物理最新文献

In this paper, we investigate Holst gravity by examining two different examples. The first example involves minimal coupling to torsion, while the second explores non-minimal coupling. The motivation for the first example stems from the recent work by Dombriz et al. (Phys Lett B 834:137488, 2022), which utilized a technique of imposing constraint constant coefficients to massive torsion in the model Lagrangian to determine parameters for the Einstein–Cartan–Holst gravity. We extend this methodology to investigate dark photons, where axial torsion transforms into axions. Interest in elucidating the abundance of dark photons within the framework of general relativity was sparked by Agrawal et al. (Phys Lett B 801:135136, 2020). Building on the work of Barman et al. (Phys Rev D 101:075017, 2020), who explored minimal coupling of massive torsion mediated by dark matter (DM) with light torsion on the order of 1.7 TeV, we have derived a Barbero–Immirzi (BI) parameter of approximately 0.775. This value falls within the range established by Panza et al. at TeV scales, specifically (0le {beta } le {1.185}) (Phys Rev D 90:125007, 2014). To the best of our knowledge, this is the first time a BI parameter has been induced by dark photons on a minimal Einstein–Cartan (EC) gravity. Very recently, implications of the finding of a BI parameter in cosmological bounces have appeared in the literature (Phys Dark Universe 44:141078, 2024). For a smaller BI parameter, a higher torsion mass of 1.51 TeV is obtained. Nevertheless, this figure is still a signature of light torsion which can be compatible with light dark photon masses. The magnetic helicity instability of the dark photons is investigated. The axion oscillation frequency is shown to depend on the BI parameter, and the BI spectra are determined by a histogram. This study not only broadens the understanding of Holst gravity but also provides crucial insights into the interplay between torsion, dark photons, and axions in the cosmological context.

In this paper, we delve into the thermodynamic topology of AdS Einstein–Gauss–Bonnet black holes, employing non-extensive entropy formulations such as Barrow, Rényi, and Sharma–Mittal entropy within two distinct frameworks: bulk boundary and restricted phase space (RPS) thermodynamics. Our findings reveal that in the bulk boundary framework, the topological charges, influenced by the free parameters and the Barrow non-extensive parameter ((delta )), exhibit significant variability. Specifically, we identify three topological charges ((omega = +1, -1, +1)). When the parameter (delta ) increases to 0.9, the classification changes, resulting in two topological charges ((omega = +1, -1)). When (delta ) is set to zero, the equations reduce to the Bekenstein–Hawking entropy structure, yielding consistent results with three topological charges. Additionally, setting the non-extensive parameter (lambda ) in Rényi entropy to zero increases the number of topological charges, but the total topological charge remains (W = +1). The presence of the Rényi non-extensive parameter alters the topological behavior compared to the Bekenstein–Hawking entropy. Sharma–Mittal entropy shows different classifications and the various numbers of topological charges influenced by the non-extensive parameters (alpha ) and (beta ). When (alpha ) and (beta ) have values close to each other, three topological charges with a total topological charge ((W = +1)) are observed. Varying one parameter while keeping the other constant significantly changes the topological classification and number of topological charges. In contrast, the RPS framework demonstrates remarkable consistency in topological behavior. Under all conditions and for all free parameters, the topological charge remains ((omega = +1)) with the total topological charge ((W = +1)). This uniformity persists even when reduced to Bekenstein–Hawking entropy, suggesting that the RPS framework provides a stable environment for studying black hole thermodynamics across different entropy models. These findings underscore the importance of considering various entropy formulations and frameworks to gain a comprehensive understanding of black hole thermodynamics.

