Nuclear Theory·nucl-th

Monday·November 11, 2019

11 papers—5 primary·6 cross-listed

01
Pasta fluctuations in symmetric matter at finite temperature
Celso C. Barros Jr🇧🇷 · Debora P. Menezes🇧🇷 · Francesca Gulminelli🇫🇷
The equilibrium distributions of the different pasta geometries and their linear sizes are calculated from the mean field Gibbs energy functional in symmetric nuclear matter at finite temperature. The average sizes and shapes coincide approximately with the ones predicted by a standard pasta calculation in the coexisting phase approximation, but fluctuations are additionally calculated and seen to increase with temperature and baryonic density. The different pasta shapes are shown to coexist in a wide domain of density and temperature, in qualitative agreement with the findings of large scale molecular dynamics simulations, but with a much less expensive computational cost.
nucl-thPRC(2020)·14 citations
02
Study of Some Aspects of Astronuclear System
Shamim Haque Mondal · Mahamadun Hasan · Murshid Alam · Md. Abdul Khan
In this work we have studied the bulk properties of compact stellar object which is largely motivated by the recent work of Potekhin group who studied the structure and evolution of compact star on the basis of unified EoS of Brussels-Montreal group. Here we solved ToV equation of state numerically using three sets of parameter models to compute pressure, baryon density and bulk modulus etc over a wide range of matter density. The computed values of the observables like the stellar interior pressure, bulk modulus and baryon density have been presented as a function of mass density in the tabular form. Graphical analysis of computed observables and their comparison with reference data wherever available have been presented as representative cases.
nucl-thastro-ph.SR0 citations
03
Transport coefficients of hot and dense matter
O. Soloveva🇩🇪 · P. Moreau🇩🇪 · L. Oliva🇩🇪 · T. Song🇩🇪 · W. Cassing🇩🇪 · E. Bratkovskaya🇩🇪
We present calculations for the shear viscosity of the hot and dense quark-gluon plasma (QGP) using the partonic scattering cross sections as a function of temperature $T$ and baryon chemical potential $μ_{B}$ from the dynamical quasiparticle model (DQPM) that is matched to reproduce the equation of state of the partonic system above the deconfinement temperature $T_{c}$ from lattice QCD. To this aim we calculate the collisional widths for the partonic degrees of freedom at finite $T$ and $μ_{B}$ in the time-like sector and conclude that the quasiparticle limit holds sufficiently well. Furthermore, the ratio of shear viscosity $η$ over entropy density $s$ , i.e. $η / s$ , is evaluated using these collisional widths and are compared to lQCD calculations for $μ_{B}$ = 0 as well. We find that the ratio $η / s$ is in agreement with the results of calculations within the original DQPM on the basis of the Kubo formalism. Furthermore, there is only a very modest change of $η / s$ with the baryon chemical $μ_{B}$ as a function of the scaled temperature $T / T_{c} (μ_{B})$ .
nucl-thhep-phSpringer Proc.Phys.(2020)·4 citations
04
Pairing dynamics in low energy nuclear collisions
M. C. Barton · S. Jin · P. Magierski · K. Sekizawa · G. Wlazłowski · A. Bulgac
Superfluidity is a generic feature of various quantum systems at low temperatures and it is in particular important for the description of dynamics of low energy nuclear reactions. The time-dependent density functional theory (TDDFT) is, to date, the only microscopic method which takes into account in a consistent way far from equilibrium dynamics of pairing field and single-particle degrees of freedom. The local version of TDDFT, so called TDSLDA, is particularly useful for the description of nuclear reactions and is well suited for leadership class computers of hybrid (CPU+GPU) architecture. The preliminary results obtained for collisions involving both medium-mass and heavy nuclei at the energies around the Coulomb barrier are presented.
