Nuclear Theory·nucl-th

Thursday·September 22, 2022

10 papers—7 primary·3 cross-listed

01
[Submitted on 20 Sept 2022]
Radiative processes on a quantum computer
Paulo F. Bedaque🇺🇸 · Ratna Khadka🇺🇸 · Gautam Rupak🇺🇸 · Muhammad Yusf🇺🇸
Radiative processes, where a photon/neutrino is emitted as a result of a collision or decay of a particle, play a central role in atomic, nuclear and particle physics. Their rate is determined by certain off-diagonal matrix elements with different initial and final states. We propose a method to compute them using quantum computers. It relies on a single extra qubit that, in a certain sense, represents the photon/neutrino. The generic formula relating this matrix element to the amplitude and frequency of oscillations of the extra qubit follows simply in the near resonance case. We demonstrate the feasibility of the method by using it in actual quantum computations and simulations of simple systems.
Comments:
5 pages, 2 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2209.09962 [pdf]
PRC(2025)·15 citations
02
[Submitted on 20 Sept 2022]
Elucidating the finite temperature quasiparticle random phase approximation
E. M. Ney · A. Ravlić · J. Engel · N. Paar
In numerous astrophysical scenarios, such as core-collapse supernovae and neutron star mergers, as in well as heavy-ion collision experiments, transitions between thermally populated nuclear excited states have been shown to play an important role. Due to its simplicity and excellent extrapolation ability, the finite-temperature quasiparticle random phase approximation (FT-QRPA) presents itself as an efficient method to study the properties of hot nuclei. The statistical ensembles in the FT-QRPA make the theory much richer than its zero-temperature counterpart, but also obscure the meaning of various physical quantities. In this work, we clarify several aspects of the FT-QRPA, including notations seen in the literature, and demonstrate how to extract physical quantities from the theory. To exemplify the correct treatment of finite-temperature transitions, we place special emphasis on the charge-exchange transitions described within the proton-neutron FT-QRPA (FT-PNQRPA). With the FT-PNQRPA built on the nuclear energy-density functional theory, we obtain solutions using a relativistic matrix approach and also the non-relativistic finite amplitude method. We show that the Ikeda sum rule is fulfilled with the proper treatment of de-excitations from thermally populated excited states. Additionally, we demonstrate the impact of these transitions on stellar electron capture (EC) rates in $^{58, 78}$ Ni. While their inclusion does not influence the EC rates in $^{58}$ Ni, the rates in $^{78}$ Ni are dominated by de-excitations for temperatures $T > 0.5$ MeV. In systems with a large negative $Q$ -value, the inclusion of de-excitations within the FT-QRPA is necessary for a complete description of reaction rates at finite temperature.
Comments:
19 pages, 4 figures, submitted for publication
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2209.10009 [pdf]
EPJA(2025)·7 citations
03
[Submitted on 21 Sept 2022]
Pion-mediated Cooper pairing of neutrons: beyond the bare vertex approximation
Hao-Fu Zhu · Guo-Zhu Liu
In some quantum many particle systems, the fermions could form Cooper pairs by exchanging intermediate bosons. This then drives a superconducting phase transition or a superfluid transition. Such transitions should be theoretically investigated by using proper non-perturbative methods. Here we take the neutron superfluid transition as an example and study the Cooper pairing of neutrons mediated by neutral $π$ -mesons in the low density region of a neutron matter. We perform a non-perturbative analysis of the neutron-meson coupling and compute the pairing gap $Δ$ , the critical density $ρ_{c}$ , and the critical temperature $T_{c}$ by solving the Dyson-Schwinger equation of the neutron propagator. We first carry out calculations under the widely used bare vertex approximation and then incorporate the contribution of the lowest-order vertex correction. This vertex correction is not negligible even at low densities and its importance is further enhanced as the density increases. The transition critical line on density-temperature plane obtained under the bare vertex approximation is substantially changed after including the vertex correction. These results indicate that the vertex corrections play a significant role and need to be seriously taken into account.
