The European Physical Journal C最新文献

We formulate a holographic weak-link construction in which Josephson transport is controlled by a near-extremal Reissner–Nordstrom–AdS background while the superconducting junction is carried by a dynamically distinct Abelian-Higgs probe sector. The RN–AdS geometry is supported by a homogeneous background Maxwell field ({mathcal {B}}_mu ,) whereas the junction gauge field (A_mu ) and charged scalar (Psi ) enter the action with an overall factor (lambda ^2.) After deriving the field equations, the limit (lambda rightarrow 0) leaves the nonlinear Maxwell–scalar equations intact on a fixed RN–AdS geometry while their stress tensor affects the metric only at ({mathcal {O}}(lambda ^2).) This makes the fixed-background approximation a controlled leading-order truncation even for a finite spatial modulation of the probe chemical potential. The Josephson phase difference is defined from the gauge-invariant boundary data of the probe condensate, not from the RN charge itself. We identify the current-phase relation, critical current, coherence length, and small-phase stiffness as the principal transport quantities. In the SNS regime, the critical current and midpoint condensate probe the same spatial proximity scale, while higher harmonics diagnose enhanced transparency or departure from the opaque weak-link limit. The near-extremal RN–AdS throat introduces a radial scale distinct from the spatial proximity length. We derive its domain of validity and distinguish the AdS(_2) response coefficient from the Josephson current obtained after ultraviolet matching. For the canonical scalar mass (m^2L^2=-2,) the homogeneous normal probe throat violates the AdS(_2) stability bound at extremality for every real probe electric field. A real-index power law therefore requires a different stable reference sector and a separate derivation of its overlap with the junction response. The analysis provides a probe formulation, analytic proximity references, and infrared constraints; it does not constitute a numerical solution of the nonlinear RN–AdS junction.

The trace anomaly and anomaly-induced action are evaluated for the two-dimensional 2D vector theory with classical conformal symmetry. Implementing local conformal symmetry while preserving the gauge invariance requires either giving up locality of the classical action or, equivalently, introducing an auxiliary scalar field. The two-dimensional limit in such a theory is singular. However, in the dimensional regularization, the limit (D rightarrow 2) in the one-loop divergence is smooth. As a result, we arrive at the expression for anomaly, which has a rich general structure, typical for the dimensions (D ge 4). For comparison and completeness, we also evaluate anomalies for conformal scalar and fermions, also in the presence of auxiliary external scalars.

We present the Ising noise filter, a highly portable, graph-based filtering algorithm for early-stage background suppression in particle accelerators and astrophysical detectors. Standard noise rejection methods relying on track fitting suffer from severe combinatorial explosion. Our method bypasses this by mapping individual detector hits to a network of binary spins and minimizing an energy functional. The entire algorithm reduces to vectorized array operations, making it fast and easy to deploy. The interaction kernels are physics-informed, tailored to the underlying physics and geometry of the experiment. We demonstrate the efficacy of this approach in two distinct experimental regimes. Applied to the Baikal-GVD neutrino telescope the filter yields fast, standard-quality noise rejection with 97% recall for astrophysical neutrinos. For the SPD detector at the NICA collider the filter attains 96.7% precision and 97.4% recall on a toy Monte Carlo sample. Furthermore, when combined with a Peterson–Hopfield network for track finding, our physics-informed coupling improves the TrackML score from 0.5 to 0.91.