nucl-thActa Phys.Polon.B(2020)·3 citations
05
On introducing Charge-Symmetry-Breaking terms to nuclear Energy Density Functionals
P. Bączyk🇵🇱 · M. Konieczka🇵🇱 · K.M.L. Martinez🇦🇺 · S. Antić🇦🇺 · P.A.M Guichon🇫🇷 · W. Satuła🇵🇱 · J.R. Stone🇬🇧 · A.W. Thomas🇦🇺
The Charge-Symmetry-Breaking (CSB) character of the nucleon-nucleon interaction is well established. This work presents two different ways of introducing such effects into a nuclear Energy Density Functional (EDF). CSB terms are either coming from the effective theory expansion or are derived from electromagnetic mixing of $ρ^{0}$ and $ω$ mesons. These terms are then introduced to Skyrme and Quark-Meson-Coupling EDFs, respectively.
nucl-thActa Phys.Polon.B(2020)·0 citations
06
Electromagnetic contribution to $Σ$ - $Λ$ mixing using lattice QCD+QED
Z.R. Kordov🇦🇺 · R. Horsley🇬🇧 · Y. Nakamura🇯🇵 · H. Perlt🇩🇪 · P.E.L. Rakow🇬🇧 · G. Schierholz🇩🇪 · H. Stüben🇩🇪 · R.D. Young🇦🇺 · J.M. Zanotti🇦🇺
Mixing in the $Σ^{0}$ - $Λ^{0}$ system is a direct consequence of broken isospin symmetry and is a measure of both isospin-symmetry breaking as well as general SU(3)-flavour symmetry breaking. In this work we present a new scheme for calculating the extent of $Σ^{0}$ - $Λ^{0}$ mixing using simulations in lattice QCD+QED and perform several extrapolations that compare well with various past determinations. Our scheme allows us to easily contrast the QCD-only mixing case with the full QCD+QED mixing.
↳ hep-lathep-phnucl-thPRD(2020)·15 citations
07
Pions in hot dense matter and their astrophysical implications
Bryce Fore🇺🇸 · Sanjay Reddy🇺🇸
We study the role of pions in hot dense matter encountered in astrophysics. We find that strong interactions enhance the number density of negatively charged pions and that this enhancement can be calculated reliably for a relevant range of density and temperature using the virial expansion. We assess the influence of pions and muons on the equation of state (EOS) and weak interaction rates in hot dense matter. We find that thermal pions increase the proton fraction and soften the EOS. We also find that charged current weak reactions involving pions and muons $ν ˉ_{μ} + μ^{-} \to π$ and $ν_{μ} + π^{-} \to μ^{-}$ make an important contribution to the opacity of muon neutrinos. This could influence the dynamics of core-collapse supernovae and neutron star mergers. Finally, we note that pion-nucleon reactions can alter the evolution of the proton fraction when weak interactions are not in equilibrium.
↳ astro-ph.HEnucl-thPRC(2020)·100 citations
08
Roper State from Overlap Fermions
Mingyang Sun🇺🇸 · Ying Chen🇨🇳 · Gen Wang🇺🇸 · Andrei Alexandru🇺🇸 · Shao-Jing Dong🇺🇸 · Terrence Draper🇺🇸 · Jacob Fallica🇺🇸 · Ming Gong🇨🇳 · Frank X. Lee🇺🇸 · Anyi Li🇺🇸 · Jian Liang🇺🇸 · Keh-Fei Liu🇺🇸 · Nilmani Mathur🇮🇳 · Yi-Bo Yang🇨🇳
The Roper state is extracted with valence overlap fermions on a $2 + 1$ -flavor domain-wall fermion lattice (spacing $a = 0.114$ fm and $m_{π} = 330$ MeV) using both the Sequential Empirical Bayes (SEB) method and the variational method. The results are consistent, provided that a large smearing-size interpolation operator is included in the variational calculation to have better overlap with the lowest radial excitation. Similar calculations carried out for an anisotropic clover lattice with similar parameters find the Roper $\approx 280$ MeV higher than that of the overlap fermion. The fact that the prediction of the Roper state by overlap fermions is consistently lower than those of clover fermions, chirally improved fermions, and twisted-mass fermions over a wide range of pion masses has been dubbed a "Roper puzzle." To understand the origin of this difference, we study the hairpin $Z$ -diagram in the isovector scalar meson ( $a_{0}$ ) correlator in the quenched approximation. Comparing the $a_{0}$ correlators for clover and overlap fermions, at a pion mass of 290 MeV, we find that the spectral weight of the ghost state with clover fermions is smaller than that of the overlap at $a = 0.12$ fm and $0.09$ fm, whereas the whole $a_{0}$ correlators of clover and overlap at $a = 0.06$ fm coincide within errors. This suggests that chiral symmetry is restored for clover at $a \leq 0.06$ fm and that the Roper should come down at and below this $a$ . We conclude that this work supports a resolution of the "Roper puzzle" due to $Z$ -graph type chiral dynamics. This entails coupling to higher components in the Fock space (e.g. $N π$ , $N π π$ states) to induce the effective flavor-spin interaction between quarks as prescribed in the chiral quark model, resulting in the parity-reversal pattern as observed in the experimental excited states of $N, Δ$ and $Λ$ .
