Nuclear Theory·nucl-th

Wednesday·June 10, 2026

18 papers—10 primary·8 cross-listed

11
[Submitted on 24 May 2026] (cross-list from astro-ph.HE)
Pulse Modulation as a Signature of the Asteroid-Neutron Star Collision Model for High-Energy Transients
Partha Bagchi🇮🇳 · Biswanath Layek🇮🇳 · Dheeraj Saini🇮🇳 · Anjishnu Sarkar🇮🇳 · Ajit M. Srivastava🇮🇳 · Deepthi Godaba Venkata🇮🇳
Asteroid-neutron star collision models have been proposed as possible sources of high-energy transients, such as gamma-ray bursts (GRBs) and fast radio bursts (FRBs). The sequence of events following the impact of the asteroid and finally dissolving into the neutron star can have several other observable consequences. We propose that due to the development of the off-diagonal moment of inertia (MI) components, the merger's aftermath can lead to the wobbling of the pulsar (assuming the neutron star happens to be a pulsar). Using sample values of various parameters, viz., size, shape, the locations of the deposits, and the pre-existing pulsar deformation parameter ( $η$ ), we calculate the detailed pulse profile modulation of the pulsar. We observe a distinct pattern of pulse profile modulation on a characteristic timescale enhanced by a factor of $1/ η$ compared to the pulse timing. Importantly, even small changes in the MI components, of order $ϵ$ , can produce large pulse profile modulations of order $ϵ / η$ (depending on the relative location of asteroid material deposition). Thus, if an asteroid-neutron star collision is responsible for a high-energy transient, the associated pulse profile modulation may serve as a falsifiable observational signature of such an event.
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); physics.class-ph (physics.class-ph); Computational Physics (physics.comp-ph)
arXiv:
2605.24886 [pdf]
MNRAS(2026)·1 citation
12
[Submitted on 8 Jun 2026] (cross-list from cs.LG)
Integrating Out, Twice:The Open-System Case That Neural-Network Ensemble Theory Is Missing
Jin Lei
Averaging a neural network over its random parameters and marginalizing a Gaussian sector are the same operation, the Schur complement of the eliminated block, and when that block is closed it returns a covariance and its inverse. That is all a network ensemble produces, the closed case. The open case is missing, and nuclear reaction theory has it worked out. Projecting a scattering problem onto a chosen set of channels, with the rest carrying probability irreversibly to a continuum, leaves a non-Hermitian effective generator that conserves and itemizes exactly what it loses: the nuclear optical model and its generalized optical theorem. I set the two cases side by side using only the moments of a distribution, the algebra of Gaussians, and block inversion, no field theory, and give the closed-case dictionary in full: the neural tangent kernel is the Fisher sensitivity kernel, the infinite-width Gaussian limit is the Gaussian-process emulator, and the lazy-to-feature transition is the validity boundary of a reduced-basis emulator. I then test the open export on a truncated attention map, a token-level transfer operator, and a sparse expert router, and report a mostly negative result. The conserved flux ledger ports wherever openness is genuinely present, but its distinctive content is absent, an artifact of the chosen partition, or pinned near a floor by the training objective, and the operationally useful uncertainty turns out to be epistemic, living in the closed half of the correspondence, not the open one. The negative has a structural reason this note makes precise: the open case needs an eliminated sector with a continuous spectrum and wave-like, not relaxational, dynamics, which mainstream learning's finite or dissipative objects do not supply. This is a note, not a result; its main finding is that negative one, and its value is the map that locates it.
Subjects:
Machine Learning (cs.LG); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph); Data Analysis, Statistics and Probability (physics.data-an)
arXiv:
2606.09950 [pdf]
0 citations
13
[Submitted on 8 Jun 2026] (cross-list from hep-lat)
Momentum Dependence of Heavy Quark Diffusion in a Thermal Gluonic Plasma on the Lattice
Harshit Pandey🇮🇳 · Sayantan Sharma🇮🇳
We study the dynamics of a heavy quark in a thermal plasma consisting of non-perturbatively interacting soft momentum gluons at high temperatures, described in terms of an effective theory of QCD. Discretizing this effective field theory on a three-dimensional lattice, we propose a numerical strategy that allows us to simulate the dynamics of a heavy quark for different values of initial momenta and for a wide temperature range, higher than $480$ MeV. This allows us, for the first time, to extract the momentum dependence of the heavy quark drag and diffusion coefficients in a non-perturbatively interacting thermal, non-Abelian plasma.
Comments:
v2; few typos corrected; figures updated
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2606.10049 [pdf]
0 citations
14
[Submitted on 8 Jun 2026] (cross-list from astro-ph.HE)
Internal constitution of the outer crust of non-accreted neutron stars and magnetars
Juliette Servais · Nicolas Chamel
Context. Determining the internal constitution of the outer crust of magnetars is important for interpreting several of their astrophysical manifestations. In particular, the crustal composition is a key input for simulations of r-process nucleosynthesis in giant flare ejecta. However, traditional methods are computationally expensive, limiting their use in large-scale studies. Although faster iterative approaches exist, they are restricted to unmagnetized matter and strongly quantizing magnetic fields, leaving the intermediate field strengths characteristic of observed magnetars without an efficient treatment. Aims. We developed the program magcrust to extend these existing iterative approaches, enabling the rapid computation of the outer-crust composition of cold, non-accreted magnetars over the full range of the magnetic-field strengths inferred for these objects. Methods. Transitions between adjacent crustal layers are computed by solving approximate equilibrium conditions at the interface. Nuclear abundances and layer depths are estimated from approximate solutions of Einstein's equations of general relativity. Results. The performance and accuracy of the program were assessed against detailed numerical calculations. Relative deviations from exact transition properties remain within a few percent, and crustal compositions are well reproduced across 17 nuclear mass tables and 1300 magnetic-field strengths from 1E13 to 1E16 G. Computation times are reduced by factors of 1E3-1E7 compared to traditional approaches. Conclusions. This program provides a robust and efficient tool for determining the stratification of magnetars' outer crust over the full range of astrophysically relevant magnetic-field strengths. Its computational speed makes it well suited to systematic calculations, including sensitivity analyses, uncertainty quantification, and ensemble studies.
Comments:
9 pages, 2 figures. Accepted for publication in Astronomy & Astrophysics
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2606.10118 [pdf]
Astron.Astrophys.(2026)·0 citations
15
[Submitted on 9 Jun 2026] (cross-list from hep-ph)
Light and Strange Baryons in Medium
T. Massimino🇺🇸 · T. Klähn🇺🇸 · Z. Papp🇺🇸
We solve the Goldstone-boson-exchange (GBE) relativistic constituent quark model of light and strange baryons by using the Faddeev approach. The model reproduces the vacuum mass spectrum of light and strange baryons below $2$ GeV reasonably well. To test the sensitivity of the model to possible medium-induced effects, we vary the masses of the constituent quarks and the exchange bosons, the confinement strength, and the quark-meson coupling constant. In a parametric study, we consider a set of power law scaling relations for these parameters, including some motivated by constituent quark level current algebra relations. We find that the baryon spectrum is most sensitive to the quark-meson coupling constant, and generally observe a decrease in baryon mass with decreasing constituent quark mass. We qualitatively estimate the impact of these mass shifts on ideal-gas baryon yields and yield ratios. Absolute yields can change significantly already for mass shifts of a few $10$ ~MeV, whereas yield ratios are strongly modified only when the compared baryons have different constituent-quark-mass dependence.
Comments:
10 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2606.10356 [pdf]
0 citations
16
[Submitted on 9 Jun 2026] (cross-list from hep-ex)
$Λ$ (1520) as a probe of resonance-driven deuteron formation at the LHC
Sushanta Tripathy🇸🇪 · Peter Christiansen🇸🇪
Light nuclei such as deuterons are produced abundantly in high-energy proton-proton and nuclear collisions despite their tiny binding energies. Their production mechanism remains unresolved, as both nucleon coalescence and statistical thermal models reproduce inclusive LHC yields. We propose a direct invariant-mass observable that discriminates between these scenarios using the long-lived $Λ (1520) \to pK$ resonance. If decay protons coalesce into deuterons, the produced nuclei remain correlated with the kaon, allowing the resonance peak to be reconstructed experimentally through proxy masses, $M_{(d/2) K}$ , formed from kaons and half the deuteron four-momentum. Using Thermal-FIST and PYTHIA with a deuteron coalescence afterburner, we show that a $M_{(d/2) K}$ peak emerges only in the coalescence scenario. This observable provides a direct experimental probe of resonance-fed deuteron production and of late-stage coalescence dynamics in high-energy collisions.
Comments:
5 pages and 4 captioned figures
Subjects:
High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2606.10668 [pdf]
1 citation
17
[Submitted on 9 Jun 2026] (cross-list from hep-th)
Chiral Plasma under Strong Magnetic Fields: A Holographic Analysis of Transport Phenomena
Michael Lublinsky🇮🇱 · Hadas Tzarfati🇮🇱
Chiral plasma appears in several areas of physics, historically starting from primordial plasma in the early Universe, then in quark-gluon plasma produced in heavy ion collisions, and, more recently, in Dirac and Weyl semimetals. The major signature of the plasma is the non-conservation of the axial current due to the chiral anomaly and the emergence of new, anomaly-induced transport phenomena. In this paper, we study the plasma exposed to arbitrarily strong constant magnetic and weak electric fields. Employing all-order gradient resummation, we write down constitutive relations for electric and axial currents parameterized by thirteen momentum- and magnetic- field-dependent transport coefficient functions. The latter are computed utilizing a theoretical lab for a realistic plasma, namely a holographic $U (1)_{V} \times U (1)_{A}$ Maxwell--Chern--Simons theory in Schwarzschild--AdS $_{5}$ , in the probe limit. As an application, we revisit the phenomena of negative magnetoresistance and chiral magnetic waves, beyond the naive hydrodynamic limit.
Comments:
36 pages
Subjects:
High Energy Physics — Theory (hep-th); cond-mat.mtrl-sci (cond-mat.mtrl-sci); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2606.10689 [pdf]
0 citations
18
[Submitted on 9 Jun 2026] (cross-list from nucl-ex)
Hindered $Δ K = 1$ Dipole Strength in octupole bands in $N = 90$ $^{154}$ Gd from Lifetime Measurements with $γ - γ$ fast timing technique
A. Pal🇮🇳 · S. Basak🇮🇳 · D. Kumar🇮🇳 · T. Bhattacharjee🇮🇳 · B. Maheshwari🇮🇳 · K. Nomura🇯🇵 · P. Van Isacker🇫🇷 · D. Banerjee🇮🇳 · S. S. Alam🇮🇳 · A. K. Jain🇮🇳
The lifetimes of the low-lying negative-parity $1^{-}$ state at 1414~keV and $2^{-}$ state at 1398~keV in $^{154}$ Gd have been measured using the $γ$ -- $γ$ fast-timing technique with the VENTURE array at VECC, Kolkata. The states were populated through the $β$ decay of $^{154}$ Tb, produced in proton-induced reactions at the K130 cyclotron. From the measured lifetimes, absolute $B (E 1)$ transition strengths were deduced. The extracted $B (E 1)$ values are compared with those of neighboring Gd isotopes and with Gogny-HFB-based $s df$ -IBM calculations. The results show that the measured $E 1$ strengths from these states are strongly hindered compared with the corresponding $Δ K = 0$ transitions, providing evidence for weak $Δ K = 1$ dipole strength in $^{154}$ Gd.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2606.11143 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE