Nuclear Theory·nucl-th

Wednesday·February 20, 2019

8 papers—5 primary·3 cross-listed

01
Absence of Landau-Peierls Instability in the Magnetic Dual Chiral Density Wave Phase of Dense QCD
Efrain J Ferrer🇺🇸 · Vivian de la Incera🇺🇸
We investigate the stability of the Magnetic Dual Chiral Density Wave (MDCDW) phase of cold and dense QCD against collective low-energy fluctuations of the order parameter. The appearance of additional structures in the system free-energy due to the explicit breaking of the rotational and isospin symmetries by the external magnetic field and the field-induced asymmetry of the lowest Landau level modes play a crucial role in the analysis. The new structures not only affect the condensate minimum equations, but also the spectrum of the thermal fluctuations, which lacks the transverse soft modes that typically affect single-modulated inhomogeneous phases in the absence of a magnetic field. Consequently, the long-range order of the MDCDW phase is preserved at finite temperature. The lack of Landau-Peierls instabilities in the MDCDW phase makes this inhomogeneous phase of dense quark matter particularly relevant for the physics of neutron stars.
nucl-thastro-ph.HEhep-phPRD(2020)·28 citations
02
Nuclear electromagnetic currents to fourth order in chiral effective field theory
H. Krebs🇩🇪 · E. Epelbaum🇩🇪 · U.-G. Meißner🇩🇪
Recently, we have shown that the continuity equation for the nuclear vector and axial current operators acquires additional terms if the latter depend on the energy transfer. We analyze in detail the electromagnetic single-nucleon four-current operators and verify the validity of the modified continuity equation for all one- and two-nucleon contributions up to fourth order in the chiral expansion. We also derive, for the first time, the leading contribution to the three-nucleon charge operator which appears at this order. Our study completes the derivation of the electroweak nuclear currents to fourth order in the chiral expansion.
nucl-thFew Body Syst.(2019)·53 citations
03
Bayesian analysis of the crust-core transition with a compressible liquid-drop model
Thomas Carreau🇫🇷 · Francesca Gulminelli🇫🇷 · Jérôme Margueron🇫🇷
The crust-core phase transition of neutron stars is quantitatively studied within a unified meta-modelling of the nuclear Equation of State (EoS). The variational equations in the crust are solved within a Compressible Liquid Drop (CLD) approach, with surface parameters consistently optimized for each EoS set on experimental nuclear mass data. When EoS parameters are taken from known Skyrme or RMF functionals, the transition point of those models is nicely reproduced. A model-independent probability distribution of EoS parameters and of the transition density and pressure is determined with a Bayesian analysis, where the prior is given by an uncorrelated distribution of parameters within the present empirical uncertainties, and constraints are applied both from neutron star physics and ab-initio modelling. We show that the characteristics of the transition point are largely independent of the high density properties of the EoS, while ab-initio EoS calculations of neutron and symmetric matter are far more constraining. The most influential parameter for the determination of the transition point governs the surface properties of extremely neutron rich matter, and it is strongly unconstrained. This explains the large dispersion of existing predictions of the transition point. Only if the surface tension is fixed to a reasonable but somewhat arbitrary value, strong correlations with isovector parameters ( $L_{sy m}, K_{sy m}$ and $Q_{sy m}$ ) are recovered. Within the present experimental and theoretical uncertainties on those parameters, we estimate the transition density as $n_{t} = 0.072 \pm 0.011$ fm $^{- 3}$ and the transition pressure as $P_{t} = 0.339 \pm 0.115$ MeV fm $^{- 3}$ .
nucl-thEPJA(2019)·96 citations
04
Quadrupole collectivity and shell closure in neutron-rich nuclei around $N = 126$
X. Y. Wu · J. M. Yao
We present a comprehensive study on the low-lying states of neutron-rich Er, Yb, Hf, and W isotopes across the $N = 126$ shell with a multi-reference covariant density functional theory. Beyond mean-field effects from shape mixing and symmetry restoration on the observables that are relevant for understanding quadrupole collectivity and underlying shell structure are investigated. The general features of low-lying states in closed-shell nuclei are retained in these four isotopes around $N = 126$ , even though the shell gap is overall quenched by about 30\% with the beyond mean-field effects. These effects are consistent with the previous generator-coordinate calculations based on Gogny forces, but much smaller than that predicted by the collective Hamiltonian calculation. It implies that the beyond mean-field effects on the $r$ -process abundances before the third peak at $A \sim 195$ might be more moderate than that found in A. Arcones and G. F. Bertsch, Phys. Rev. Lett. 108, 151101 (2012).