We formulate a compact dynamical representation of quantum-information diagnostics for time-dependent two-mode bosonic systems in terms of the Bogoliubov ratio (lambda _k(eta )=beta _k(eta )/alpha _k(eta )). For vacuum-evolved pure Gaussian pair states generated by a Hermitian quadratic Hamiltonian, (lambda _k) obeys a closed complex Riccati equation. After one partner mode is traced out, the reduced-state spectrum is determined by (q_k=|lambda _k|^2), from which the purity, linear entropy, Rényi-2 entropy, and von Neumann entropy follow directly. These Gaussian results are mathematically equivalent to those obtained from the standard density-matrix or covariance-matrix formalism; the advantage of the ratio representation is a compact separation between model-dependent dynamics and universal state diagnostics. Writing (lambda _k=sqrt{q_k}e^{itheta _k}) further exposes how pair production drives radial growth, whereas frequency rotation and detuning act through the phase and can suppress coherent squeezing accumulation. We also establish an exact extension to non-Gaussian SU(1, 1) sectors. For a lowest-weight Fock seed with conserved number difference d, the same ratio equation governs the evolution, while the reduced spectrum becomes a negative-binomial distribution determined by ((q_k,d)). The Gaussian formulas are recovered at (d=0). Cosmological perturbations and a chirped-pulse optical parametric amplifier illustrate the common dynamical mechanism and its information-theoretic consequences.

In High Energy Physics, as in many other fields of science, the application of machine learning techniques has been crucial in advancing our understanding of fundamental phenomena. Increasingly, deep learning models are applied to analyze both simulated and experimental data. In most experiments, a rigorous regime of testing for physically motivated systematic uncertainties is in place. The numerical evaluation of these tests for differences between the data on the one side and simulations on the other side quantifies the effect of potential sources of mismodelling on the machine learning output. In addition, thorough comparisons of marginal distributions and (linear) feature correlations between data and simulation in “control regions” are applied. However, the guidance by physical motivation, and the need to constrain comparisons to specific regions, does not guarantee that all possible sources of deviations have been accounted for. We therefore propose a new adversarial attack – the CONSERVAttack – designed to exploit the remaining space of hypothetical deviations between simulation and data after the above mentioned tests. The resulting adversarial perturbations are consistent within the uncertainty bounds — evading standard validation checks — while successfully fooling the underlying model. We further propose strategies to mitigate such vulnerabilities and argue that robustness to adversarial effects must be considered when interpreting results from deep learning in particle physics.

We explore the properties of quark stars by combining the microscopic axion-extended Polyakov–Nambu–Jona-Lasinio model with the macroscopic framework of four-dimensional Einstein–Gauss–Bonnet (4D EGB) gravity. Specifically, axion effects are incorporated through the background phase (theta =a/f_a) in the thermodynamics of quark matter. Our results show that the inclusion of axion-induced interactions stiffens the quark-matter equation of state, thereby increasing the sound speed and the maximum mass of quark stars. The 4D EGB correction effectively weakens gravitational compression and further modifies the stellar structure, allowing for larger radii and higher maximum masses while reducing the compactness and the surface gravitational redshift. The combined effects can support quark stars above (2,M_odot ,) with mass–radius sequences overlapping the observational regions in the indicative phenomenological comparison. These findings reveal that the interplay between axion-induced modifications of dense quark matter and 4D EGB gravity may provide a viable phenomenological framework for describing massive quark stars.

We investigate dynamical mass generation in pseudo-Proca quantum electrodynamics (PPQED) using Schwinger–Dyson equations in rainbow-quenched and unquenched truncations. The pseudo-Proca screening scale m, together with the fine-structure constant (alpha ), the flavor number N, and the ultraviolet cutoff (varLambda ), controls the critical thresholds for chiral symmetry breaking in the reduced ((2 + 1))D theory. Within these truncation schemes, we obtain analytical estimates for both the critical coupling (alpha _c(m,varLambda )) and the critical number of fermion flavors (N_c(m,varLambda ,g)), and show that increasing m suppresses dynamical mass generation through Yukawa screening. We further assess the robustness of this physical picture by incorporating a Ball–Chiu vertex construction; our results show that while vertex corrections modify the quantitative values of the critical parameters, they preserve the qualitative screening-driven suppression of dynamical mass generation. In addition, within the static approximation, our anisotropic extension shows that the critical coupling is a monotonically decreasing function of the ratio (v_F/c). Taken together, our results suggest that the scale m plays an important role in modulating criticality in PPQED.

The recently announced NA62 measurement of the ({K^+ rightarrow pi ^+nu bar{nu }}) branching ratio, based on 2016–2024 data, is fully consistent with its very accurate Standard Model (SM) prediction. While it is not excluded that the final result based on 2016–2026 data will deviate from the SM prediction, the question arises whether a similar fate awaits the ({K_L rightarrow pi ^0nu bar{nu }}) decay. This decay is currently being searched for by the KOTO experiment, with the present upper bound roughly two orders of magnitude above its very precise SM prediction. The proposed KOTO II experiment aims to provide the first discovery of the ({K_L rightarrow pi ^0nu bar{nu }}) decay and measure its branching ratio. Building on the findings of several previous papers we demonstrate that in the presence of suitably chosen large new complex phases and of a small amount of new right-handed (bar{s} d) couplings, in addition to the left-handed ones, the ({K_L rightarrow pi ^0nu bar{nu }}) branching ratio can still be enhanced by one order of magnitude with respect to the SM prediction while keeping both ({K^+ rightarrow pi ^+nu bar{nu }}) and (varepsilon _K) SM-like. Simultaneously the decays (K_Srightarrow mu ^+mu ^-), studied by LHCb, and (K_Lrightarrow pi ^0ell ^+ell ^-), searched for by KOTO II, can be strongly enhanced and the anomaly in the ratio (varepsilon '/varepsilon ), as claimed by Dual QCD, removed. We illustrate this with an example of a specific (Z^prime ) scenario.

Vector-like leptons (VLLs) are well-motivated candidates for physics beyond the standard model. We investigate the sensitivity of the 6 TeV muon collider to the neutral doublet VLL (denoted by N) via its pair production in an SU(2)(_L) doublet model with hypercharge (Y=-frac{1}{2}). Assuming mixing with muons, we study the subsequent decay (Nrightarrow W^+ mu ^-) and analyze two representative signals, namely (4j2mu ) and (2ell 2mu Ehspace{-5.83328pt}/), arising from the hadronic and leptonic decays of the W boson, respectively. The signal and background events are simulated within a Monte Carlo framework, and a cut-based analysis is performed at the 6 TeV muon collider with an integrated luminosity (mathcal {L}=4) ab(^{-1}) for the unpolarized and polarized beam configurations, ((P_{mu ^+},P_{mu ^-})=(0,0)) and ((P_{mu ^+},P_{mu ^-})=(-1,1)). We consider VLL masses in the range of (1300{-}2980) GeV and evaluate the corresponding search sensitivity. Our results show that the 6 TeV muon collider could provide strong sensitivity to neutral doublet VLLs through the (4j2mu ) and (2ell 2mu Ehspace{-5.83328pt}/) signals, particularly for the idealized fully polarized beam configuration, under the detector, polarization, luminosity and background assumptions adopted in this analysis.

Motivated by the observation of numerous charmed-strange hadrons lying close to the (K^{(*)}bar{D}^{(*)}) and (K^{(*)}D^{(*)}) thresholds, we systematically investigate their mass spectra and electromagnetic characteristics, explicitly incorporating the S-D wave mixing and coupled-channel effects. For the mass spectra, we employ the one-boson-exchange model and obtain several promising (K^{(*)}bar{D}^{(*)}) and (K^{(*)}D^{(*)}) molecular candidates awaiting future experimental confirmation. The coupled-channel dynamics is found to play an essential role: it not only enhances binding in existing channels but also generates new loosely bound states that are absent in the single-channel approximation. Regarding the electromagnetic characteristics, we discuss the M1 radiative decay widths and magnetic moments of these charmed-strange molecular tetraquarks based on our obtained mass spectra and spatial wave functions within the constituent quark model. Our results demonstrate that the electromagnetic observables serve as valuable discriminants for clarifying the nature of these hadronic molecules. We encourage experimental collaborations to focus on such predicted charmed-strange molecular tetraquark candidates, especially the genuinely exotic (K^{(*)}bar{D}^{(*)}) states comprising four different flavors with valence quark content (bar{c} bar{s} u d).