81 research outputs found
Hawking Radiation of a Quantum Black Hole in an Inflationary Universe
The quantum stress-energy tensor of a massless scalar field propagating in
the two-dimensional Vaidya-de Sitter metric, which describes a classical model
spacetime for a dynamical evaporating black hole in an inflationary universe,
is analyzed. We present a possible way to obtain the Hawking radiation terms
for the model with arbitrary functions of mass. It is used to see how the
expansion of universe will affect the dynamical process of black hole
evaporation. The results show that the cosmological inflation has an
inclination to depress the black hole evaporation. However, if the cosmological
constant is sufficiently large then the back-reaction effect has the
inclination to increase the black hole evaporation. We also present a simple
method to show that it will always produce a divergent flux of outgoing
radiation along the Cauchy horizon where the curvature is a finite value. This
means that the Hawking radiation will be very large in there and shall modify
the classical spacetime drastically. Therefore the black hole evaporation
cannot be discussed self-consistently on the classical Vaidya-type spacetime.
Our method can also be applied to analyze the quantum stress-energy tensor in
the more general Vaidya-type spacetimes.Comment: Proper boundary will lead to anti-evaporation of schwarzschild-de
Sitter black holes, as corrected in Class. Quantum Grav. 11 (1994) 28
Reproductive exocrine and endocrine profile of female langur monkeys, Presbytis entellus
In 5 caged langurs menstrual cycle length (for 125 cycles) varied from 18 to 45 days with a mean ± s.d. of 26·3 ± 3·6 days. Menstruation lasted for 2 days. A distinct cycle of vaginal smear cells was observed with a maximum cornification on Day 10 coinciding with the serum oestradiol peak. A monophasic pattern of vaginal temperature with a significant nadir on Day 11, 1 day after the oestradiol peak, was observed. Serum sialic acid concentrations directly reflected the oestrogenic activity and showed a significant peak on Day 10, coinciding with the oestradiol peak and was followed by a progesterone rise. Langurs menstruated throughout the year without showing any sign of summer amenorrhoea. We suggest that maximum cornification, vaginal temperature nadir and serum sialic acid peak could be used as markers for prediction and detection of the time of ovulation in langur monkeys
Functional recombinant antibodies against human chorionic gonadotropin expressed in plants
Single-chain variable fragments, diabodies and chimeric antibodies (mouse variable domains and human immunoglobulin constant domains) were engineered by DNA recombinant technique and expressed transiently in tobacco leaves. The plants expressed the three types of antigen-binding moieties, accurately and faithfully. The yield obtained was 32 mg, 40 mg and 20 mg respectively, per kg of wet weight of leaves. The chimeric antibody had high affinity for human chorionic gonadotropin (Ka=1.9Ă1010Mâ1). All three forms of the recombinant antibodies expressed by plants inhibited the binding of hCG to receptor on Leydig cells
Benzothiazol-2-yl-hydrazone derivatives as potential antioxidant agents
A series of benzothiazol-2-yl-hydrazone derivatives (4a-i) have been synthesized and characterized using elemental analysis, FT-IR, 1H-NMR and Mass spectroscopy techniques. The synthesized compounds have been screened for antioxidant activity by DPPH radical scavenging activity method. The compounds bearing methoxy substitution4c, 4e, 4f, 4g, 4h and 4i have shown promising antioxidant activity, better than the standard drug ascorbic acid
Behavior of Quasilocal Mass Under Conformal Transformations
We show that in a generic scalar-tensor theory of gravity, the ``referenced''
quasilocal mass of a spatially bounded region in a classical solution is
invariant under conformal transformations of the spacetime metric. We first
extend the Brown-York quasilocal formalism to such theories to obtain the
``unreferenced'' quasilocal mass and prove it to be conformally invariant. The
appropriate reference term in this case is defined by generalizing the
Hawking-Horowitz prescription, which was originally proposed for general
relativity. For such a choice of reference term, the referenced quasilocal mass
for a general spacetime solution is obtained. This expression is shown to be a
conformal invariant provided the conformal factor is a monotonic function of
the scalar field. We apply this expression to the case of static spherically
symmetric solutions with arbitrary asymptotics to obtain the referenced
quasilocal mass of such solutions. Finally, we demonstrate the conformal
invariance of our quasilocal mass formula by applying it to specific cases of
four-dimensional charged black hole spacetimes, of both the asymptotically flat
and non-flat kinds, in conformally related theories.Comment: LaTeX, 31 pages, one ps figur
Scalar Field Quantum Inequalities in Static Spacetimes
We discuss quantum inequalities for minimally coupled scalar fields in static
spacetimes. These are inequalities which place limits on the magnitude and
duration of negative energy densities. We derive a general expression for the
quantum inequality for a static observer in terms of a Euclidean two-point
function. In a short sampling time limit, the quantum inequality can be written
as the flat space form plus subdominant correction terms dependent upon the
geometric properties of the spacetime. This supports the use of flat space
quantum inequalities to constrain negative energy effects in curved spacetime.
