Nuclear Theory·nucl-th

Thursday·April 2, 2015

10 papers—4 primary·6 cross-listed

01
[Submitted on 1 Apr 2015]
Thermodynamics of isospin-asymmetric nuclear matter from chiral effective field theory
Corbinian Wellenhofer · Jeremy W. Holt · Norbert Kaiser
The density and temperature dependence of the nuclear symmetry free energy is investigated using microscopic two- and three-body nuclear potentials constructed from chiral effective field theory. The nuclear force models and many-body methods are benchmarked to properties of isospin-symmetric nuclear matter in the vicinity of the saturation density as well as the virial expansion of the neutron matter equation of state at low fugacities. The free energy per particle of isospin-asymmetric nuclear matter is calculated assuming a quadratic dependence of the interaction contributions on the isospin asymmetry. The spinodal instability at subnuclear densities is examined in detail.
Comments:
20 pages, 15 figures, 2 tables. additional typos corrected, cf. footnote 2 in arXiv:1603.02935
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.00177 [pdf]
PRC(2015)·110 citations
02
[Submitted on 1 Apr 2015]
Diffuse approximation to the kinetic theory in a Fermi system
V.M. Kolomietz · S.V. Lukyanov
We suggest the diffuse approach to the relaxation processes within the kinetic theory for the Wigner distribution function. The diffusion and drift coefficients are evaluated taking into consideration the interparticle collisions on the distorted Fermi surface. Using the finite range interaction, we show that the momentum dependence of the diffuse coefficient $D_{p} (p)$ has a maximum at Fermi momentum $p = p_{F}$ whereas the drift coefficient $K_{p} (p)$ is negative and reaches a minimum at $p \approx p_{F}$ . For a cold Fermi system the diffusion coefficient takes the non-zero value which is caused by the relaxation on the distorted Fermi-surface at temperature $T = 0$ . The numerical solution of the diffusion equation was performed for the particle-hole excitation in a nucleus with $A = 16$ . The evaluated relaxation time $τ_{r} \approx 8.3 \cdot 1 0^{- 23} s$ is close to the corresponding result in a nuclear Fermi-liquid obtained within the kinetic theory.
Comments:
16 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.00216 [pdf]
IJMPE(2015)·6 citations
03
[Submitted on 1 Apr 2015]
Effect of neutron skin thickness on projectile fragmentation
Z. T. Dai · D. Q. Fang · Y. G. Ma · X. G. Cao · G. Q. Zhang · W. Q. Shen
The fragment production in collisions of $^{48, 50}$ Ca+ $^{12}$ C at 50 MeV/nucleon are simulated via the Isospin-Dependent Quantum Molecular Dynamics (IQMD) model followed by the {GEMINI code}. {By changing the diffuseness parameter of neutron density distribution to obtain different neutron skin size, the effects of neutron skin thickness ( $δ_{n p}$ ) on projectile-like fragments (PLF) are investigated. The sensitivity of isoscaling behavior to neutron skin size is studied, from which it is found that the isoscaling parameter $α$ has a linear dependence on $δ_{n p}$ . A linear dependence between $δ_{n p}$ and the mean $N / Z$ [N(Z) is neutron(proton) number] of PLF is obtained as well.} The results show that thicker neutron skin will lead to smaller {isoscaling parameter} $α$ and N/Z. Therefore, it may be probable to extract information of neutron skin thickness from {isoscaling parameter} $α$ and N/Z.
Comments:
7 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1504.00226 [pdf]
PRC(2015)·16 citations
04
[Submitted on 1 Apr 2015]
Dissipative effects on quarkonium spectral functions
Yusuf Buyukdag🇺🇸 · Clint Young🇺🇸
