11090952
Cosmic ray threshold anomaly and kinematics in the dS spacetime
We present a covariant framework of kinematics in the dS spacetime, which is a natural postulate of recent astronomical observations ($\Lambda>0)$. One-particle states are presented explicitly. It is noticed that the dispersion relation of free particles is dependent on the degrees of freedom of angular momentum and spin. This fact can be referred to as the effects of the cosmological constant on kinematics of particles. The kinematics in dS spacetime is used to investigate the phenomenon of ultra high energy cosmic rays. We emphasize the possibility of solving the threshold anomalies of the interactions between ultra high energy cosmic rays and soft photons in the covariant framework of kinematics in the dS spacetime.
120446208
Construction and commissioning of the first wiggler at BEPC
Abstract The SRW1 at BEPC is under normal operation now. This article describes the construction and commissioning of the wiggler. Some experimental results are reported and suggestions for improvement are discussed.
195378147
Effects of cosmological constant on motion of UHECR particles
Recent astronomical observations manifest that about two-thirds of the whole energy in the Universe is contributed by a small positive cosmological constant Λ (>0). Then, an asymptotically de Sitter spacetime is premised naturally. However, physics in the de Sitter spacetime is very different from that in the Minkowski spacetime. As the first step, a covariant formalism of the kinematics in the de Sitter spacetime is presented here. By solving exactly the equations of motion for a field, we obtain the dispersion relation of a free particle. It is noticed that the dispersion relation is dependent on the degree of freedom of angular momentum of the particle. We show the threshold anomaly of the ultra high energy cosmic ray disappears naturally in the framework of the de Sitter kinematics.
118505725
Quasinormal modes of charged squashed Kaluza-Klein black holes in the Gödel universe
We study the quasinormal modes of scalar perturbation in the background of five-dimensional charged Kaluza-Klein black holes with squashed horizons immersed in the G\"odel universe. Besides the influence due to the compactness of the extra dimension, we disclose the cosmological rotational effect in the wave dynamics. The wave behavior affected by the G\"odel parameter provides an interesting insight into the G\"odel universe.
118397522
Gravitational field of a slowly rotating black hole with a phantom global monopole
We present a slowly rotating black hole solution with a phantom global monopole by solving Einstein's field equation and find that the presence of the global monopole changes the black hole structure. The metric coefficient gtϕ contains the hypergeometric function of the polar coordinate r, which is more complex than that in the usual slowly rotating black hole. The energy scale of symmetry breaking η affects the black hole horizon and the deficit solid angle. In particular, the solid angle is surplus rather than deficit for the black hole with the phantom global monopole. We also study the effects of the global monopole on the angular velocity of the horizon ΩH, Kepler's third law, the innermost stable circular orbit and the radiative efficiency ϵ in the thin accretion disc model. Our results also show that for a phantom black hole, the radiative efficiency ϵ is positive only in the case η ⩽ ηc. The threshold value ηc increases with the rotation parameter a.
119252617
Holographic superconductor models with $RF^{2}$ corrections
We investigate the effect of the RF 2 correction on the holographic superconductor model in the background of AdS black hole. We find that, similar to the effect caused by the Weyl correction, the higher RF 2 correction term can make it easier for the scalar operator to condense and result in the larger deviations from the expected relation in the gap frequency. However, if a non-trivial hair for the black hole has been triggered, we observe that the RF 2 correction and the Weyl correction do play different roles in the behavior of the condensation, which can be used to support the existing findings. PACS numbers: 11.25.Tq, 04.70.Bw, 74.20.-z ∗ panqiyuan@126.com † csb3752@hunnu.edu.cn ‡ jljing@hunnu.edu.cn
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.
119205704
Strong gravitational lensing in a noncommutative black-hole spacetime
Noncommutative geometry may be a starting point to a quantum gravity. We study the influence of the spacetime noncommutative parameter on the strong field gravitational lensing in the noncommutative Schwarzschild black-hole spacetime and obtain the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy can be described by this metric, we estimate the numerical values of the coefficients and observables for strong gravitational lensing. In comparison to the Reissner-Norstroem black hole, we find that the influences of the spacetime noncommutative parameter is similar to those of the charge, but these influences are much smaller. This may offer a way to distinguish a noncommutative black hole from a Reissner-Norstroem black hole, and may permit us to probe the spacetime noncommutative constant {theta} by the astronomical instruments in the future.