Search Results (1,642)

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 already change significantly 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. Full article

Background: price dynamics in financial markets exhibit scale-invariant volatility, quantized liquidity and collective behaviour that resist single-paradigm models; Multiscale Relativistic Quantum Finance (MRQF) reconciles these facets on an energy–entropy $(E,S)$ plane, but its translation into a deployable decision system has remained open. Methods: we propose MRQF-MAS, a cooperative multi-agent system (MAS) in which institutional, commercial and retail operators become first-class agents, each decomposed into signal, energy, entropy, risk and execution sub-agents that share beliefs through a horizontal cooperation layer and a shared knowledge base (SKB) of $(E,S)$ trajectories. The framework is benchmarked as a high-volatility regime classifier on 6978 daily EUR/USD reference rates published by the European Central Bank (ECB) over 1999–2026 against four baselines including Generalized Autoregressive Conditional Heteroscedasticity (GARCH)(1,1). Results: on the full official ECB EUR/USD series, MRQF-MAS attains 83.0% accuracy, precision 0.552 and Matthews correlation coefficient (MCC) 0.479 with 95% bootstrap CI [0.46, 0.51] and a one-day median detection latency, improving slightly on a rolling-volatility baseline while remaining below a GARCH(1,1) reference. Conclusions: MRQF-MAS delivers a structurally interpretable, agent-traceable regime decomposition complementary to scalar volatility estimators. Full article

We derive the geodesic equation for point particles propagating in Moyal-type noncommutative spacetimes using a field-theoretic approach based on the quasi-classical limit of the noncommutative Klein–Gordon equation. Starting from a twisted-geometric construction of the covariant Laplace–Beltrami operator, we obtain the noncommutative Hamilton–Jacobi equation and show that all noncommutative effects are absorbed into an effective, position-dependent mass function $M\left(x\right)$ appearing in an otherwise standard relativistic dispersion relation. The corresponding particle dynamics then acquires an additional term in the geodesic equation that takes the form of a fixed external force $F_{\mathrm{NC}}^{\mu }=-{\displaystyle \frac{1}{2}}{g}^{\mu \nu }{\partial }_{\nu }{M}^2\left(x\right)$, sourced entirely by the quantum nature of spacetime. We compute this effective mass perturbatively up to fourth order in the noncommutativity parameter for a general metric, proving that all odd-order corrections vanish identically. For the specific case of an $(r-\theta )$ twist applied to spherically symmetric backgrounds, we obtain explicit expressions demonstrating that the leading correction to geodesic motion appears at order ${\mathsf{\Theta }}^2$ and is proportional to the probe particle’s mass, while massless particles remain unaffected. Full article

Gamma-ray bursts (GRBs) represent the most powerful explosions in the Universe, releasing extreme fluxes of non-thermal radiation across the electromagnetic spectrum. A central enigma in GRB physics remains the mechanism responsible for accelerating electrons, positrons, and hadrons to the required ultra-relativistic energies. Conventional theories primarily invoke diffusive shock acceleration (DSA), magnetic reconnection, and relativistic turbulence. This short review first examines these canonical acceleration methods, then discusses the principles and successes of plasma wakefield acceleration as a powerful future technique for ground-based applications. Finally, we critically analyze the feasibility of applying this mechanism to the cosmological environment of GRBs, exploring why the terrestrial success of wakefield acceleration has not yet been definitively confirmed “on the sky”. Full article

In this article, we present a methodological and systematic approach to solving the Klein–Gordon–Fock equation using the separation of variables method, with particular emphasis on its formulation in light-front coordinates. Although the plane-wave solution is well known in relativistic quantum mechanics, the explicit procedure leading to this solution is not always developed in detail, especially when the equation is written in light-front variables. We first revisit the Klein–Gordon–Fock equation for a free particle in Minkowski spacetime, showing how the usual separation between temporal and spatial variables leads to the expected plane-wave form. This treatment is used as a reference for the corresponding analysis in light-front coordinates. We then rewrite the equation in light-front coordinates, adopting ${\alpha }_{LF}=\sqrt{2}$, and apply the separation of variables method to the coordinates $x^{+}$, $x^{-}$, and $x^{\perp }$. In this formulation, $x^{+}$ and $x^{-}$ appear coupled through the mixed derivative term ${\partial }_{+}{\partial }_{-}$, with the separation process requiring an additional decoupling step involving an inverse relation and a nonzero constant $\lambda$. We show that an appropriate choice of this constant, together with a suitable choice of the superposition coefficients, allows the separated solution to recover the plane-wave structure obtained from the covariant transformation of the scalar product $p_{\mu }{x}^{\mu }$. Thus, the results clarify the consistency between the direct coordinate-transformation approach and the explicit solution of the differential equation in light-front coordinates, while also highlighting the usefulness of separation of variables as a methodological tool in the study of relativistic wave equations. Full article

The spin of an electron is an intrinsic quantum property that cannot be explained using classical mechanics. Nevertheless, it is possible to conceive semiclassical systems with internal degrees of freedom that exhibit spin-like properties. Building on the analysis of phase modulation by elliptical gears and kinematically equivalent antiparallelogram linkages, we present a novel semiclassical model of Zitterbewegung, a rapid oscillatory motion closely connected with spin. The kinematical analog is based on including the internal rotation of the linkage represented in spacetime. The system’s dynamics is related to two-center electron models, which describe the constant momentum of the center of mass and the lightlike oscillation of the center of charge at twice the Compton frequency for a particle at rest. A two-dimensional extension provides an intuitive illustration of topological spin properties and can be used to calculate the spin and magnetic moment of an electron. Full article

We present an extensive set of theoretical results for differential, integrated, and momentum-transfer cross sections for the elastic scattering of electrons by zinc, cadmium, and mercury. Our approach is a self-consistent relativistic calculation, with a semi-empirically adjustable cutoff radius of the polarization potential. This study further extends the application of our method of calculations, previously employed for stable inert gases and alkaline-earth metals. Based on the satisfactory agreement of our previous investigations with experimental values and other precise theoretical results, we expect to provide a set of accurate data for Zn, Cd and Hg. Full article

We introduce a single dimensionless landscape function $J_{\mathrm{chem}}\left(\rho \right)=cosh(\rho ln\phi )-1$, with $\phi =(1+\sqrt{5})/2$, defined on the noble gas-centred coordinate $\rho =d/L_p\in [0,1)$, and show that it organizes four central within-period atomic observables, first ionization energy ${\mathrm{IE}}_1$, electron affinity $\mathrm{EA}$, Mulliken electronegativity ${\chi }_M$, and Pearson chemical hardness $\eta$, on a single periodic-table axis. The outward step $\Delta J_{\mathrm{chem}}^{+}$ delivers ${\mathrm{IE}}_1$, the inward gap $\Delta J_{\mathrm{chem}}^{-}=J_{\mathrm{chem}}\left(1\right)-J_{\mathrm{chem}}\left(\rho \right)$ delivers $\mathrm{EA}$ and $\eta$, and ${\chi }_M$ follows from Mulliken’s identity. Benchmarked against NIST and Pearson tabulated atomic data, the framework reproduces the within-period ${\mathrm{IE}}_1$ envelope across periods 2–6 and localizes every upward deviation on the textbook anomaly sites $\{p^3,d^5,f^7,s^2,d^{10}\}$; it yields two parameter-free golden ratio ionization-energy identities (${\phi }^{1/4}$ on heavy noble gas pairs and ${\phi }^2$ on halogen/alkali pairs, agreeing with data to MAD $\approx 1\%$ and $\approx 5\%$); and it provides single-parameter analytical fits for $\mathrm{EA}$ (MAE $0.3$–$0.4$ eV), Pearson hardness $\eta$, and Mulliken ${\chi }_M$ ($R^2=0.73$ on a 15-atom 4-class benchmark). By assembling four periodic-table observables under one golden ratio cosh coordinate, the construction provides a compact analytical reference against which relativistic and shell-anomaly corrections can be quantified. Full article

Accurate ionization energies are essential for understanding the electronic structures of atoms and molecules and benchmarking quantum-chemical methods. We report the calculated ionization energies of the H, C, N, O, F, P, and S atoms using several quantum-chemical approaches, aiming at reproducing the experimental values within chemical accuracy. The methods include the electron propagator approximations OVGF and P3+, the coupled-cluster methods CCSD(T), CCSDT, and IP-EOM-CCSD, and the composite methods G3 and CBS-QB3. The CCSD(T), CCSDT, G3, and CBS-QB3 methods, together with the DFT method with B2PLYP density functional and several post-Hartree–Fock methods, were used in conjunction with the energy-difference approach. The coupled-cluster calculations were combined with the aug-cc-pVXZ-DK, aug-cc-pVXZ, and ANO-RCC basis sets, all-electron correlation, DKH2 scalar relativistic corrections, atomic spin–orbit corrections, and extrapolation to the complete basis set (CBS) limit. The OVGF and P3+ methods do not achieve chemical accuracy on average, while CCSD(T) and CCSDT combined with the aug-cc-pVXZ-DK basis set and CBS extrapolation reach mean absolute errors of 0.0030 and 0.0026 eV, respectively, an order of magnitude below the chemical accuracy threshold. CCSD(T)/aug-cc-pVXZ-DK with CBS extrapolation provides the best compromise between accuracy and computational cost and can be used as a reference atomic benchmark for these ionization energies. Full article

Fast radio bursts (FRBs) are millisecond-duration radio transients of extragalactic origin, while ultra-high-energy cosmic rays (UHECRs; $E\gtrsim {10}^{18}$ eV) remain among the most important unresolved problems in astroparticle physics. This review examines the viability of FRBs and their central engines as sources of UHECRs within a comprehensive multi-messenger framework. We summarize the observational constraints on UHECR source populations imposed by the energy spectrum, nuclear composition, anisotropy measurements, diffuse $\gamma$-ray background, and high-energy neutrino observations, which, together, favor source classes capable of accelerating heavy nuclei with hard injection spectra, modest cosmological evolution, and sufficiently high source densities. We then review the current landscape of FRB progenitor and engine models, including magnetars, supramassive neutron stars, compact-object mergers, and accretion-powered systems, emphasizing their energetics, environments, and particle-acceleration capabilities through relativistic shocks, magnetic reconnection, magnetar wind nebulae, and direct electromagnetic acceleration by ultra-relativistic FRB pulses. We discuss how these scenarios are constrained by neutrino and $\gamma$-ray observations from IceCube, KM3NeT, and Fermi-LAT, as well as by large-scale UHECR anisotropy measurements from the Pierre Auger Observatory and Telescope Array. Finally, we examine the observational tests that will become possible in the coming decade through large samples of localized FRBs, composition-resolved UHECR measurements, next-generation neutrino observatories, and wide-field $\gamma$-ray facilities. We emphasize that FRB dispersion and rotation measures provide unique probes of the baryonic and magnetic environments relevant for UHECR acceleration and propagation, enabling a new form of multi-messenger tomography of cosmic-ray source environments and allowing the FRB–UHECR connection to become a quantitatively testable astrophysical framework. Full article

We review the recent developments on the decoupling limit zooming in on a BPS string state in heterotic string theory. In this limit, the target-space geometry lacks any ten-dimensional metric description and acquires various non-Lorentzian features. We present the supersymmetric worldsheet sigma model in the decoupling limit. This sigma model describes the heterotic version of non-relativistic string theory, whose second quantization is related to heterotic matrix string theory. We introduce bookkeeping to separate the Yang–Mills gauge and gravitational anomaly analyses. We review the Yang–Mills gauge anomaly analysis in the sigma models before and after the decoupling limit is performed and provide further details on how the quantum calculation commutes with the decoupling limit. We comment on how the analogous calculation can be performed for the gravitational anomaly. This contribution is based on a talk at the University of Science and Technology of China. Full article

This paper establishes the global-in-time existence and uniqueness of mild solutions to the relativistic Vlasov–Maxwell–Fokker–Planck (VMFP) system near a global Maxwellian equilibrium. We adopt a low-regularity functional framework, namely the mixed-norm space $L_k^1{L}_T^{\infty }{L}_p^2$ introduced for kinetic equations, which requires only integrability in the Fourier frequency variable and avoids high-order spatial differentiability. By employing a macro–micro decomposition, we derive macroscopic estimates for the hydrodynamic density and electric field, complemented by coercive estimates for the microscopic dissipation. Under a smallness assumption on the initial perturbation measured in this low-regularity norm, we derive a uniform a priori bound for the associated energy functional. This work provides the global existence result for the relativistic VMFP system in such low-regularity spaces, significantly relaxing the regularity requirements of previous classical Sobolev approaches. Full article

We investigate the correlations between IceCube high-energy neutrinos and Fermi-LAT $\gamma$-ray sources using an unbinned likelihood analysis. In previous analyses of the same IceCube public dataset, only the spatial information of neutrino events was utilized, while the energy term in the probability density functions (PDFs) was neglected, limiting the achievable sensitivity. In this work, we incorporate both spatial and energy terms into the likelihood, with the energy PDFs constructed from the effective areas and smearing matrices. We focus on the Third Catalog of Hard Fermi-LAT Sources (3FHL) and the Fourth LAT AGN Catalog (4LAC-DR2). To account for the significant difference in IceCube’s sensitivity between the two hemispheres, we perform stacking analyses for the all-sky, Northern hemisphere, and Southern hemisphere source subsets separately, under both equal weighting and flux weighting schemes. No statistically significant neutrino excess is found in any configuration. We therefore derive 95% confidence level upper limits on the total neutrino flux contributed by these source populations. For a spectral index of $\Gamma =-2.5$, the all-sky stacking analysis indicates that the 3FHL and 4LAC-DR2 populations contribute at most 3.12% and 2.83% (equal weighting), and 4.45% and 3.49% (flux weighting) of the IceCube diffuse neutrino flux, respectively. Compared to the spatial-only analysis, the inclusion of the energy term improves the constraints on hard-spectrum emission by over one order of magnitude. Our results further demonstrate that the 3FHL and 4LAC-DR2 sources are subdominant contributors to the diffuse astrophysical neutrino flux observed by IceCube. Full article

The aim of this paper is to characterize a relativistic bulk viscous fluid string spacetime whose energy–momentum tensor satisfying certain geometric symmetries. At first, it is shown that a relativistic bulk viscous fluid string spacetime is a generalized quasi-Einstein manifold. Then, we characterize such a spacetime, satisfying Codazzi type of energy–momentum tensor (denoted by ${\mathcal{T}}^{\oslash }$), covariant constant ${\mathcal{T}}^{\oslash }$, recurrent and generalized recurrent ${\mathcal{T}}^{\oslash }$, and almost pseudo-symmetric and weakly symmetric ${\mathcal{T}}^{\oslash }$, respectively. Next, we consider quadratic Killing ${\mathcal{T}}^{\oslash }$ in such a spacetime. Finally, we provide a concrete example using partial differential equations. Full article

Previously reported atomic data for Cs XI, including spectral lines, wavelengths, energy levels, and transition probabilities, were collected and systematically analyzed. The present theoretical investigation was supported by extensive calculations performed for Cs XI using the pseudo-relativistic Hartree–Fock (HFR) method with configuration interaction, as implemented in Cowan’s codes. In this work, all previously reported energy levels and their allowed transition assignments were confirmed. A critically evaluated dataset is presented, including optimized energy levels with their uncertainties, observed and Ritz wavelengths with their corresponding uncertainties, and theoretical transition probabilities with estimated uncertainties. Full article