PaperPanorama

Nuclear Theory·nucl-th

Tue·Oct 6, 2026

2 papers—1 primary·1 cross-listed

All2Primary1Cross-lists1
  1. 01

    Emulation of coupled-channels scattering for strongly deformed nuclei

    M. Catacora-Rios · Kyle Beyer · Jin Lei · Filomena Nunes

    Nucleon scattering off strongly deformed nuclei such as the actinides requires coupled-channels (CC) calculations in which several members of the ground-state rotational band are coupled explicitly, which makes Bayesian uncertainty quantification of deformed global optical potentials costly. We reformulate the direct boundary matching method (DBMM) by imposing its outgoing-wave boundary condition through a generalized Bloch operator; the resulting Bloch-DBMM solver converges as fast as the modern R-matrix method and extends to charged projectiles on targets with deformed charge distributions. On top of it we build a reduced-basis emulator, CCB-ROM, whose basis vectors span all channels of a block simultaneously, and generalize the coupled-channels empirical interpolation method to arbitrary non-affine deformed interactions. For Th inelastic scattering with the ground-state band coupled through the state, at 4 and 35 MeV, the Bloch-DBMM solver is benchmarked against Frescox, and the emulator replaces a 2700-dimensional system by one of dimension , with a cost of independent of the number of channels, reproducing the exact solver calculations for all five band members with speed-ups of over two orders of magnitude. CCB-ROM thus delivers differential cross sections, transmission coefficients and reaction cross sections from one calculation, at a cost compatible with Bayesian calibration of deformed optical potentials for neutrons and protons alike, and extends naturally to closed channels and to compound-nucleus reaction codes.

    nucl-th
  2. 02

    No Einstein Relation, No Problem: How Relativistic Weakly Coupled Heavy Quarks Equilibrate Beyond Leading Logarithm Anyway

    Jean F. Du Plessis · Bruno Scheihing-Hitschfeld

    Relativistic heavy quarks equilibrate even when their microscopic drag and momentum diffusion violate the Einstein relation. We investigate how equilibration proceeds as a function of the coupling and compared to simplified Fokker-Planck models. To do this, we present a detailed calculation of the momentum-transfer kernel in weakly coupled non-Abelian plasmas through strict , and study the resulting dynamics at leading order in the inverse heavy-quark mass. Beyond leading logarithm, its non-Gaussian structure plays a crucial role in equilibration. We examine closely the analytic structure of the evolution kernel, determine the large-order asymptotics of the momentum-transfer cumulants, and show how the kernel's bounded analytic domain fixes asymmetric exponential tails at the level of the momentum transfer probability. Strongly coupled SYM also features an approximately Gaussian core and exponential tails, but differs in the nature of the kernel's singularities and the velocity dependence of the transport coefficients and tail exponents. These differences have distinct dynamical consequences: for the parameters studied, the persistence of the relativistic population in steeply falling spectra is largely explained by drag alone at very weak coupling, whereas fluctuation-induced survivor bias produces a large relative enhancement at strong coupling. Nevertheless, the shared qualitative structure between weak and strong coupling points the way towards a practical phenomenological description of heavy quarks anchored in first-principles field theory.

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