With the increase in energy consumption, resources are decreasing while costs are rising. The Covid-19 pandemic and wars in some countries have also led to increased costs. Considering the environmental damage, the search for new energy sources and the demand for existing renewable energy sources have increased. Among renewable energy sources, wind energy is one of the most prominent energy sources due to its environmental friendliness. In recent years, studies on wind characteristics and wind energy distribution have been conducted in many parts of the world. But, it has not been conducted that a detailed study using different probability density functions specifically for Sivas province in Türkiye. This study investigated the wind energy potential for Sivas province using various probability density functions. Data from two nearby stations were used in the calculations. Despite the proximity of the stations, it was determined that the emerging wind trends showed some differences. For Station A, it is observed that probability density functions other than Rayleigh provide a better fit, especially at low wind speeds. However, deviations from actual values are observed at certain wind speeds. For Station B, functions other than Weibull show a better fit, although it can be said that the wind characteristics are more irregular in the winter season, and the predicted functions do not provide a better fit. Stations A and B exhibited different wind characteristics, except for the autumn season. It was observed that collecting data and analyzing wind power at the site where a wind farm will be established is quite important. As a result of the study, it was concluded that the potential wind powers at both stations were quite low and not very suitable for wind farm installation.

This study investigates the significant impact of cross-phase modulation (XPM) on modulation instability (MI) in a nonlinear tunnel-coupled oppositely directed coupler, with a focus on its practical applications in nonlinear optical systems. Our linear stability analysis reveals that XPM substantially enhances MI, leading to a considerable increase in the maximum gain and bandwidth of the instability gain spectrum. This enhancement is particularly pronounced when nonlinearity is concentrated in both channels of the coupler, making it an essential consideration for the design of optical devices. Furthermore, our analysis demonstrates that XPM induces instability breakup in the gain spectra, resulting in optical wave breaking. As MI is often a precursor to soliton formation, understanding the role of XPM in controlling soliton dynamics is crucial for predicting and manipulating soliton behavior in various applications, such as optical communication systems, ultrafast optics, and photonics. By elucidating the interplay between XPM and MI, this study provides valuable insights for the development of advanced nonlinear optical devices and systems, enabling the creation of stable and controllable soliton sources for a wide range of applications.

The results obtained at the LHC for constraining the trilinear Higgs self-coupling of the detected Higgs boson at about 125 GeV, (lambda _{hhh}), via the Higgs pair production process have significantly improved during the last years. We investigate the impact of potentially large higher-order corrections and interference effects on the comparison between the experimental results and the theoretical predictions for the pair production of the 125 GeV Higgs boson at the LHC. We use the theoretical framework of the Two Higgs Doublet Model (2HDM), containing besides the SM-like ({mathcal{C}mathcal{P}})-even Higgs boson h a second ({mathcal{C}mathcal{P}})-even Higgs boson H, which we assume to be heavier, (mH > mh). We analyze in particular the invariant mass distribution of the two produced Higgs bosons and show that the loop corrections to the trilinear Higgs couplings (lambda _{hhh}) and (lambda _{hhH}) as well as interference contributions give rise to important effects both for the differential and the total cross section. We point out the implications for the experimental limits that can be obtained in the 2HDM for the case of the resonant production of the heavy Higgs boson H. We emphasize the importance of the inclusion of interference effects between resonant and non-resonant contributions in the experimental analysis for a reliable determination of exclusion bounds for a heavy resonance of an extended Higgs sector.

In this work, a new system of Ca₉Gd_0.96−xBi_0.04Eu_x(PO₄)₇ phosphor is successfully obtained via high temperature solid-state method and calcined at 1300 °C. All samples can be well indexed to the XRD pattern of Ca₉Nd(PO₄)₇ (space group: R3c (161), JCPDS No. 45-0346), indicating the addition of Bi³⁺/Eu³⁺ does not change the structure of the crystal. According to the XPS results, Bi³⁺ and Eu³⁺ are successfully dispersed and stably embedded in Ca₉Gd(PO₄)₇ material. Ca₉Gd_0.96−xBi_0.04Eu_x(PO₄)₇ phosphors show different emission peaks at 420 nm (the ³P₁ → ¹S₀ transition of Bi³⁺) and 612 nm (the ⁵D₀ → ⁷F₂ transition of Eu³⁺) under near-ultraviolet excitation at 375 nm. The intensity of Eu emission varies as the concentration of Eu³⁺, and the emission intensity is strongest when the concentration of Eu³⁺ is about 80 at%. By monitoring the Eu³⁺ emission, a Bi³⁺ excitation band is observed on the PLE spectrum, indicating the occurrence of energy transfer from Bi³⁺ to Eu³⁺, with an efficiency of 65%. Furthermore, the value of critical distance R_c is calculated to be 11.2 Å, indicating that the main cause of the quenching mechanism is the multipole interaction. Meanwhile, the energy transfer mechanism of the Ca₉Gd_0.96−xBi_0.04Eu_x(PO₄)₇ samples is primarily controlled by the dipole–dipole interaction. The temperature-dependent (in the range of 300–500 K) analysis has been obtained. The emission intensity at 500 K can maintain 63% of the room temperature, and the activation energy E_a is 240 meV. The relative high activation energy indicates that the new systems of Ca₉Gd_0.96−xBi_0.04Eu_x(PO₄)₇ phosphors have good thermal stability. The Ca₉Gd_0.96−xBi_0.04Eu_x(PO₄)₇ phosphor developed in this work is an promising candidate for application in LEDs and expected to be widely used in lighting and display applications.

We studied the late-time acceleration scenarios using a quintessence field initially trapped in a metastable false vacuum state. The false vacuum has non-zero vacuum energy and can drive exponential expansion if not coupled with gravity. Upon decay of the false vacuum, the quintessence field is released and begins to evolve. We assumed conditions where the effective scalar potential gradient must satisfy (nabla V_{text {eff}} > A), characterised by a pressure term approximately (Delta p / p > mathcal {O} (hbar )) invoking the string swampland criteria. We then derived the effective potential of the scalar with an upper bound on the coupling constant (lambda < 0.6). Further analysis revealed that (V_{text {eff}}) shows a slow-roll behaviour for (0.1> lambda > -0.04) in the effective dark energy equation of state (EoS) (-0.8< w_0 < -0.4), stabilising at points between (1< A < 2.718). Our results suggest a stable scalar decoupled from its initial metastable state can indeed lead to a more stable Universe at later times. However, slight deviations in parameter orders can potentially violate the swampland criteria if (V_{text {eff}}) grows too rapidly. Since this is not something we expect, it opens up the possibility that the current dark energy configuration might be a result of a slowly varying scalar potential rather than being arbitrary.

Dark matter is hypothesized to interact with ordinary matter solely through gravity and may be present in compact objects such as strange quark stars. We treat strange quark stars admixed with dark matter as two-fluid systems to investigate the potential effects of dark matter on strange quark stars. Quark matter is described by the quasiparticle model and the extended MIT bag model for comparison. Dark matter is treated as asymmetric, self-interacting, and composed of massive fermionic particles. The two-fluid Tolman–Oppenheimer–Volkoff (TOV) equations are employed to solve for specific stellar properties. Our analysis yields relations between central energy density and mass, radius and mass, as well as tidal deformability and mass. The calculated curves generally align with observational data. In particular, we find that the pattern in which fermionic asymmetric dark matter affects the properties of strange quark stars may not be influenced by the equation of state (EOS) of strange quark matter.

We investigate the null geodesic structure and corresponding black hole shadows in the accelerating Kerr–Newman–Taub–NUT (AKNTN) spacetime-a highly generalized solution that incorporates rotation, electric charge, acceleration, and NUT charge. By deriving a separable Hamilton–Jacobi equation for null test particles, we demonstrate that the additional parameters enable equatorial circular photon orbits, a feature absent in generic accelerating spacetimes. Building on this framework, we analyze the influence of acceleration, spin, electric (or tidal) charge, and NUT parameters on the shadow observables, such as the shadow radius and distortion. Furthermore, we extend our study to include tidal charged black holes in the RS-II braneworld scenario by replacing the electric charge parameter with a tidal charge, (mathcal {Q}), which may assume either sign. Our numerical results reveal that increasing the acceleration parameter compresses the photon capture region and reduces the shadow size, while a negative tidal charge deepens the gravitational potential, enlarging the shadow. These findings offer new insights into the interplay between extra-dimensional effects and classical gravitational parameters, with potential implications for future astrophysical observations.