IMSRG(4)] remains unfeasible due to prohibitive computational costs, we have achieved the first IMSRG(4) calculation by using the stochastic technique, demonstrating a substantial improvement toward the full configuration-interaction limit. This stochastic framework provides a practical pathway to higher-order IMSRG calculations.
Comments:
5 pages, 3 figures; with Supplemental Material
Subjects:
Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Experiment (nucl-ex)
arXiv:
2607.08830 [pdf]
1 citation
02
[Submitted on 9 Jul 2026]
Magnetised Dense Nuclear Matter in Neutron Stars: A Relativistic Mean-Field Study of the Equation of State
Mojdeh Banafsheh
We study the static response of dense neutron-star matter to a prescribed magnetic-field strength within a deliberately minimal and internally consistent relativistic mean-field (RMF) baseline. The model includes neutrons, protons, electrons, and muons in beta equilibrium and charge neutrality, with a uniform external magnetic field incorporated through Landau quantisation of the charged species. The equation of state is evaluated self-consistently at zero temperature, while moderate finite-temperature effects are estimated through leading-order degenerate Sommerfeld corrections. Magnetic pressure anisotropy is included through the Maxwell contribution in the no-magnetisation approximation. The purpose of this baseline is to isolate the hierarchy of magnetic-field effects before introducing additional microphysics or dynamical magnetic-field evolution. We compare the linear QHD-I parameterisation, used as a stiff benchmark, with the nonlinear GM1 model as a more realistic reference. The results show that canonical magnetar-scale fields produce negligible changes in the bulk core equation of state, while visible Landau-quantisation and pressure-anisotropy effects emerge only as the field approaches the strongly quantising regime. The comparison between QHD-I and GM1 further shows that nuclear-model dependence dominates over static magnetic-field corrections up to the field strengths explored here. As an exploratory diagnostic, we use the isotropised equation of state to estimate the sensitivity of ordinary TOV mass--radius sequences to the prescribed magnetic field. This should not be interpreted as a fully anisotropic magnetised-star calculation. Anomalous magnetic moments, hyperons, quark degrees of freedom, and dynamical magnetic-field evolution are left for future extensions.
Comments:
14 pages, 6 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2607.08850 [pdf]
0 citations
03
[Submitted on 9 Jul 2026]
Ab initio calculations of $^{229}$ Th band-to-band internal conversion rate in $^{229}$ ThO $_{2}$
Udeshika C. Perera · H. B. Tran Tan · H. W. T. Morgan · Eric Hudson · Daniel A. Rehn · Andrei Derevianko
We present an ab initio calculation of the band-to-band internal-conversion rate of the $ℏ ω_{nuc} \approx 8.35$ eV isomeric transition in $^{229}$ ThO $_{2}$ . Because the nuclear transition energy exceeds the electronic band gap of ThO $_{2}$ , the isomer can decay nonradiatively by resonantly promoting a valence electron into the conduction band. We formulate this process as a Brillouin-zone sum over vertical interband transitions weighted by local Th-centered hyperfine matrix elements, which are evaluated directly from all-electron full-potential linearized augmented-plane-wave Bloch spinors. A finite nuclear magnetization model is included to regularize the short-range hyperfine interaction and to account for the Bohr-Weisskopf effect. After applying scissor shifts to span the experimentally reported ThO $_{2}$ band gaps, we find calculated internal-conversion lifetimes in the range of $1 - 16 μ s$ . The lifetime increases strongly as the band gap approaches $ω_{nuc}$ because the resonant interband phase space at the nuclear transition energy is reduced. For the larger reported ThO $_{2}$ gaps, the calculated lifetime is comparable to the measured conversion-electron Mössbauer lifetime [Nature 648, 300 (2025)]. Our analysis implies that choosing solid-state hosts with band-gap values slightly lower than $ω_{nuc}$ can optimize solid-state nuclear clock performance with internal-conversion electron readout.
