物理最新文献

Spacelike and timelike generalized parton distributions (GPDs) have been investigated at charged-lepton accelerator facilities, for example, by the virtual Compton scattering and the two-photon process, respectively. In this work, we show the (pi ^pm ) and (pi ^0) production cross sections in neutrino (antineutrino) reactions (nu ,(bar{nu }) + N rightarrow ell + pi + N') for studying the GPDs of the nucleon by using the theoretical formalism of Pire, Szymanowski, and Wagner. The (pi ^pm )-production cross sections are useful for finding mainly gluon GPDs, whereas the (pi ^0) production probes quark GPDs, although there are sizable quark-gluon interference terms in the (pi ^pm ) production. In particular, we show the roles of the pion- and rho-pole terms, the contribution from each GPD term (H, E, ({tilde{H}}), ({tilde{E}})), the effects of the gluon GPDs (H_g) and (E_g), and the dependence on the energy of the process in the neutrino cross sections. These cross sections could be measured at Fermilab in future. The neutrino GPD studies will play a complementary role to the projects of charged-lepton and hadron reactions for determining the accurate GPDs.

We study the effect of the double potentials (barrier, well) on the Goos–Hänchen (GH) shifts in phosphorene. We determine the solutions of the energy spectrum associated with the five regions that make up our system. By studying the phase shifts, we find that the GH shifts are highly sensitive to the incident energy, the y directional wave vector, the potential heights and widths. To validate our findings, we perform a numerical analysis of the GH shifts as a function of the transmission probability under various conditions. In particular, we observe a consistent pattern in which a positive peak in the GH shift is always followed by a negative valley, a behavior evident at all potential height values. Notably, the energies at which the GH shift changes sign coincide exactly with the points at which transmission drops to zero. In particular, the transmission resonances that occur just before and just after the transmission gap region are strongly correlated with the points at which the GH shift changes sign. This study advances our understanding of how the double potential influences the GH shift behaviors in phosphorene. The ability to fine-tune the GH shifts by changing system parameters suggests potential applications in optical and electronic devices using this two-dimensional material.

We present excitation cross-sections of hydrogen (H) atoms by hydrogen-like ions (({X}^{+})), employing a four-body classical and quasiclassical trajectory Monte Carlo model (CTMC and QCTMC models). Our calculations encompass impact energies ranging from 1.0 to 100 keV, which hold significant importance in fusion research and plasma physics. We present the total excitation cross-sections, alongside partial excitation cross-sections for the 2s, 2p, 3s, and 3p states of the target atom. A comparison is made between the total and partial excitation cross-sections with previously obtained theoretical and experimental results. Our recent total cross-sections for (n=2) excitation in ({He}^{+}+{H}_{T} (n=1)) collision shows a good agreement with the Vainshtein-Presnyakov-Sobel'man approximation (VPSA) data, while also presenting lower results compared to the previous Born approximation results and experimental data. Moreover, the CTMC results for partial excited state transitions from 1 to 2s in ({He}^{+} + {H}_{T} (n=1)) collisions agree well with previously obtained experimental data. On the other hand, the QCTMC results for partial excited state transitions from 1s to 2p in ({He}^{+}+ {H}_{T} (n=1)) collisions agree well with previous theoretical calculations, especially for energy above 10 keV. Furthermore, the QCTMC cross-section results are higher than the standard CTMC data, demonstrating the significance of the Heisenberg correction term, particularly in the low-energy regime.

A contribution of free charge carriers in an ensemble of anisotropic silicon nanocrystals to the optical properties in the infrared region has been numerically analyzed. Utilizing a generalized effective medium model that accounts for the shape anisotropy of silicon nanocrystals and mobile charge carriers the reflectance, absorption, and transmittance were found to be strongly dependent on the concentration of free charge carriers. For charge carrier (hole) concentrations ranging from (10^{16}) to (10^{20}) (cm^{-3}), significant birefringence and linear dichroism (absorption anisotropy) are observed, along with a non-monotonic dependence of the refractive index and transmittance coefficients for perpendicular polarization directions. The simulation results align well with experimentally measured transmittance spectra of in-plain anisotropic porous silicon films prepared electrochemically from heavily boron-doped (110)-oriented crystalline silicon wafers. Furthermore, the obtained results are discussed in view potential applications in all-silicon based optical switches and modulators and other active elements of the silicon photonics.

We consider the bending of light around a compact astrophysical object with both the electric field and the magnetic field in Einstein–Born–Infeld theory. From the null geodesic of a light ray passing a massive object with electric charge and magnetic dipole, the effective metric was obtained from the light cone condition reflecting the nonlinear electromagnetic effects. We found the asymptotic form of the effective metric up to the first order in gravitational constant G and Born–Infeld parameter (1/beta ^2) on the equatorial plane. Then we compute the bending angle of light from the geodesic equation. The result includes particular cases where only one type of field is present taking the appropriate limits.

This study investigates properties of static, electrically charged black hole within string theory using the non-rotating case of the Kerr–Sen solution. We derive the equilibrium condition for a test particle outside the black hole and examine perturbations via the combined Einstein–Maxwell equations. We extend the analysis to the extreme case, where the black hole’s electric charge reaches (sqrt{2}) times of its mass. Formulating and solving perturbation equations for both extreme and non-extreme cases, we obtain and graph numerical solutions for the perturbation function L(r) in comparison with the standard Reissner–Nordström solution. We show that these two solutions behave identically at large distances, starting from the orbit of the perturbing source. Considerable difference can be observed only in the region between this orbit and the central black hole. These results provide insights into the influence of source mass and electric charge on perturbation behavior, contributing to our understanding of charged stringy black holes and paving the way for further investigations into their stability.

We compute the rate of change of mass and angular momentum of a black hole, namely tidal heating, in an eccentric orbit. The change is caused due to the tidal field of the orbiting companion. We compute the result for both the spinning and non-spinning black holes in the leading order of the mean motion, namely (xi ). We demonstrate that the rates get enhanced significantly for nonzero eccentricity. Since eccentricity in a binary evolves with time we also express the results in terms of an initial eccentricity and azimuthal frequency (xi _{phi }). In the process, we developed a prescription that can be used to compute all physical quantities in a series expansion of initial eccentricity, (e_0). These results are computed taking account of the spin of the binary components. The prescription can be used to compute very high-order corrections of initial eccentricity. We use it to find the contribution to eccentricity up to ({mathcal {O}}(e_0^5)) in the spinning binary. Using the computed expression of eccentricity, we derived the rate of change of mass and angular momentum of a black hole, both rotating and non-rotating, in terms of initial eccentricity and azimuthal frequency up to ({mathcal {O}}(e_0^6)). With the computed fluxes we also compute for the first time the leading order dephasing in both cases analytically up to ({mathcal {O}}(e_0^6)) and study its impact. We argue that for high signal-to-noise ratio sources, these contributions require inclusion in the waveform modeling.

La₂Ti₂O₇ ceramic has a perovskite-like structure with super-high Cuire temperature (T_c ~ 1460 ℃), which is an excellent candidate for the application as a high-temperature accelerator sensor used at beyond 1000 ℃. The high temperature electrical conductivity resulting from charge carrier transport has a major influence on the sensitivity of sensors. Here, Zn was introduced as an acceptor into La₂Ti₂O₇ ceramics for high-temperature electrical properties. All the samples show pure perovskite-like structure with P2₁ space group and compact microstructure. With the introduction of Zn up to x = 0.08, the insulation resistance of the ceramics was enhanced more than 1000 times. Impedance spectroscopy and modulus spectroscopy were used to investigate the high-temperature transport of charged carrier. Interestingly, the acceptor doping resulted in an increasing concentration of oxygen vacancies, but a significant increase in both electrical insulation and activation energy of the ceramics was observed. The thermal activation mechanism is responsible for the high-temperature charge carrier transport. It is suggested that although the concentration of oxygen vacancies increase, Zn doping depresses the motion of oxygen vacancies in perovskite-like structure. The results provide a method to improve the insultation of high-temperature piezoelectric ceramics.

The current study is concerned with understanding the synthesis and application of the diversified BaS₃:La₂S₃:Dy_1.8 dithiocarbamate sulphide by the single source precursor (SSP) approach. Analytical approaches were used to evaluate the optical, crystalline, vibrational crosslinking, morphological, and thermal properties of BaS₃:La₂S₃:Dy_1.8 chalcogenide. The synthesized chalcogenide has an average crystallite size of 16.35 nm and mixed phases, with a direct band gap energy of 3.9 eV. The study of functional groups revealed the presence of metal sulphide bonds. In terms of morphology, BaS₃:La₂S₃:Dy_1.8 chalcogenide has an uneven shape with a small amount of aggregation. The electrochemical charge storage behavior of BaS₃:La₂S₃:Dy_1.8 was studied using a nickel foam electrode. The trichalcogenide-decorated electrode exhibited charge-storing behavior, with a specific capacitance of 723 F g^− 1 determined by cyclic voltammetry. The electrode has a specific power density of 11,166 W kg^− 1 and a low series resistance of 0.9 Ω, as shown by impedance measurements.