Nuclear Theory·nucl-th

Friday·May 1, 2020

13 papers—7 primary·6 cross-listed

08
[Submitted on 29 Apr 2020] (cross-list from hep-th)
On the canonical formulation of gauge field theories and Poincare transformations
Daniel N. Blaschke🇺🇸 · Francois Gieres🇫🇷
We address the Hamiltonian formulation of classical gauge field theories while putting forward results some of which are not entirely new, though they do not appear to be well known. We refer in particular to the fact that neither the canonical energy momentum vector $(P^{μ})$ nor the gauge invariant energy momentum vector $(P_{inv}^{μ})$ do generate space-time translations of the gauge field by means of the Poisson brackets: In a general gauge, one has to consider the so-called kinematical energy momentum vector and, in a specific gauge (like the radiation gauge in electrodynamics), one has to consider the Dirac brackets rather than the Poisson brackets. Similar arguments apply to rotations and to Lorentz boosts and are of direct relevance to the "nucleon spin crisis" since the spin of the proton involves a contribution which is due to the angular momentum vector of gluons and thereby requires a proper treatment of the latter. We conclude with some comments on the relationships between the different approaches to quantization (canonical quantization based on the classical Hamiltonian formulation, Gupta-Bleuler, path integrals, BRST, covariant canonical approaches).
Comments:
43 pages; Version accepted for publication in Nucl. Phys. B. Includes the interpretation of results on Hamiltonian symmetry generators as well as a concise and unified derivation of the gauge invariant currents associated to conformal invariance
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.14406 [pdf]
NPB(2021)·11 citations
09
[Submitted on 30 Apr 2020] (cross-list from hep-ph)
Thermodynamic properties and transport coefficients of QCD matter within the non-extensive Polyakov-Nambu-Jona-Lasinio model
Ya-Peng Zhao🇨🇳
We present a non-extensive version of the Polyakov-Nambu-Jona-Lasinio model which is based on the non-extentive statistical mechanics. This new statistics is characterized by a dimensionless non-extensivity parameter $q$ that accounts for all possible effects violating the assumptions of the Boltzmann-Gibbs statistics (when $q \to 1$ , it returns to the Boltzmann-Gibbs case). Using this q-Polyakov-Nambu-Jona-Lasinio model and including two different Polyakov-loop potentials, we discussed the influence of the parameter $q$ on chiral and deconfinement phase transition, various thermodynamic quantities and transport coefficients at finite temperature and zero quark chemical potential. We found that the Stefan-Boltzmann limit is actually related to the choice of statistics. For example, in the Tsallis statistics, the thermodynamic quantities $\frac{ϵ}{T ^{4}}$ , $\frac{p}{T ^{4}}$ and $\frac{s}{T ^{3}}$ all increase with $q$ , exceed their usual Stefan-Boltzmann limits and tend to a new $q$ -related Tsallis limit at temperature high enough. Interestingly, however, due to a surprising cancellation, the high temperature limit of $c_{s}^{2}$ is still its SB limit $1/3$ . In addition, we found some similarities between the non-extensive effect and the finite-size effect. For example, as $q$ increases (size decreases), the criticality of $\frac{c _{v}}{T ^{3}}$ and $c_{s}^{2}$ gradually disappears. Besides, in order to better study the non-extensive effect, we defined a new susceptibility and calculated the response of thermodynamic quantities and transport coefficients to $q$ . And found that their response patterns are different.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.14556 [pdf]
PRD(2020)·37 citations
10
[Submitted on 30 Apr 2020] (cross-list from hep-ph)
QCD Hidden-Color Hexa-diquark in the Central Core of Nuclei
Jennifer Rittenhouse West🇺🇸 · Stanley J. Brodsky🇺🇸 · Guy F. de Teramond🇨🇷 · Alfred S. Goldhaber🇺🇸 · Ivan Schmidt🇨🇱
Hidden-color configurations are a key prediction of QCD with important physical consequences. In this work we examine a QCD color-singlet configuration in nuclei formed by combining six scalar $[u d]$ diquarks in a strongly bound $SU (3)_{C}$ channel. The resulting hexadiquark state is a charge-2, spin-0, baryon number-4, isospin-0, color-singlet state. It contributes to alpha clustering in light nuclei and to the additional binding energy not saturated by ordinary nuclear forces in \he as well as the alpha-nuclei sequence of interest for nuclear astrophysics. We show that the strongly bound combination of six scalar isospin-0 $[u d]$ diquarks within the nuclear wave function - relative to free nucleons - provides a natural explanation of the EMC effect measured by the CLAS collaboration's comparison of nuclear parton distribution function ratios for a large range of nuclei. These experiments confirmed that the EMC effect; i.e., the distortion of quark distributions within nuclei, is dominantly identified with the dynamics of neutron-proton (``isophobic'') short-range correlations within the nuclear wave function rather than proton-proton or neutron-neutron correlations.
