673 research outputs found
The causal structure of dynamical charged black holes
We study the causal structure of dynamical charged black holes, with a
sufficient number of massless fields, using numerical simulations. Neglecting
Hawking radiation, the inner horizon is a null Cauchy horizon and a curvature
singularity due to mass inflation. When we include Hawking radiation, the inner
horizon becomes space-like and is separated from the Cauchy horizon, which is
parallel to the out-going null direction. Since a charged black hole must
eventually transit to a neutral black hole, we studied the neutralization of
the black hole and observed that the inner horizon evolves into a space-like
singularity, generating a Cauchy horizon which is parallel to the in-going null
direction. Since the mass function is finite around the inner horizon, the
inner horizon is regular and penetrable in a general relativistic sense.
However, since the curvature functions become trans-Planckian, we cannot
saymore about the region beyond the inner horizon, and it is natural to say
that there is a 'physical' space-like singularity. However, if we assume an
exponentially large number of massless scalar fields, our results can be
extended beyond the inner horizon. In this case, strong cosmic censorship and
black hole complementarity can be violated.Comment: 23 pages, 23 figure
The horizon-entropy increase law for causal and quasi-local horizons and conformal field redefinitions
We explicitly prove the horizon-entropy increase law for both causal and
quasi-locally defined horizons in scalar-tensor and gravity theories.
Contrary to causal event horizons, future outer trapping horizons are not
conformally invariant and we provide a modification of trapping horizons to
complete the proof, using the idea of generalised entropy. This modification
means they are no longer foliated by marginally outer trapped surfaces but
fixes the location of the horizon under a conformal transformation. We also
discuss the behaviour of horizons in "veiled" general relativity and show,
using this new definition, how to locate cosmological horizons in flat
Minkowski space with varying units, which is physically identified with a
spatially flat FLRW spacetime.Comment: 23 page
The no-boundary measure in scalar-tensor gravity
In this article, we study the no-boundary wave function in scalar-tensor
gravity with various potentials for the non-minimally coupled scalar field. Our
goal is to calculate probabilities for the scalar field - and hence the
effective gravitational coupling and cosmological constant - to take specific
values. Most calculations are done in the minisuperspace approximation, and we
use a saddle point approximation for the Euclidean action, which is then
evaluated numerically. We find that for potentials that have several minima,
none of them is substantially preferred by the quantum mechanical
probabilities. We argue that the same is true for the stable and the runaway
solution in the case of a dilaton-type potential. Technically, this is due to
the inclusion of quantum mechanical effects (fuzzy instantons). These results
are in contrast to the often held view that vanishing gravitation or
cosmological constants would be exponentially preferred in quantum cosmology,
and they may be relevant to the cosmological constant problem and the dilaton
stabilization problem.Comment: 31 pages, 9 figure
Can the Horowitz-Maldacena proposal be an alternative to the firewall?
Recently, there have been discussions that black hole complementarity is
inconsistent and that the firewall is required to prohibit the observation of
duplicated information. It is thought that if the Horowitz-Maldacena proposal
works as a selection principle, then this may be an alternative to the
firewall. In this paper, we first point out that the Horowitz-Maldacena
proposal seems to help black hole complementarity for charged black holes.
However, if we consider the Hayden-Preskill argument further, which states that
a black hole can function as an information mirror after the information
retention time, then we can show that the Horowitz-Maldaceana proposal cannot
help black hole complementarity. This can be extended to neutral black hole
cases. Therefore, in conclusion, we find that dynamical black holes do not
respect complementarity, even with the Horowitz-Maldacena proposal.Comment: 11 pages, 3 figure
Insights into the Second Law of Thermodynamics from Anisotropic Gas-Surface Interactions
Thermodynamic implications of anisotropic gas-surface interactions in a
closed molecular flow cavity are examined. Anisotropy at the microscopic scale,
such as might be caused by reduced-dimensionality surfaces, is shown to lead to
reversibility at the macroscopic scale. The possibility of a self-sustaining
nonequilibrium stationary state induced by surface anisotropy is demonstrated
that simultaneously satisfies flux balance, conservation of momentum, and
conservation of energy. Conversely, it is also shown that the second law of
thermodynamics prohibits anisotropic gas-surface interactions in "equilibrium",
even for reduced dimensionality surfaces. This is particularly startling
because reduced dimensionality surfaces are known to exhibit a plethora of
anisotropic properties. That gas-surface interactions would be excluded from
these anisotropic properties is completely counterintuitive from a causality
perspective. These results provide intriguing insights into the second law of
thermodynamics and its relation to gas-surface interaction physics.Comment: 28 pages, 11 figure
Comparison and Correlation Analysis of Different Swine Breeds Meat Quality
This study was performed to determine the influence of pig breed and gender on the ultimate pH and physicochemical properties of pork. The correlations between pH and pork quality traits directly related to carcass grade, and consumer’s preference were also evaluated. The pH and meat grading scores for cold carcasses of 215 purebred pigs (Duroc, Landrace, and Yorkshire) from four different farms were obtained. Meat quality parameters of the pork loin were analyzed. Duroc and female animals were more affected compared to other breeds and male pigs. Duroc animals had the highest ultimate pH, carcass back fat thickness, marbling scores, yellowness, and fat content (p<0.05). Landrace pigs had the highest color lightness and cooking loss values (p<0.05). Among all trait parameters, marbling scores showed the highest significant differences when evaluating the impact of breed and gender on meat quality characteristics (p<0.001). Ultimate pH was positively correlated with carcass weight (0.20), back fat thickness (0.19), marbling score (0.17), and color score (0.16) while negatively correlated with cooking loss (−0.24) and shear force (−0.20). Therefore, pork samples with lower ultimate pH had lower cooking loss, higher lightness, and higher shear force values irrespective of breed
The Ligand Binding Domain of GCNF Is Not Required for Repression of Pluripotency Genes in Mouse Fetal Ovarian Germ Cells
In mice, successful development and reproduction require that all cells, including germ cells, transition from a pluripotent to a differentiated state. This transition is associated with silencing of the pluripotency genes Oct4 and Nanog. Interestingly, these genes are repressed at different developmental timepoints in germ and somatic cells. Ovarian germ cells maintain their expression until about embryonic day (E) 14.5, whereas somatic cells silence them much earlier, at about E8.0. In both somatic cells and embryonic stem cells, silencing of Oct4 and Nanog requires the nuclear receptor GCNF. However, expression of the Gcnf gene has not been investigated in fetal ovarian germ cells, and whether it is required for silencing Oct4 and Nanog in that context is not known. Here we demonstrate that Gcnf is expressed in fetal ovarian germ cells, peaking at E14.5, when Oct4 and Nanog are silenced. However, conditional ablation of the ligand-binding domain of Gcnf using a ubiquitous, tamoxifen-inducible Cre indicates that Gcnf is not required for the down-regulation of pluripotency genes in fetal ovarian germ cells, nor is it required for initiation of meiosis and oogenesis. These results suggest that the silencing of Oct4 and Nanog in germ cells occurs via a different mechanism from that operating in somatic cells during gastrulation.Howard Hughes Medical InstituteNational Institutes of Health (U.S.) (2R01HG00257-20)National Human Genome Research Institute (U.S.) (2R01HG00257-20
Stereochemical and Skeletal Diversity Arising from Amino Propargylic Alcohols
An efficient synthetic pathway to the possible stereoisomers of skeletally diverse heterocyclic small molecules is presented. The change in shape brought about by different intramolecular cyclizations of diastereoisomeric amino propargylic alcohols is quantified using principal moment-of-inertia (PMI) shape analysis.Chemistry and Chemical Biolog
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