Comments:
27 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Superconductivity (cond-mat.supr-con); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2209.10172 [pdf]
J.Phys.G(2023)·0 citations
04
[Submitted on 21 Sept 2022]
Cumulants of net-strangeness multiplicity distributions at energies available at the BNL Relativistic Heavy Ion Collider
Changfeng Li🇨🇳 · Deeptak Biswas🇮🇳 · Nihar Ranjan Sahoo🇨🇳
The higher-order cumulants of net-proton number, net-charge, and net-strangeness multiplicity distributions are widely studied to search for the quantum-chromodynamics critical point and extract the chemical freeze-out parameters in heavy-ion collisions. In this context, the event-by-event fluctuations of the net-strangeness multiplicity distributions play important roles in extracting the chemical freeze-out parameter in the strangeness sector. Due to having difficulties in detecting all strange hadrons event by event, the kaon ( $K$ ) and lambda ( $Λ$ ) particles serve as a proxy for the strangeness-related observables in heavy-ion collisions. We have studied the net- $K$ , net- $Λ$ , and net-( $K$ + $Λ$ ) multiplicity distributions and calculated their different order of cumulants using the ultrarelativistic quantum molecular dynamics model and hadron resonance gas calculation. To adequately account for the net-strangeness cumulants, it has been found that the inclusion of resonance decay contributions in $K$ and $Λ$ is necessary.
Comments:
The title has been modified. Updated following the published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2209.10343 [pdf]
PRC(2023)·1 citation
05
[Submitted on 21 Sept 2022]
Exact results for the Boltzmann collision operator in $λ ϕ^{4}$ theory
Gabriel S. Denicol (Niteroi, Fluminense U.)🇧🇷 · Jorge Noronha (Illinois U., Urbana)🇺🇸
We analytically determine all the eigenvalues and eigenfunctions of the linearized Boltzmann collision operator in massless scalar $λ ϕ^{4}$ theory in the high-temperature (classical) regime. This is used to exactly compute the shear viscosity and particle diffusion transport coefficients of this system. The corresponding relaxation time approximation for this linearized Boltzmann equation is also derived.
Comments:
10 pages including supplemental material
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2209.10370 [pdf]
PLB(2024)·34 citations
06
[Submitted on 21 Sept 2022]
Reply to "Comment on Sequential Single-pion Production Explaining the dibaryon $d^{*} (2380)$ peak''
R. Molina🇪🇸 · N. Ikeno🇪🇸 · E. Oset🇪🇸
In a comment [arXiv:2106.00494] to our paper on ``Sequential single-pion production explaining the dibaryon $d^{*} (2380)$ peak'' the authors provide arguments that apparently invalidate our claims and present what they call ``proofs'' of the dibaryon explanation of the $n p \to π^{0} π^{0} d$ fusion reaction. In this reply we refute the arguments of the comment and show that no existing experiment proves the dibaryon nature of the peak of the fusion reaction.
Comments:
4 pages
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2209.10459 [pdf]
CPC(2023)·30 citations
07
[Submitted on 21 Sept 2022]
Stability studies of first order spin-hydrodynamic frameworks
Asaad Daher🇵🇱 · Arpan Das🇵🇱 · Radoslaw Ryblewski🇵🇱
We study the stability of first-order dissipative spin-hydrodynamic frameworks. We considered two different first-order dissipative spin-hydrodynamic frameworks. The first one considers the spin chemical potential ( $ω^{α β}$ ) to be first order ( $O (\partial)$ ) in the hydrodynamic gradient expansion. The hydrodynamic gradient ordering of the spin chemical potential is a debatable issue within the frameworks of spin hydrodynamics. Therefore as a second choice, we also consider the spin hydrodynamic equations with $ω^{α β} \sim O (1)$ . We find that for both frameworks, at the level of linear perturbations some spin modes can be unstable. To remove these generic instabilities we consider the Frenkel condition. We argue that Frenkel condition helps get rid of the unstable solutions in both cases, but with a physical drawback for the case where $ω^{μν} \sim O (\partial)$ .
