The European Physical Journal C最新文献

We investigate quantum steering of Dirac field for different types of Bell states in Schwarzschild–de Sitter (SdS) spacetime that has a black hole event horizon (BEH) and a cosmological event horizon (CEH). We find that fermionic steerability from Bob to Alice is greater than fermionic steerability from Alice to Bob, while bosonic steerability exhibits the opposite behavior in SdS spacetime. These different properties between fermionic and bosonic steering arise from the differences between Fermi–Dirac statistics and Bose–Einstein statistics. We also find that the Hawking effect of the black hole decreases fermionic steerability. However, the Hawking effect of the expanding universe can enhance fermionic steerability, which differs from the properties of quantum steering in single-event horizon spacetime. Interestingly, we can indirectly protect quantum steering by using appropriate types of Bell states in multi-event horizon spacetime. These conclusions are helpful to guide the task of processing relativistic quantum information for quantum steering in SdS spacetime.

In this paper, an analytic generalization of the weak field deflection angle (WDA) is derived by utilizing the current non-asymptotically flat generalization of the Gauss–Bonnet theorem. The derived formula is valid for any Schwarzschild-like spacetime, which deviates from the classical Schwarzschild case through some constant parameters. This work provided four examples, including Schwarzschild-like solutions in the context of Bumblebee gravity theory and the Kalb–Ramond framework, as well as one example from a black hole surrounded by soliton dark matter. These examples explore distinct mechanisms of Lorentz symmetry breaking, with results that are either new or in agreement with existing literature. The WDA formula provided a simple calculation, where approximations based on some conditions can be done directly on it, skipping the preliminary steps. For the shadow size analysis, it is shown how it depends solely on the parameter associated with the metric coefficient in the time coordinate. A general formula for the constrained parameter is also derived based on the Event Horizon Collaboration (EHT) observational results. Finally, the work realized further possible generalizations on other black hole models, such as RN-like, dS/AdS-like black hole solutions, and even black hole solutions in higher dimensions.

We demonstrate that neural networks can be used to improve search strategies, over existing strategies, in LHC searches for light electroweak-charged scalars that decay to a muon and a heavy invisible fermion. We propose a new search involving a neural network discriminator as a final cut and show that different signal regions can be defined using networks trained on different subsets of signal samples (distinguishing low-mass and high-mass regions). We also present a workflow using publicly-available analysis tools, that can lead, from background and signal simulation, to network training, through to finding projections for limits using an analysis and ONNX libraries to interface network and recasting tools. We provide an estimate of the sensitivity of our search from Run 2 LHC data, and projections for higher luminosities, showing a clear advantage over previous methods.

In celestial holography, the massive and massless scalars in 4d space-time are represented by the Fourier transform of the bulk-to-boundary propagators and the Mellin transform of plane waves respectively. Recently, the 3pt celestial amplitude of one massive scalar and two massless scalars was discussed in arXiv:2312.08597. In this paper, we compute the 3pt celestial amplitude of two massive scalars and one massless scalar. Then we take the massless limit (mrightarrow 0) for one of the massive scalars, during which process the gamma function (Gamma (1-Delta )) appears. By requiring the resulting amplitude to be well-defined, that is it goes to the 3pt amplitude of arXiv:2312.08597, the scaling dimension of this massive scalar has to be conformally soft (Delta rightarrow 1). The pole (1/(1-Delta )) coming from (Gamma (1-Delta )) is crucial for this massless limit. Without it the resulting amplitude would be zero. This can be compared with the conformal soft limit in celestial gluon amplitudes, where a singularity (1/(Delta -1)) arises and the leading contribution comes from the soft energy (omega rightarrow 0). The phase factors in the massless limit of massive conformal primary wave functions, discussed in arXiv:1705.01027, plays an import and consistent role in the celestial massive amplitudes. Furthermore, the subleading orders (m^{2n}) can also contribute poles when the scaling dimension is analytically continued to (Delta =1-n) or (Delta = 2), and we find that this consistent massless limit only exists for dimensions belonging to the generalized conformal primary operators (Delta in 2-{mathbb {Z}}_{geqslant 0}) of massless bosons.

We compute the two-loop BSM contributions to the (hlongrightarrow gamma gamma ) decay width in the SM extended with a real triplet of SU(2). We consider scenarios in which the neutral components of doublet and triplet do not mix, so that the lighter neutral scalar h has (at least approximately) SM-like couplings to fermions and gauge bosons. We focus on the two-loop corrections controlled by the quartic scalar couplings, and obtain explicit and compact formulas for the (h gamma gamma ) amplitude by means of a low-energy theorem that connects it to the derivative of the photon self-energy w.r.t. the Higgs field. We briefly discuss the numerical impact of the newly-computed contributions, showing that they may be required for a precise determination of (Gamma [hrightarrow gamma gamma ]) in scenarios where the quartic scalar couplings are large.

We investigate nonperturbative aspects of the interplay of chiral transitions in the standard model in the course of the renormalization flow. We focus on the chiral symmetry breaking mechanisms provided by the QCD and the electroweak sectors, the latter of which we model by a Higgs-top-bottom Yukawa theory. The interplay becomes quantitatively accessible by accounting for the fluctuation-induced mixing of the electroweak Higgs field with the mesonic composite fields of QCD. In fact, our approach uses dynamical bosonization and treats these scalar fields on the same footing. Varying the QCD scale relative to the Fermi scale we quantify the mutual impact of the symmetry-breaking mechanisms, specifically the departure from the second order quantum phase transition of the pure Yukawa sector in favor of a crossover upon the inclusion of the gauge interactions. This allows to discuss the “naturalness” of the standard model in terms of a pseudo-critical exponent which we determine as a function of the ratio of the QCD and the Fermi scale. We also estimate the minimum value of the W boson mass in absence of the Higgs mechanism.

We address a dynamical, spherically symmetric background in beyond Horndeski theory and formulate a set of linear stability conditions for high energy perturbation modes in the parity odd sector above an arbitrary solution. In this general setting we derive speeds of propagation in both radial and angular directions for the only dynamical degree of freedom in the parity odd sector. We also briefly comment on the propagation speeds of the parity even modes over a dynamical, spherically symmetric background. In particular, we demonstrate that the class of beyond Horndeski theories, which satisfy the equality of gravity waves’ speed to the speed of light over a cosmological background, feature gravity waves propagating at luminal speeds above a time-dependent inhomogeneous background as well.

In the context of the gravity-thermodynamics conjecture based on the Tsallis entropy-area relation, we investigate the standard (varLambda )CDM cosmology and examine some potential deviations from it. Utilizing recent updates from geometrical datasets, including the DESI BAO measurements (2024), Planck CMB anisotropy measurements (2018), and the Pantheon+ catalogue for SNIa (2022), we conduct a thorough analysis via the window of Tsallis cosmology. In the first step, our analysis reveals no significant deviation from the standard model when using DESI BAO data alone, Pantheon+ data alone, or a combination of both. In the next step, we incorporate all datasets by adding the CMB data to our analysis, indicating a potential deviation from the standard model within the framework of Tsallis cosmology. Imposing the Planck prior to the sound horizon at the baryon drag epoch, we observe support for the standard model and consistency between our constraints on the Hubble constant and the Planck value. Finally, we compare the Tsallis and (varLambda )CDM cosmologies using the Akaike Information Criterion (AIC).

In this paper, we study the shadows and images of the accretion disk of Kerr–Newman (KN) black hole (BH) in modified gravity (MOG) theory by using the backward ray-tracing method. And, the influence of spin parameter (a), charge (Q), and MOG parameter ((alpha )) on the observed features of BHs are carefully addressed. Interestingly, as (alpha ) increases, the flat edge of the BH’s shadow gradually becomes more rounded, the size of shadow enlarges, and the deviation rate ((delta s)) correspondingly decreases. By tracing the photon around BH, we observe that the trajectory of photon exhibits distortion behavior, i.e., the formation of two “tails” near the Einstein ring, which elongate as a increases. For the accretion disk, it shows that the inner shadow expands with (alpha ), while decreases with Q. The increase of (alpha ) exhibits an increasing effect on redshift. At the same parameter level, (alpha ) has a more obvious effect on inner shadow and image of BH by comparing with that of Q. Our study implies that both (alpha ) and Q have relatively significant effects on the image of the KN-MOG BH with the thin disk accretion, but the influence of (alpha ) is much greater. So, this indicates that (alpha ) plays a dominant role in this spacetime.

We study thermalization in closed non-integrable quantum systems using the Krylov basis. We demonstrate that for thermalization to occur, the matrix representation of typical local operators in the Krylov basis should exhibit a specific tridiagonal form with all other elements in the matrix being exponentially small, reminiscent of the eigenstate thermalization hypothesis. Within this framework, we propose that the nature of thermalization, whether weak or strong, can be examined by the infinite time average of the Krylov complexity. Moreover, we analyze the variance of Lanczos coefficients as another probe for the nature of thermalization. One observes that although the variance of Lanczos coefficients may capture certain features of thermalization, it is not as effective as the infinite time average of complexity.