物理最新文献

We apply Wald’s formalism to a Lagrangian within generalised Proca gravity that admits a Schwarzschild black hole with a non-trivial vector field. The resulting entropy differs from that of the same black hole in General Relativity by a logarithmic correction modulated by the only independent charge of the vector field. We find conditions on this charge to guarantee that the entropy is a non-decreasing function of the black hole area, as is the case in GR. If this requirement is extended to black hole mergers, we find that for Planck scale black holes, a non-decreasing entropy is possible only if the area of the final black hole is several times larger than the initial total area of the merger. Finally, we discuss some implications of the vector Galileon entropy from the point of view of entropic gravity.

We present a complete and consistent exposition of the regularization, renormalization, and resummation procedures in the setup of having a contraction and then non-singular bounce followed by inflation with a sharp transition from slow-roll (SR) to ultra-slow roll (USR) phase for generating primordial black holes (PBHs). We consider following an effective field theory (EFT) approach and study the quantum loop corrections to the power spectrum from each phase. We demonstrate the complete removal of quadratic UV divergences after renormalization and softened logarithmic IR divergences after resummation and illustrate the scheme-independent nature of our renormalization approach. We further show that the addition of a contracting and bouncing phase allows us to successfully generate PBHs of solar-mass order, (M_textrm{PBH}sim mathcal{O}(M_{odot })), by achieving the minimum e-folds during inflation to be (Delta N_{textrm{Total}}sim mathcal{O}(60)) and in this process successfully evading the strict no-go theorem. We notice that varying the effective sound speed between (0.88leqslant c_{s}leqslant 1), allows the peak spectrum amplitude to lie within (10^{-3}leqslant A leqslant 10^{-2}), indicating that causality and unitarity remain protected in the theory. We analyse PBHs in the extremely small, (M_{textrm{PBH}}sim mathcal{O}(10^{-33}-10^{-27})M_{odot }), and the large, (M_{textrm{PBH}}sim mathcal{O}(10^{-6}-10^{-1})M_{odot }), mass limits and confront the PBH abundance results with the latest microlensing constraints. We also study the cosmological beta functions across all phases and find their interpretation consistent in the context of bouncing and inflationary scenarios while satisfying the pivot scale normalization requirement. Further, we estimate the spectral distortion effects and shed light on controlling PBH overproduction.

Recently, the LHCb Collaboration provided updated measurements for the lepton flavour ratios (R_K) and (R_{K^*}). The currently observed values align with the predictions of the standard model. In light of these recent updates, our investigation delves into the repercussions of new physics characterized by universal couplings to electrons and muons. We specifically focus on their impact on various observables within the (Brightarrow K_2^*(1430)(rightarrow Kpi )mu ^+ mu ^-) decay. These observables include the differential branching ratio, forward-backward asymmetry ((A_{FB})), longitudinal polarization asymmetry ((F_L)), and a set of optimized observables ((P_i)). Our findings indicate that the branching ratio of (Brightarrow K_2^*(rightarrow Kpi )mu ^+ mu ^-) decay can be suppressed up to (25%) for various new physics solutions. Furthermore, all permissible new physics scenarios demonstrate finite enhancement in the muon forward-backward asymmetry ((A_{FB})) as well as an increase in the value of the optimized angular observable (P_2). Moreover, in the presence of new physics zero crossing points for (A_{FB}) and (P_2) shift towards higher (q^2). The current data have a mild deviation from SM predictions in (P_5') observable in the low-(q^2) bin. We also explored massive (Z') models, which can generate universal 1D new physics scenarios, characterized by (C_9^{NP}<0), (C_9^{NP}=-C_{10}^{NP}), and (C_9^{NP}=-C_9'). Using additional constraints coming from (B_s-overline{B_s}) mixing and neutrino trident process, we find that the conclusions of the model-independent analysis remain valid.

This work is devoted to exploring the formation and stability of thin-shell wormholes developed through the two similar copies of black holes bounded by the pseudo-isothermal dark matter halo. It is found that the horizon radius of a black hole decreases in the appearance of a pseudo-isothermal dark matter halo. The primary goal of the work is to investigate the stable composition of such wormholes using the analysis of linearized radial perturbation. It is worth mentioning that the existence of a pseudo-isothermal dark matter halo reduces the violation of energy bounds for the developed thin-shell wormholes. We investigate the impact of variable equations of state, such as barotropic, variable Chaplygin, and phantom-like equations of state, on the stability of the wormholes. The inquiry highlights that the appearance of a pseudo-isothermal dark matter halo portrays remarkable importance in preserving the stable compositions of thin-shell wormholes. The wormholes show maximal stable conduct for the selection of pseudo-isothermal dark matter halo as compared to already published research charged as well as regular thin-shell wormholes. The results reveal light on the interplay between wormholes and pseudo-isothermal dark matter halo, which increases our understanding of both conjectures and their potential implications for further space travel.

We are investigating the localization of matter that interacts non-minimally with gravity within thick braneworld models generated by a scalar bulk. We focus on two models of scalar thick branes. The natural mechanism is used to analyze the localization of the fields. Without losing the point of field localization, we examine matter field localizations by considering the asymptotic behavior of the warp function on z toward infinity. The massless mode of the non-minimally coupled scalar field is localized on the brane in both models. A non-minimally coupled vector field behaves similarly to the non-minimally coupled scalar field, the massless mode in both models is localized. For a non-minimally coupled spinor field, in model 1, the field is not localized for both massless and massive modes, while in model 2, the massless spinor field is localized. This represents an improvement, as in the case of minimal coupling, massless vector and spinor fields are not localized in the brane model 2.

A topological index (or descriptor) is a numerical demonstration of a molecular graph associated with a chemical compound that directly correlates with its physical and chemical characteristics through quantitative structure–property relationship (QSPR) analysis. This article is concerned with the mathematical bounds and expressions of the Nirmala index for chemical graphs and its comparison with the Sombor index through QSPR analysis. More precisely, a comparative study between the Nirmala index and the Sombor index is presented using the linear, quadratic and multi-linear regression analysis over the physico-chemical properties of octane isomers to test the predictive potential of the index. Further, the degeneracy and smoothness (structure sensitivity and abruptness) are calibrated of the Nirmala and Sombor indices using the chemical isomers data sets such as octane, nonane and decane. Finally, the lower and upper bounds of the Nirmala index are investigated using the sets of chemical graphs and trees. Additionally, the expressions of the Nirmala index and its extremal values are also examined for different types of hexagonal systems. The obtained correlation values and p-values of both indices through multi-linear regression analysis are more significant, indicating the reliability and applicability of the findings. Therefore, these indices may be utilized to predict the properties of various chemical compounds and drugs in the QSPR studies.

We study the compressible simple uniaxial deformation within the quasilinear viscoelasticity theory. We impose a longitudinal stretch (in both extension and compression), and we investigate the role of compressibility in such a deformation by computing the lateral deformation and the uniaxial stress for an isotropic homogeneous material sample under lateral-free traction conditions. Several tests are examined, and conclusions are drawn based on a set of three strain energy densities that describe compressible hyperelastic behaviours by varying the set of involved parameters. The dissipated energy is also computed for a typical one-cycle experimental test. Furthermore, we examine recent experiments on visco-elastomeric syntactic foams in light of our results, comparing them with the simplified model using the rate-independent nonlinear Poisson functions.

The birefringence cratering of reflection, transmission and corresponding Goos Hänchen (GH) shift are investigated in reflection and transmission beams through four level chiral atomic medium of structured light. The reflection and transmission of left and right circularly polarized light obey normalization condition and strong cratering oscillation functions of positions and azimuthal quantum number (ell ) of control field. Crater types reflection and transmission are investigated whose numbers increase with azimuthal quantum numbers having varying in shapes. The GH shifts in reflection and transmission is positive and oscillated with position (x/lambda ) and (y/lambda ). The numbers of crater in GH shifts depend on the azimuthal quantum number (ell ) of control field. The values of both GH shift in reflection and transmission varies in the range of (6lambda le S_R^{(-)}le 12lambda ) and (6lambda le S_T^{(-)}le 12lambda ) with increasing craters to increase azimuthal quantum number (ell ) of control field. The modified results of the GH shifts are useful for biosensor and plasmonster technology.

Nanostructured layers of zinc oxide are promising compounds for sensor and solar cell applications. Such layers can be obtained by combining both sol–gel and pulsed laser deposition (PLD) preparation methods. Gallium-doped zinc oxide (GZO) nanoparticles were synthesized using the sol–gel method. The obtained powder was used to deposit thin films of GZO on glass and p-silicon substrates by PLD. The effect of Ga doping concentration on the morphological, optical and electrical properties of the GZO thin films was investigated. Scanning electron microscopy images reveals particle homogenous surface and particles in nonmetric size. GZO thin films showed more than 90% transparency in the entire visible region. The relationship between electrical properties and Ga doping concentration was clarified by analyzing the current–voltage (I-V), capacitance–voltage (C-V), and conductance-frequency (G-ω) characteristics of the Ag/GZO/Si:p/Au structure over a wide range of temperature, frequency, and voltage bias. I-V and C-V characteristics show that our structure is formed by two back-to-back diodes. The GZO/Si:p heterojunction governs the electrical response at low temperatures and the Ag/GZO Schottky junction takes over at higher temperatures. At low temperature (T ≤ 160 K), high rectifying behavior of the Si:p/GZO p-n heterojunction was observed for Ga doping concentration 1 at%. The carrier concentration of the GZO thin films is calculated from the C⁻²-V characteristics. The analysis of impedance dependent on frequency, reveals that the relaxation is a thermally activation process. Activation energies of defects in GZO thin films and their effects on the electronic properties of Ag/GZO/Si:p/Au structure are obtained. This investigation makes a valuable contribution to the behavior of defects in GZO thin films to optimize their properties for solar cell applications.