Nuclear Theory·nucl-th

Wed·Oct 14, 2026Wednesday·October 14, 2026

8 papers—6 primary·2 cross-listed

01
Comment on arXiv:2604.27678
V. A. Kizka
Shuang-Jie Liu et al. (arXiv:2604.27678) reported that the momentum-dependent nuclear mean field (MDI) with $K_{0} = 230$ MeV 'can fit fairly' the experimental data for Au + Au collisions at $s_{N N} = 3$ GeV, whereas the momentum-independent nuclear mean fields (MID) with $K_{0} = 230$ MeV and $K_{0} = 380$ MeV 'can only partially describe' the experimental results. We quantify these statements by performing $χ^{2}$ goodness-of-fit tests for the comparison between the theoretical calculations and the experimental distributions presented in that work. For the complete set of data, all three calculations show highly statistically significant disagreement with the experimental data, with (p-value) p < 0.001. For the $0 - 10%$ centrality class, however, the MDI calculation with $K_{0} = 230$ MeV gives p = 0.49, indicating no statistically significant disagreement with the experimental data for the proton transverse-momentum distributions and the rapidity dependence of the mean transverse momentum, whereas both MID calculations give p < 0.001. For the $10 - 40%$ centrality class, the analysis of the directed flows of protons, $K^{+}$ mesons, and $Λ$ -hyperons gives the largest p-values for MDI with $K_{0} = 230$ MeV and MID with $K_{0} = 380$ MeV, with p = 1.00 and p = 0.97, respectively. In contrast, the analysis of the corresponding elliptic flow data gives p < 0.001 for all three calculations. Our results demonstrate that the qualitative statements 'fit fairly' and 'only partially describe' depend substantially on the particular observables and centrality classes considered and cannot by themselves establish statistically acceptable agreement between the calculations and the experimental data.
nucl-th
02
Competitive constraints on exotic tensor currents from $E C / β^{+}$ ratios
Victor Dumenil · Leendert Hayen
We introduce the ratio of electron capture to positron decay rates of unstable nuclei as a probe for exotic tensor currents in the electroweak sector. We calculate nuclear structure corrections and newly derived radiative corrections and obtain competitive limits on exotic tensor couplings using historically available data to find $ε_{T} = (1.06 \pm 0.76) \times 1 0^{- 3}$ which is competitive with collider searches and the global $β$ -decay database. In doing so, we resolve a 50-year-old tension in the strongly hindered $^{22}$ Na transition by retaining higher-order operators, obtaining a consistent description of its different weak-decay observables. Finally, we discuss the potential of this method to significantly improve tensor constraints using modern cryogenic quantum sensors.
nucl-thnucl-ex
03
Separating entanglement at emission from femtoscopic correlations
Isaac Vidaña
We investigate how femtoscopic correlations modify the relation between the spin entanglement of emitted particle pairs and that of pairs selected at a given relative momentum. For two spin- $\frac{1}{2}$ particles, we show that the momentum-selected spin state can be entangled even when the corresponding state at emission is separable. We derive a momentum-dependent separability criterion that determines whether the observed spin correlations require entanglement at emission. As an application, we consider a pair of identical $Λ$ hyperons, for which quantum statistics and final-state interactions affect the singlet and triplet spin channels differently at low relative momentum. Our results provide a framework for using experimentally accessible spin correlations to investigate entanglement at emission.
nucl-thquant-ph
04
Deconfinement and the Charge Susceptibility Matrix of QCD
Christopher Grace · Brady Mowbray · Christopher Plumberg
At sufficiently high temperatures, lattice Quantum Chromodynamics (QCD) calculations predict that nuclear matter undergoes a rapid crossover to a novel, deconfined state known as the quark-gluon plasma (QGP), in which quark flavors essentially behave like independent particles. Here we explore the nature of this transition by introducing two new thermodynamic observables which we refer to as the diagonality and the rescaled curvature of the QCD equation of state (EoS). By comparing these observables in the case of lattice QCD calculations with those of simple toy models and more sophisticated hadronic resonance models, we show that both the diagonality and the rescaled curvature provide complementary insights into the degree of independence between different quark flavors and the underlying degrees of freedom in the system as functions of temperature. We propose that these observables may help to clarify the nature of the transition region and the onset of deconfinement in nuclear matter.
nucl-thnucl-ex
05
Higher-order corrections to beta decays and nuclear structure
Grigor Sargsyan · Ayala Glick-Magid
Precision measurements of nuclear $β$ decay offer a powerful route to tests of physics beyond the Standard Model, but interpreting measurements spectra and correlation observables requires control of subtle nuclear-structure effects. This chapter develops a framework for calculating higher-order corrections--small contributions that can become important at the precision sought in searches for new interactions. After motivating their role in $β$ -decay observables (with radiative corrections treated in the accompanying chapter), we introduce the relevant kinematics and multipole expansion of the shape factor, identify the subleading contributions, and present the impulse-approximation multipole operators. We then describe the nuclear many-body methods used to obtain the required states and transition densities, and derive the corresponding operator matrix elements in the harmonic-oscillator basis. Taken together, these ingredients enable systematic calculations of nuclear shape factors beyond the long-wavelength approximation, including higher-order multipoles where needed. By helping distinguish Standard-Model recoil effects from possible signatures of new physics, this framework supports the interpretation of increasingly precise $β$ -decay experiments.
nucl-thnucl-ex
06
The $Σ N$ threshold structure in the $K^{-} d \to π^{-} Λ p$ reaction
Shunsuke Yasunaga · Daisuke Jido
The $Λ p$ invariant-mass spectrum near the two physical $Σ N$ thresholds in the $K^{-} d \to π^{-} Λ p$ reaction is studied as a probe of the low-energy $Σ N$ interaction. The reaction is formulated up to two-step processes, and the coupled $Λ p$ , $Σ^{+} n$ , and $Σ^{0} p$ channels are described within a constant- $K$ -matrix model constrained by spin-triplet scattering lengths. The dependence of the $Σ N \to Λ p$ conversion amplitude on these scattering lengths is examined, and the relation between its line shape and nearby pole positions is investigated. The resulting invariant-mass spectra are studied at different incident kaon momenta and compared qualitatively with existing experimental data. The effects of the spin-singlet $Y N$ amplitude and the deuteron wave function are also examined. The line shape near the $Σ N$ thresholds is found to be particularly sensitive to the complex spin-triplet $I = 1/2$ $Σ N$ scattering length, indicating that measurements of this spectrum can provide useful constraints on the low-energy $Σ N$ interaction.
nucl-th
07
Signal-to-noise problems in fault-tolerant quantum computation
Hyunwoo Oh
Quantum computation offers a promising alternative to classical Monte Carlo methods by naturally avoiding sign problems through unitary evolution. A common misconception follows from this: because quantum simulation sidesteps the sign problem, it is often assumed to be an essentially perfect substitute for classical sampling. This is false---quantum measurements are intrinsically stochastic, and estimating observables often requires a number of samples that grows exponentially with system size, time separation, or inverse temperature, exactly as in the classical signal-to-noise problem. In this work, we analyze the origin and structure of signal-to-noise problems in quantum computation, drawing parallels with classical Monte Carlo, and demonstrate that such noise persists even in sign-problem-free regimes. We discuss strategies to mitigate it, in particular a quantum generalization of Stein control variates construction, in which unbiased estimators are built from operator commutators $[X, A]$ and their discrete diagonal counterparts, and validate the approach with exactly solvable numerical examples that quantify the achievable variance reduction. Our results underscore that variance reduction, not merely sign-problem avoidance, is required to make quantum algorithms practically viable for many-body physics.
↳ quant-phhep-latnucl-th
08
Relativistic Covariance from Hamiltonian Hydrodynamics in the Chiral Limit
ZiHao Liu · Mei Huang
We derive the covariant equations of nondissipative chiral hydrodynamics from their equal-time Hamiltonian formulation and identify the Lie--Poisson structure implicit in the chiral brackets. This structure combines fluid motion with local chiral transformations. For a parity-invariant Hamiltonian quadratic in chiral charge densities and pion gradients, without external backgrounds, we derive and solve the constraints imposed by Lorentz boosts. Their coupled nonlinear sector is equivalent to the linear boost transformation laws of a symmetric tensor, which determine the velocity dependence from rest-frame data. For finite, positive rest-frame coefficients, finite ordinary-fluid energy density and thermodynamic derivatives, and a momentum--velocity relation that can be solved in either direction, the chiral Hamiltonian coefficients remain finite at every fluid speed below light speed if and only if the rest-frame pion propagation speed does not exceed the speed of light. This formulation makes symmetry constraints explicit and provides a starting point for future thermodynamically consistent dissipative extensions.
↳ hep-thhep-phnucl-th