Subjects:
Nuclear Theory (nucl-th); cond-mat.mtrl-sci (cond-mat.mtrl-sci); Atomic Physics (physics.atom-ph)
arXiv:
2607.08941 [pdf]
0 citations
04
[Submitted on 10 Jul 2026]
Monte Carlo rate uncertainty of the $^{8}$ Li(n, $γ$ ) $^{9}$ Li reaction within $R$ -matrix framework
Sk Mustak Ali · Rajkumar Santra
The $^{8}$ Li $(n, γ)^{9}$ Li reaction is considered significant for the synthesis of nuclei beyond the $A = 8$ stability gap in inhomogeneous big-bang nucleosynthesis models, as well as in $r$ -process nucleosynthesis scenarios. However, direct measurement of this reaction is precluded by the short half-life of $^{8}$ Li and the absence of a neutron target. Consequently, existing reaction rate estimates based on indirect experimental methods and theoretical calculations differ by orders of magnitude. In the present work, the $^{8}$ Li(n, $γ$ ) $^{9}$ Li neutron-capture cross section and the corresponding thermonuclear reaction rate are evaluated within a phenomenological $R$ -matrix framework, including both non-resonant direct capture (DC) and resonant capture through the $5/ 2^{-}$ state at $E_{x} = 4.30$ ~MeV. The uncertainties associated with the $R$ -matrix input parameters are propagated using Monte Carlo sampling, while the sensitivity to the channel radius is treated as an $R$ -matrix model uncertainty. The effective total uncertainties in the calculated cross sections and reaction rates are obtained by adding these two uncertainty contributions in quadrature. We obtain a total capture rate of $983. 9_{- 261.5}^{+ 410.9} c m^{3} mo l^{- 1} s^{- 1}$ at $T = 1$ ~GK, with DC dominating at low temperatures ( $T = 0.01 - 0.4$ ~GK) and the $5/ 2^{-}$ resonance at higher temperatures ( $T = 0.5 - 5$ ~GK). The present results are consistent with the upper limit of Kobayashi et al.~\cite{Kobayashi2003}, which previous theoretical predictions exceed by factors of 3-50.
Comments:
11 Pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.09158 [pdf]
0 citations
05
[Submitted on 10 Jul 2026]
The impact of nuclear uncertainties on the p-process nucleosynthesis in Supernovae
S. Martinet · S. Goriely · A. Choplin
The p-process is responsible for the production of the stable neutron-deficient nuclei heavier than iron observed in the solar system. However, important nuclear uncertainties still limit our understanding of this nucleosynthesis process. Among the most significant are the nuclear level densities (NLDs) and photon strength functions (PSFs) entering the calculation of photodisintegration rates under supernova conditions. We investigate both model (systematic) and parameter (statistical) uncertainties affecting NLDs and PSFs and quantify their impact on p-process nucleosynthesis in type-Ia and type-II supernovae. Correlated model uncertainties are estimated using several NLD and PSF models that reproduce available experimental observables. Uncorrelated parameter uncertainties are evaluated with a backward-forward Monte Carlo approach, in which parameter variations are constrained by measured reaction rates before being propagated to unknown cross sections of neutron-deficient nuclei. The resulting uncertainties are propagated through p-process calculations while preserving model correlations. To identify the reactions driving abundance uncertainties, we combine regularized linear-response modeling, stability analysis, and contribution and interaction decompositions. We find that photoneutron-emission uncertainties dominate the overall uncertainty budget. The leading source of uncertainty arises from local parameter variations still compatible with current experimental constraints, highlighting the lack of constraining nuclear data in the neutron-deficient region. For many p-nuclei, the dominant contribution originates either from the photoneutron emission of the p-nucleus itself or from a nearby $(γ, n)$ reaction along the same isotopic chain. While improved nuclear models remain important, many key reactions involve stable or near-stable nuclei and should be experimentally accessible.
Comments:
20 pages, 10 figures, accepted in A&A
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
2607.09208 [pdf]
0 citations
06
[Submitted on 10 Jul 2026]
Medium-mass nuclei with neural quantum states
Bryce Fore · Jane Kim · Alessandro Lovato · Anthony Tropiano
We compute ground-state energies and charge radii of light- to medium-mass nuclei with up to $A = 58$ nucleons, leveraging a variational Monte Carlo method based on Pfaffian-Jastrow neural quantum states. To further understand which elements of the nuclear Hamiltonian are "essential" to predict binding energies and charge radii across the nuclear chart with few-percent errors, we consider different interactions inspired by pionless effective field theory. Specifically, in addition to model "o" of [Phys. Rev. C 103, 054003 (2021)], we study the impact of charge-symmetry-breaking and charge-dependent terms in the nucleon-nucleon force, as well as $p$ -wave contributions, which have been found to be critical for the stability of $p$ -shell nuclei. In addition to its intrinsic interest, our work assesses the performance of neural quantum states in the medium-mass regime and examines the impact of these interaction modifications. Using the resulting ground-state simulations, we analyze the computational scaling of variational Monte Carlo with neural quantum states as a function of system size and computational resources, enabling projections for future large-scale calculations.
Comments:
15 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.09223 [pdf]
0 citations
07
[Submitted on 10 Jul 2026]
Accelerator neutrinos as a probe of in-medium hyperon potentials
Jaroslaw Nowak🇬🇧
Charged-current (anti)neutrino interactions create $Λ$ and $Σ$ hyperons \emph{inside} the nucleus, making hyperon final-state interactions a terrestrial probe of the in-medium potentials that govern hyperon onset in neutron stars. In the StrangeMC simulation the trapped- $Λ$ fraction, escaping hyperon momenta, and a kaon-vetoed $Σ^{+}$ tag respond monotonically to $U_{Λ}$ and $U_{Σ}$ at SBND and DUNE. Marginalised over the low-density slope, a forecast gives $δ U_{Λ} \approx 6 \MeV$ with systematics distinct from hypernuclear data; $U_{Σ}$ is limited by hyperon--nucleon cross sections.
