32703258
Quasinormal modes of a black hole surrounded by quintessence
Using the third-order WKB approximation, we evaluate the quasinormal frequencies of massless scalar field perturbation around a black hole which is surrounded by static and spherically symmetric quintessence. Our result shows that due to the presence of quintessence, the scalar field damps more rapidly. Moreover, we also note that the quintessential state parameter (the ratio of pressure pq to the energy density ρq) plays an important role for the quasinormal frequencies. As the state parameter increases, so does the real part and the absolute value of the imaginary part decreases. This means that the scalar field decays more slowly in the larger quintessence case.
118567951
Phantom scalar emission in the Kerr black hole spacetime
We study the absorption probability and Hawking radiation spectra of a phantom scalar field in the Kerr black hole spacetime. We find that the presence of negative kinetic energy terms modifies the standard results in the graybody factor, super-radiance and Hawking radiation. Comparing with the usual scalar particle, the phantom scalar emission is enhanced in the black hole spacetime.
118654249
Particle acceleration on the background of the Kerr―Taub―NUT spacetime
Abstract We study the collision of two particles with the different rest masses moving in the equatorial plane of a Kerr–Taub–NUT spacetime and get the center-of-mass (CM) energy for the particles. We find that the CM energy depends not only on the rotation parameter, a , but also on the NUT charge of the Kerr–Taub–NUT spacetime, n . Especially, for the extremal Kerr–Taub–NUT spacetime, an unlimited CM energy can be approached if the parameter a is in the range [ 1 , 2 ] , which is different from that of the Kerr and Kerr–Newman black holes.
119127372
Rotating charged black hole with Weyl corrections
We present firstly a four-dimensional spherical symmetric black hole with small Weyl corrections and find that with increasing Weyl corrections the region of the event horizon existence for the black hole in the parameter space increases for the negative Weyl coupling parameter and decreases for the positive one. Moreover, we also obtain a rotating charged black hole with weak Weyl corrections by the method of complex coordinate transformation. Our results show that the sign of Weyl coupling parameter $\alpha$ yields the different spatial topology of the event horizons for the black hole with its parameters lied in some special regions in the parameter space. We also analyze the dependence of the ergosphere on the Weyl coupling parameter $\alpha$ and find that with the increase of the Weyl corrections the ergosphere in the equatorial plane becomes thick for a black hole with $\alpha>0$, but becomes thin in the case with $\alpha<0$, which means that the energy extraction become easier in the background of a black hole with the positive Weyl coupling parameter, but more difficult in the background of a black hole with the negative one.
119285485
$P-V$ criticality of AdS black hole in $f(R)$ gravity
We study thermodynamics of a charged AdS black hole in the special $f(R)$ correction with the constant Ricci scalar curvature. Our results show that the the $f(R)$ correction influences the Gibbs free energy and the phase transition of system. The ratio $\rho_c$ occurred at the critical point increases monotonically with the derivative term $f'(R_0)$. We also disclose that the critical exponents are the same as those of the liquid-gas phase transition in the Van der Waals model, which does not depend on the $f(R)$ correction considered here.
121869215
Dirac quasinormal modes of the Garfinkle-Horowitz-Strominger dilaton black-hole spacetime
Adopting the P?schl?Teller potential approximation, the quasinormal frequencies of the massless Dirac fields are evaluated in the Garfinkle?Horowitz?Strominger dilaton black-hole spacetime. We find that the real parts of the quasinormal frequencies increase as the orbital angular momentum k or a increases, where a is a parameter related to the dilaton field. The magnitude of imaginary parts decreases with k for the fixed a and overtone number n, while for fixed k and n, it is not a monotonic function of a and has a maximum at a point near a = 1.4?1.6, where the waves decay most rapidly. Another interesting feature is that the imaginary parts tend to zero and the real parts to k/2 as a approaches 2. We also find that the variation of the imaginary parts with the real parts in the Garfinkle?Horowitz?Strominger dilaton hole spacetimes is nonlinear, which becomes more complex than that in the Reissner?Nordstr?m black-hole spacetime.
117323209
Search for GRB counterparts using the ARGO‐YBJ experiment in shower mode
In this paper, the effective area of the ARGO‐YBJ experiment to detect the gamma rays with energy range from 10 GeV to 1 TeV for different incident zenith angles (0,10,20,30,40 degrees) is given respectively. The optimal event selections to search for GRB counterparts with different cutoff energy models (Ecut = 100 GeV and 1 TeV) are studied. Using these selections and their corresponding angular resolutions the searches are done within two hours around the GRB trigger time via different time windows. Finally, the result for the 20 GRBs in the field of view of ARGO between July 2006 and July 2008 is presented, and the fluence upper limit for each GRB is set at 99% confidence level.
119228301
The big bang and inflation united by an analytic solution
Exact analytic solutions for a class of scalar-tensor gravity theories with a hyperbolic scalar potential are presented. Using an exact solution we have successfully constructed a model of inflation that produces the spectral index, the running of the spectral index, and the amplitude of scalar perturbations within the constraints given by the WMAP 7 years data. The model simultaneously describes the big bang and inflation connected by a specific time delay between them so that these two events are regarded as dependent on each other. In solving the Friedmann equations, we have utilized an essential Weyl symmetry of our theory in 3+1 dimensions which is a predicted remaining symmetry of 2T-physics field theory in 4+2 dimensions. This led to a new method of obtaining analytic solutions in the 1T field theory which could in principle be used to solve more complicated theories with more scalar fields. Some additional distinguishing properties of the solution includes the fact that there are early periods of time when the slow-roll approximation is not valid. Furthermore, the inflaton does not decrease monotonically with time; rather, it oscillates around the potential minimum while settling down, unlike the slow-roll approximation. While the model we used for illustrationmore » purposes is realistic in most respects, it lacks a mechanism for stopping inflation. The technique of obtaining analytic solutions opens a new window for studying inflation, and other applications, more precisely than using approximations.« less
124511058
THE COUPLED RESONATOR MODEL AND THE DISTRIBUTION OF THE ELECTRIC FIELD ON THE AXIS IN THE PERIODIC CAVITY CHAIN. (IN CHINESE)
The Coupled resonator model and the distribution of the electric Field on the axisin the singly periodic cavity chain and biperiodic chain with full-cavity terminationsare analysed by Helmholtz Equation using the symmetry properties of the structure.It is another method to check coupled circuit theory. The results given in this paper forthe singly periodic cavity chain with full- cavity terminations was verified by a 600MHZ linac model of IHEP.
119179510
Properties and performance of two wide field of view Cherenkov/fluorescence telescope array prototypes
A wide field of view Cherenkov/fluorescence telescope array is one of the main components of the Large High Altitude Air Shower Observatory project. To serve as Cherenkov and fluorescence detectors, a flexible and mobile design is adopted for easy reconfiguring of the telescope array. Two prototype telescopes have been constructed and successfully run at the site of the ARGO-YBJ experiment in Tibet. The features and performance of the telescopes are presented. (C) 2010 Elsevier B.V. All rights reserved.
2001409
Molecular organization of Gram-negative peptidoglycan
The stress-bearing component of the bacterial cell wall—a multi-gigadalton bag-like molecule called the sacculus—is synthesized from peptidoglycan. Whereas the chemical composition and the 3-dimensional structure of the peptidoglycan subunit (in at least one conformation) are known, the architecture of the assembled sacculus is not. Four decades' worth of biochemical and electron microscopy experiments have resulted in two leading 3-D peptidoglycan models: “Layered” and “Scaffold”, in which the glycan strands are parallel and perpendicular to the cell surface, respectively. Here we resolved the basic architecture of purified, frozen-hydrated sacculi through electron cryotomography. In the Gram-negative sacculus, a single layer of glycans lie parallel to the cell surface, roughly perpendicular to the long axis of the cell, encircling the cell in a disorganized hoop-like fashion.