Nuclear Theory·nucl-th

Thursday·December 7, 2023

13 papers—4 primary·9 cross-listed

01
Numerical Convergence of Electromagnetic Responses with the Finite-Amplitude Method
Tong Li · Nicolas Schunck
The response of a nucleus to an electromagnetic probe is a key quantity to simulate photabsorption or photodeexcitation processes. For large calculations at the scale of the entire mass table, this response can be estimated by linear response theory. Thanks to the introduction of the finite-amplitude method (FAM), calculations are computationally efficient. In this paper, we investigate in more details the convergence of FAM calculations of the response function as a function of the parameters controlling the numerical implementation of the theory. We show that the response is much less sensitive to the details of the single-particle basis than, e.g., Hartree-Fock-Bogoliubov calculations.
nucl-thEPJ Web Conf.(2024)·1 citation
02
Speed of Sound in Magnetized Nuclear Matter
Rajkumar Mondal🇮🇳 · Nilanjan Chaudhuri🇮🇳 · Pradip Roy🇮🇳 · Sourav Sarkar🇮🇳
Employing the non-linear Walecka model we investigate the characteristics of nuclear matter under the influence of a background magnetic field at a finite temperature and baryon chemical potential. In the presence of the magnetic field the spinodal lines and the critical end point (CEP) undergo changes in the $T - μ_{B}$ plane. The squared speed of sound exhibits anisotropic behavior, dividing into parallel and perpendicular components. Additionally, the presence of a magnetic field induces anisotropy in the isothermal compressibility. It is found that the parallel component is smaller than the perpendicular one for all values of temperature, chemical potential and magnetic field indicating that the equation of state is stiffer along the magnetic field direction.
nucl-thhep-phPRC(2024)·10 citations
03
Low-momentum relativistic nucleon-nucleon potentials I: Nuclear matter
Chencan Wang🇨🇳 · Sibo Wang🇨🇳 · Hui Tong🇩🇪 · Jinniu Hu🇨🇳 · Jiangming Yao🇨🇳
A series of relativistic one-boson-exchange potentials for two-nucleon system, denoted as OBEP $Λ$ , is constructed with a momentum cutoff $Λ$ ranging from $\infty$ to 2 fm $^{- 1}$ . These potentials are developed by simultaneous fitting to nucleon-nucleon ( $N N$ ) scattering phase shifts, low-energy scattering length, effective range, and the binding energy of the deuteron. The momentum-space matrix elements of the low-momentum OBEP $Λ$ ( $Λ ⩽ 3$ fm $^{- 1}$ ) demonstrate consistency with the universal behaviors observed in other realistic $N N$ potentials evolved by renormalization group methods. These OBEP $Λ$ s are applied to calculate the equation of state of symmetric nuclear matter (SNM) within either the nonrelativistic (NR) Brueckner-Hartree-Fock (BHF) or relativistic Brueckner-Hartree-Fock (RBHF) frameworks. The results show that the saturation properties of SNM are reproduced qualitatively from the RBHF calculation, but not from the NR-BHF calculation. This study highlights the relativistic mechanism in explaining the saturation properties of nuclear matter. The remaining discrepancy in reproducing empirical saturation properties in the RBHF calculation using the OBEP $Λ$ s signals the necessity of including three-nucleon correlations or genuine three-nucleon forces.
nucl-thPRC(2024)·7 citations
04
Higher order dynamical charge fluctuations in heavy-ion collisions
Bhanu Sharma🇮🇳 · P. K. Sahu🇮🇳
The event-by-event charge fluctuation measurements are proposed to provide the signature of quark-gluon plasma (QGP) in heavy-ion collisions. Measure of dynamical charge fluctuations is expected to carry information of initial fractional charge of the QGP phase at the final state. We propose the higher order charge fluctuation measurement to study the QGP signal in heavy-ion collisions. This higher order charge fluctuation observable can amplify the signature of QGP. Also, the SMASH model is used to study the behavior of these observable in heavy-ion collisions at center of mass energies accessible in the STAR beam energy scan program.
nucl-thhep-exhep-phnucl-ex1 citation
05
$σ$ exchange in the one-boson exchange model involving the ground state octet baryons
Bing Wu🇨🇳 · Xiong-Hui Cao🇨🇳 · Xiang-Kun Dong🇩🇪 · Feng-Kun Guo🇨🇳
Based on the one-boson-exchange framework that the $σ$ meson serves as an effective parameterization for the correlated scalar-isoscalar $π π$ interaction, we calculate the coupling constants of the $σ$ to the $\frac{1}{2}^{+}$ ground state light baryon octet $B$ by matching the amplitude of $B B ˉ \to π π \to B ˉ B$ to that of $B B ˉ \to σ \to B ˉ B$ . The former is calculated using a dispersion relation, supplemented with chiral perturbation theory results for the $B B π π$ couplings and the Muskhelishvili-Omnès representation for the $π π$ rescattering. Explicitly, the coupling constants are obtained as $g_{N N σ} = 8. 7_{- 1.9}^{+ 1.7}$ , $g_{ΣΣ σ} = 3. 5_{- 1.3}^{+ 1.8}$ , $g_{ΞΞ σ} = 2. 5_{- 1.4}^{+ 1.5}$ , and $g_{ΛΛ σ} = 6. 8_{- 1.7}^{+ 1.5}$ . These coupling constants can be used in the one-boson-exchange model calculations of the interaction of light baryons with other hadrons.