↳ hep-phhep-latnucl-thPRD(2020)·18 citations
09
From Parton Saturation to Proton Spin: the Impact of BFKL Equation and Reggeon Evolution
Yuri V. Kovchegov🇺🇸
Lev Lipatov was a giant in the field of strong interactions and a dominant force in high-energy QCD for many decades. His work deeply influenced both how we think about QCD and how we perform calculations in the theory. Below we describe the work in two related research directions: the physics of parton saturation and proton spin at small $x$ . Both developments would have been impossible without Lipatov's groundbreaking work. Saturation physics would not have happened without the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equation. The recent progress in our theoretical understanding of the proton spin contribution coming from small- $x$ partons started with the seminal paper by Kirschner and Lipatov resumming double logarithms of energy in the Reggeon evolution.
↳ hep-phnucl-exnucl-th0 citations
10
Anisotropic Compact Stars in Rastall-Rainbow Gravity
Clésio E. Mota🇧🇷 · Luis C. N. Santos🇧🇷 · Franciele M. da Silva🇧🇷 · Cesar V. Flores🇧🇷 · Tiago J. N. da Silva🇧🇷 · Débora P. Menezes🇧🇷
In this work, we have investigated anisotropic neutron stars in the framework of Rastall-Rainbow gravity. All our calculations were computed using the IU-FSU realistic equation of state (EoS), in which was considered two cases: standard nucleonic composition and the one with the eight lightest baryons. From the neutron star masses and radii obtained we conclude that anisotropic pressure has significant consequences on the structure of stellar objects. In particular, when anisotropy is considered within the general relativity framework, it significantly modifies the maximum stellar mass. On the other hand, when Rastall-Rainbow gravity and anisotropy are simultaneously considered, they provide the best results for mass and radius values, including important astrophysical objects such as the LMXB NGC 6397 and the extremely massive pulsar millisecond MSP J0740 + 6620. Although the expected inclusion of hyperons in the nuclear model reproduces stellar masses smaller than those produced by standard nucleonic matter, we shown that the hyperon puzzle problem can be solved by including anisotropic effects on compact stars in the context of the Rastall-Rainbow gravity.
↳ astro-ph.HEgr-qcnucl-th9 citations
11
Binomial acceptance corrections for particle number distributions in high-energy reactions
Oleh Savchuk🇺🇦 · Roman V. Poberezhnyuk🇺🇦 · Volodymyr Vovchenko🇩🇪 · Mark I. Gorenstein🇺🇦
The binomial acceptance correction procedure is studied for particle number distributions detected in high energy reactions in finite regions of the momentum space. We present acceptance correction formulas for scaled variance, skewness, and kurtosis. Our considerations include various specific types of particles - positively or negatively charged, baryons and antibaryons - as well as conserved charges, namely, the net baryon number and electric charge. A simple model with effects of exact charge conservation, namely the Bessel distribution, is studied in some detail where effects of multi-particle correlations are present. The accuracy of the binomial filter is studied with UrQMD model simulations of inelastic proton-proton reactions. Binomial acceptance correction procedure works well when used inside a small region of phase space as well as for certain efficiency corrections, in particular for constructing net proton fluctuation from net baryon ones. Its performance is less accurate when applied to obtain UrQMD fluctuations in a finite rapidity window from fluctuations in the full $4 π$ space.
↳ hep-phhep-exnucl-thPRC(2020)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE