Nuclear Theory·nucl-th

Thursday·September 24, 2020

12 papers—6 primary·6 cross-listed

07
Rapidly Spinning Compact Stars with Deconfinement Phase Transition
Tuna Demircik🇮🇱 · Christian Ecker🇩🇪 · Matti Järvinen🇮🇱
We study rapidly spinning compact stars with equations of state featuring a first order phase transition between strongly coupled nuclear matter and deconfined quark matter by employing the gauge/gravity duality. We consider a family of models, which allow purely hadronic uniformly rotating stars with masses up to approximately $2.9 M_{⊙}$ , and are therefore compatible with the interpretation that the secondary component ( $2.5 9_{- 0.09}^{+ 0.08} M_{⊙}$ ) in GW190814 is a neutron star. These stars have central densities several times the nuclear saturation density so that strong coupling and non-perturbative effects become crucial. We construct models where the maximal mass of static (rotating) stars $M_{TOV}$ ( $M_{max}$ ) is either determined by the secular instability or a phase transition induced collapse. We find largest values for $M_{max} / M_{TOV}$ in cases where the phase transition determines $M_{max}$ , which shifts our fit result to $M_{max} / M_{TOV} = 1.22 7_{- 0.016}^{+ 0.031}$ , a value slightly above the Breu-Rezzolla bound $1.20 3_{- 0.022}^{+ 0.022}$ inferred from models without phase transition.
↳ astro-ph.HEgr-qchep-thnucl-thApJL(2021)·55 citations
08
Evolution of Non-Gaussian Hydrodynamic Fluctuations
Xin An🇺🇸 · Gokce Basar🇺🇸 · Mikhail Stephanov🇺🇸 · Ho-Ung Yee🇺🇸
In the context of the search for the QCD critical point using non-Gaussian fluctuations, we obtain the evolution equations for non-Gaussian cumulants to the leading order of the systematic expansion in the magnitude of thermal fluctuations. We develop a diagrammatic technique in which the leading order contributions are given by tree diagrams. We introduce a Wigner transform for multipoint correlators and derive the evolution equations for three- and four-point Wigner functions for the problem of nonlinear stochastic diffusion with multiplicative noise.
↳ hep-thcond-mat.stat-mechhep-phnucl-thPRL(2021)·60 citations
09
Repulsive properties of hadrons in lattice QCD data and neutron stars
Anton Motornenko🇩🇪 · Somenath Pal🇮🇳 · Abhijit Bhattacharyya🇮🇳 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪
Second-order susceptibilities $χ_{ij}^{11}$ of baryon, electric, and strangeness, $B$ , $Q$ , and $S$ , charges, are calculated in the Chiral Mean Field (CMF) model and compared to available lattice QCD data. The susceptibilities are sensitive to the short range repulsive interactions between different hadron species, especially to the hardcore repulsion of hyperons. Decreasing the hyperons size, as compared to the size of the non-strange baryons, does improve significantly the agreement of the CMF model results with the Lattice QCD data. The electric charge-dependent susceptibilities are sensitive to the short range repulsive volume of mesons. The comparison with lattice QCD data suggests that strange baryons, non-strange mesons and strange mesons have significantly smaller excluded volumes than non-strange baryons. The CMF model with these modified hadron volumes allows for a mainly hadronic description of the QCD susceptibilities significantly above the chiral pseudo-critical temperature. This improved CMF model which is based on the lattice QCD data, has been used to study the properties of both cold QCD matter and neutron star matter. The phase structure in both cases is essentially unchanged, i.e. a chiral first-order phase transition occurs at low temperatures ( $T_{CP} \approx 17$ MeV), and hyperons survive deconfinement to higher densities than non-strange hadrons. The neutron star maximal mass remains close to 2.1 $M_{⊙}$ and the mass-radius diagram is only modified slightly due to the appearance of hyperons and is in agreement with astrophysical observations.
↳ hep-phastro-ph.HEnucl-thPRC(2021)·23 citations
10
Screening Effects on Electron Capture Rates and Type Ia Supernova Nucleosynthesis
Kanji Mori · Toshio Suzuki · Michio Honma · Michael A. Famiano · Toshitaka Kajino · Motohiko Kusakabe · A. Baha Balantekin