Quarkonium at finite temperature is described as an open quantum system whose dynamics are determined by a potential $V_{R} (x)$ and drag coefficient $η$ , using a path integral with a non-local term. Path-integral Monte Carlo calculations determine the Euclidean Green function for this system to an accuracy greater than one part in a thousand and the maximum entropy method is used to determine the spectral function; challenges facing any kind of deconvolution are discussed in detail with the aim of developing intuition for when deconvolution is possible. Significant changes to the quarkonium spectral function in the $1 S$ channel are found, suggesting that any description of quarkonium at finite temperature, using a potential, must also carefully consider the effect of dissipation.
Comments:
13 pages, 7 figures, This is the version accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.00343 [pdf]
PRC(2015)·1 citation
05
[Submitted on 2 Mar 2015] (cross-list from hep-ph)
Quantum field theory in a magnetic field: From quantum chromodynamics to graphene and Dirac semimetals
Vladimir A. Miransky🇨🇦 · Igor A. Shovkovy🇺🇸
A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chiral magnetic and separation effects, we also review their possible phenomenological implications in heavy-ion collisions and compact stars. We also discuss the application of the magnetic catalysis ideas for the description of the quantum Hall effect in monolayer and bilayer graphene, and conclude that the generalized magnetic catalysis, including both the magnetic catalysis condensates and the quantum Hall ferromagnetic ones, lies at the basis of this phenomenon. We also consider how an external magnetic field affects the underlying physics in a class of three-dimensional quasirelativistic condensed matter systems, Dirac semimetals. While at sufficiently low temperatures and zero density of charge carriers, such semimetals are expected to reveal the regime of the magnetic catalysis, the regime of Weyl semimetals with chiral asymmetry is realized at nonzero density...
Comments:
244 pages, 49 figures; published in Physics Reports; typos corrected and refernces added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1503.00732 [pdf]
Phys.Rept.(2015)·708 citations
06
[Submitted on 29 Mar 2015] (cross-list from nucl-ex)
Precise determination of $_{Λ}^{12}$ C level structure by $γ$ -ray spectroscopy
K. Hosomi🇯🇵 · T. Ma🇯🇵 · S. Ajimura🇯🇵 · K. Aoki🇯🇵 · S. Dairaku🇯🇵 · Y. Y. Fu🇨🇳 · H. Fujioka🇯🇵 · K. Futatsukawa🇯🇵 · W. Imoto🇯🇵 · Y. Kakiguchi🇯🇵 · M. Kawai🇯🇵 · S. Kinoshita🇯🇵 and 21 other authors
Level structure of the $_{Λ}^{12}$ C hypernucleus was precisely determined by means of $γ$ -ray spectroscopy. We identified four $γ$ -ray transitions via the $^{12}$ C $(π^{+}, K^{+} γ)$ reaction using a germanium detector array, Hyperball2. The spacing of the ground-state doublet $(2_{1}^{-}, 1_{1}^{-})$ was measured to be $161.5 \pm 0.3 (stat) \pm 0.3 (syst)$ \,keV from the direct $M 1$ transition. Excitation energies of the $1_{2}^{-}$ and $1_{3}^{-}$ states were measured to be $2832 \pm 3 \pm 4$ \,keV and $6050 \pm 8 \pm 7$ \,keV, respectively. The obtained level energies provide definitive references for the reaction spectroscopy of $Λ$ hypernuclei.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1503.08372 [pdf]
PTEP(2015)·14 citations
07
[Submitted on 31 Mar 2015] (cross-list from hep-th)
Gluon Propagation in Curved Space
Su Kyeong Lee🇰🇷 · Eun-Joo Kim🇰🇷 · Jong Bum Choi🇰🇷
In quantum chromodynamics (QCD), the vacuum structures are taken to be formed by nonperturbative interactions between gluons. The contributions of gluonic interactions can be parametrized by gluon condensates and especially the dimension-2 condensate $⟨ A_{μ}^{2} ⟩$ can be used to generalize the $θ$ vacuum. In the generalized picture, each gauge fixed slice forms a curved surface around a hadron and other strongly interacting objects, and the propagation of a gluon has to be considered on this curved surface. The gluon propagator turns out to be massive due to the curvature of the gauge fixed surface implementing the possibility that the massless gauge bosons might provide the majority of the hadronic mass and even behave as dark matter in cosmological scales.
Comments:
27 pages, 8 figures
