Time-Dependent Scalar Fields in Modified Gravities in a Stationary Spacetime

Most no-hair theorems involve the assumption that the scalar field is independent of time. Recently in [Phys. Rev. D90 (2014) 041501(R)] the existence of time-dependent scalar hair outside a stationary black hole in general relativity was ruled out. We generalize this work to modified gravities and non-minimally coupled scalar field with an additional assumption that the spacetime is axisymmetric. It is shown that in higher-order gravity such as metric $f(R)$ gravity the time-dependent scalar hair doesn't exist. While in Palatini $f(R)$ gravity and non-minimally coupled case the time-dependent scalar hair may exist.Comment: 6 pages, no figure

Dual accelerating Airy-Talbot recurrence effect

We demonstrate the dual accelerating Airy-Talbot recurrence effect, i.e., the self-imaging of accelerating optical beams, by propagating a superposition of Airy beams with successively changing transverse displacements. The dual Airy-Talbot effect is a spontaneous recurring imaging of the input and of the input with alternating component signs. It results from the constructive interference of Airy wave functions, which is also responsible for other kinds of Airy beams, for example, Airy breathers. An input composed of finite-energy Airy beams also displays the dual Airy-Talbot effect, but it demands a large transverse displacement and diminishes fast along the propagation direction.Comment: 7 pages, 3 figure

A Model for Residential Building Energy Consumption Characteristics and Energy Demand: A Case in Chongqing

AbstractThis study adopts a bottom-up typical method to establish the microscopic model to simulate the urban residential building energy consumption. The model is composed of a three-hierarchy structure: a) the classification according to the climate; b) according to the energy use; c) according to the energy intensity. Based on the model, energy consumption of urban residential building in Chongqing is calculated as an example. The calculation results of the model and the actual energy consumption are compared and validated. The residential building energy consumption model can be used to analyze the energy consumption in the past years using the existing data, as well as the development trend of the related factors so that the appropriate energy saving measures can be selected properly

Stochastic Electron Acceleration in Shell-Type Supernova Remnants II

We discuss the generic characteristics of stochastic particle acceleration by a fully developed turbulence spectrum and show that resonant interactions of particles with high speed waves dominate the acceleration process. To produce the relativistic electrons inferred from the broadband spectrum of a few well-observed shell-type supernova remnants in the leptonic scenario for the TeV emission, fast mode waves must be excited effectively in the downstream and dominate the turbulence in the subsonic phase. Strong collisionless non-relativistic astrophysical shocks are studied with the assumption of a constant Aflven speed. The energy density of non-thermal electrons is found to be comparable to that of the magnetic field. With reasonable parameters, the model explains observations of shell-type supernova remnants. More detailed studies are warranted to better understand the nature of supernova shocks.Comment: 5 pages, 7 figures, submitted to Proceedings of the Conference on "2008 Heidelberg International Symposium on High Energy Gamma-Ray Astronomy

Low hysteresis and large room temperature magnetocaloric effect of Gd 5Si2.05-xGe1.95-xNi2x (2x 0.08, 0.1) alloys

Gd5Si2.05-xGe1.95-xNi2x (2x ¼ 0.08, 0.1) alloys were prepared by arc melting followed by annealing at 1273 K for 96 h. Mixed monoclinic Gd5Si2Ge2-type phase, orthorhombic Gd5Si4-type phase, and a small amount of Gd5Si3-type phase were obtained in these alloys. Gd5Si2.01Ge1.91Ni0.08 alloy undergoes a second-order transition (TC) around 300 K, whereas Gd5Si2Ge1.9Ni0.1 alloy exhibits two II I transitions including a first-order transition (TC ) at rv295 K and second-order transition (TC ) at rv301 K. Ni substitution can effectively reduce the thermal hysteresis and magnetic hysteresis while max maintaining large magnetic entropy change. The maximum magnetic entropy changes (|DSM |) of 1 -1 Gd5Si2.05-xGe1.95-xNi2x alloys with 2x ¼ 0.08 and 0.1 are 4.4 and 5.0 J kg- K, respectively, for 0–2 T, and are 8.0 and 9.1 J kg-1 K-1, respectively, for 0–5 T. Low hysteresis performance and relatively large magnetic entropy change make these alloys favorable for magnetic refrigeration applications