Using the exact Euclidean two-point function method, we develop the quantum
inequalities for perfectly reflecting planar mirrors in flat spacetime. We then
look at the quantum inequalities in static de~Sitter spacetime, Rindler
spacetime and two- and four-dimensional black holes. In the case of a
four-dimensional Schwarzschild black hole, explicit forms of the inequality are
found for static observers near the horizon and at large distances. It is show
that there is a quantum averaged weak energy condition (QAWEC), which states
that the energy density averaged over the entire worldline of a static observer
is bounded below by the vacuum energy of the spacetime. In particular, for an
observer at a fixed radial distance away from a black hole, the QAWEC says that
the averaged energy density can never be less than the Boulware vacuum energy
density.Comment: 27 pages, 2 Encapsulated Postscript figures, uses epsf.tex, typeset
in RevTe
Radiative falloff in Schwarzschild-de Sitter spacetime
We consider the time evolution of a scalar field propagating in
Schwarzschild-de Sitter spacetime. At early times, the field behaves as if it
were in pure Schwarzschild spacetime; the structure of spacetime far from the
black hole has no influence on the evolution. In this early epoch, the field's
initial outburst is followed by quasi-normal oscillations, and then by an
inverse power-law decay. At intermediate times, the power-law behavior gives
way to a faster, exponential decay. At late times, the field behaves as if it
were in pure de Sitter spacetime; the structure of spacetime near the black
hole no longer influences the evolution in a significant way. In this late
epoch, the field's behavior depends on the value of the curvature-coupling
constant xi. If xi is less than a critical value 3/16, the field decays
exponentially, with a decay constant that increases with increasing xi. If xi >
3/16, the field oscillates with a frequency that increases with increasing xi;
the amplitude of the field still decays exponentially, but the decay constant
is independent of xi.Comment: 10 pages, ReVTeX, 5 figures, references updated, and new section
adde
Observational constraints on phantom power-law cosmology
We investigate phantom cosmology in which the scale factor is a power law,
and we use cosmological observations from Cosmic Microwave Background (CMB),
Baryon Acoustic Oscillations (BAO) and observational Hubble data, in order to
impose complete constraints on the model parameters. We find that the power-law
exponent is , while the Big Rip is realized
at Gyr, in 1 confidence level.
Providing late-time asymptotic expressions, we find that the dark-energy
equation-of-state parameter at the Big Rip remains finite and equal to
, with the dark-energy density and pressure diverging.
Finally, we reconstruct the phantom potential.Comment: 11 pages, 1 figure, version published at Phys. Lett. B Minor
correction in introductory sectio
On exact solutions for quantum particles with spin S= 0, 1/2, 1 and de Sitter event horizon
Exact wave solutions for particles with spin 0, 1/2 and 1 in the static
coordinates of the de Sitter space-time model are examined in detail. Firstly,
for a scalar particle, two pairs of linearly independent solutions are
specified explicitly: running and standing waves. A known algorithm for
calculation of the reflection coefficient on the background of
the de Sitter space-time model is analyzed. It is shown that the determination
of R_{\epsilon j} requires an additional constrain on quantum numbers \epsilon
\rho / \hbar c >> j, where \rho is a curvature radius. When taken into account
of this condition, the R_{\epsilon j} vanishes identically. It is claimed that
the calculation of the reflection coefficient R_{\epsilon j} is not required at
all because there is no barrier in an effective potential curve on the
background of the de Sitter space-time. The same conclusion holds for arbitrary
particles with higher spins, it is demonstrated explicitly with the help of
exact solutions for electromagnetic and Dirac fields.Comment: 30 pages. This paper is an updated and more comprehensive version of
the old paper V.M. Red'kov. On Particle penetrating through de Sitter
horizon. Minsk (1991) 22 pages Deposited in VINITI 30.09.91, 3842 - B9
The global burden of cancer attributable to risk factors, 2010-19: a systematic analysis for the Global Burden of Disease Study 2019
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