1,507 research outputs found
Generic features of Einstein-Aether black holes
We reconsider spherically symmetric black hole solutions in Einstein-Aether
theory with the condition that this theory has identical PPN parameters as
those for general relativity, which is the main difference from the previous
research. In contrast with previous study, we allow superluminal propagation of
a spin-0 Aether-gravity wave mode. As a result, we obtain black holes having a
spin-0 "horizon" inside an event horizon. We allow a singularity at a spin-0
"horizon" since it is concealed by the event horizon. If we allow such a
configuration, the kinetic term of the Aether field can be large enough for
black holes to be significantly different from Schwarzschild black holes with
respect to ADM mass, innermost stable circular orbit, Hawking temperature, and
so on. We also discuss whether or not the above features can be seen in more
generic vector-tensor theories.Comment: 9 pages, 9 figures, basic equations and their analytic arguments are
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Born-Infeld black holes coupled to a massive scalar field
Born-Infeld black holes in the Scalar-Tensor Theories of Gravity, in the case
of massless scalar field, have been recently obtained. The aim of the current
paper is to study the effect from the inclusion of a potential for the scalar
field in the theory, through a combination of analytical techniques and
numerical methods. The black holes coupled to a massive scalar field have
richer causal structure in comparison to the massless scalar field case. In the
latter case, the black holes may have a second, inner horizon. The presence of
potential for the scalar field allows the existence of extremal black holes for
certain values of the mass of the scalar field and the magnetic (electric)
charge of the black hole. The linear stability against spherically symmetric
perturbations is studied. Arguments in favor of the general stability of the
solutions coming from the application of the "turning point" method are also
presented.Comment: 26 pages, 16 figure
Flattened 1D fragments of fullerene C₆₀ that exhibit robustness toward multi-electron reduction
フラーレンに迫る電子受容能をもつ平坦な一次元π共役炭化水素の開発. 京都大学プレスリリース. 2023-05-15.Flat fullerene fragments attractive to electrons. 京都大学プレスリリース. 2023-06-01.Fullerenes are compelling molecular materials owing to their exceptional robustness toward multi-electron reduction. Although scientists have attempted to address this feature by synthesizing various fragment molecules, the origin of this electron affinity remains unclear. Several structural factors have been suggested, including high symmetry, pyramidalized carbon atoms, and five-membered ring substructures. To elucidate the role of the five-membered ring substructures without the influence of high symmetry and pyramidalized carbon atoms, we herein report the synthesis and electron-accepting properties of oligo(biindenylidene)s, a flattened one-dimensional fragment of fullerene C₆₀. Electrochemical studies corroborated that oligo(biindenylidene)s can accept electrons up to equal to the number of five-membered rings in their main chains. Moreover, ultraviolet/visible/near-infrared absorption spectroscopy revealed that oligo(biindenylidene)s exhibit enhanced absorption covering the entire visible region relative to C₆₀. These results highlight the significance of the pentagonal substructure for attaining stability toward multi-electron reduction and provide a strategy for the molecular design of electron-accepting π-conjugated hydrocarbons even without electron-withdrawing groups
Improvement of exercise capacity by sarpogrelate as a result of increased collateral blood flow in patients with effort angina
Detector decoy quantum key distribution
Photon number resolving detectors can enhance the performance of many
practical quantum cryptographic setups. In this paper, we employ a simple
method to estimate the statistics provided by such a photon number resolving
detector using only a threshold detector together with a variable attenuator.