Comments:
11 pages. No figures. Comments are welcome
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2209.10460 [pdf]
PRD(2023)·48 citations
08
[Submitted on 20 Sept 2022] (cross-list from hep-ph)
Theoretical discrepancies in the nucleon spin structure and the hyperfine splitting of muonic hydrogen
Vladimir Pascalutsa (JGU)🇩🇪 · Franziska Hagelstein (JGU & PSI)🇩🇪 · Vadim Lensky (JGU)🇩🇪
Two groups, ours (Mainz) and Bochum, have recently been re-evaluating the spin polarizabilities and spin structure functions at low $Q$ , using the baryon chiral perturbation theory (B $χ$ PT), the manifestly-covariant counterpart of the heavy-baryon chiral perturbation theory (HB $χ$ PT). Whilst the two groups agree that the B $χ$ PT framework works better than HB $χ$ PT in this sector, their quantitative results disagree in some of the quantities; most notably, the proton spin polarizabilities $γ_{0}$ and $δ_{L T}$ . These discrepancies are especially intriguing in light of new experimental data coming from the Jefferson Lab "Spin Physics Program". The preliminary data on the proton are reported by Karl Slifer in a plenary session of this workshop. Another theoretical discrepancy is emerging in the proton-polarizability contribution to the hyperfine splitting (hfs) in hydrogen and muonic hydrogen. Our B $χ$ PT calculation shows a significantly smaller effect than the state-of-the-art data-driven evaluations based on empirical spin structure functions. The smaller polarizability contribution leads to a smaller Zemach radius of the proton. This discrepancy could be relevant for the planned first-ever measurement of the ground-state hfs in muonic hydrogen.
Comments:
10 pages, 5 figures, to appear in the proceedings of the 10th International Workshop on Chiral Dynamics - CD2021, 15-19 November 2021, Beijing, China (Online)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2209.09995 [pdf]
PoS(2024)·2 citations
09
[Submitted on 21 Sept 2022] (cross-list from hep-ph)
Unified Balance Functions
Claude Pruneau🇺🇸 · Victor Gonzales🇺🇸 · Brian Hanley🇺🇸 · Ana Marin🇩🇪 · Sumit Basu🇸🇪
The use of charge balance functions in heavy-ion collision studies was initially proposed as a probe of delayed hadronization and two-stage quark production in these collisions. It later emerged that general balance functions can also serve as a probe of the diffusivity of light quarks as well as the evolution of the systems formed in heavy-ion collisions. In this work, we reexamine the formulation of general balance functions and consider how to best define and measure these correlation functions in terms of differences of conditional densities of unlike-sign and like-sign particle pairs. We define general balance functions in terms of associated particle functions and show these obey a simple sum rule. We additionally proceed to distinguish between balance functions expressed as differences of conditional densities valid irrespective of experimental acceptance boundaries and bound balance functions that explicitly account for the limited acceptance of experiments. General balance functions are additionally extended to accommodate strange, baryon, as well as charm and bottom quantum numbers based on the densities of these quantum numbers.
Comments:
19 pages. 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2209.10420 [pdf]
PRC(2023)·16 citations
10
[Submitted on 21 Sept 2022] (cross-list from hep-ph)
Far-off-equilibrium expansion trajectories in the QCD phase diagram
Chandrodoy Chattopadhyay (North Carolina State University)🇺🇸 · Ulrich Heinz (Ohio State University)🇺🇸 · Thomas Schaefer (North Carolina State University)🇺🇸
We consider the hydrodynamic evolution of a quark-gluon gas with non-zero quark masses and net baryon number in its phase diagram. For far-off-equilibrium initial conditions the expansion trajectories appear to violate simple rules based on the second law of thermodynamics that were previously established for ideal or weakly dissipative fluids. For Bjorken flow we present a detailed analysis within kinetic theory that provides a full microscopic understanding of these macroscopic phenomena and establishes their thermodynamic consistency. We point out that, for certain far-off-equilibrium initial conditions, the well-known phenomenon of "viscous heating" turns into "viscous cooling" where, driven by dissipative effects, the temperature decreases faster than in adiabatic expansion.
Comments:
25 pages, 14 figures (manuscript now in PRC format, added references)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2209.10483 [pdf]
PRC(2023)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE