6,995 research outputs found
Particle collisions in the lower dimensional rotating black hole space-time with the cosmological constant
In this paper, we study the effect of ultra-high energy collisions of two
particles with different energies near the horizon of a 2+1 dimensional BTZ
black hole (BSW effect). We find that the particle with the critical angular
momentum could exist inside the outer horizon of BTZ black hole regardless of
the particle energy. Therefore, for the non-extremal BTZ black hole, the BSW
process is possible on the inner horizon with the fine tuning of parameters
which are characterized by the motion of particle. While for the extremal BTZ
black hole, the particle with the critical angular momentum could only exist on
the degenerate horizon, and the BSW process could also happen there.Comment: 12 pages,3 figure
What Powered the Optical Transient AT2017gfo Associated with GW170817?
The groundbreaking discovery of the optical transient AT2017gfo associated with GW170817 opens a unique opportunity to study the physics of double neutron star (NS) mergers. We argue that the standard interpretation of AT2017gfo as being powered by radioactive decay of r-process elements faces the challenge of simultaneously accounting for the peak luminosity and peak time of the event, as it is not easy to achieve the required high mass, and especially the low opacity of the ejecta required to fit the data. A plausible solution would be to invoke an additional energy source, which is probably provided by the merger product. We consider energy injection from two types of the merger products: (1) a post-merger black hole powered by fallback accretion; and (2) a long-lived NS remnant. The former case can only account for the early emission of AT2017gfo, with the late emission still powered by radioactive decay. In the latter case, both early- and late-emission components can be well interpreted as due to energy injection from a spinning-down NS, with the required mass and opacity of the ejecta components well consistent with known numerical simulation results. We suggest that there is a strong indication that the merger product of GW170817 is a long-lived (supramassive or even permanently stable), low magnetic field NS. The result provides a stringent constraint on the equations of state of NSs
Topolgical Charged Black Holes in Generalized Horava-Lifshitz Gravity
As a candidate of quantum gravity in ultrahigh energy, the
-dimensional Ho\v{r}ava-Lifshitz (HL) gravity with critical exponent
, indicates anisotropy between time and space at short distance. In the
paper, we investigate the most general Ho\v{r}ava-Lifshitz gravity in
arbitrary spatial dimension , with a generic dynamical Ricci flow parameter
and a detailed balance violation parameter . In arbitrary
dimensional generalized HL gravity with at long distance, we
study the topological neutral black hole solutions with general in
HL, as well as the topological charged black holes with
in HL. The HL gravity in the Lagrangian formulation
is adopted, while in the Hamiltonian formulation, it reduces to DiracDe
Witt's canonical gravity with . In particular, the topological
charged black holes in HL, HL, HL and
HL with are solved. Their asymptotical behaviors near the
infinite boundary and near the horizon are explored respectively. We also study
the behavior of the topological black holes in the -dimensional HL
gravity with gauge field in the zero temperature limit and finite
temperature limit, respectively. Thermodynamics of the topological charged
black holes with , including temperature, entropy, heat capacity,
and free energy are evaluated.Comment: 51 pages, published version. The theoretical framework of z=d HL
gravity is set up, and higher curvature terms in spatial dimension become
relevant at UV fixed point. Lovelock term, conformal term, new massive term,
and Chern-Simons term with different critical exponent z are studie
Discovery of gamma-ray emission from a strongly lobe-dominated quasar 3C 275.1
We systematically analyze the 6-year {\it Fermi}/LAT data of the
lobe-dominated quasars (LDQs) in the complete LDQ sample from 3CRR survey and
report the discovery of high-energy -ray emission from 3C 275.1. The
-ray emission of 3C 207 is confirmed and significant variability of the
lightcurve is identified. We do not find statistically significant -ray
emission from other LDQs. 3C 275.1 is the known -ray quasar with the
lowest core dominance parameter (i.e., ). We also show that both the
northern radio hotspot and parsec jet models can reasonably reproduce the
-ray data. The parsec jet model, however, is favored by the potential
-ray variability at the timescale of months. We suggest that some
dimmer -ray LDQs will be detected in the future and LDQs could
contribute non-negligibly to the extragalactic -ray background.Comment: 26 pages, 10 figures, 3 tables; ApJ in pres
Hybrid quantum device based on NV centers in diamond nanomechanical resonators plus superconducting waveguide cavities
We propose and analyze a hybrid device by integrating a microscale diamond
beam with a single built-in nitrogen-vacancy (NV) center spin to a
superconducting coplanar waveguide (CPW) cavity. We find that under an ac
electric field the quantized motion of the diamond beam can strongly couple to
the single cavity photons via dielectric interaction. Together with the strong
spin-motion interaction via a large magnetic field gradient, it provides a
hybrid quantum device where the dia- mond resonator can strongly couple both to
the single microwave cavity photons and to the single NV center spin. This
enables coherent information transfer and effective coupling between the NV
spin and the CPW cavity via mechanically dark polaritons. This hybrid
spin-electromechanical de- vice, with tunable couplings by external fields,
offers a realistic platform for implementing quantum information with single NV
spins, diamond mechanical resonators, and single microwave photons.Comment: Accepted by Phys. Rev. Applie
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