Nuclear Theory·nucl-th

Wednesday·July 9, 2025

8 papers—5 primary·3 cross-listed

06
[Submitted on 6 Jul 2025] (cross-list from cond-mat.quant-gas)
Thermal relaxation and the complete set of second order transport coefficients for the unitary Fermi gas from kinetic theory
Christian Hall · Thomas Schaefer
We compute the complete set of second order transport coefficients of the unitary Fermi gas, a dilute gas of spin 1/2 particles interacting via an $s$ -wave interaction tuned to infinite scattering length. The calculation is based on kinetic theory and the Chapman-Enskog method at second order in the Knudsen expansion. We take into account the exact two-body collision integral. We extend previous results on second order coefficients related to shear stress by including terms related to heat flow and gradients of the fugacity. We confirm that the thermal relaxation time is given by the simple estimate $τ_{κ} = κm / (c_{P} T)$ even if the full collision kernel is taken into account. Here, $κ$ is the thermal conductivity, $m$ is the mass of the particles, $c_{P}$ is the specific heat at constant pressure, and $T$ is the temperature.
Comments:
34 pages, no figures. Minor revisions. To appear in Phys. Rev. A
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
2507.04202 [pdf]
PRA(2025)·0 citations
07
[Submitted on 7 Jul 2025] (cross-list from hep-ph)
Gravitational form factors of pions, kaons and nucleons from dispersion relations
Xiong-Hui Cao🇨🇳 · Feng-Kun Guo🇨🇳 · Qu-Zhi Li🇨🇳 · Bo-Wen Wu🇨🇳 · De-Liang Yao🇨🇳
The gravitational form factors of pions, kaons and the nucleons are investigated by employing modern dispersive techniques and chiral perturbation theory. We determine the gravitational form factors of pions and kaons, extending our analysis to explore the pion mass dependence of these form factors at several unphysical pion masses up to 391 MeV, for which lattice results exist for the meson-meson scattering phase shifts. We also review our analysis on the nucleon gravitational form factors at the physical pion mass, and then systematically calculate various three-dimensional spatial and two-dimensional transverse density distributions for the nucleons. These results provide new insights into the mass distribution inside nucleons. As a by-product, we match our dispersion relation results and those obtained from chiral perturbation theory with external gravitational source at the next-to-next-to-leading order, yielding values for the low-energy constants $c_{8} = - 4.2 8_{- 0.38}^{+ 0.37} GeV^{- 1}$ and $c_{9} = - 0.6 8_{- 0.05}^{+ 0.06} GeV^{- 1}$ . These results offer a robust benchmark for future experimental and theoretical studies.
Comments:
v2: 55 pages, 17 pages, 3 tables; references added, typos corrected, discussions of spectral functions and sum rules added; accepted for publication as a review in EPJST
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2507.05375 [pdf]
Eur.Phys.J.ST(2026)·25 citations
08
[Submitted on 8 Jul 2025] (cross-list from physics.atom-ph)
The nuclear charge radius of $^{13} C$
Patrick Müller · Matthias Heinz · Phillip Imgram · Kristian König · Bernhard Maass · Takayuki Miyagi · Wilfried Nörtershäuser · Robert Roth · Achim Schwenk
The size is a key property of a nucleus. Accurate nuclear radii are extracted from elastic electron scattering, laser spectroscopy, and muonic atom spectroscopy. The results are not always compatible, as the proton-radius puzzle has shown most dramatically. Beyond helium, precision data from muonic and electronic sources are scarce in the light-mass region. The stable isotopes of carbon are an exception. We present a laser spectroscopic measurement of the root-mean-square (rms) charge radius of $^{13} C$ and compare this with ab initio nuclear structure calculations. Measuring all hyperfine components of the $2^{3} S \to 2^{3} P$ fine-structure triplet in $^{13} C^{4 +}$ ions referenced to a frequency comb allows us to determine its center-of-gravity with accuracy better than $2 MHz$ although second-order hyperfine-structure effects shift individual lines by several $GHz$ . We improved the uncertainty of $R_{c} (^{13} C)$ determined with electrons by a factor of $6$ and found a $3 σ$ discrepancy with the muonic atom result of similar accuracy.
Comments:
Published in Nature Communications, 14 pages, 4 figures, 3 tables
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th)
arXiv:
2507.05680 [pdf]
Nature Commun.(2025)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE

Thermal relaxation and the complete set of second order transport coefficients for the unitary Fermi gas from kinetic theory

Gravitational form factors of pions, kaons and nucleons from dispersion relations

The nuclear charge radius of 13C

Affiliations

The nuclear charge radius of $^{13} C$