Type Ia supernovae (SNe Ia) are believed to be a thermonuclear explosion of a white dwarf, but the mass of their progenitors is still an open problem. In near-Chandrasekhar-mass (near-M_Ch) models of SNe Ia, the central density reaches >10^9 g cm^{-3}. The electron chemical potential becomes higher than the Q-values of electron capture (EC) transitions between fp-shell nuclei, so a portion of the available electrons is captured by iron group elements and thus neutron-rich isotopes are formed. Since EC reaction rates are sensitive to the density, the degree of neutronization is a key to distinguish near- and sub-M_Ch models. In order to compare observations and theoretical models, an accurate treatment of EC reactions is necessary. In previous theoretical works, however, effects of electron screening on ECs are ignored. Screening lowers EC rates and thus leads to a higher electron fraction. We implement electron screening on ECs to calculate explosive SN Ia nucleosynthesis in a near-M_Ch single degenerate model. It is found that some of neutron-rich nuclear abundances, namely those of 46,48Ca, 50Ti, 54Cr, 58Fe, 64Ni and 67,70Zn, decrease when screening effects on ECs are considered. Of these, 50Ti, 54Cr and 58Fe are particularly interesting because a significant portion of the solar abundance of these nuclei is presumed to originate from SNe Ia. We conclude that implementing the screening effect on ECs in modern SN Ia models is desirable to precisely calculate abundances of neutron-rich nuclides.
↳ astro-ph.HEastro-ph.SRnucl-thApJ(2020)·11 citations
11
The lightest flavor--singlet qqq baryons as witnesses to color
Jonathan Estévez🇪🇸 · Felipe J. Llanes-Estrada (Univ. Complutense Madrid)🇪🇸 · Víctor Martínez-Fernández (Nat. Center for Nuclear Research, Warsaw)🇵🇱 · Álvaro Pastor-Gutiérrez (Univ. Heidelberg)🇩🇪
We present a new computation in a field-theoretical model of Coulomb gauge QCD of the first radial and angular excitations of a qqq system in a SU(3) flavor singlet state, Lambda_S. The traditional motivation for the study is that the absence of flavor singlets in the lowest-lying spectrum is a direct consequence of the color degree of freedom. (The calculation is tested with decuplet baryons Delta(1232) and Omega(1672).) We also analyze decay branching fractions of the flavor singlet baryon for various masses with the simplest effective Lagrangians.
↳ hep-phnucl-thPRD(2020)·4 citations
12
Directed flow of D mesons at RHIC and LHC: non-perturbative dynamics, longitudinal bulk matter asymmetry and electromagnetic fields
Lucia Oliva🇩🇪 · Salvatore Plumari🇮🇹 · Vincenzo Greco🇮🇹
We present a study of the directed flow $v_{1}$ for $D$ mesons discussing both the impact of initial vorticity and electromagnetic field. Recent studies predicted that $v_{1}$ for $D$ mesons is expected to be surprisingly much larger than that of light charged hadrons; we clarify that this is due to a different mechanism leading to the formation of a directed flow with respect to the one of the bulk matter at both relativistic and non-relativistic energies. We point out that the very large $v_{1}$ for $D$ mesons can be generated only if there is a longitudinal asymmetry between the bulk matter and the charm quarks and if the latter have a large non-perturbative interaction in the QGP medium. A quite good agreement with the data of STAR and ALICE is obtained if the diffusion coefficient able to correctly predict the $R_{AA} (p_{T})$ , $v_{2} (p_{T})$ and $v_{3} (p_{T})$ of $D$ meson is employed. Furthermore, the mechanism for the build-up of the $v_{1} (y)$ is associated to a quite small formation time that can be expected to be more sensitive to the initial high-temperature dependence of the charm diffusion coefficient. We discuss also the splitting of $v_{1}$ for $D^{0}$ and $D ˉ^{0}$ due to the electromagnetic field that is again much larger than the one observed for charged particles and in agreement with the data by STAR that have however still error bars comparable with the splitting itself, while at LHC standard electromagnetic profile assuming a constant conductivity is not able to account for the huge splitting observed.
↳ hep-phnucl-thJHEP(2021)·46 citations

Affiliations

first authorsco-authorsvia INSPIRE

Rapidly Spinning Compact Stars with Deconfinement Phase Transition

Evolution of Non-Gaussian Hydrodynamic Fluctuations

Repulsive properties of hadrons in lattice QCD data and neutron stars

Screening Effects on Electron Capture Rates and Type Ia Supernova Nucleosynthesis

The lightest flavor--singlet qqq baryons as witnesses to color

Directed flow of D mesons at RHIC and LHC: non-perturbative dynamics, longitudinal bulk matter asymmetry and electromagnetic fields

Affiliations