Comments:
4 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2607.09255 [pdf]
0 citations
08
[Submitted on 10 Jul 2026]
Neutrino-induced hyperon final-state interactions as constraints on the in-medium hyperon potential
Jaroslaw Nowak🇬🇧
Hyperon single-particle potentials $U_{Y} (ρ)$ control propagation in nuclei and hyperon onset in dense matter, where they soften the neutron-star equation of state and reduce the maximum mass -- the ``hyperon puzzle''. We show that charged-current accelerator (anti)neutrino interactions on $^{40}$ Ar, producing $Λ$ and $Σ$ inside the nucleus, can constrain these potentials. At SBND and DUNE energies, the trapped- $Λ$ fraction and escaping-hyperon momenta vary monotonically with $U_{Λ}$ and $U_{Σ}$ , with a kaon-vetoed FSI- $Σ^{+}$ tag adding sensitivity. Inserted in a GM1 relativistic mean-field equation of state at established hypernuclear/ $Σ$ -atom depths, the same potentials give $M_{max} = 1.94 M_{⊙}$ and $Λ_{1.4} = 1034$ , below the heaviest pulsars and above the GW170817 bound typical of GM1-class mean fields. A detector-level Fisher forecast yields $δ U_{Λ} ≃ 0.3$ MeV and $δ U_{Σ} ≃ 3$ - $4$ MeV for fixed low-density exponent $γ$ . Since hyperons are produced below saturation, $U_{Λ} (ρ_{0})$ and $γ$ are 99.8\% anti-correlated; marginalising over $γ$ degrades the anchor to $δ U_{Λ} ≃ 5.6$ MeV ( $1.3$ MeV with a $\pm 0.2$ prior), while $δ U_{Σ}$ is unchanged. For $U_{Λ}$ , comparable systematics arise from hyperon-nucleon final-state cross sections ( $- 5/ + 2$ MeV) and the exit-shift/gradient transport prescription ( $- 6$ MeV). For $U_{Σ}$ , the same $Y N$ uncertainty biases the fit by $O (150)$ MeV; removing the $Σ^{+}$ tag does not cure this, because the $Λ$ momentum spectrum carries most $U_{Σ}$ information and is itself $Y N$ -sensitive. The low-density $U_{Λ}$ anchor is a robust handle, at several-MeV rather than sub-MeV precision. A joint fit with terrestrial and heavy-ion priors gives $M_{max} = 2.2 1_{- 0.15}^{+ 0.04}$ Msun, set mainly by the external $c_{Λ}$ prior.
Comments:
18 pages, 17 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2607.09273 [pdf]
0 citations
09
[Submitted on 10 Jul 2026]
In-medium hyperon potentials and the quarkyonic hyperon onset: charged $Σ$ 's in $β$ -equilibrium and the neutrino connection
Jaroslaw Nowak🇬🇧
Quarkyonic matter resolves the neutron-star hyperon puzzle statistically: neutrons fill low-momentum $d$ -quark phase space, shifting the $S = - 1$ threshold from $\muB = M_{Y}$ to $2 M_{Y} - M_{N}$ and suppressing residual softening by $1/ \Nc^{3}$ in the Fujimoto--Kojo--McLerran (FKM) mechanism. We dress FKM's IdylliQ model with in-medium potentials, constrained by hypernuclear data and neutrino-induced hyperon FSI, and find: (i) the dressed onset, $\muB^{onset} = (2 M_{Y} - M_{N}) + 2 U_{Y} - \UN$ , carries $U_{Y}$ at weight 2, with $d n_{onset} / d U_{Y} ≃ 0.3 \nz$ per $10 \MeV$ , twice the leverage. (ii) A self-consistent neutron potential enters at weight $- 2$ , so protection needs $\UN (n_{onset}) ≲ + 96 \MeV$ . (iii) With leptons in $β$ equilibrium, the $Σ^{-}$ ( $dd s$ ) onset becomes $\mue \geq 258 \MeV + \US - \UN$ , never reached inside a $2 \Msun$ core: $Σ^{-}$ switches from first hyperon to forbidden and the $Σ$ ordering inverts. (iv) The $\kY \geq \kbu$ continuation gives TOV softening below $0.05 \Msun$ in the FKM ansatz family and below $0.025 \Msun$ for the realistic interacting star, $4$ -- $8$ below hadronic models. In the family this is a ceiling; generally it is a floor, since hyperons above $\kbu$ are omitted. (v) In an interacting low-density sector calibrated to $\Mmax = 2.12 \Msun$ , core strangeness is controlled by $(\UL (\nz), c_{Λ})$ : at $\UL (\nz) = - 28 \MeV$ , the maximum-mass star is hyperon-free once the supra-saturation $Y N N$ turn-over exceeds a few-MeV threshold $c_{Λ}^{*}$ . Projected SBND+DUNE FSI precision pins $\UL (\nz)$ but leaves $c_{Λ}$ -- to which neutrino data are blind -- decisive: with the heavy-ion prior, $P (hyperon \mbox - free core) = 0.90$ , versus $0.89$ from priors alone, prior-dominated rather than measured. The sharpest observable is differential: $d \Mmax / d U_{Y}$ is an order of magnitude smaller than in mean-field models, discriminating the two resolutions.
