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ARCHIVE
2004
Seminar Number
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Seminar Date
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Speaker(s)
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Title and Abstract
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| No.142 |
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| No.141 |
August,
10
|
A. Klypin
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Dark Matter Halo
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| No.140 |
June,
30
|
S.Kopeykin,
I.Vlasov
|
Equation
of Motion of Extended Objects in
Post-Newton Formalism with Two Parameters and Case of
Spherically Symmetric Bodies
Abstract
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| No.139 |
June,
23
|
Nobuyuki
Sakai
(Yamagata University, Japan) |
Hybrid
Monopole
Inflation and Massive Black-Hole Formation
We study the dynamics
of magnetic monopoles in hybrid inflation. If the vacuum expectation
value is of large enough, massive (astronomical-sized) black holes are
created. We therefore expect the scenario that astronomical black holes
( say, MACHOs) could be formed in the early universe. However, the mass
density of those black holes are so large that the universe after
inflation becomes too inhomogeneous. Hence, our attempt does not
succeed in the original model of hybrid inflation. Instead, this gives
another constraint on the model.
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| No.138 |
June,
16
|
D.V.Nesterov,
A.O.Barvinsky
(Lebedev Physical
Institute, Moscow) |
Effective equations
in quantum cosmology of the early universe, braneworld effective
action and new nonperturbative methods for
effective action
We develop a general
framework for effective equations of expectation values in quantum
cosmology and pose for them the quantum Cauchy problem with no-boundary
and
tunneling wavefunctions. Cosmological configuration space is decomposed
into two sectors (field-theoretical sector of inhomogeneous modes
and quantum mechanical sector of spatially homogeneous modes)
that give qualitatively different contributions to the radiation
currents in effective equations. We apply this framework in the model
with a
big negative nonminimal coupling of inflaton, which incorporatesa low
energy (GUT scale) mechanism of the quantum origin of the inflationary
Universe and study the effects of quantum inflaton mode. Also we
develop
general "holographic" formalism for constructing the effective action
in
models with branes. In this approach the effective action turns out to
be the functional of "brane" fields which have direct physical and
geometrical meaning for observers living on branes. We apply these
algorithms to two-brane Randall-Sundrum like models with curved branes
imbedded into antideSitter bulk. Also we show that two different
calculational methods we used, lead to the same result for the
effective action due
to nontrivial relation between special boundary operators related to
different boundary value problems in the bulk.
|
| No.137 |
May, 19 |
V.V.Kiselev
(IHEP,
Protvino)
|
Vector
field as a
quintessence partner and a dark matter
We derive generic
equations for a vector field driving the evolution of flat homogeneous
isotropic universe and give a comparison with a scalar filed dynamics
in the cosmology. Two exact solutions are shown as examples, which can
serve to describe an inflation and a slow falling down of dynamical
``cosmological constant'' like it is given by the scalar quintessence.
An attractive feature of vector field description is a generation of
``induced mass'' proportional to a Hubble constant, which result
in a dynamical suppression of actual cosmological constant during the
evolution.
We study equations of
a non-gauge vector field in a spherically
symmetric static metric. The constant vector field with a scale
arrangement of components: the temporal component about the Planck mass
$m_{\rm Pl}$ and the radial component about $M$ suppressed with respect
to the Planck mass, serves as a source of metric reproducing flat
rotation curves in dark halos of spiral galaxies, so that the velocity
of rotation $v_0$ is determined by the hierarchy of scales: $
\sqrt{2}\, v_0^2= M/m_{\rm Pl}$, and $M\sim10^{12}$ GeV. A natural
estimate of Milgrom's acceleration about the Hubble rate is
obtained.
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| No.136 |
March,
31
|
V.R.Gavrilov,
V.N.Melnikov,
S.T.Abdyrakhmanov |
Friedmann
universe
with dust and scalar field
We study a spatially flat
Friedmann model containing a
pressureless perfect fluid (dust) and a scalar field with
an unbounded from below potential of the form $ V(\fii) =
W_0
- V_0\sinh(\sqrt{3/2}\kappa\fii) $, where the parameters $ W_0 $
and
$V_0$ are arbitrary and $ \kappa=\sqrt{8\pi
G_N} = M_p^{-1} $. The model is integrable and all exact
solutions
describe then recollapsing
universe. The behavior of the model
near both initial and final points of evolution is
analyzed. The model is
consistent with the observational
parameters. We single out the exact
solution with the present-day values of acceleration parameter
$q_0=0.5$ and dark matter density paramete $ \Omega_{\rho 0}=0.3 $
describing the evolution within the time approximately equal to
$2H_0^{-1}$.
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| No.135 |
March,
17 |
V.B.
Semikoz,
D.D.
Sokoloff |
Large-scale
magnetic field generation by $\alpha$-effect driven by collective
neutrino-plasma
interaction
We suggest a new
mechanism
for generation of large-scale magnetic field in the hot plasma of early
universe
which is based on the parity violation in weak interactions and depends
neither
on helicity of matter turbulence resulting in the standard
$\alpha$-effect
nor on general rotation. The mechanism can result in a self-excitation
of
an (almost) uniform cosmological magnetic field.
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No.134
|
February, 25
|
E. Babichev,
V.
Dokuchaev and
Yu. Eroshenko
(INR RAS)
|
Dissolution
of black holes in phantom energy
Solution for a
stationary accretion of the relativistic perfect fluid with an equation
of state $p(\rho)$ onto the Schwarzschild black hole is presented. This
solution is a generalization of Michel solution and applicable to the
problem of dark energy accretion. It is shown that accretion of phantom
energy is accompanied by the gradual decrease of the black hole mass.
Masses of all black holes tend to zero in the phantom energy universe
approaching to the Big Rip.
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No.133
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February,18
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A. Toporensky (SAI MSU)
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Some
aspects of Loop Quantum Gravity
I review some
aspects
of Loop Quantum Gravity in comparison with String Theory, as well as
morden
attempts of LQG applications to cosmology and high-energy astrophysics.
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No.132
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February,4
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K.A.Bronnikov, B.E.Meierovich
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Self-Gravitating Global Monopole and Nonsingular
Cosmology
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