Nuclear Theory·nucl-th

Thursday·November 7, 2024

12 papers—7 primary·5 cross-listed

01
Assessing the impact of uniform rotation on the structure of neutron stars
Marc Salinas · Jorge Piekarewicz
Driven by recent laboratory experiments and astronomical observations, significant advances have deepened our understanding of neutron-star physics. NICER's Pulse Profile Modeling has refined our knowledge of neutron star masses and radii, while gravitational-wave detections have revealed key insights into the structure of neutron stars. Particularly relevant is the extraction of the tidal deformability by the LIGO-Virgo collaboration and the most recent determination of stellar radii by NICER, both suggesting a relatively soft equation of state (EOS) at intermediate densities. Additionally, measurements from the PREX collaboration and from pulsar timing suggest instead that the EOS is stiff in the vicinity of saturation density and at the highest densities accessible to date. But how stiff can the EOS be at these very high densities? Recent events featuring compact objects near the "lower mass gap" have raised questions about the existence of very massive neutron stars. Motivated by this finding and in light of new refinements to theoretical models, we explore the possibility that these massive objects may indeed be rapidly rotating neutron stars. We explore how rotation affects both the maximum neutron star mass and their associated radii, and discuss the implications they may have on the equation of state.
nucl-thastro-ph.HEastro-ph.SRnucl-exPRC(2025)·3 citations
02
A pathway to unveiling neutrinoless $β β$ decay nuclear matrix elements via $γ γ$ decay
Beatriz Romeo🇺🇸 · Damiano Stramaccioni🇮🇹 · Javier Menéndez🇪🇸 · Jose Javier Valiente-Dobón🇮🇹
We investigate the experimental feasibility of detecting second-order double-magnetic dipole ( $γ γ$ - $M 1 M 1$ ) decays from double isobaric analog states (DIAS), which have recently been found to be strongly correlated with the nuclear matrix elements of neutrinoless $β β$ decay. Using the nuclear shell model, we compute theoretical branching ratios for $γ γ$ - $M 1 M 1$ decays and compare them with other competing processes, such as single- $γ$ decay and proton emission, which represent the dominant decay channels. We also estimate the potential competition from internal conversion and internal pair creation, which can influence the decay dynamics. Additionally, we propose an experimental strategy based on using LaBr $_{3}$ scintillators to identify $γ γ$ - $M 1 M 1$ transitions from the DIAS amidst the background of the competing processes. Our approach emphasizes the challenges of isolating the rare $γ γ$ - $M 1 M 1$ decay and suggests ways to enhance the experimental detection sensitivity. Our simulations suggest that it may be possible to access experimentally $γ γ$ - $M 1 M 1$ decays from DIAS, shedding light on the neutrinoless $β β$ decay nuclear matrix elements.
nucl-thhep-exhep-phnucl-exPLB(2025)·4 citations
03
Non-Equilibrium Aspects of Fission Dynamics within the Time Dependent Density Functional Theory
A. Bulgac · M. Kafker · I. Abdurrahman · I. Stetcu
We will cover briefly the time-dependent density functional theory approach, extended to include pairing correlations, to induced fission of $^{238}$ U(n,f), $^{241, 243}$ Pu, and $^{238}$ Np, and also results on scission neutrons and a number of very nontrivial aspects of induced fission.
nucl-thEPJ Web Conf.(2025)·1 citation
04
Triple- $α$ reaction rates below $T_{9} = 3$ by a non-adiabatic three-body model
M. Katsuma
The triple- $α$ reaction from the ternary continuum states at off-resonant energies, $α + α + α \to^{12}$ C, remains an open question. This direct process is scrutinized using a non-adiabatic Faddeev hyperspherical harmonics $R$ -matrix expansion method, and the derived reaction rates are discussed. After reviewing the model, the resultant photo-disintegration of $^{12}$ C( $2_{1}^{+} \to 0^{+}$ ) is shown to be much smaller than the values predicted by the adiabatic models for $0.15 \leq E \leq 0.35$ MeV. Despite the large difference, the derived reaction rates are illustrated to be concordant with the current evaluated rates for $0.08 \leq T_{9} \leq 3$ . The difference below $E = 0.20$ MeV can be seen in the rates for $T_{9} \leq 0.07$ . In comparison with the calculations, the rates are found to be reduced by a factor of 10 $^{- 4}$ at $T_{9} = 0.05$ , because of an accurate description for $^{8}$ Be break-up. Uncertainties of the rates are also estimated by examining the sensitivity to the 3 $α$ potentials. By introducing three-body $S$ -factors and a resonant term, the present rates are expressed in an analytic form, and they are provided in a tabular form for astrophysical applications. To update the evaluated rates, non-resonant sequential process between $α +^{8}$ Be could be removed. The astrophysical impact is not expected to be large, although the rates are reduced around $T_{9} = 0.05$ .
nucl-thastro-ph.SRJ.Phys.G(2025)·0 citations
05
RHIC $s_{N N} = 200$ GeV hadron yields and the isospin dependent equation of state
Feyisola Nana · Jordi Salinas San Martín · Jacquelyn Noronha-Hostler
The statistical hadronization model has been successful in extracting information at chemical freeze-out in heavy-ion collisions. At RHIC, with a collision energy of $s_{N N} = 200$ GeV, many different ion species have been used for $A$ + $A$ collisions. This allows for a scan across the charge fraction $Y_{Q} = Z / A$ , where $Z$ is the proton number and $A$ is the baryon number. We first make predictions for $A$ + $A$ collisions that do not yet have published experimental data on hadron yield ratios (O+O, Ru+Ru, Zr+Zr). We then use both the experimental and predicted yield ratios to perform thermal fits across $Y_{Q}$ , enabling us to extract $s / n_{B}$ and other thermodynamic information at chemical freeze-out. Using the relation between $s / n_{B}$ and $Y_{Q}$ , we can calculate a new constraint on the finite temperature equation of state at finite densities. We discuss implications of this constraint and propose future runs that can help connect to the equation of state relevant for neutron star mergers.
nucl-thhep-ph3 citations
06
Tetraneutron resonance and its isospin analogues
A. M. Shirokov · A. I. Mazur · I. A. Mazur · V. A. Kulikov
We discuss isospin analogues of the tetraneutron resonance and their possible manifestations in nuclear structure and reactions.
nucl-thIJMPE(2024)·0 citations
07
Hyperon Production in Bi+Bi Collisions at NICA and Angular Dependence of Hyperon Spin Polarization
Nikita S. Tsegelnik · Vadym Voronyuk · Evgeni E. Kolomeitsev
The strange baryon production in Bi+Bi collisions at $s_{N N} = 9.0$ \,GeV is studied using the PHSD transport model. Hyperon and anti-hyperon yields, transverse momentum spectra, and rapidity spectra are calculated, their centrality dependence and the effect of rapidity and transverse momentum cuts are studied. The rapidity distributions for $L amb d a$ , $Ξ$ , $X i$ baryons are found to be systematically narrower than for $Λ$ s. The $p_{T}$ slope parameters for anti-hyperons vary more with centrality than those for hyperons. Restricting the accepted rapidity range to $∣ y ∣ < 1$ increases the slope parameters by 13--30\,MeV depending on the centrality class and the hyperon mass. Hydrodynamic velocity and vorticity fields are calculated and the formation of two oppositely rotating vortex rings moving in opposite directions along the collision axis is found. The hyperon spin polarization induced by the medium vorticity within the thermodynamic approach is calculated and the dependence of the polarization on the transverse momentum and rapidity cuts and on the centrality selection is analyzed. The cuts have stronger effect on the polarization of $Λ$ and $Ξ$ hyperons than on the corresponding anti-hyperons. The polarization signal is maximal for the centrality class 60-70\%. We show that for the considered hyperon polarization mechanism the structure of the vorticity field makes an imprint on the polarization signal as a function of the azimuthal angle in the transverse momentum plane, $ϕ_{H}$ , $cos ϕ_{H} = p_{x} / p_{T}$ . For particles with positive longitudinal momentum, $p_{z} > 0$ , the polarization increases with $cos ϕ_{H}$ , while for particles with $p_{z} < 0$ it decreases.