This idea is similar in spirit to that of the decoy state technique, and is
specially suited for those scenarios where only a few parameters of the photon
number statistics of the incoming signals have to be estimated. As an
illustration of the potential applicability of the method in quantum
communication protocols, we use it to prove security of an entanglement based
quantum key distribution scheme with an untrusted source without the need of a
squash model and by solely using this extra idea. In this sense, this detector
decoy method can be seen as a different conceptual approach to adapt a single
photon security proof to its physical, full optical implementation. We show
that in this scenario the legitimate users can now even discard the double
click events from the raw key data without compromising the security of the
scheme, and we present simulations on the performance of the BB84 and the
6-state quantum key distribution protocols.Comment: 27 pages, 7 figure
Equivalence of black hole thermodynamics between a generalized theory of gravity and the Einstein theory
We analyze black hole thermodynamics in a generalized theory of gravity whose
Lagrangian is an arbitrary function of the metric, the Ricci tensor and a
scalar field. We can convert the theory into the Einstein frame via a
"Legendre" transformation or a conformal transformation. We calculate
thermodynamical variables both in the original frame and in the Einstein frame,
following the Iyer--Wald definition which satisfies the first law of
thermodynamics. We show that all thermodynamical variables defined in the
original frame are the same as those in the Einstein frame, if the spacetimes
in both frames are asymptotically flat, regular and possess event horizons with
non-zero temperatures. This result may be useful to study whether the second
law is still valid in the generalized theory of gravity.Comment: 14 pages, no figure
Crystal Field Triplets: A New Route to Non-Fermi Liquid Physics
A model for crystal field triplet ground states on rare earth or actinide
ions with dipolar and quadrupolar couplings to conduction electrons is studied
for the first time with renormalization group methods. The quadrupolar coupling
leads to a new nontrivial, non-Fermi liquid fixed point, which survives in an
intermediate valence Anderson model. The calculated magnetic susceptibility
displays one parameter scaling, going as ()
at intermediate temperatures, reminiscent of the non-Fermi liquid alloy
UCu_{5-x}Pd_x.Comment: 4 pages, 3 figures, REVTe
Extreme viral partitioning in a marine-derived High Arctic lake
ABSTRACT
High-latitude, perennially stratified (meromictic) lakes are likely to be especially vulnerable to climate warming because of the importance of ice in maintaining their water column structure and associated distribution of microbial communities. This study aimed to characterize viral abundance, diversity, and distribution in a meromictic lake of marine origin on the far northern coast of Ellesmere Island, in the Canadian High Arctic. We collected triplicate samples for double-stranded DNA (dsDNA) viromics from five depths that encompassed the major features of the lake, as determined by limnological profiling of the water column. Viral abundance and virus-to-prokaryote ratios were highest at greater depths, while bacterial and cyanobacterial counts were greatest in the surface waters. The viral communities from each zone of the lake defined by salinity, temperature, and dissolved oxygen concentrations were markedly distinct, suggesting that there was little exchange of viral types among lake strata. Ten viral assembled genomes were obtained from our libraries, and these also segregated with depth. This well-defined structure of viral communities was consistent with that of potential hosts. Viruses from the monimolimnion, a deep layer of ancient Arctic Ocean seawater, were more diverse and relatively abundant, with few similarities to available viral sequences. The Lake A viral communities also differed from published records from the Arctic Ocean and meromictic Ace Lake in Antarctica. This first characterization of viral diversity from this sentinel environment underscores the microbial richness and complexity of an ecosystem type that is increasingly exposed to major perturbations in the fast-changing Arctic.
IMPORTANCE
The Arctic is warming at an accelerating pace, and the rise in temperature has increasing impacts on the Arctic biome. Lakes are integrators of their surroundings and thus excellent sentinels of environmental change. Despite their importance in the regulation of key microbial processes, viruses remain largely uncharacterized in Arctic lacustrine environments. We sampled a highly stratified meromictic lake near the northern limit of the Canadian High Arctic, a region in rapid transition due to climate change. We found that the different layers of the lake harbored viral communities that were strikingly dissimilar and highly divergent from known viruses. Viruses were more abundant in the deepest part of the lake containing ancient Arctic Ocean seawater that was trapped during glacial retreat and were genomically unlike any viruses previously described. This research demonstrates the complexity and novelty of viral communities in an environment that is vulnerable to ongoing perturbation
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