Nuclear Theory·nucl-th

Monday·February 3, 2025

11 papers—3 primary·8 cross-listed

04
Magnetic field evolution of X-ray emitting radio-quiet pulsars
Debasis Atta · Vinay Singh · D. N. Basu
The intense magnetic fields present in neutron stars are closely linked to their observed temperature and spectral characteristics, timing properties, including spin period and its derivatives. Therefore, a comprehensive theoretical analysis of magnetic field evolution is essential for understanding how the strength of the magnetic field change over time. The decay rate of magnetic field in isolated, non-accreting neutron stars can be assessed by evaluating the second derivative of the spin frequency. Another method to estimate this rate involves monitoring an increase in thermal emission beyond what is expected from standard cooling processes, assuming no additional heating mechanisms are present. Our findings indicate that for X-ray emitting isolated neutron stars, the evolution rate of spin period derivative aligns with the dissipation rate of magnetic energy from the dipolar field, provided that a substantial portion of the released energy is emitted as X-rays. The time scale of magnetic field decay is found to be much shorter than typical age of radio pulsars.
↳ astro-ph.HEastro-ph.SRnucl-th0 citations
05
Novel Scalings of Neutron Star Properties from Analyzing Dimensionless Tolman--Oppenheimer--Volkoff Equations
Bao-Jun Cai🇨🇳 · Bao-An Li🇨🇳
The TOV equations govern the radial evolution of pressure and energy density in static neutron stars (NSs) in hydrodynamical equilibrium. Using the reduced pressure and energy density with respect to the NS central energy density, the original TOV equations can be recast into dimensionless forms. While the traditionally used integral approach for solving the original TOV equations require an input nuclear Equation of State (EOS), the dimensionless TOV equations can be anatomized by using the reduced pressure and energy density as polynomials of the reduced radial coordinate without using any input nuclear EOS. Interesting and novel perspectives about NS core EOS can be extracted directly from NS observables using this new approach based on Intrinsic and Perturbative Analyses of the Dimensionless (IPAD) TOV equations (IPAD-TOV). In this review, we first discuss the length and energy density scales of NSs as well as the dimensionless TOV equations for scaled variables and their perturbative solutions near NS cores. We then review several new insights into NS physics gained from using the IPAD-TOV. We also demonstrate that the strong-field gravity plays a fundamental role in extruding a peak in the density/radius profile of the speed of sound squared (SSS) in massive NS cores independent of the nuclear EOS. Finally, some future perspectives of NS research using the IPAD-TOV are outlined.
↳ astro-ph.HEastro-ph.SRgr-qcnucl-ex+1EPJA(2025)·25 citations
06
Visualizing How the Structure of Large-Radius Jets Shapes Their Wakes
Arjun Srinivasan Kudinoor🇺🇸 · Daniel Pablos🇪🇸 · Krishna Rajagopal🇺🇸
The ATLAS collaboration has introduced and implemented a strategy for selecting and analyzing large-radius jets composed of skinny $R = 0.2$ subjets in heavy ion collisions at the LHC. We show how measurements of these jets teach us about the resolution length $L_{res}$ of quark-gluon plasma (QGP) and can teach us how jet substructure shapes the wakes that jets excite in the QGP droplets through which they pass. We use Hybrid Model calculations to reproduce measurements of $R_{AA}$ for large-radius jets in PbPb collisions, and study their dependence on the angle between the two skinny subjets involved in the final reclustering step of an $R = 1$ jet. We show how these observables can constrain the value of $L_{res}$ and demonstrate that the ATLAS data rule out any picture in which an entire parton shower loses energy coherently as if it were a single entity. Determining the degree to which the QGP can resolve partons within a jet is central to the broader program of using jet quenching measurements to probe QGP. We make further use of this setup by analyzing the response of the medium to the passage of large-radius $R = 2$ jets containing two skinny subjets in gamma-jet events. We introduce novel jet-shape observables that allow us to visualize the angular shape of the soft hadrons originating from the wakes that wide jets with two skinny subjets excite in a droplet of QGP, as a function of the angular separation between the subjets. We find that even when they are $\sim 0.8 - 1$ radian apart, a single broad wake is produced. Only when the two subjets are even farther apart is the presence of two sub-wakes revealed. We show that the way in which jet structure shapes jet wakes can be visualized with similar clarity in experiments by using only those hadrons with low $p_{T}$ . These observables thus offer a new and distinctive way of seeing jet wakes in heavy ion collision data.
↳ hep-phnucl-thJHEP(2026)·11 citations
07
Deviations from the Porter-Thomas Distribution due to Nonstatistical $γ$ Decay below the $^{150}$ Nd Neutron Separation Threshold
O. Papst · J. Isaak · V. Werner · D. Savran · N. Pietralla · G. Battaglia · T. Beck · M. Beuschlein · S. W. Finch · U. Friman-Gayer · K. E. Ide · R. V. F. Janssens and 8 other authors
We introduce a new method for the study of fluctuations of partial transition widths based on nuclear resonance fluorescence experiments with quasimonochromatic linearly polarized photon beams below particle separation thresholds. It is based on the average branching of decays of $J = 1$ states of an even-even nucleus to the $2_{1}^{+}$ state in comparison to the ground state. Between 5 and 7 MeV, a constant average branching ratio for $γ$ decays from $1^{-}$ states of 0.490(16) is observed for the nuclide $^{150}$ Nd. Assuming $χ^{2}$ -distributed partial transition widths, this average branching ratio is related to a degree of freedom of $ν = 1.93 (12)$ , rejecting the validity of the Porter-Thomas distribution, requiring $ν = 1$ . The observed deviation can be explained by nonstatistical effects in the $γ$ -decay behavior with contributions in the range of 9.4(10)% up to 94(10)%.
↳ nucl-exnucl-thPRL(2025)·4 citations
08
Hydrodynamic attractor in periodically driven ultracold quantum gases
Aleksas Mazeliauskas · Tilman Enss
Hydrodynamic attractors are a universal phenomenon of strongly interacting systems that describe the hydrodynamic-like evolution far from local equilibrium. In particular, the rapid hydrodynamization of the Quark-Gluon Plasma is behind the remarkable success of hydrodynamic models of high-energy nuclear collisions. So far, hydrodynamic attractors have been explored only in systems undergoing monotonic expansion, such as Bjorken flow. We demonstrate that a system with an oscillating isotropic expansion exhibits a novel cyclic attractor behavior. This phenomenon can be investigated in ultracold quantum gases with externally modulated scattering length, offering a new avenue for experimentally discovering hydrodynamic attractors.
↳ cond-mat.quant-gashep-phnucl-thPRL(2026)·9 citations
09
Exploring the DGLAP resummation in the JIMWLK Hamiltonian
Néstor Armesto🇪🇸 · Alex Kovner🇺🇸 · Víctor López-Pardo🇪🇸
We explore the recently derived equation that resums DGLAP corrections to the JIMWLK Hamiltonian in the simplified setting of the SU(2) gauge theory. We solve the equation numerically for the scattering matrix of a dressed gluon for a particular initial condition, that corresponds to a dipole initial state. As expected, the $S$ -matrix of a single dressed gluon state ceases to be unitary if evolved to significant $ln Q^{2} / Q_{s}^{2}$ . Our numerical results indicate an interesting universal (independent of the coupling constant) pattern for this deviation from unitarity.
↳ hep-phnucl-thJHEP(2025)·2 citations
10
Kilonova Emission from Neutron Star Mergers with Different Equations of State
Wu-Zimo Qiumu · Meng-Hua Chen · Qiu-Hong Chen · En-Wei Liang
Kilonova is an optical-infrared transient powered by the radioactive decay of heavy nuclei from binary neutron star mergers. Its observational characteristics depend on the mass and the nuclide composition of meger ejecta, which are sensitive to the equation of state (EoS) of neutron star. We use astrophysical conditions derived from different EoSs as nucleosynthesis inputs to explore the impact of various EoS on the $r$ -process nucleosynthesis and the kilonova emission. Our results show that both the abundance patterns of merger ejecta and kilonova light curves are strongly dependent on the neutron star EoSs. Given the mass of two neutron stars, the merger with a softer EoS tends to generate a larger amount of ejected material, and may lead to a brighter kilonova peak luminosity. The relationship between the neutron star EoS and the peak luminosity provides a probe for constraining the properties of EoS in multi-messenger observations of neutron star mergers.
↳ astro-ph.HEnucl-thRes.Astron.Astrophys.(2025)·3 citations
11
Viscous effects of a hot QGP medium in time dependent magnetic field and their phenomenological significance
Debarshi Dey🇮🇳 · Gowthama K K🇮🇳 · Sadhana Dash🇮🇳 · Basanta Kumar Nandi🇮🇳
In this work, we have studied, for the first time, the impact of a realistic picture of a time dependent electric and magnetic field on the shear and bulk viscosities of the medium. Both the electric and magnetic fields are considered to be exponentially decaying with time, and the study is valid in the regime where the magnetic field strength is weak ( $e B ≪ T^{2}$ ). The evaluation has been done in the kinetic theory framework wherein we have solved the relativistic Boltzmann transport equation within the relaxation time approximation collision kernel. We have shown that the constant weak field results as well as the $B = 0$ results in the literature can be obtained as special cases of our general results. We have observed that the shear and bulk viscosities increase with time or equivalently, decrease with the strength of the magnetic field. To connect these observations with experiments, we have calculated the thermalization time, shear viscosity to entropy ratio ( $η / s$ ), and bulk viscosity to entropy ratio ( $ζ / s$ ).
↳ hep-phnucl-thPRD(2025)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE