Pseudoscalar and vector toponia in a Dyson--Schwinger--Bethe--Salpeter frameworkZhang, H. -R.; Cui, Z. -F.; Segovia, J.
doi: 10.48550/arxiv.2603.17503pmid: N/A
Abstract:We study the pseudoscalar ($J^{PC}=0^{-+}$) and vector ($1^{--}$) top--antitop (toponium) systems within the rainbow--ladder truncation of the Dyson--Schwinger and Bethe--Salpeter equations, employing the Qin--Chang effective interaction. After validating the framework in the charmonium and bottomonium sectors, we extend it consistently to the top sector, incorporating renormalisation-group running of the current quark mass and a careful treatment of the number of active flavours. We compute masses and leptonic decay constants for $N_f=5$ and $6$, then analyse their dependence on the renormalisation scale in the range $\mu=400-800\,\text{GeV}$. The resulting toponium masses lie near $344-346\,\text{GeV}$ with hyperfine splittings below $0.14-0.17\,\text{GeV}$, while the decay constants are large, $6-7\,\text{GeV}$, and exhibit the expected heavy-quark scaling behaviour. We find only mild sensitivity to the renormalisation point and a systematic reduction of binding when increasing $N_f$. Although the physical top quark decays weakly before hadronisation, our results demonstrate that, within a Poincaré-covariant nonperturbative framework, quantum chromodynamics (QCD) generates tightly correlated pseudoscalar and vector toponium systems in that extreme heavy-quark limit.
Inelastic nucleon-nucleus scattering from a microscopic point of viewVorabbi, Matteo; Gennari, Michael; Finelli, Paolo; Giusti, Carlotta; Navrátil, Petr
doi: 10.48550/arxiv.2603.26265pmid: N/A
Abstract:We apply to the nucleon-nucleus inelastic process a fully coherent microscopic multiple scattering approach. Our study addresses the complexities inherent in characterizing inelastic scattering events, offering a comprehensive theoretical model grounded in the reaction theory. The approach is based on the distorted-wave approximation and requires the knowledge of three potentials, which give the initial and final distorted wave functions and the transition potential. All of them are derived just like the microscopic optical potential for elastic nucleon-nucleus scattering we derived in previous papers of ours within the framework of the Watson multiple scattering theory and adopting the impulse approximation. The potentials are obtained by folding nonlocal ab initio nuclear densities from the No-Core Shell Model (NCSM) with a nucleon-nucleon $t$ matrix computed with a chiral interaction consistent with the one used in the calculation of the density. The only difference in the formal expressions of the three potentials resides in the nuclear density, where we use the ground and excited state densities of the target and the transition density. By extending methods traditionally applied to elastic scattering, we incorporate the effects of inelastic transitions enabling an accurate description of the experimental differential cross section. The predictive power of our numerical results is benchmarked against empirical data of inelastic proton scattering off $^{12}$C, for the transition to the $2^+$ state at 4.44 MeV, in a range of projectile energies of 65-300 MeV. The generally good description of the experimental cross sections as functions of the scattering angle gives clear evidence of the reliability and robustness of a model that does not contain any free adjustable parameters.
Hydrodynamics of dilation and spin currentsZhang, Zhong-Hua; Lv, Xi-Hu; Huang, Xu-Guang
doi: 10.48550/arxiv.2603.17794pmid: N/A
Abstract:We formulate a relativistic hydrodynamic theory for fluids with spin and intrinsic dilation charges. Using an entropy-current analysis, we derive constitutive relations featuring a bulk viscosity and a dilation conductivity governing the relaxation and diffusion of dilation charge. Linear mode analysis reveals a gapped dilation excitation and the freeze-out of long-wavelength sound modes, similar to the superhorizon modes in cosmology. In the nonrelativistic limit, the theory reduces to that of microstretch fluids. Upon coupling to electromagnetic field, we show that the scale anomaly permits additional contributions in the electric current, dilation current, and energy-momentum tensor. Our theory naturally applies to nearly conformal fluids undergoing rapid expansion or contraction.
Critical dynamics of the superfluid phase transition in Model FChattopadhyay, Chandrodoy; Maguire, Robert; Ott, Josh; Schaefer, Thomas; Skokov, Vladimir V.
doi: 10.48550/arxiv.2603.21479pmid: N/A
Abstract:We describe numerical simulations of the critical dynamics near the superfluid phase transition. The calculations are based on an implementation of a stochastic hydrodynamic theory known as model F in the classification of Hohenberg and Halperin. This theory is expected to describe dynamic scaling near the lambda transition in liquid $^4$He, Bose-Einstein condensation in ultracold atomic gases, and the superfluid transition in the unitary Fermi gas. Our simulation is based on a Metropolis algorithm previously applied to the critical endpoint of the liquid-gas phase transition in ordinary fluids. In the model E truncation of model F we obtain the expected dynamical exponent $z\simeq 3/2$. We observe the emergence of a propagating second sound mode at the phase transition. The second sound diffusivity $D_s$ is consistent with the scaling relation $D_s\sim \xi^{x_\kappa}$, where $\xi$ is the correlation length and $x_\kappa=1/2$.
Prediction of Alpha-Decay Half-Lives of Actinide Nuclei Using the DDM3Y Effective Interaction PotentialSowmya, N.; Manjunatha, H. C.; N, Roshini. K.; Susheela, R. S.
doi: 10.48550/arxiv.2603.16199pmid: N/A
Abstract:The prediction of nuclear half-lives is vital for understanding nuclear stability with significant applications in astrophysics, nuclear energy, and medical physics. This study investigates the $\alpha$-decay half-lives of 154 actinide nuclei in the atomic number range $89 \le Z \le 103$ using the Density-Dependent M3Y (DDM3Y) effective interaction potential. The theoretical framework utilizes a double-folding model where the densities of the $\alpha$-particle and the daughter nucleus are folded to derive the nuclear interaction this http URL half-lives were calculated using the WKB approximation and compared against experimental data and established semi-empirical models, including the Viola-Seaborg (VSS), CPPM, GLDM, and ELDM frameworks. The DDM3Y model demonstrates a systematically improved agreement with experimental half-lives across the actinide series, effectively capturing the inverse correlation between $Q$-values and decay times. Statistical analysis yielded a standard deviation of 1.76, confirming the reliability of this approach for predicting the stability and decay properties of heavy and new isotopes.
Centrifugal-corrected harmonic oscillator model for spherical proton emittersZhu, Xiao-Yan; Gao, Wei; Liu, Jia; Zhu, Li-Qiang; Lin, Wen-Bin; Li, Xiao-Hua
doi: 10.48550/arxiv.2603.07960pmid: N/A
Abstract:In the present work, we propose an improved harmonic oscillator model to systematically evaluate the proton radioactivity half-lives in spherical nuclei, incorporating centrifugal potential effects. By fitting the experimental data, the centrifugal parameter $d = 0.143$ for the correction term $dl(l+1)$ and nuclear potential depth $V_0 = 62.4$ MeV are obtained. The model integrates the relativistic mean field (RMF) theory with the BCS method based on the DD-ME2 force to determine spectroscopic factors $S_p$. Moreover, by verifying the linear relationship between the logarithm of the normalized width $\log_{10}{\gamma^2}$ and fragmentation potential $V_{frag}$, the connection between nuclear structure and tunneling dynamics is confirmed, and an analytical expression for the adjustable parameter $d$ corresponding to the centrifugal potential is derived as $d^{\rm{Ae}}$ $\approx$ 0.167. Compared with $d^{\rm{Ae}}$, the modified model based on $d$ yields results in better agreement with experimental half-lives, and is able to control the error of the experimental data within a factor of 2.4. Furthermore, the extended improved model is used to predict the half-lives of some possible proton radioactivity candidates in NUBASE2020 that are energetically allowed or have been observed but not yet quantified. This work improves the accuracy of proton radioactivity studies and provides a robust theoretical framework for future nuclear structure research.
A Note on the Consistent-$Q$ Scheme for Odd-Odd NucleiLi, Xiao Tong; Deng, Xi; Zhang, Yu
doi: 10.48550/arxiv.2603.14932pmid: N/A
Abstract:Compared with even-even nuclear systems, the dynamical structure of low-lying excited states in odd-odd nuclei poses significantly greater theoretical challenges. The interacting boson fermion fermion model provides an effective framework for capturing the structural properties of odd-odd nuclei. Within this algebraic framework, the consistent-$Q$ scheme, which was widely used to map nuclear shape phase diagram, is extended to odd-odd systems to examine how unpaired nucleons influence level structures and their evolution across prototypical transitional regions. The results demonstrate that the presence of unpaired nucleons does not suppress the critical behavior characterizing level evolution across the U(5)-SU(3), U(5)-O(6) and SU(3)-O(6) shape transitions, suggesting that shape phase transitions remain a fundamental mechanism governing the low-lying structural evolution of odd-odd nuclei in the heavy and intermediately-heavy mass regions.
Architecture as physical prior: cooperative neural network for nuclear massesZai, Peiwen; Cheng, Wei; Zhang, Feng-Shou
doi: 10.48550/arxiv.2603.09747pmid: N/A
Abstract:Machine learning approaches to nuclear mass prediction have achieved remarkable accuracy, but typically rely on existing theoretical baselines or hand-crafted physics features. Here we demonstrate that these prerequisites can be supplanted by structural inductive biases embedded directly in the network architecture. We present the Cooperative Neural Network (CoNN), which predicts binding energies from raw proton and neutron numbers (Z,N) alone by additively combining four structurally constrained modules: a smooth network for bulk liquid-drop trends, discrete scalar embeddings for shell effects, a learnable two-dimensional grid for regional collective correlations, and a parity-aware network for odd--even staggering. On the AME2020 dataset, the CoNN achieves a root-mean-square deviation of 0.269 MeV across all 3558 nuclei, with 0.419 MeV on a held-out interpolation subset and 0.728 MeV on 122 nuclei newly measured since AME2016, placing it among the most accurate baseline-free approaches to direct mass prediction. Notably, the learned embeddings develop pronounced extrema at canonical magic numbers and the pairing module reproduces the expected odd--even staggering along isotopic chains, both emerging from the data without explicit supervision. These results demonstrate that physically motivated architectural constraints can effectively substitute for feature engineering, establishing architecture as physical prior as a promising paradigm for neural-network mass modeling.