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Nuclear Theory·nucl-th

Monday·March 23, 2026

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 04

    Global hyperon polarization in low-energy heavy ion collisions -- a scenario without vorticity

    Feng Liu🇺🇸 · Zhoudunming Tu🇺🇸

    Since its discovery, global polarization of the hyperon in heavy-ion collisions has been firmly established and is widely attributed to the large vorticity generated in the rotating quark-gluon plasma. In contrast, nearly fifty years after the first observation of unexpectedly large transverse polarization in unpolarized hadron collisions, its underlying mechanism remains an open and long-standing puzzle, despite being observed across a broad range of collision systems. Although these two phenomena exhibit notable similarities, they are generally regarded as arising from distinct physical origins. In this work, we propose a direct connection between global polarization in heavy-ion collisions and the long-standing transverse polarization observed in unpolarized collision systems. We demonstrate that the alignment between the production plane and the reaction plane, driven by directed flow, can transfer transverse polarization into the measured global polarization signal. Realistic Monte Carlo simulations of Au+Au collisions at GeV indicate that this mechanism can generate a sizable global polarization, accounting for approximately of the magnitude reported by the STAR Collaboration. Our results establish, for the first time, a quantitative link between these two well-known phenomena and have important implications for the interpretation of global polarization measurements in low-energy heavy-ion collisions.

    ↳ hep-phhep-exnucl-exnucl-thPRD(2026)·1 citation
  2. 05

    Phase Diagram and Finite Temperature Properties of Negative Coupling Scalar Field Theory

    Paul Romatschke🇦🇹

    In this work, I consider scalar field theory with negative quartic self-interaction, corresponding to an upside-down classical potential. Despite not possessing a classically stable ground state, such potentials are known to behave properly when treated quantum mechanically, leading to stable and unitary time evolution. Using two different saddle-point expansions for the same theory, I discuss the phase diagram in terms of bare parameters in Euclidean dimensions one to four, as well as the generalization to finite temperature. Comparing to other methods where available, I find that negative coupling field theory is a promising candidate for an interacting scalar field theory in the continuum. In particular, in four dimensions it exploits a loophole in mathematical proofs of quantum triviality, suggesting that negative coupling scalar field theory could offer a UV-complete and interacting description of the Higgs.

    ↳ hep-thmath-phmath.MPnucl-th1 citation
  3. 06

    Interrogating the composition and distribution of nuclear magnetization via the hyperfine anomaly: experiment meets nuclear and atomic theory for short-lived K

    M. L. Bissell🇨🇭 · M. Jankowski🇨🇭 · A. Antušek🇸🇰 · N. Azaryan🇨🇭 · B. C. Backes🇬🇧 · M. Baranowski🇵🇱 · M. Chojnacki🇨🇭 · K. M. Dziubińska-Kühn🇨🇭 · 1 R. Han🇫🇮 · A. Hurajt🇸🇰 · B. Karg🇨🇭 · I. Michelon🇨🇭 and 13 other authors

    To date, the magnetic structure of nuclei has been poorly constrained, with limited information on its spatial distribution. In this work, we address the composition and distribution of nuclear magnetization in a precision study of short-lived K. We measure the Larmor frequency with part-per-million precision using liquid-state -detected nuclear magnetic resonance at CERN-ISOLDE, improving determination of the experimental differential hyperfine anomaly relative to K by more than an order of magnitude. By combining these experimental results with relativistic all-orders atomic calculations and nuclear density functional theory, we obtain the relative spin and orbital contributions to the nuclear magnetic moments. Our analysis reveals an overestimation of the spin contribution predicted by nuclear theory, that persists even after considering two-body currents. Conversely, we show that the measured hyperfine anomaly is reproduced when adopting the spatial distribution of nuclear magnetization provided by density functional theory. The methodology introduced in this work establishes a means to probe the detailed magnetic structure of the nucleus. This is critical for benchmarking nuclear structure theory and calculations of symmetry-violating nuclear moments relevant to searches for physics beyond the Standard Model in atoms and molecules.

    ↳ nucl-exnucl-th2 citations
  4. 07

    Detecting the 3D Ising model phase transition with a ground-state-trained autoencoder

    Ahmed Abuali🇺🇸 · David A. Clarke🇩🇪 · Morten Hjorth-Jensen🇳🇴 · Ioannis Konstantinidis🇺🇸 · Claudia Ratti🇺🇸 · Jianyi Yang🇺🇸

    We develop a one-class, deep-learning framework to detect the phase transition and recover critical behavior of the 3D Ising model. A 3D convolutional neural network autoencoder (CAE) is trained on ground-state configurations only, without prior knowledge of the critical temperature, the Hamiltonian, or the order parameter. After training, the model is applied to Monte Carlo configurations across a wide temperature range and different lattice sizes. The mean-square reconstruction error is shown to be sensitive to the transition. Finite-size scaling of the peak location for the reconstruction error susceptibility yields the critical temperature and the correlation-length critical exponent , consistent with results from the literature. Our results show that a one-class CAE, trained on zero-temperature configurations only, can recover nontrivial critical behavior of the 3D Ising model.

    ↳ cond-mat.stat-mechhep-latnucl-thphysics.data-anAPS Open Sci.(2026)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE