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Nuclear Theory·nucl-th

Thursday·June 27, 2024

3 papers—1 primary·2 cross-listed

All3Primary1Cross-lists2
  1. 01

    Neural Network Emulation of Flow in Heavy-Ion Collisions at Intermediate Energies

    Nicholas Cox🇺🇸 · Xavier Grundler🇺🇸 · Bao-An Li🇺🇸

    Applications of new techniques in machine learning are speeding up progress in research in various fields. In this work, we construct and evaluate a deep neural network (DNN) to be used within a Bayesian statistical framework as a faster and more reliable alternative to the Gaussian Process (GP) emulator of an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model simulator of heavy-ion reactions at intermediate beam energies. We found strong evidence of DNN being able to emulate the IBUU simulator's prediction on the strengths of protons' directed and elliptical flow very efficiently even with small training datasets and with accuracy about ten times higher than the GP. Limitations of our present work and future improvements are also discussed.

    nucl-thhep-phnucl-exPRC(2024)·6 citations
  2. 02

    Initial Data for First-order Causal Viscous Conformal Fluids in General Relativity

    Marcelo M. Disconzi · James Isenberg · David Maxwell

    We solve the Einstein constraint equations for a first-order causal viscous relativistic hydrodynamic theory in the case of a conformal fluid. For such a theory, a direct application of the conformal method does not lead to a decoupling of the equations, even for constant-mean curvature initial data. We combine the conformal method applied to a background perfect fluid theory with a perturbative argument in order to obtain the result.

    ↳ gr-qcmath.APnucl-thJ.Math.Phys.(2024)·4 citations
  3. 03

    On the time-dependent Aharonov-Bohm effect and the 4-dimensional Stokes theorem

    Masashi Wakamatsu🇯🇵

    The time-dependent Aharonov-Bohm (AB) effect considers the situation in which the magnetic flux inside the solenoid changes time-dependently. Different from the standard AB-effect, the problem is unexpectedly subtle and not easy to solve without any doubt, which is the reason why it is still in a state of unsettlement even theoretically. The difficulty originates from the fact that its theoretical analysis requires line-integrals of the time-dependent vector potential along paths in the 4-dimensional Minkowski space. Owing to the 4-dimensional Stokes theorem, this closed line-integral of the vector potential can be related to the integral of the electric and magnetic fields over the 2-dimensional area, the boundary of which is given by the above-mentioned closed path. The central controversy concerns the success or failure of the claim by Singleton and collaborators based on the 4-dimensional Stokes theorem, which states that the time-dependent part of the AB-phase shift due to the magnetic vector potential is precisely cancelled by the effect of induced electric field generated by the time-variation of the magnetic flux. In the present paper, we carefully reanalyze their cancellation argument by going back to the basic quantum mechanical analysis of the charged particle motion under the presence of the time-dependent external electromagnetic potential combined with more careful treatment of the 4-dimensional Stokes theorem. Careful analysis of the 4-dimensional Stokes theorem shows that the cancellation argument by Singleton et al. is partially correct but their central claim that only the time-independent part of the magnetic field contributes to the AB-phase shift so that there is no time-dependent AB-effect is not justified, thereby supporting likely existence of the time-dependent AB-effect.

    ↳ quant-phhep-phnucl-thphysics.ed-phAnnals Phys.(2025)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE