Science China Physics, Mechanics & Astronomy最新文献

We study perturbations of Schwarzschild-de Sitter black holes in semi-open systems by using the Heun functions. For the semi-open system, a partially reflective wall is added around the event horizon. Three aspects of this model are investigated, namely the quasinormal mode (QNM) spectra, the greybody factor (GF), and the exceptional point (EP). For the QNM aspect, we identify three distinct behaviors as the frequency-independent reflectivity (cal K) increases. The first-type modes approach the real axis and form long-lived quasi-bound states. The second-type modes move toward but do not reach the real axis and retain a finite decay rate. The third-type modes eventually lie on the imaginary axis becoming purely decaying modes. For the GF aspect, GFs exhibit strong oscillations controlled by the distance between the potential and the reflective wall with a real constant reflectivity. In contrast, a Boltzmann-type reflectivity produces only small corrections. Finally, by promoting (cal K) to a complex parameter, the modified boundary conditions give rise to a second-order EP. Parameterizing the vicinity of such EP, we observe the mode exchange phenomenon, and the deviation of spectra scale with the square root of the deviation of the parameter, as predicted by a Puiseux series expansion.

In this paper, we investigate the frame-dragging effect on an accretion disk and test gyroscope orbiting around a rotating regular black hole with a Minkowski core. Firstly, we perturb a bound timelike circular orbit around the black hole, and analyze the periastron precession and Lense-Thirring (LT) precession frequencies of the orbit’s epicyclic oscillations. Since these epicyclic oscillations can be used to explain the quasiperiodic oscillations (QPOs) phenomena of the accretion disc around this rotating regular black hole, we then employ the Markov chain Monte Carlo (MCMC) simulation to fit our theoretical results with five QPOs events (GRO J1655-40, GRS 1915+105, XTE J1859+226, H1743-322, and XTE J1550-564). The simulations give the relevant physical parameter space of the black hole, including the characteristic radius r, the mass related parameter M, the spinning parameter a, and the quantum gravity effect α. The results give the constraint on the quantum effect parameter, with an upper limit α/M^2/3 < 0.60 at the 95% C.L., which is tighter than < 0.7014 in our previous study within static case. Then, we theoretically explore the LT precession frequency, geodetic precession frequency, and the general spin precession frequency of a test gyro attached to a stationary observer in this black hole background. We find that the quantum gravity effect suppresses the precession frequencies comparing against those in Kerr black hole, further providing a theoretical diagnostic of the potential quantum gravity effect.

We present a comprehensive theoretical analysis of the general standard model (GSM), a recently proposed framework that unifies particle physics and cosmology within the gravitational quantum field theory (GQFT). Constructed from first principles based exclusively on the intrinsic properties of leptons and quarks, the GSM reveals an enlarged gauge symmetry structure, WS_c(1,3)×GS(1)×Z₂, which extends beyond the conventional U_Y(1)×SU_L(2)×SU_C(3) symmetry of the standard model. Here, WS_c(1,3) = SP(1,3)⋊W^1,3⋊SP_c(1,1) emerges as the conformal inhomogeneous spin gauge symmetry. Within GQFT, the GSM provides a consistent unification of the standard model of particle physics with cosmological models. It incorporates the four known fundamental interactions, electromagnetic, weak, strong, and gravitational, plus the Higgs scalar interaction, and also predicts novel interactions. These include spin gauge, chirality boost-spin gauge, chiral conformal-spin gauge, and scaling gauge forces, as well as additional scalar interactions. Furthermore, the GSM offers profound insights into the nature of gravity and spacetime and elucidates key mysteries of the dark side of the universe, such as the origins of dark matter, the dynamics of dark energy, and the physics of the early inflationary epoch. By establishing a new theoretical bridge between quantum field theory and general relativity, the GSM opens novel pathways for addressing long-standing challenges in fundamental physics. It provides a unified description of both fundamental interactions and cosmic evolution.

We report a constraint on the cosmological variation of the proton g-factor, g_p. By comparing the measured redshifts between Hi 21 cm and OH 18 cm lines observed with the newly commissioned Five-hundred-meter Aperture Spherical radio Telescope (FAST) toward PKS 1413+135 at z = 0.24671, we obtain Δg_p/g_p = (−4.3 ± 2.5) × 10⁻⁵, which is more than two orders of magnitude more sensitive than previous constraints. In addition, we obtain sensitive constraints of Δ(μα²)/(μα²) = (2.0 ± 1.2) × 10⁻⁵ and Δ(μα²g ^0.64_p )/(μα²g ^0.64_p ) = (−4.7 ± 1.9) × 10⁻⁶.

A geometrically characteristic and thermodynamically consistent theory is proposed to describe the full-life mechanics of metallic solids undergoing large deformation. The theory is geometrically characteristic in the sense that the inelastic deformation caused by various crystalline defects is decomposed into a deviatoric part, a volumetric part, and a geometrically insensitive part, and the system thermodynamics is then formulated. The theory reaches its closure by including a finite-strain plastic flow rule originating from the postulate of maximum dissipation, and a set of thermodynamically consistent kinetic equations for the geometrically characteristic field quantities. The present theory is distinguished from existing ductile damage models in the following aspects. Firstly, the proposed geometrically characteristic measure of plasticity is conceptually valid throughout the whole deformation stage, enabling the calibration of the present theory simply against uniaxial loading data. Secondly, the stress calculation here is shown to be unconditionally convergent, and this is in contrast to the use of incremental tangent stiffness matrices whose eigenvalues inevitably turn negative in the softening stage. Thirdly, the anisotropic hardening behaviour can be modelled with low calibration requirements.

The development of new high-temperature ultrasmall-size skyrmion materials holds immense significance for the promising applications of topological spintronic devices. In this study, we demonstrate that a high-pressure synthesis technique can significantly elevate the Curie temperature of Mn₅Ge_3.2 crystals, from 294 to 350 K. It is possible that this enhancement arises from the combined effects of lattice contraction and increased Ge content, a conclusion supported by our Density Functional Theory calculations. Additionally, our real-space magnetic imaging reveals the stability of dipolar skyrmions with diameters of approximately 50 nm at room temperature and zero magnetic field. Our micromagnetic simulations closely replicate the diverse experimental topological magnetic textures observed. Furthermore, magnetotransport measurements indicate the potential for the electrical distinction between various topological magnetic textures in skyrmion-based devices. We also report deterministic manipulations on single dipolar skyrmions in confined nanostructures by using in-plane currents. The observation, electrical manipulation, and electrical detection of room-temperature ultrasmall topological magnetic textures underscore the potential of Mn₅Ge_3.2 as a promising platform for spintronic device applications.

Solar prominences usually have a horizontally elongated body with many feet extending to the solar surface, resembling a multi-arch bridge with many bridge piers. The basic mechanism by which solar prominences acquire these common structures during their evolution, however, remains an unresolved question. For the first time, our three-dimensional magneto-frictional simulation, driven by supergranular motions, self-consistently replicates the commonly observed multi-arch bridge morphology and its characteristic structures of solar quiescent prominences in a magnetic flux rope. In comparison with traditional views, our simulations demonstrate that the spine, feet, and voids (bubbles) are inherent prominence structures spontaneously forming as the flux rope evolves to a mature state. The voids mainly consist of legs of sheared magnetic loops caused by unbalanced supergranular flows, and prominence feet settle at the bottom of helical field lines piled up from the photosphere to the spine. Similarities between the simulated prominences and observed real prominences by the Chinese Hα Solar Explorer, the New Vacuum Solar Telescope, and NASA’s Solar Dynamics Observatory suggest the high validity of our model. This work corroborates the pivotal role of photospheric supergranulation as a helicity injection source in the formation and shaping of quiescent prominence structures within the solar atmosphere, thereby paving a new avenue for future investigations into their fine dynamics and stability.

The discovery of superconductivity (SC) with critical temperature T_c above the boiling point of liquid nitrogen in pressurized La₃Ni₂O₇ has sparked a surge of exploration of high-T_c superconductors in the Ruddlesden-Popper (RP) phase nickelates. More recently, the RP phase nickelate La₅Ni₃O₁₁, which hosts a layered structure with alternating bilayer and single-layer NiO₂ planes, has been reported to accommodate SC under pressure, exhibiting a dome-shaped pressure dependence with the highest T_c ≈ 64 K, capturing a lot of interest. Here, using density functional theory (DFT) and random phase approximation (RPA) calculations, we systematically study the electronic properties and superconducting mechanism of this material. Our DFT calculations yield a band structure including two nearly decoupled sets of sub-band structures, with one set originating from the bilayer subsystem and the other from the single-layer one. RPA-based analysis demonstrates that SC in this material occurs primarily within the bilayer subsystem exhibiting an s^± wave pairing symmetry similar to that observed in pressurized La₃Ni₂O₇, while the single-layer subsystem mainly serves as a bridge facilitating the inter-bilayer phase coherence through the interlayer Josephson coupling (IJC). Since the IJC thus attained is extremely weak, it experiences a prominent enhancement under pressure, leading to the increase of the bulk T_c with pressure initially. When the pressure is high enough, the T_c gradually decreases due to the reduced density of states on the γ-pocket. In this way, the dome-shaped pressure dependence of T_c observed experimentally is naturally understood.

Among the rich spectrum of GW sources, galactic compact binaries (GCBs) and extreme mass-ratio inspirals (EMRIs) stand out as crucial targets for space-based detectors. GCBs pose challenges in signal extraction due to their overlapping nature. This paper introduces a deep learning framework designed to separate overlapping GCB and EMRI GW signals. The framework employs a two-stage approach: initially, we consider the mixed GCB waveforms as an ensemble, and an ensemble separation method is utilized to separate the mixed GCBs and EMRI signals; subsequently, a recursive reasoning process is applied to further isolate individual GCB signals from the mixed GCB ensemble. We demonstrate the model’s robust performance across varying signal-to-noise ratios (SNRs) and overlapping signal counts. The framework exhibits high separation fidelity, particularly for the ensemble separation stage, with overlap metrics exceeding 0.998 under the same parameter ranges of the training set, thereby ensuring accurate signal extraction for subsequent recursive reasoning. For the recursive reasoning process, we have empirically demonstrated that the deep learning framework is capable of effectively separating mixed GCB GW signals even when the frequency differences between them are near or marginally below the frequency resolution limit. We have also observed that the proposed framework exhibits generalization capabilities when applied to GW strain data characterized by lower SNR ranges and larger numbers of mixed GCB signals.