Comments:
9 pages. References with positive preliminary results from the MARATHON experiment added, clarifications and minor edits. Version accepted for publication
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2004.14659 [pdf]
NPA(2021)·20 citations
11
[Submitted on 28 Apr 2020] (cross-list from hep-th)
Spin versus Helicity Equilibration Times and Lagrangian for Strange Quarks in Rotating Quark-Gluon Plasma
Joseph I. Kapusta🇺🇸 · Ermal Rrapaj🇺🇸 · Serge Rudaz🇺🇸
Measurements of the net polarization of $Λ$ and $Λ ˉ$ hyperons at the Relativistic Heavy Ion Collider (RHIC) have stimulated much interest in how strange quarks might align their spin with the vorticity of the matter created in heavy ion collisions. We calculate the Lagrangian in the rest frame of a fluid element undergoing rotation with angular velocity $ω$ including photon and gluon fields. There is an additional coupling between the quarks and the gauge fields proportional to $ω$ , but this vertex does not change the spin of the quarks. We also show that the times to equilibrate quark helicity and spin parallel to the vorticity are the same so long as $ω$ is small compared to the temperature.
Comments:
8 pages, 0 figures. arXiv admin note: text overlap with arXiv:1907.10750
Subjects:
High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2004.14807 [pdf]
PRC(2020)·24 citations
12
[Submitted on 30 Apr 2020] (cross-list from hep-ph)
One-loop Matching for Spin-Dependent Quasi-TMDs
Markus A. Ebert🇺🇸 · Stella T. Schindler🇺🇸 · Iain W. Stewart🇺🇸 · Yong Zhao🇺🇸
Transverse momentum dependent parton distribution functions (TMDPDFs) provide a unique probe of the three-dimensional spin structure of hadrons. We construct spin-dependent quasi-TMDPDFs that are amenable to lattice QCD calculations and that can be used to determine spin-dependent TMDPDFs. We calculate the short-distance coefficients connecting spin-dependent TMDPDFs and quasi-TMDPDFs at one-loop order. We find that the helicity and transversity distributions have the same coefficient as the unpolarized TMDPDF. We also argue that the same is true for pretzelosity and that this spin universality of the matching will hold to all orders in $α_{s}$ . Thus, it is possible to calculate ratios of these distributions as a function of longitudinal momentum and transverse position utilizing simpler Wilson line paths than have previously been considered.
Comments:
24 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2004.14831 [pdf]
JHEP(2020)·55 citations
13
[Submitted on 30 Apr 2020] (cross-list from astro-ph.HE)
Transport coefficients of nucleon neutron star cores for various nuclear interactions within the Brueckner-Hartree-Fock approach
Peter Shternin · Marcello Baldo
We consider the thermal conductivity, shear viscosity, and momentum relaxation rates in the nucleon cores of the neutron stars. We study how the choice of the nuclear interaction and the model for three-body forces may affect these transport coefficients calculated within the Brueckner-Hartree-Fock many-body nuclear theory. We find that at relatively large densities the model dependence of the results is substantial. In addition we provide the analytical approximations which allow to incorporate our results in practical simulations.
Comments:
18 pages; 17 figures; minor edits to match the accepted version
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2004.14909 [pdf]
PRD(2020)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE

On the canonical formulation of gauge field theories and Poincare transformations

Thermodynamic properties and transport coefficients of QCD matter within the non-extensive Polyakov-Nambu-Jona-Lasinio model

QCD Hidden-Color Hexa-diquark in the Central Core of Nuclei

Spin versus Helicity Equilibration Times and Lagrangian for Strange Quarks in Rotating Quark-Gluon Plasma

One-loop Matching for Spin-Dependent Quasi-TMDs

Transport coefficients of nucleon neutron star cores for various nuclear interactions within the Brueckner-Hartree-Fock approach

Affiliations