nucl-thPRC(2019)·9 citations
05
New paradigm for fluctuations in heavy-ion collisions
Giuliano Giacalone🇫🇷 · Pablo Guerrero-Rodríguez🇪🇸 · Matthew Luzum🇧🇷 · Cyrille Marquet🇫🇷 · Jean-Yves Ollitrault🇫🇷
Since their discovery, fluctuations in the initial state of heavy-ion collisions have been understood as originating mostly from the random positions of nucleons within the colliding nuclei. We consider an alternative approach where all the focus is on fluctuations generated by QCD interactions, that we evaluate at leading logarithmic accuracy in the color glass condensate effective theory. We validate our approach using BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) data on anisotropic flow. In particular, we show that, compared to standard Glauber-inspired calculations, our formalism provides a better description of the centrality dependence of the ratio of elliptic flow and triangular flow. It also naturally explains the evolution of elliptic flow fluctuations between RHIC and LHC energies.
nucl-thhep-exhep-phnucl-exPRC(2019)·35 citations
06
The role of the stochastic color field fluctuations on $J / ψ$ suppression in ultra-relativistic heavy-ion collisions
Ashik Ikbal Sheikh🇮🇳 · Zubayer Ahammed🇮🇳 · M.G. Mustafa🇮🇳
We consider the effect of the stochastic color field fluctuations in addition to the collisional as well as the radiative energy losses in the propagation of charm quarks in the hot and dense deconfined medium of quarks and gluons created in ultra-relativistic heavy-ion collisions. These fluctuations lead to energy gain of the propagating charm quarks. We construct and solve Langevin transport equations for charm quarks under the evolving background matter described by the ( $3 + 1$ )-D relativistic viscous hydrodynamics. Considering the energy gain of charm quarks, the nuclear modification factor $R_{AA}$ of $J / ψ$ is calculated. Interestingly, the experimental measurements for $J / ψ$ suppression in $A u - A u$ collisions at $s_{N N} = 200$ GeV by PHENIX Collaboration and $P b - P b$ collisions at $s_{N N} = 2.76$ TeV by ALICE and CMS Collaborations, can be nicely described with the effect of these field fluctuations without invoking the regeneration phenomena.
↳ hep-phnucl-th0 citations
07
Thermodynamics of Bose gases from functional renormalization with a hydrodynamic low-energy effective action
Felipe Isaule · Michael C. Birse · Niels R. Walet
The functional renormalization group for the effective action is used to construct an effective hydrodynamic description of weakly interacting Bose gases. We employ a scale-dependent parametrization of the boson fields developed previously to start the renormalization evolution in a Cartesian representation at high momenta and interpolate to an amplitude-phase one in the low-momentum regime. This technique is applied to Bose gases in one, two and three dimensions, where we study thermodynamic quantities such as the pressure and energy per particle. The interpolation leads to a very natural description of the Goldstone modes in the physical limit, and compares well to analytic and Monte-Carlo simulations at zero temperature. The results show that our method improves aspects of the description of low-dimensional systems, with stable results for the superfluid phase in two dimensions and even in one dimension.
↳ cond-mat.quant-gasnucl-thphysics.atom-phAnnals Phys.(2020)·13 citations
08
Elliptical flow coalescence to identify the $f_{0}$ (980) content
An Gu🇺🇸 · Terrence Edmonds🇺🇸 · Jie Zhao🇺🇸 · Fuqiang Wang🇺🇸
We use a simple coalescence model to generate $f_{0}$ (980) particles for three configurations: a $s s ˉ$ meson, a $u u ˉ s s ˉ$ tetraquark, and a $K^{+} K^{-}$ molecule. The phase-space information of the coalescing constituents is taken from a multi-phase transport (AMPT) simulation of heavy-ion collisions. It is shown that the number of constituent quarks scaling of the elliptic flow anisotropy can be used to discern $s s ˉ$ from $u u ˉ s s ˉ$ and $K^{+} K^{-}$ configurations.
↳ nucl-exnucl-thPRC(2020)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE