Nuclear Theory·nucl-th

Tuesday·April 21, 2020

15 papers—9 primary·6 cross-listed

10
The fourth- and fifth-order virial coefficients from weak-coupling to unitarity
Y. Hou · J. E. Drut
In the current era of precision quantum many-body physics, one of the most scrutinized systems is the unitary limit of the nonrelativistic spin- $1/2$ Fermi gas, due to its simplicity and relevance for atomic, condensed matter, and nuclear physics. The thermodynamics of this strongly correlated system is determined by universal functions which, at high temperature, are governed by universal virial coefficients $b_{n}$ that capture the effects of the $n$ -body system on the many-body dynamics. Currently, $b_{2}$ and $b_{3}$ are well understood, but the situation is less clear for $b_{4}$ , and no predictions have been made for $b_{5}$ . To answer these open questions, we implement a nonperturbative analytic approach based on the Trotter-Suzuki factorization of the imaginary-time evolution operator, using progressively finer temporal lattice spacings. Implementing these factorizations and automated algebra codes, we obtain the interaction-induced change $Δ b_{n}$ from weak coupling to unitarity. At unitarity, we find: $Δ b_{3} = - 0.356 (4)$ , in agreement with previous results; $Δ b_{4} = 0.062 (2)$ , in agreement with all previous theoretical estimates but at odds with experimental determinations; and $Δ b_{5} = 0.078 (6)$ , which is a prediction. We show the impact of those answers on the density equation of state and Tan contact, and track their origin back to their polarized and unpolarized components.
↳ cond-mat.quant-gasnucl-thPRL(2020)·16 citations
11
Magnetic susceptibility of QCD matter and its decomposition from the lattice
Gunnar S. Bali (1 and 2)🇩🇪 · Gergely Endrődi (3 and 4)🇩🇪 · Stefano Piemonte (1) ((1) Regensburg U., (2) Tata Inst., (3) Bielefeld U., (4) Frankfurt U.)🇩🇪
We determine the magnetic susceptibility of thermal QCD matter by means of first principles lattice simulations using staggered quarks with physical masses. A novel method is employed that only requires simulations at zero background field, thereby circumventing problems related to magnetic flux quantization. After a careful continuum limit extrapolation, diamagnetic behavior (negative susceptibility) is found at low temperatures and strong paramagnetism (positive susceptibility) at high temperatures. We revisit the decomposition of the magnetic susceptibility into spin- and orbital angular momentum-related contributions. The spin term -- related to the normalization of the photon lightcone distribution amplitude at zero temperature -- is calculated non-perturbatively and extrapolated to the continuum limit. Having access to both the full magnetic susceptibility and the spin term, we calculate the orbital angular momentum contribution for the first time. The results reveal the opposite of what might be expected based on a free fermion picture. We provide a simple parametrization of the temperature- and magnetic field-dependence of the QCD equation of state that can be used in phenomenological studies.
↳ hep-lathep-phnucl-thJHEP(2020)·64 citations
12
Magnetic field-induced anisotropic interaction in heavy quark bound states
Salman Ahamad Khan🇮🇳 · Binoy Krishna Patra🇮🇳 · Mujeeb Hasan🇮🇳
We have investigated how a strong magnetic field (B) could decipher the anisotropic interaction in heavy quark ( $Q$ ) and antiquark ( $Q ˉ$ ) bound states through the perturbative thermal QCD in real-time formalism. So we thermalize Schwinger propagator for quarks in LLL and the Feynman propagator for gluons to calculate the gluon self-energy. For the quark-loop contribution to the self-energy, the medium does not have any temperature correction and the vacuum term gives rise an anisotropic term whereas the gluon-loop yields temperature correction. This finding in quark-loop contribution corroborates the equivalence of a massless QED in (1+1)-dimension with the massless thermal QCD in strong B, which (quark sector) is reduced to (1+1)-dimension (longitudinal). Thus the permittivity of the medium behaves like as a tensor. Thus the permittivity of medium makes the $Q Q ˉ$ potential anisotropic, which resembles with a contemporary results found in lattice studies. As a result, potential for $Q Q ˉ$ -pairs aligned transverse to B is more attractive than parallel alignment. However, potential is always more attractive compared to B=0 due to softening of screening mass. However, the imaginary-part of potential becomes smaller compared to B=0. We have next investigated the effects of strong $B$ on binding energies (B.E.) and thermal widths ( $Γ$ ) of ground states of $c c ˉ$ and $b b ˉ$ in a time-independent perturbation theory, where binding energies gets increased and widths gets decreased, compared to $B = 0$ . Finally we have studied the quasi-free dissociation of bound states in a strong B. The dissociation temperatures estimated for $J / ψ$ and $Υ$ states are obtained as $1.59 T_{c}$ and $2.22 T_{c}$ , respectively, which are higher than the estimate in B=0 , thus preventing early dissolution of $Q Q ˉ$ bound states.
↳ hep-phcond-mat.softcond-mat.str-elnucl-thPoS(2026)·6 citations
13
Bose-Einstein condensation phenomenology in systems with repulsive interactions
Oleh Savchuk🇺🇦 · Yehor Bondar🇺🇦 · Oleksandr Stashko🇺🇦 · Roman V. Poberezhnyuk🇺🇦 · Volodymyr Vovchenko🇺🇸 · Mark I. Gorenstein🇩🇪 · Horst Stoecker🇩🇪
The role of repulsive interactions in statistical systems of Bose particles is investigated. Three different phenomenological frameworks are considered: a mean field model, an excluded volume model, and a model with a medium dependent effective mass. All three models are tuned to yield similar equations of state, with only minor deviations from the ideal Bose gas at small chemical potentials. Our analysis indicates, however, that these models lead to qualitatively different results for the Bose-Einstein condensation phenomenon. We discuss the different aspects of this phenomenon, namely, an onset of the Bose-Einstein condensation, particle number fluctuations, and a behavior of the Bose condensate. The obtained results can be helpful for interpreting the lattice QCD data at small temperature and large isospin chemical potential and the data on multiple pion production in high energy nuclear collisions.
↳ hep-phnucl-thPRC(2020)·15 citations
14
Topological susceptibility, divergent chiral density and phase diagram of chirally imbalanced QCD medium at finite temperature
Marco Ruggieri🇨🇳 · Maxim N. Chernodub🇫🇷 · Zhen-Yan Lu🇨🇳
We show that the nonlocal two-flavor Nambu--Jona-Lasinio model predicts the enhancement of both chiral and axial symmetry breaking as the chiral imbalance of hot QCD matter, regulated by a chiral chemical potential $μ_{5}$ , increases. The two crossovers are reasonably close to each other in the range of $μ_{5}$ examined here and the pseudocritical temperatures rise with $μ_{5}$ . The curvatures of the chiral and axial crossovers for the chiral quark chemical potential approximately coincide and give $κ_{5} ≃ - 0.011$ . We point out that the presence of $μ_{5}$ in thermodynamic equilibrium is inconsistent with the fact that the chiral charge is not a Noether-conserved quantity for massive fermions. The chiral chemical potential should not, therefore, be considered as a true chemical potential that sets a thermodynamically stable environment in the massive theory, but rather than as a new coupling that may require a renormalization in the ultraviolet domain. The divergence of an unrenormalized chiral density, \corr{coming from zero-point fermionic fluctuations,} is a consequence of this property. We propose a solution to this problem via a renormalization procedure.
↳ hep-phhep-lathep-thnucl-thPRD(2020)·24 citations
15
Generic size dependences of pairing in ultrasmall systems: electronic nano-devices and atomic nuclei
A. Pastore🇬🇧 · P Schuck🇫🇷 · X. Viñas🇪🇸
Average, global pairing behaviours of electronic devices, like films, wires, and grains are studied with semiclassical methods, as Weyl and Thomas-Fermi approximations, in the ultrasmall, i.e., quantal regime, which exhibits strong quantum fluctuations and shell effects. This is the case also for superfluid nuclei. Results, mostly analytic, are elaborated for average size dependences, ready for easy use also in other circumstances. Comparisons with experimental results are given where possible.
↳ nucl-thcond-mat.mes-hallEPJA(2023)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE

The fourth- and fifth-order virial coefficients from weak-coupling to unitarity

Magnetic susceptibility of QCD matter and its decomposition from the lattice

Magnetic field-induced anisotropic interaction in heavy quark bound states

Bose-Einstein condensation phenomenology in systems with repulsive interactions

Topological susceptibility, divergent chiral density and phase diagram of chirally imbalanced QCD medium at finite temperature

Generic size dependences of pairing in ultrasmall systems: electronic nano-devices and atomic nuclei

Affiliations