PaperPanorama
FAQ

Nuclear Theory·nucl-th

Thursday·June 26, 2025

8 papers—5 primary·3 cross-listed

All8Primary5Cross-lists3
  1. 06

    Comparison between Causal and Acausal Diffusion: a Schwinger-Keldysh Effective Field Theory Perspective

    Navid Abbasi🇨🇳 · Matthias Kaminski🇺🇸 · Dirk H. Rischke🇩🇪

    In Fick's time-honored theory of diffusion, the system responds instantaneously to external perturbations, resulting in acausal behavior. Maxwell-Cattaneo theory addresses this issue by introducing a relaxation time, rendering the diffusion process causal. We focus on systems where this relaxation time is comparable to the diffusion time and significantly larger than the relaxation times of all other non-conserved operators. In such systems, late-time diffusion is influenced by this relaxation process, leading to a theory of quasi-diffusion. Using the Schwinger-Keldysh Effective Field Theory (SK-EFT) framework, we compare the theories of diffusion and quasi-diffusion by analyzing the real-time dynamics of correlation functions both in linear response and at one-loop order. In particular, we show that the one-loop corrections in the causal (quasi-diffusion) theory, in both the underdamped and the overdamped cases, are governed by two universal functions. In the overdamped case, the behavior mirrors that of the acausal (diffusion) theory, which has recently been applied for precision tests of SK-EFT in diffusive systems. We suggest that our results in the underdamped limit can also be used for precision tests in quasi-diffusive systems.

    ↳ hep-thcond-mat.stat-mechcond-mat.str-elnucl-thJHEP(2026)·8 citations
  2. 07

    Reflection positivity in Euclidean formulations of relativistic quantum mechanics of particles

    Gohin Shaikh Samad · W.N.Polyzou

    This paper discusses the general structure of reflection positive Euclidean covariant distributions that can be used to construct Euclidean representations of relativistic quantum mechanical models of systems of a finite number of degrees of freedom. Because quantum systems of a finite number of degrees of freedom are not local, reflection positivity is not as restrictive as it is in a local field theory. The motivation for the Euclidean approach is that it is straightforward to construct exactly Poincaré invariant quantum models of finite number of degrees of freedom systems that satisfy cluster properties and a spectral condition. In addition the quantum mechanical inner product can be computed without requiring an analytic continuation. Whether these distributions can be generated by a dynamical principle remains to be determined, but understanding the general structure of the Euclidean covariant distributions is an important first step.

    ↳ hep-thmath-phmath.MPnucl-th0 citations
  3. 08

    DeepQuark: A Deep-Neural-Network Approach to Multiquark Bound States

    Wei-Lin Wu🇨🇳 · Lu Meng🇩🇪 · Shi-Lin Zhu🇨🇳

    For the first time, we implement the deep-neural-network-based variational Monte Carlo approach for the multiquark bound states, whose complexity surpasses that of electron or nucleon systems due to strong SU(3) color interactions. We design a novel and high-efficiency architecture, DeepQuark, to address the unique challenges in multiquark systems such as stronger correlations, extra discrete quantum numbers, and intractable confinement interaction. Our method demonstrates competitive performance with state-of-the-art approaches, including diffusion Monte Carlo and Gaussian expansion method, in the nucleon, doubly heavy tetraquark, and fully heavy tetraquark systems. Notably, it outperforms existing calculations for pentaquarks, exemplified by the triply heavy pentaquark. For the nucleon, we successfully incorporate three-body flux-tube confinement interactions without additional computational costs. In tetraquark systems, we consistently describe hadronic molecule and compact tetraquark with an unbiased form of wave function ansatz. In the pentaquark sector, we obtain weakly bound molecule with and its bottom partner . They can be viewed as the analogs of the molecular . We recommend experimental search of in the D-wave channel. DeepQuark holds great promise for extension to larger multiquark systems, overcoming the computational barriers in conventional methods. It also serves as a powerful framework for exploring confining mechanism beyond two-body interactions in multiquark states, which may offer valuable insights into nonperturbative QCD and general many-body physics.

    ↳ hep-phcs.AIhep-exhep-lat+1PRL(2026)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE