Nuclear Theory·nucl-th

Thursday·November 7, 2024

12 papers—7 primary·5 cross-listed

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

Helium as an Indicator of the Neutron-Star Merger Remnant Lifetime and its Potential for Equation of State Constraints

Phase transition on superfluid vortices in Higgs-Confinement crossover

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

Impurities in Schrödinger field theories and s-wave resonance

Astrophysical constraints on color-superconducting phases in compact stars within the RG-consistent NJL model

Affiliations