nucl-thParticles(2024)·5 citations
08
Helium as an Indicator of the Neutron-Star Merger Remnant Lifetime and its Potential for Equation of State Constraints
Albert Sneppen🇩🇰 · Oliver Just🇩🇪 · Andreas Bauswein🇩🇪 · Rasmus Damgaard🇩🇰 · Darach Watson🇩🇰 · Luke J. Shingles🇩🇪 · Christine E. Collins🇮🇪 · Stuart A. Sim🇩🇰 · Zewei Xiong🇩🇪 · Gabriel Martinez-Pinedo🇩🇪 · Theodoros Soultanis🇩🇪 · Vimal Vijayan🇩🇪
The time until black hole formation in a binary neutron-star (NS) merger contains invaluable information about the nuclear equation of state (EoS) but has thus far been difficult to measure. We propose a new way to constrain the merger remnant's NS lifetime, which is based on the tendency of the NS remnant neutrino-driven winds to enrich the ejected material with helium. Based on the He I $λ 1083.3$ nm line, we show that the feature around 800-1200 nm in AT2017gfo at 4.4 days seems inconsistent with a helium mass fraction of $X_{He} ≳ 0.05$ in the polar ejecta. Our recent neutrino-hydrodynamic simulations of merger remnants are only compatible with this limit if the NS remnant collapses within 20-30 ms. Such a short lifetime implies that the total binary mass of GW170817, $M_{tot}$ , lay close to the threshold binary mass for direct gravitational collapse, $M_{thres}$ , for which we estimate $M_{thres} ≲ 2.93 M_{⊙}$ . This upper bound on $M_{thres}$ yields upper limits on the radii and maximum mass of cold, non-rotating NSs, which rule out simultaneously large values for both quantities. In combination with causality arguments, this result implies a maximum NS mass of $M_{max} ≲ 2.3 M_{⊙}$ . The combination of all limits constrains the radii of 1.6 M $_{⊙}$ NSs to about 12 $\pm$ 1 km for $M_{max}$ = 2.0 M $_{⊙}$ and 11.5 $\pm$ 1 km for $M_{max}$ = 2.15 M $_{⊙}$ . This $\sim 2$ km allowable range then tightens significantly for $M_{max}$ above $\approx 2.15$ M $_{⊙}$ . This rules out a significant number of current EoS models. The short NS lifetime also implies that a black-hole torus, not a highly magnetized NS, was the central engine powering the relativistic jet of GRB170817A. Our work motivates future developments... [abridged]
↳ astro-ph.HEnucl-thPRD(2026)·19 citations
09
Phase transition on superfluid vortices in Higgs-Confinement crossover
Tomoya Hayata🇯🇵 · Yoshimasa Hidaka🇯🇵 · Dan Kondo🇯🇵
We propose a novel method to distinguish states of matter by identifying spontaneous symmetry breaking on extended objects, such as vortices, even in the absence of a bulk phase transition. As a specific example, we investigate the phase transition on superfluid vortices in the Higgs-confinement crossover using a $U (1)_{gauge} \times U (1)_{global}$ model. This model exhibits superfluidity of $U (1)_{global}$ symmetry and allows for a crossover between the Higgs and confinement regimes by varying the gauge coupling constant from weak to strong. We demonstrate that, on vortices, spontaneous breaking of the $Z_{2}$ flavor symmetry occurs in the weak coupling (Higgs) regime, while it does not in the strong coupling (confinement) regime. We also confirm that those regimes are separated by a second-order phase transition through Monte Carlo simulations, whose universality class corresponds to the two-dimensional Ising model.
