PaperPanorama
FAQ

Nuclear Theory·nucl-th

Thursday·November 10, 2022

9 papers—7 primary·2 cross-listed

All9Primary7Cross-lists2
  1. 01

    Spin polarization induced by magnetic field and the relativistic Barnett effect

    Matteo Buzzegoli🇺🇸

    First, I study the analogy between the magnetization of a material and the spin polarization of particles in a fluid. Using the relativistic version of the Barnett effect, i.e. the magnetization of a material induced by mechanical rotation, the spin polarization induced by thermal vorticity is obtained within a purely classical model, where spin is treated as an intrinsic magnetic moment and rotation is included as a non-inertial effect. I argue that since spin polarization induced by thermal vorticity can be obtained in a classical theory, it can not be dominated by quantum anomalies. Second, the spin polarization induced by magnetic field is obtained for a fluid at local thermal equilibrium using statistical quantum field theory. The obtained formula is valid beyond the weak field approximation and when contributions from the non-homogeneity of the magnetic field are small. The exact form of spin polarization is studied for a free Dirac field at global equilibrium, and, like magnetic susceptibility, it oscillates according to the de Haas - van Alphen effect. Finally, I briefly review how magnetic field contributes to the difference between the spin polarization of and observed in heavy-ion collisions.

    nucl-thNPA(2023)·22 citations
  2. 02

    Lattice-QCD-based equations of state at finite temperature and density

    Jamie M. Karthein🇺🇸 · Debora Mroczek🇺🇸 · Angel Nava Acuna🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Paolo Parotto🇺🇸 · Damien R. P. Price🇺🇸 · Claudia Ratti🇺🇸

    The equation of state (EoS) of QCD is a crucial input for the modeling of heavy-ion-collision (HIC) and neutron-star-merger systems. Calculations of the fundamental theory of QCD, which could yield the true EoS, are hindered by the infamous Fermi sign problem which only allows direct simulations at zero or imaginary baryonic chemical potential. As a direct consequence, the current coverage of the QCD phase diagram by lattice simulations is limited. In these proceedings, two different equations of state based on first-principle lattice QCD (LQCD) calculations are discussed. The first is solely informed by the fundamental theory by utilizing all available diagonal and non-diagonal susceptibilities up to in order to reconstruct a full EoS at finite baryon number, electric charge and strangeness chemical potentials. For the second, we go beyond information from the lattice in order to explore the conjectured phase structure, not yet determined by LQCD methods, to assist the experimental HIC community in their search for the critical point. We incorporate critical behavior into this EoS by relying on the principle of universality classes, of which QCD belongs to the 3D Ising Model. This allows one to study the effects of a singularity on the thermodynamical quantities that make up the equation of state used for hydrodynamical simulations of HICs. Additionally, we ensure that these EoSs are valid for applications to HICs by enforcing conditions of strangeness neutrality and fixed charge-to-baryon-number ratio.

    nucl-thhep-thRev.Mex.Fis.Suppl.(2022)·0 citations
  3. 03

    Constraints on hadron resonance gas interactions via first-principles Lattice QCD susceptibilities

    Jamie M. Karthein🇺🇸 · Volker Koch🇺🇸 · Claudia Ratti🇺🇸 · Volodymyr Vovchenko🇺🇸

    We investigate extensions of the Hadron Resonance Gas (HRG) Model beyond the ideal case by incorporating both attractive and repulsive interactions into the model. When considering additional states exceeding those measured with high confidence by the Particle Data Group, attractive corrections to the overall pressure in the HRG model are imposed. On the other hand, we also apply excluded-volume corrections, which ensure there is no overlap of baryons by turning on repulsive (anti)baryon-(anti)baryon interactions. We emphasize the complementary nature of these two extensions and identify combinations of conserved charge susceptibilities that allow us to constrain them separately. In particular, we find interesting ratios of susceptibilities that are sensitive to one correction and not the other. This allows us to constrain the excluded volume and particle spectrum effects separately. Analysis of the available lattice results suggests the presence of both the extra states in the baryon-strangeness sector and the repulsive baryonic interaction, with indications that hyperons have a smaller repulsive core than non-strange baryons. We note that these results are interesting for heavy-ion-collision systems at both the LHC and RHIC.

    nucl-thhep-lathep-phEPJ Web Conf.(2023)·1 citation
  4. 04

    Solving the nuclear pairing model with neural network quantum states

    Mauro Rigo · Benjamin Hall · Morten Hjorth-Jensen · Alessandro Lovato · Francesco Pederiva

    We present a variational Monte Carlo method that solves the nuclear many-body problem in the occupation number formalism exploiting an artificial neural network representation of the ground-state wave function. A memory-efficient version of the stochastic reconfiguration algorithm is developed to train the network by minimizing the expectation value of the Hamiltonian. We benchmark this approach against widely used nuclear many-body methods by solving a model used to describe pairing in nuclei for different types of interaction and different values of the interaction strength. Despite its polynomial computational cost, our method outperforms coupled-cluster and provides energies that are in excellent agreement with the numerically-exact full configuration interaction values.

    nucl-thcond-mat.dis-nnquant-phPRE(2023)·22 citations
  5. 05

    Resolving the spurious-state problem in the Dirac equation with finite difference method

    Ying Zhang · Yuxuan Bao · Jinniu Hu · Hong Shen

    To solve the Dirac equation with the finite difference method, one has to face up to the spurious-state problem due to the fermion doubling problem when using the conventional central difference formula to calculate the first-order derivative on the equal interval lattices. This problem is resolved by replacing the central difference formula with the asymmetric difference formula, i.e., the backward or forward difference formula. To guarantee the hermitian of the Hamiltonian matrix, the backward and forward difference formula should be used alternatively according to the parity of the wavefunction. This provides a simple and efficient numerical prescription to solve various relativistic problems in the microscopic world.

    nucl-thPRC(2022)·8 citations
  6. 06

    Finite-temperature equation of state with hyperons

    Hristijan Kochankovski🇪🇸 · Angels Ramos🇪🇸 · Laura Tolos🇪🇸

    We present the novel finite-temperature FSU2H equation-of-state model that covers a wide range of temperatures and lepton fractions for the conditions in proto-neutron stars, neutron star mergers and supernovae. The temperature effects on the thermodynamical observables and the composition of the neutron star core are stronger when the hyperonic degrees of freedom are considered. We pay a special attention to the temperature and density dependence of the thermal index in the presence of hyperons and conclude that the true thermal effects cannot be reproduced with the use of a constant law.

    nucl-thastro-ph.HEEPJ Web Conf.(2022)·3 citations
  7. 07

    Testing the phase transition parameters inside neutron stars with the production of protons and lambdas in relativistic heavy-ion collisions

    Ang Li🇨🇳 · Gao-Chan Yong🇨🇳 · Ying-Xun Zhang🇨🇳

    We demonstrate the consistency of the quark deconfinement phase transition parameters in the beta-stable neutron star matter and in the nearly symmetric nuclear matter formed in heavy-ion collisions (HICs). We investigate the proton and flow in Au+Au collisions at 3 and 4.5 GeV/nucleon incident beam energies with the pure hadron cascade version of a multi-phase transport model. The phase transition in HICs and neutron stars is described based on a class of hybrid equations of state from the quark mean-field model for the hadronic phase and a constant-speed-of-sound parametrization for the high-density quark phase. The measurements of the anisotropic proton flow at 3 GeV/nucleon by the STAR collaboration favor a relatively low phase transition density lower than times saturation density indicated by the gravitational wave and electromagnetic observations of neutron stars. And the proton flow data at the higher energy of 4.5 GeV/nucleon can be used to effectively constrain the softness of high-density quark matter equations of state. Finally, compared to the proton flow, the flow is found to be less sensitive and not constraining to the equations of state.

    nucl-thastro-ph.HEnucl-exPRD(2023)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE