Nuclear Theory·nucl-th

Thursday·July 22, 2021

11 papers—8 primary·3 cross-listed

09
[Submitted on 21 Jul 2021] (cross-list from hep-lat)
Second order cumulants of conserved charge fluctuations revisited I. Vanishing chemical potentials
D. Bollweg🇩🇪 · J. Goswami🇩🇪 · O. Kaczmarek🇩🇪 · F. Karsch🇩🇪 · Swagato Mukherjee🇺🇸 · P. Petreczky🇺🇸 · C. Schmidt🇩🇪 · P. Scior🇺🇸
We update lattice QCD results for second order cumulants of conserved charge fluctuations and correlations at non-zero temperature and vanishing values of the conserved charge chemical potentials. We compare these results to hadron resonance gas calculations with and without excluded volume terms as well as S-matrix results in the hadronic phase of QCD, and comment on their current limitations. We, furthermore, use these results to characterize thermal conditions in the vicinity of the pseudo-critical line of the chiral transition in QCD. We argue that the ratio of strange to baryon chemical potentials is a robust observable that, on the one hand, deviates only little from hadron resonance gas results, but, on the other hand, is very sensitive to the spectrum of strange baryon resonances.
Comments:
18 pages, reference updated, Journal reference added
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2107.10011 [pdf]
PRD(2021)·94 citations
10
[Submitted on 21 Jul 2021] (cross-list from hep-ph)
Light mesons around critical end points in $T - μ_{B} - μ_{I} - e B$ space
Luyang Li🇨🇳 · Shijun Mao🇨🇳
Light mesons $(σ, π^{0}, π^{\pm})$ are investigated in $T - μ_{B} - μ_{I} - e B$ space by using a two-flavor NJL model, which are related to the chiral symmetry restoration and pion superfluid phase transition. In $T - μ_{B} - e B$ space, during the chiral restoration process, the mass of pseudo-Goldstone mode $π^{0}$ keeps increasing, together with the sudden mass jump. At the critical end point region, $π^{0}$ meson has a very sharp but continuous mass increase, together with a sudden mass jump at the Mott transition, and in the first order chiral phase transition region nearby, we observe twice $π^{0}$ mass jumps, induced by the Mott transition and quark mass jump, respectively. The mass of Higgs mode $σ$ first decreases and then increases associated with the chiral symmetry restoration, and shows a jump at the first order chiral phase transition. We plot the chiral phase diagram in terms of the change of quark mass, the Mott transition of $π^{0}$ and the minimum mass of $σ$ . Due to the explicit breaking of chiral symmetry in physical case, the chiral restoration phase boundaries in $T - μ_{B}$ plane from the order parameter and meson side are different from each other. In $T - μ_{I}$ plane, the competition between pion superfluid phase transition and chiral symmetry restoration under magnetic fields is studied in terms of the Goldstone mode $π^{+}$ and the pseudo-Goldstone mode $π^{0}$ . The separation of the two phase boundaries is enhanced by the external magnetic field. Different from the twice mass jumps of $π^{0}$ in the first order chiral phase transition region, the $π^{+}$ meson displays several mass jumps in the chiral crossover region. At the critical end point, $π^{+}$ also shows very sharp but continuous mass changes, together with a mass jump at the Mott transition.
Comments:
20 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2107.10067 [pdf]
CPC(2022)·1 citation
11
[Submitted on 21 Jul 2021] (cross-list from hep-ph)
On non-conformal kinetic theory and hydrodynamics for Bjorken flow
Sunil Jaiswal (1) · Chandrodoy Chattopadhyay (2) · Lipei Du (2) · Ulrich Heinz (2) · Subrata Pal (1) ((1) TIFR · Mumbai · (2) Ohio State U.)
Using and comparing kinetic theory and second-order Chapman-Enskog hydrodynamics, we study the non-conformal dynamics of a system undergoing Bjorken expansion. We use the concept of `free-streaming fixed lines' for scaled shear and bulk stresses in non-conformal kinetic theory and hydrodynamics, and show that these `fixed lines' behave as early-time attractors and repellors of the evolution. In the conformal limit, the free-streaming fixed lines reduce to the well-known fixed points of conformal Bjorken dynamics. A new fixed point in the free streaming regime is identified which lies at the intersection of these fixed lines. Contrary to the conformal scenario, both kinetic theory and hydrodynamics predict the absence of attractor behavior in the normalised shear stress channel. In kinetic theory a far-off-equilibrium attractor is found for the normalised effective longitudinal pressure, driven by rapid longitudinal expansion. Second-order viscous hydrodynamics fails to accurately describe this attractor. From a thorough analysis of the free-streaming dynamics in Chapman-Enskog hydrodynamics we conclude that this failure results from an inaccurate approximation of the fixed lines and a related incorrect description of the nature of the fixed point. A modified anisotropic hydrodynamic description is presented that provides excellent agreement with kinetic theory results and reproduces the far-from-equilibrium attractor for the scaled longitudinal pressure.
Comments:
28 pages, 22 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2107.10248 [pdf]
PRC(2022)·58 citations

Affiliations

first authorsco-authorsvia INSPIRE

Second order cumulants of conserved charge fluctuations revisited I. Vanishing chemical potentials

Light mesons around critical end points in T−μB​−μI​−eB space

On non-conformal kinetic theory and hydrodynamics for Bjorken flow

Affiliations

Light mesons around critical end points in $T - μ_{B} - μ_{I} - e B$ space