↳ hep-thcond-mat.supr-conhep-lathep-ph+1JHEP(2025)·3 citations
10
Speed of sound and trace anomaly in a unified treatment of the two-color diquark superfluid, the pion-condensed high-isospin matter, and the 2SC quark matter
Kenji Fukushima🇯🇵 · Shuhei Minato🇯🇵
In a unified perturbative treatment from the high-density side, we compute the speed of sound and the trace anomaly as functions of the chemical potential $μ$ for the two-color diquark superfluid, the pion-condensed high-isospin matter, and the 2SC quark matter. We find that the corrections induced by the gap energy $Δ$ involve nontrivial interplay between the dimensionless magnitude $∣Δ/ μ ∣$ and the derivative $∣ \partial Δ/ \partial μ ∣$ . Even though the gap equation has a common structure for these phases of our interest, different numerical constants cause drastic changes in the speed of sound corrections. As long as $∣Δ/ μ ∣$ is dominant over the derivative, the gap effects increase the speed of sound, which is consistent with the expected behavior of exhibiting a peak at intermediate density. We then discuss the trace anomaly which is pushed down generally by the gap effects and turns out to be negative widely in the high density regime. For demonstration of non-perturbative enhancement, we take account of the instanton-induced interaction. We confirm a further increase in the speed of sound for the two-color diquark superfluid and the pion-condensed high-isospin matter, while the speed of sound for the 2SC quark matter deviates far below the conformal limit due to the derivative contribution.
↳ hep-phnucl-thPRD(2025)·35 citations
11
Impurities in Schrödinger field theories and s-wave resonance
Avia Raviv-Moshe · Siwei Zhong
We study point impurities in non-relativistic quantum field theories, with a focus on scale-invariant fixed points. We establish the framework of conformal defects in Schrödinger field theories and their correspondence to many-body states in a harmonic trap. We discuss a multi-critical quantization of the one-body wave function induced by an impurity, with examples of free and unitary Fermi gases. Our results can potentially be tested in experimental setups.
↳ cond-mat.quant-gascond-mat.str-elhep-thnucl-thJHEP(2025)·6 citations
12
Astrophysical constraints on color-superconducting phases in compact stars within the RG-consistent NJL model
Hosein Gholami🇩🇪 · Ishfaq Ahmad Rather🇩🇪 · Marco Hofmann🇩🇪 · Michael Buballa🇩🇪 · Jürgen Schaffner-Bielich🇩🇪
We determine parameters of the renormalization group-consistent three-flavor color-superconducting Nambu-Jona-Lasinio (NJL) model that are suited to investigate possible compact-star configurations. Our goal is to provide quark-matter equations of state (EoS) that can be used for hadron-quark hybrid-star constructions. To that end, we mainly focus on the parameters of the quark-matter model. By varying the vector and diquark coupling constants, we analyze their impact on the EoS, the speed of sound, the maximum diquark gap, and the mass-radius relation. In almost all configurations, a stable color-flavor-locked (CFL) phase appears in the core of the maximum-mass configurations, typically spanning several kilometers in radius. In other cases, the star's two-flavor color-superconducting (2SC) branch of the EoS becomes unstable before reaching the CFL transition density. At neutron-star densities, the speed of sound squared reaches up to $c_{s}^{2} \sim 0.6$ and the CFL gap up to $Δ \sim 250$ MeV. We argue that adding a hadronic EoS at lower densities by performing a Maxwell construction does not increase the maximum mass substantially. Thus we use the $2.0 M_{⊙}$ constraint to constrain the NJL model parameters that are suited for the construction of hybrid-star EoS. We construct three examples of the hybrid-star model, demonstrating that there is room for different color-superconducting compositions. The hybrid EoSs obtained in this way can have no 2SC matter or different ratios of 2SC and CFL quark matter in the core. We show that early hadron-quark transitions are possible that can modify the tidal deformability at 1.4 $M_{⊙}$ . We find that these EoSs are consistent with the imposed constraints from astrophysics and perturbative QCD. They allow for different hybrid-star scenarios with a hadronic EoS that is soft at low to intermediate densities ( $\sim 1 - 3 n_{sat}$ ).
↳ hep-phastro-ph.SRnucl-thPRD(2025)·55 citations

Affiliations

first authorsco-authorsvia INSPIRE