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Nuclear Theory·nucl-th

Wednesday·June 13, 2018

8 papers—3 primary·5 cross-listed

All8Primary3Cross-lists5
  1. 04

    Hadron-quark phase transition: the QCD phase diagram and stellar conversion

    Clebson A. Graeff🇧🇷 · Marcelo D. Alloy🇧🇷 · Kauan D. Marquez🇧🇷 · Constança Providência🇵🇹 · Débora P. Menezes🇧🇷

    Different extensions of the Nambu-Jona-Lasinio model, known to satisfy expected QCD chiral symmetry aspects, are used to investigate a possible hadron-quark phase transition at zero temperature and to build the corresponding binodal sections. We have shown that the transition point is very sensitive to the model parameters and that both pressure and chemical potential increase drastically with the increase of the vector interaction strength in the quark sector. Within the same framework, the possibility of quark and hybrid star formation is analyzed. The same conclusions drawn before with respect to the coexistence pressure and chemical potentials are reinforced. We conclude that even if a transition from a metastable hadronic star to a quark star is thermodinamically possible, it is either energetically forbidden or gives rise to a blackhole. Nevertheless, conversions from metastable to hybrid stars are possible, but the mass difference between both compact objects is very small, never larger than 0.2 M.

    ↳ astro-ph.HEnucl-thJCAP(2019)·15 citations
  2. 05

    Energy dependent chemical potentials of light particles and quarks from yield ratios of antiparticles to particles in high energy collisions

    Hai-Ling Lao🇨🇳 · Ya-Qin Gao🇨🇳 · Fu-Hu Liu🇨🇳

    We collect the yields of charged pions ( and ), charged kaons ( and ), anti-protons (), and protons () produced in mid-rapidity interval (in most cases) in central gold-gold (Au-Au), central lead-lead (Pb-Pb), and inelastic or non-single-diffractive proton-proton () collisions at different collision energies. The chemical potentials of light particles and quarks are extracted from the yield ratios, , , and , of antiparticles to particles over an energy range from a few GeV to above 10 TeV. At a few GeV ( GeV), the chemical potentials show, and the yield ratios do not show, different trends comparing with those at other energies, though the limiting values of the chemical potentials and the yield ratios at very high energy are 0 and 1 respectively.

    ↳ hep-phhep-exnucl-exnucl-thUniverse(2019)·6 citations
  3. 06

    Hybrid stars from the NJL model with a tensor interaction

    H. Matsuoka (Kochi Univ., Japan)🇯🇵 · Y. Tsue (Kochi Univ., Japan)🇯🇵 · J. da Providencia (Univ. de Coimbra, Portugal)🇵🇹 · C. Providencia (Univ. de Coimbra, Portugal)🇵🇹 · M. Yamamura (Kansai Univ., Japan)🇯🇵

    In order to obtain the equation of state and construct hybrid stars, we calculate the thermodynamic potential in the two-flavor Nambu--Jona-Lasinio model with tensor-type four-point interaction between quarks. In addition, we impose the beta equilibrium and charge neutrality conditions on the system. We show that the tensor condensate appears at large chemical potential, however, it is difficult to hold hybrid stars with two-solar mass by using the equation of state with the tensor interaction. Although we cannot obtain the stars with two-solar mass because of the absense of the repulsive interaction, the estimated magnetic moment density is very large. Therefore, we expect that the tensor interaction descrobes the magnetic fields of compact stars.

    ↳ hep-phnucl-thPRD(2018)·9 citations
  4. 07

    Renormalization group consistency and low-energy effective theories

    Jens Braun🇩🇪 · Marc Leonhardt🇩🇪 · Jan M. Pawlowski🇩🇪

    Low-energy effective theories have been used very successfully to study the low-energy limit of QCD, providing us with results for a plethora of phenomena, ranging from bound-state formation to phase transitions in QCD. These theories are consistent quantum field theories by themselves and can be embedded in QCD, but typically have a physical ultraviolet cutoff that restricts their range of validity. Here, we provide a discussion of the concept of renormalization group consistency, aiming at an analysis of cutoff effects and regularization-scheme dependences in general studies of low-energy effective theories. For illustration, our findings are applied to low-energy effective models of QCD in different approximations including the mean-field approximation. More specifically, we consider hot and dense as well as finite systems and demonstrate that violations of renormalization group consistency affect significantly the predictive power of the corresponding model calculations.

    ↳ hep-phhep-thnucl-thSciPost Phys.(2019)·98 citations
  5. 08

    Nucleon resonances in Compton scattering

    Gernot Eichmann🇵🇹 · G. Ramalho🇧🇷

    We calculate the nucleon resonance contributions to nucleon Compton scattering, including all states with J^P = 1/2^{+-} and J^P = 3/2^{+-} where experimental data for their electromagnetic transition form factors exist. To this end, we construct a tensor basis for the Compton scattering amplitude based on electromagnetic gauge invariance, crossing symmetry and analyticity. The corresponding Compton form factors provide a Lorentz-invariant description of the process in general kinematics, which reduces to the static and generalized polarizabilities in the appropriate kinematic limits. We derive the general forms of the offshell nucleon-to-resonance transition vertices that implement electromagnetic and spin-3/2 gauge invariance, which automatically also defines onshell transition form factors that are free of kinematic constraints. We provide simple fits for those form factors, which we use to analyze the resulting Compton form factors and extract their contributions to the nucleon's polarizabilities. Apart from the Delta(1232), the resonance contributions to the scalar and spin polarizabilites are very small, although the N(1520) could play a role for the proton's magnetic polarizability.

    ↳ hep-phhep-thnucl-thPRD(2018)·36 citations

Affiliations

first authorsco-authorsvia INSPIRE