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1503.08984 [pdf]
J.Korean Phys.Soc.(2015)·1 citation
08
[Submitted on 31 Mar 2015] (cross-list from hep-th)
A perturbative description of the deconfinement transition in Yang-Mills theories
Julien Serreau🇫🇷
We investigate the deconfinement transition of static quarks in SU(N) Yang-Mills theories using a perturbative approach based on a massive extension of the Landau-DeWitt gauge-fixed action, where the gluon mass term is related to the issue of Gribov ambiguities. A leading-order, one-loop calculation of the effective potential for the Polyakov loop produces a deconfinement transition of second order for the SU(2) theory and of first order for SU(3) with transition temperatures in qualitative agreement with known values. We also report on the results of a two-loop calculation of the critical temperature and of thermodynamical quantities in the SU(2) case.
Comments:
Contribution to the conference CPOD 2014 (10 pages); Minor corrections and citation added; To appear in PoS
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1504.00038 [pdf]
PoS(2015)·5 citations
09
[Submitted on 1 Apr 2015] (cross-list from hep-ph)
Medium effects on the relaxation of dissipative flows in a hot pion gas
Sukanya Mitra🇮🇳 · Utsab Gangopadhyaya🇮🇳 · Sourav Sarkar🇮🇳
The relaxation times over which dissipative fluxes restore their steady state values have been evaluated for a pion gas using the 14-moment method. The effect of the medium has been implemented through a temperature dependent pi-pi cross-section in the collision integral which is obtained by including one-loop self-energies in the propagators of the exchanged rho and sigma mesons. To account for chemical freeze out in heavy ion collisions, a temperature dependent pion chemical potential has been introduced in the distribution function. The temperature dependence of the relaxation times for shear and bulk viscous flows as well as the heat flow is significantly affected.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1504.00184 [pdf]
PRD(2015)·22 citations
10
[Submitted on 1 Apr 2015] (cross-list from physics.atom-ph)
Electric dipole moment of $^{225}$ Ra due to P- and T-violating weak interactions
Yashpal Singh🇮🇳 · B. K. Sahoo🇮🇳
We report rigorous calculations of electric dipole moment (EDM) in $^{225}$ Ra due to parity and time-reversal violating tensor-pseudotensor (T-PT) and nuclear Schiff moment (NSM) interactions between the electrons and nucleus by employing the relativistic all order coupled-cluster (RCC) methods at various levels of approximation. The most accurate EDM ( $d_{A}$ ) results are obtained as $d_{A} = - 10.04 \times 1 0^{- 20} C_{T} < σ_{n} > ∣ e ∣ c m$ and $d_{A}^{N S M} = - 6.79 \times 1 0^{- 17} S (∣ e ∣ f m^{3})^{- 1} ∣ e ∣ c m$ with $C_{T}$ and $S$ are the T-PT coupling constant and NSM respectively. Due to exhaustive treatment of the electron correlation effects in these calculations, the EDM results for the corresponding T-PT and NSM interactions reduce by about 45\% and 23\%, respectively, from the previously known values. Nonetheless they are still found to be 2-3 times larger than the $^{199}$ Hg results. Validity of the RCC results are countenanced by comparing our calculations at the zeroth order Dirac-Fock method and all order random-phase approximation with the other groups. In view of the current experimental progress in the $^{225}$ Ra EDM measurement, our high accuracy calculations are very useful to yield limits on $C_{T}$ and $S$ in this atom. Thusly, it is possible to realize more accurate limits on the electron-quark T-PT interaction and $θ_{QC D}$ parameter of particle physics in future.
Comments:
5 pages, 1 figure and 2 tables. Comments and suggestions are welcome
Subjects:
Atomic Physics (physics.atom-ph); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1504.00269 [pdf]
PRA(2015)·22 citations

Affiliations

first authorsco-authorsvia INSPIRE