17,055 research outputs found
Features and stability analysis of non-Schwarzschild black hole in quadratic gravity
Black holes are found to exist in gravitational theories with the presence of
quadratic curvature terms and behave differently from the Schwarzschild
solution. We present an exhaustive analysis for determining the quasinormal
modes of a test scalar field propagating in a new class of black hole
backgrounds in the case of pure Einstein-Weyl gravity. Our result shows that
the field decay of quasinormal modes in such a non-Schwarzschild black hole
behaves similarly to the Schwarzschild one, but the decay slope becomes much
smoother due to the appearance of the Weyl tensor square in the background
theory. We also analyze the frequencies of the quasinormal modes in order to
characterize the properties of new back holes, and thus, if these modes can be
the source of gravitational waves, the underlying theories may be testable in
future gravitational wave experiments. We briefly comment on the issue of
quantum (in)stability in this theory at linear order.Comment: 18 pages, 4 figures, 1 table, several references added, version
published on JHE
Analysis and Improvement of a Threshold Signature Scheme Based on the General Access Structure
AbstractHua-wang Qin et al. proposed a novel threshold signature scheme based on the general access structure in order to break the applied limitation of the conventional threshold signature schemes. The security of the scheme was analyzed in this paper, and it is pointed out that the scheme is insecure because it cannot withstand conspiracy attacks and what's more, the identity of signer cannot be investigated. To overcome these security vulnerabilities, this paper proposed an improved threshold signature scheme, and the security analysis results show that the improved scheme can not only resist the conspiracy attack, but also have the properties of anonymity and traceability simultaneously
Interfacial thermal conductance in graphene/black phosphorus heterogeneous structures
Graphene, as a passivation layer, can be used to protect the black phosphorus
from the chemical reaction with surrounding oxygen and water. However, black
phosphorus and graphene heterostructures have low efficiency of heat
dissipation due to its intrinsic high thermal resistance at the interfaces. The
accumulated energy from Joule heat has to be removed efficiently to avoid the
malfunction of the devices. Therefore, it is of significance to investigate the
interfacial thermal dissipation properties and manipulate the properties by
interfacial engineering on demand. In this work, the interfacial thermal
conductance between few-layer black phosphorus and graphene is studied
extensively using molecular dynamics simulations. Two critical parameters, the
critical power Pcr to maintain thermal stability and the maximum heat power
density Pmax with which the system can be loaded, are identified. Our results
show that interfacial thermal conductance can be effectively tuned in a wide
range with external strains and interracial defects. The compressive strain can
enhance the interfacial thermal conductance by one order of magnitude, while
interface defects give a two-fold increase. These findings could provide
guidelines in heat dissipation and interfacial engineering for thermal
conductance manipulation of black phosphorus-graphene heterostructure-based
devices.Comment: 33 pages, 22 figure
Strong cosmic censorship for a black hole in loop quantum gravity
A fine gravitational theory is essentially expected to deal with the problem
of spacetime singularities. Loop quantum gravity as one branch of quantum
gravity is potential to explore the nature of black holes. Recently, according
to the quantum Oppenheimer-Snyder model in loop quantum cosmology, a novel loop
quantum corrected black hole in de Sitter spacetime has been discovered. Here,
we focus on examining the strong cosmic censorship(SCC) based on such a quantum
modified black hole by considering a massless neutral scalar field
perturbation. As a result, we find that the SCC is destroyed as the black hole
approaches to the near-extremal limit. Notably, the critical value of the black
hole mass ratio for such a violation increases with the increase of the
cosmological constant. It was implied the cosmological constant plays an
important role in moderating the violation of the SCC
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