Comments:
9 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2607.09280 [pdf]
0 citations
10
[Submitted on 10 Jul 2026]
Bayesian inference of the dense matter equation of state built upon extended Skyrme interactions: A generalization
Mikhail V. Beznogov · Adriana R. Raduta
The nonrelativistic theory of nuclear matter (NM) based on Brussels-Skyrme interactions is employed to develop models for dense and neutron-rich matter within a Bayesian framework. We employ the following set of constraints: the four best-known nuclear empirical parameters, density dependence of the energy per particle in pure neutron matter (PNM), density dependence of the Landau effective mass ( $m_{eff}$ ) of neutrons in PNM and symmetric NM, and a lower limit on the maximum gravitational mass that neutron stars (NSs) can sustain. In addition, a number of ``sanity checks'' are added: the values of the speed of sound, neutron and proton Landau effective masses and Fermi velocities are constrained up to the central density of the most massive NS configuration and for isospin asymmetries $δ = (n_{n} - n_{p}) / (n_{n} + n_{p})$ ranging from 0 to 1. Our ensemble of models \emph{fully} explores the capacity of non-relativistic Brussels-Skyrme effective interactions to describe NM at densities exceeding several times the nuclear saturation density. This is a necessary step toward a better understanding of the properties of dense matter and possible correlations between the parameters of NSs and the parameters of NM. Due to pronounced U-shaped density-dependencies of $m_{eff}$ , all our models exhibit a non-monotonic ``rise-and-fall'' behavior of the thermal pressure ( $p_{th}$ ) as a function of density, which in extreme cases leads to $p_{th} < 0$ . This work is a generalization of [Beznogov and Raduta, Phys. Rev. C 110, 035805 (2024)].
Comments:
15 pages, 8 figures, 3 tables. Submitted to PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2607.09369 [pdf]
0 citations
11
[Submitted on 10 Jul 2026]
Electron-capture rates in the medium-mass nuclei $^{48}$ Ti, $^{56}$ Ni, $^{60}$ Zn, and $^{64}$ Ge within deformed quasiparticle random-phase approximation
Eunja Ha · Myung-Ki Cheoun · H. Sagawa · Gianluca Colò · Toshitaka Kajino
Electron-capture (EC) rates in medium-mass nuclei are governed by Gamow--Teller (GT) strength distributions and provide important input for stellar weak-interaction processes. In this work, we investigate the deformation dependence of the GT strengths and stellar EC rates in selected medium-mass nuclei in and near the $p f$ shell, namely $^{48}$ Ti, $^{56}$ Ni, $^{60}$ Zn, and $^{64}$ Ge. The GT $^{(+ / -)}$ strength distributions are calculated in the deformed quasiparticle random-phase approximation (DQRPA) on a single-particle basis obtained by the Skyrme SGII interaction, while the stellar EC rates are evaluated from the resulting $B (GT^{+})$ strengths using the standard phase-space formalism. The potential-energy curves are used to identify shape softness and possible shape coexistence in the nuclei under consideration. We find that deformation strongly modifies the GT strength distributions by changing the centroid energies, resonance splitting, and fragmentation patterns. In particular, a pronounced shape dependence of the GT $^{(+ / -)}$ strengths is found for $^{56}$ Ni and $^{64}$ Ge, whereas $^{60}$ Zn is characterized by a favoured prolate minimum and $^{48}$ Ti exhibits a soft near-spherical/prolate landscape. By contrast, the corresponding EC rates are generally much less sensitive to deformation than the differential GT response itself, except at low temperatures and low densities where the low-lying GT $^{+}$ strength becomes decisive because of the negative EC $Q$ -value in the electron phase space. Available charge-exchange data for $^{48}$ Ti and $^{56}$ Ni are used as benchmarks of the model predictions. The present results provide microscopic constraints on the role of deformation and shape coexistence in stellar weak rates for selected medium-mass nuclei, including proton-rich isotopes near the $N = Z$ line.
Comments:
21pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.09447 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE