Nuclear Theory·nucl-th

Tuesday·May 4, 2021

12 papers—5 primary·7 cross-listed

01
[Submitted on 30 Apr 2021]
Constraining free parameters of a color superconducting non-local Nambu-Jona-Lasinio model using Bayesian analysis of neutron stars mass and radius measurements
Mahboubeh Shahrbaf🇵🇱 · Sofija Antić🇵🇱 · A. Ayriyan🇷🇺 · David Blaschke🇵🇱 · Ana Gabriela Grunfeld🇦🇷
We provide a systematic study of hybrid neutron star equations of state (EoS) consisting of a relativistic density functional for the hadronic phase and a covariant nonlocal Nambu--Jona-Lasinio (nlNJL) model to describe the color superconducting quark matter phase. Changing the values of the two free parameters, the dimensionless vector and diquark coupling strengths $η_{V}$ and $η_{D}$ results in a set of EoS with varying stiffness and deconfinement onset. The favorable parameters are obtained from a systematic Bayesian analysis for which the multi-messenger constraint on the neutron star radius at $1.4$ M $_{⊙}$ and the combined mass-radius constraint for PSR J0740+6620 from NICER experiment are used as the constraints. Additionally, the transition from hadronic matter to deconfined quark matter is constrained to occur above nuclear saturation density. Hybrid stars modeled with these favorable parameters are compatible with the NICER results for the radius of the highest known mass neutron star, PSR J0740+6620. Three new observations interesting for neutron star phenomenology are reported: 1) We show that the constant sound speed (CSS) EoS provides an excellent fit to that of the nlNJL model which implies the squared speed of sound at high densities to be about $0.5$ for the optimized parameters; 2) we give a simple functional form for the mapping between the parameter spaces of these two models valid for the whole range of relevant chemical potentials and 3) we observe that the special point property of hybrid EoS based on CSS quark matter generalizes to a set of lines consisting of special points when two EoS parameters are varied instead of one. A lower limit for the maximum mass of hybrid stars as a function of the vector coupling strength is obtained.
Comments:
18 pages, 14 figures, 2 tables; major revision of v1 with Bayesian analysis, discussion of special points, new text, figures and references added
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2105.00029 [pdf]
PRD(2023)·34 citations
02
[Submitted on 1 May 2021]
Scaling of factorial moments in cumulative variables
Subhasis Samanta🇵🇱 · Tobiasz Czopowicz🇵🇱 · Marek Gazdzicki🇵🇱
A search for power-law fluctuations within the framework of the intermittency method is ongoing to locate the critical point of the strongly interacting matter. In particular, experimental data on proton and pion production in heavy-ion collisions are analyzed in transverse-momentum, $p_{T}$ , space. In this regard, we have studied the dependence of the second scaled factorial moment $F_{2}$ of particle multiplicity distribution on the number of subdivisions of transverse momentum-interval used in the analysis. The study is performed using a simple model with a power-law two-particle correlation function in $p_{T}$ . We observe that $F_{2}$ values depend on the size and position of the $p_{T}$ interval. However, when we convert the non-uniform transverse-momentum distribution to uniform one using cumulative transformation, $F_{2}$ calculated in subdivisions of the cumulative $p_{T}$ becomes independent of the cumulative- $p_{T}$ interval. The scaling behaviour of $F_{2}$ for the cumulative variable is observed. Moreover, $F_{2}$ follows a power law with the number of subdivisions of the cumulative- $p_{T}$ interval with the intermittency index close to the correlation function's exponent.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.00344 [pdf]
NPA(2021)·11 citations
03
[Submitted on 3 May 2021]
QCD equation of state and the structure of neutron stars in NJL model
Shu-Sheng Xu🇨🇳
The chiral and pion superfluidity phase transitions are studied within NJL model. The model parameters are fitted by pion mass and decay constant together with recent isospin density from lattice QCD. The dense and cold QCD matter suffered the first order chiral phase transition during the quark chemical potential increase. Based on the studies of phase structures, the equation of states~(EoS) of dense QCD matter are calculated with the conditions of $β$ equilibrium and electric charge neutrality. Take the EoS as input, the mass-radius relation of neutron stars are predicted, which is consistent with recent observations of heaviest mass and radius of $1.4 M_{⊙}$ .
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.00630 [pdf]
NPB(2021)·11 citations
04
[Submitted on 3 May 2021]
On the structure in the $Λ N$ cross section at the $Σ N$ threshold
J. Haidenbauer🇩🇪 · U.-G. Meißner🇩🇪
The complexity of threshold phenomena is exemplified on a prominent and long-known case - the structure in the $Λ p$ cross section (invariant mass spectrum) at the opening of the $Σ N$ channel. The mass splitting between the $Σ$ baryons together with the angular momentum coupling in the $^{3} S_{1}$ - $^{3} D_{1}$ partial wave imply that, in principle, up to six channels are involved. Utilizing hyperon-nucleon potentials that provide an excellent description of the available low-energy $Λ p$ and $Σ N$ scattering data, the shape of the resulting $Λ p$ cross section is discussed and the poles near the $Σ N$ threshold are determined. Evidence for a strangeness $S = - 1$ dibaryon is provided, in the form of a deuteron-like (unstable) $Σ N$ bound state. Predictions for level shifts and widths of $Σ^{-} p$ atomic states are given.
Comments:
10 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.00836 [pdf]
CPC(2021)·15 citations
05
[Submitted on 3 May 2021]
Transient Relativistic Fluid Dynamics in a General Hydrodynamic Frame
Jorge Noronha🇺🇸 · Michał Spaliński🇵🇱 · Enrico Speranza🇺🇸
We propose a new theory of second-order viscous relativistic hydrodynamics which does not impose any frame conditions on the choice of the hydrodynamic variables. It differs from Mueller-Israel-Stewart theory by including additional transient degrees of freedom, and its first-order truncation reduces to Bemfica-Disconzi-Noronha-Kovtun theory. Conditions for causality and stability are explicitly given in the conformal regime. As an illustrative example, we consider Bjorken flow solutions to our equations and identify variables which make a hydrodynamic attractor manifest.
Comments:
10 pages, 1 figure, version accepted for publication in Physical Review Letters
Subjects:
Nuclear Theory (nucl-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Theory (hep-th)
arXiv:
2105.01034 [pdf]
PRL(2022)·61 citations

Affiliations

first authorsco-authorsvia INSPIRE

Constraining free parameters of a color superconducting non-local Nambu-Jona-Lasinio model using Bayesian analysis of neutron stars mass and radius measurements

Scaling of factorial moments in cumulative variables

QCD equation of state and the structure of neutron stars in NJL model

On the structure in the ΛN cross section at the ΣN threshold

Transient Relativistic Fluid Dynamics in a General Hydrodynamic Frame

Affiliations

On the structure in the $Λ N$ cross section at the $Σ N$ threshold