↳ hep-phnucl-thPRD(2024)·13 citations
06
Real-time correlators in 3+1D thermal lattice gauge theory
Kirill Boguslavski🇦🇹 · Paul Hotzy🇦🇹 · David I. Müller🇦🇹
We present the first direct ab-initio computation of unequal-time correlation functions in non-Abelian lattice gauge theory. We demonstrate non-trivial consistency relations among correlators, time-translation invariance, and agreement with Monte-Carlo results for thermal equilibrium in 3+1 dimensions by employing our stabilized complex Langevin method. Our work sets the stage to extract real-time observables, relevant to quark-gluon plasma physics within a first-principles real-time framework.
↳ hep-latcond-mat.otherhep-phhep-th+1PRD(2024)·17 citations
07
Nonconvergence of the Feynman-Dyson diagrammatic perturbation expansion of propagators
So Hirata · Ireneusz Grabowski · J. V. Ortiz · Rodney J. Bartlett
Using a general-order ab initio many-body Green's function method, we numerically illustrate several pathological behaviors of the Feynman-Dyson diagrammatic perturbation expansion of one-particle many-body Green's functions as electron Feynman propagators. (i) The perturbation expansion of the frequency-dependent self-energy is not convergent at the exact self-energy in many frequency domains. (ii) An odd-perturbation-order self-energy has a qualitatively wrong shape and, as a result, many roots of the corresponding Dyson equation are nonphysical in that the poles may be complex or residues can exceed unity or be negative. (iii) A higher even-order self-energy consists of vertical lines at many frequencies, predicting numerous phantom poles with zero residues. (iv) Infinite partial resummations of diagrams by vertex or edge renormalization tend to exacerbate these pathologies. (v) The nonconvergence is caused by the nonanalyticity of the rational-function form of the exact Green's function at many frequencies, where the radius of convergence of its Taylor expansion is zero. This is consistent with the fact that (vi) Padé approximants (power-series expansions of a rational function) can largely restore the correct shape and poles of the Green's function. Nevertheless, not only does the nonconvergence render higher-order Feynman-Dyson diagrammatic perturbation theory useless for many lower-lying ionization or higher-lying electron-attachment states, but it also calls into question the validity of its combined use with the ansätze requiring the knowledge of all poles and residues. Such ansätze include the Galitskii-Migdal identity, the self-consistent Green's function methods, and some models of the algebraic diagrammatic construction.
↳ quant-phmath-phmath.MPnucl-th+1PRA(2024)·4 citations
08
Entanglement in massive Schwinger model at finite temperature and density
Sebastian Grieninger🇺🇸 · Kazuki Ikeda🇺🇸 · Dmitri E. Kharzeev🇺🇸 · Ismail Zahed🇺🇸
We evaluate the entanglement entropy and entropic function of massive two dimensional QED (Schwinger model) at finite temperature, density, and $θ$ -angle. In the strong coupling regime, the entropic function is dominated by the boson mass for large spatial intervals, and reduces to the CFT result for small spatial intervals. We also discuss the entanglement spectrum at finite temperature and a finite $θ$ -angle.
↳ hep-thhep-phnucl-thPRD(2024)·21 citations
09
Successful $ν p$ -process in neutrino-driven outflows in core-collapse supernovae
Alexander Friedland🇺🇸 · Payel Mukhopadhyay🇺🇸 · Amol V. Patwardhan🇺🇸
The origin of the solar system abundances of several proton-rich isotopes, especially $^{92, 94}$ Mo and $^{96, 98}$ Ru, has been an enduring mystery in nuclear astrophysics. An attractive proposal to solve this problem is the $ν p$ -process, which can operate in neutrino-driven outflows in a core-collapse supernova after the shock is launched. Years of detailed studies, however, have cast doubt over the ability of this process to generate sufficiently high absolute and relative amounts of various $p$ -nuclei. The $ν p$ -process is also thought to be excluded by arguments based on the long-lived radionuclide $^{92}$ Nb.Here, we present explicit calculations, in which both the abundance ratios and the absolute yields of the $p$ -nuclei up to $A ≲ 105$ are successfully reproduced, even when using the modern (medium enhanced) triple- $α$ reaction rates. The process is also shown to produce the necessary amounts of $^{92}$ Nb. The models are characterized by subsonic outflows and by the protoneutron star masses in the $≳ 1.7 M_{⊙}$ range. This suggests that the Mo and Ru $p$ -nuclides observed in the Solar System were made in CCSN explosions characterized by an extended accretion stage.
↳ astro-ph.HEastro-ph.SRhep-phnucl-thJCAP(2025)·8 citations
10
Gravitational wave double copy of radiation from gluon shockwave collisions
Himanshu Raj🇺🇸 · Raju Venugopalan🇺🇸
In a recent paper, we showed that the gravitational wave spectrum from trans-Planckian shockwave scattering in Einstein gravity is determined by the gravitational Lipatov vertex expressed as the bilinear double copy $Γ^{μν} = \frac{1}{2} C^{μ} C^{ν} - \frac{1}{2} N^{μ} N^{ν}$ where $C^{μ}$ is the QCD Lipatov vertex and $N^{μ}$ is the QED soft photon factor. We show here that this result can be directly obtained by careful application of the classical color-kinematic duality to the spectrum obtained in gluon shockwave collisions.
↳ hep-thgr-qchep-phnucl-thPLB(2024)·9 citations
11
Momentum anisotropy generation in a hybrid approach
Niklas Götz🇩🇪 · Lucas Constantin🇩🇪 · Hannah Elfner🇩🇪
Anisotropic flow emerges in all three of hybrid approaches: initial conditions, viscous relativistic hydrodynamics as well as hadronic transport. Previous works focus mainly on a constant or temperature dependent shear viscosity $η / s$ . Here instead, we study qualitatively the effect of a generalized $η / s (T, μ_{B})$ in the hybrid approach SMASH-vHLLE-hybrid. The parameterization takes into account the constraints of matching to the transport coefficients in the hadronic phase, as well as of recent Bayesian analysis results. We compare the effect of the different parameterizations in the intermediate energy region of $s_{N N}$ =7.7 - 39.0 GeV. We observe that using the energy density dependent parameterization decreases the effect of the point of particlization. In addition, we quantify the uncertainty due to different initial state profiles, including the SMASH initial conditions as well as TrENTo and IP-Glasma profiles. It can be shown that the initial state transverse momentum impacts final state momentum anisotropy.
↳ hep-phnucl-exnucl-th0 citations
12
Charged pion production in the annihilation reactions $e^{+} + e^{-} \to p + n ˉ + π^{-}$ and $e^{+} + e^{-} \to n + p ˉ + π^{+}$
G. I. Gakh🇺🇦 · M.I. Konchatnij🇺🇦 · N.P. Merenkov🇺🇦 · E. Tomasi-Gustafsson🇫🇷
The nonresonant mechanism in the reactions $e^{+} e^{-} \to π^{-} p n ˉ$ and $e^{+} e^{-} \to π^{+} n p ˉ$ is investigated in frame of the one-photon exchange approximation. The description of the hadronic phase space and the invariant amplitude formalism, earlier developed for the neutral pion channel, are applied here. Some modifications are required to fulfill the invariance and to account for an additional contribution due to diagram with the pion pole. Two different variants which lead to dipole and monopole asymptotic behaviour of the pion electromagnetic form factor, are considered. The double and single distributions over the invariant variables as well the total cross section, are obtained. The results are plotted for $s =$ 5,\,6,\,10,\,16\, GeV $^{2}$ . The calculations are performed for the $π^{-} p n ˉ$ channel and the rules to proceed to the $π^{+} n p ˉ$ channel are formulated for every distribution.
↳ hep-phnucl-th0 citations
13
Extracting the Asymptotic Behavior of S-matrix Elements from their Phases
Ira Z. Rothstein🇺🇸 · Michael Saavedra🇺🇸
The asymptotic kinematic limits of S-matrices are dominated by large logarithms which, roughly speaking, fall into two categories: those which are controlled by a renormalization group (RG) scale, which we may think of as logs involving ratios of invariant mass scales, and those which are functions of ratios of rapidities, so called "rapidity logs". It has been pointed out by Caron-Huot and Wilhlem [1] that RG anomalous dimension can be extracted from the phase of the S-matrix, which can greatly simplify calculations via unitarity methods. In this paper we generalize the results of [1] to show that the phase can be used to reconstruct rapidity anomalous dimensions, by performing a complex boost. The methodology introduced here also allows one to calculate without the need for a rapidity regulator. We demonstrate the use of this method to derive the rapidity anomalous dimensions in the Sudakov form factor, the two parton soft function and the Regge trajectory in QCD.
↳ hep-thhep-phnucl-thJHEP(2024)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE