Nuclear Theory·nucl-th

Thursday·March 11, 2021

11 papers—7 primary·4 cross-listed

08
Bayesian nonparametric inference of neutron star equation of state via neural network
Ming-Zhe Han🇨🇳 · Jin-Liang Jiang🇨🇳 · Shao-Peng Tang🇨🇳 · Yi-Zhong Fan🇨🇳
We develop a new nonparametric method to reconstruct the Equation of State (EoS) of Neutron Star with multimessenger data. As an universal function approximator, the Feed-Forward Neural Network (FFNN) with one hidden layer and a sigmoidal activation function can approximately fit any continuous function. Thus we are able to implement the nonparametric FFNN representation of the EoSs. This new representation is validated by its capabilities of fitting the theoretical EoSs and recovering the injected parameters. Then we adopt this nonparametric method to analyze the real data, including mass-tidal deformability measurement from the Binary Neutron Star (BNS) merger Gravitational Wave (GW) event GW170817 and mass-radius measurement of PSR J0030+0451 by {\it NICER}. We take the publicly available samples to construct the likelihood and use the nested sampling to obtain the posteriors of the parameters of FFNN according to the Bayesian theorem, which in turn can be translated to the posteriors of EoS parameters. Combining all these data, for a canonical 1.4 $M_{⊙}$ neutron star, we get the radius $R_{1.4} = 11.8 3_{- 1.08}^{+ 1.25}$ km and the tidal deformability $Λ_{1.4} = 32 3_{- 165}^{+ 334}$ (90\% confidence interval).Furthermore, we find that in the high density region ( $\geq 3 ρ_{sat}$ ), the 90\% lower limits of the $c_{s}^{2} / c^{2}$ ( $c_{s}$ is the sound speed and $c$ is the velocity of light in the vacuum) are above $1/3$ , which means that the so-called conformal limit (i.e., $c_{s}^{2} / c^{2} < 1/3$ ) is not always valid in the neutron stars.
↳ hep-phastro-ph.HEgr-qcnucl-thApJ(2021)·56 citations
09
Soft interactions in cold quark matter
Tyler Gorda🇩🇪 · Aleksi Kurkela🇳🇴 · Risto Paatelainen🇫🇮 · Saga Säppi🇮🇹 · Aleksi Vuorinen🇫🇮
Accurate knowledge of the thermodynamic properties of zero-temperature, high-density quark matter plays an integral role in attempts to constrain the behavior of the dense QCD matter found inside neutron-star cores, irrespective of the phase realized inside the stars. In this Letter, we consider the weak-coupling expansion of the dense QCD equation of state and compute the next-to-next-to-next-to-leading-order contribution arising from the non-Abelian interactions among long-wavelength, dynamically screened gluonic fields. Accounting for these interactions requires an all-loop resummation, which can be performed using hard-thermal-loop (HTL) kinematic approximations. Concretely, we perform a full two-loop computation using the HTL effective theory, valid for the long-wavelength, or soft, modes. We find that the soft sector is well-behaved within cold quark matter, contrary to the case encountered at high temperatures, and find that the new contribution decreases the renormalization-scale dependence of the equation of state at high density.
↳ hep-phnucl-thPRL(2021)·166 citations
10
Gluon PDF from Quark dressing in the Nucleon and Pion
Adam Freese🇺🇸 · Ian C. Cloët🇺🇸 · Peter C. Tandy🇺🇸
Gluon dressing of the light quarks within hadrons is very strong and extremely important in that it dynamically generates most of the observable mass through the breaking of chiral symmetry. The quark and gluon parton densities, $q (x)$ and $g (x)$ , are necessarily interrelated since any gluon emission and absorption process, especially dressing of a quark, contributes to $g (x)$ and modifies $q (x)$ . Guided by long-established results for the parton-in-parton distributions from a strict 1-loop perturbative analysis of a quark target, we extend the non-perturbative QCD approach based on the Rainbow-Ladder truncation of the Dyson-Schwinger equations to describe the interrelated valence $q_{v} (x)$ and the dressing-gluon $g (x)$ for a hadron at its intrinsic model scale. We employ the pion description from previous DSE work that accounted for the gluon-in-quark effect and introduce a simple model of the nucleon for exploratory purposes. We find typically \mbox{ $⟨ x ⟩_{g} \sim 0.20$ } for both pion and nucleon at the model scale, and the valence quark helicity contributes 52\% of nucleon spin. We deduce both $q_{v} (x)$ and $g (x)$ from 30 calculated Mellin moments, and after adopting existing data analysis results for $q_{sea} (x)$ , we find that NLO scale evolution produces $g (x)$ in good agreement with existing data analysis results for the pion at 1.3 GeV and the nucleon at 5 GeV $^{2}$ . At the scale 2 GeV typical of lattice-QCD calculations, we obtain \mbox{ $⟨ x ⟩_{g}^{N} = 0.42$ } in good agreement with 0.38 from the average of recent lattice-QCD calculations.
↳ hep-phhep-latnucl-exnucl-thPLB(2021)·16 citations
11
Parametric resonance of complex scalar field under spacetime oscillations
Shreyansh S. Dave🇮🇳 · Sanatan Digal🇮🇳
In this proceeding, we study time evolution of a complex scalar field, in symmetry broken phase, in presence of oscillating spacetime metric background. We show that spacetime oscillations lead to parametric resonance of the field. This generates excitations in the field for a wide range of frequency of spacetime oscillations which ultimately lead to the formation of topological vortices. The lowest frequency cut-off to induce this phenomena is set by system size due to finite size effects.
↳ hep-thastro-ph.HEhep-phnucl-thSpringer Proc.Phys.(2022)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Bayesian nonparametric inference of neutron star equation of state via neural network

Soft interactions in cold quark matter

Gluon PDF from Quark dressing in the Nucleon and Pion

Parametric resonance of complex scalar field under spacetime oscillations

Affiliations