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Nuclear Theory·nucl-th

Thursday·September 22, 2022

10 papers—7 primary·3 cross-listed

All10Primary7Cross-lists3
  1. 01

    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.

    nucl-thquant-phPRC(2025)·15 citations
  2. 02

    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 Ni. While their inclusion does not influence the EC rates in Ni, the rates in Ni are dominated by de-excitations for temperatures MeV. In systems with a large negative -value, the inclusion of de-excitations within the FT-QRPA is necessary for a complete description of reaction rates at finite temperature.

    nucl-thEPJA(2025)·7 citations
  3. 03

    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 -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 , the critical density , and the critical temperature 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.

    nucl-thcond-mat.supr-conhep-phJ.Phys.G(2023)·0 citations
  4. 04

    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 () and lambda () particles serve as a proxy for the strangeness-related observables in heavy-ion collisions. We have studied the net-, net-, and net-( + ) 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 and is necessary.

    nucl-thhep-exhep-phnucl-exPRC(2023)·1 citation
  5. 05

    Exact results for the Boltzmann collision operator in 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 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.

    nucl-thhep-phhep-thPLB(2024)·34 citations
  6. 06

    Reply to "Comment on Sequential Single-pion Production Explaining the dibaryon peak''

    R. Molina🇪🇸 · N. Ikeno🇪🇸 · E. Oset🇪🇸

    In a comment [arXiv:2106.00494] to our paper on ``Sequential single-pion production explaining the dibaryon peak'' the authors provide arguments that apparently invalidate our claims and present what they call ``proofs'' of the dibaryon explanation of the 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.

    nucl-thnucl-exCPC(2023)·30 citations
  7. 07

    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 () to be first order () 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 . 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 .

    nucl-thhep-phPRD(2023)·48 citations

Affiliations

first authorsco-authorsvia INSPIRE