30 research outputs found
Cosmological Model in 2d Dilaton Gravity
We apply CGHS-type dilaton gravity model to (1+1)-dimensional cosmological
situations.
First the behavior of a compact 1-dimensional universe (i.e. like a closed
string) is classified on the assumption of homogeneity of universe.
Several interesting solutions are found, which include a Misner-type universe
having closed time-like curves, and an asymptotically de Sitter universe first
pointed out by Yoshimura.
In the second half of this talk, we discuss the modification of the classical
homogeneous solutions, considering inhomogeneity of classical conformal matters
and also quantum back-reaction respectively.
(An expanded version of the talk presented by T. Mishima at Yukawa Institute
of Theoretical Physics workshop `Quantum Gravity' 24-27, November 1992.)Comment: 20 pages, phyzzx, TIT/HEP-225/COSMO-3
Physics of quantum measurement and its interdisciplinary applications
Quantum dynamics of the collective mode and individual particles on a ring is
studied as the simplest model of projective quantum measurement. In this model,
the collective mode measures an individual single quantum system. The heart of
the model is the wide separation of time scales which yields the distinction of
classical and quantum degrees of freedom beyond the standard Gross-Pitaevskii
equation. In some restricted cases we derive the Born probability rule. This
model is the quantum mechanics version of the effective action method in
quantum field theory, which describes the origin of the primordial density
fluctuation as classical variables. It turns out that the classical version of
this same model successfully describes the dynamics of geomagnetic variation
including the polarity flips over 160 million years. The essence of this
description is again the coexistence of the wide separated time scales.Comment: 8 pages, 6 figure
CO (J=1-0) Observation of the cD Galaxy of AWM7: Constraints on the Evaporation of Molecular Gas
We have searched for molecular gas in the cD galaxy of a poor cluster of
galaxies AWM7 using Nobeyama 45 m telescope. We do not detect CO emission in
the galaxy. Our limit of molecular gas in the inner 7.5 kpc is M_H_2< 4 x 10^8
M_sun. We estimate the total mass of molecular gas left in the cD galaxy when
the gas deposited by a cooling flow once becomes molecular gas and the
molecular gas is continuously evaporated by the ambient hot gas. The
observational limit of molecular gas requires f >~ 10^{-3}, where f is the
ratio of the heat conduction rate to that of Spitzer. However, this contradicts
recent X-ray observations showing f<10^{-5}. Thus, the non-detection of CO
cannot be explained by the evaporation, and most of the cooled gas predicted by
a cooling flow model may not change into molecular gas in the cD galaxy.
Moreover, we estimate the evaporation time of molecular clouds brought to a cD
galaxy through the capture of gas-rich galaxies and find that these clouds
should not be evaporated if f <~ 10^{-3}-10^{-4}. Therefore, the non-detection
of CO in a cD galaxy could constrain the total mass of the molecular clouds
brought into it.Comment: 5 pages, 1 figure, to be published in PAS
Seismic 1/f Fluctuations from Amplitude Modulated Earth's Free Oscillation
We first report that the seismic data from around the world yield 1/f
fluctuations if we exclude giant earthquakes. We investigate the origin of this
1/f fluctuation based on our recent proposal: 1/f noise is amplitude modulation
and demodulation. We speculate that this amplitude modulation is encoded by the
resonance with the Earth Free Oscillation (EFO) and demodulated by fault
rupture. We partially demonstrate this scenario by analyzing the EFO
eigenmodes. We briefly describe possible verifications of our theory of 1/f
fluctuations based on EFO.Comment: 6 pages, 6 figure
New Vector Field and BRST Charges in 2-form Einstein Gravity
A new vector field is introduced into 2-form Einstein gravity in four
dimensions to restore a large symmetry of its topological version. Two
different expressions for the BRST charge are given in the system: one of them
associated with a set of irreducible symmetries and the other with a set of
on-shell reducible symmetries.Comment: 9 pages, phyzzx, TIT/HEP-206/COSMO-2
Late-Time Mild Inflation --- a possible solution of dilemma: cosmic age and the Hubble parameter ---
We explore the cosmological model in which a late-time mild inflation is
realized after the star formation epoch. Non-vanishing curvature coupling of a
classical boson field yields this mild inflation without a cosmological
constant. Accordingly the lifetime of the present Universe is remarkably
increased in our model. Thus we show that the present observed high value of
the Hubble parameter is compatible with the
age of the oldest stars without introducing the cosmological
constant or the open Universe model. Moreover in our model, the local Hubble
parameter becomes larger than the global one. Thus we show that the present
observed local Hubble parameter measured by using the Cepheid variables is
compatible with the global Hubble parameter measured by using the
Sunyaev-Zeldovich effect. We also examine the energy conditions, evolution of
the effective gravitational constant and the nucleosynthesis process.Comment: 18 page
Statistical Mechanics of Self--Gravitating System : Cluster Expansion Method
We study statistical mechanics of the self--gravitating system applying the
cluster expansion method developed in solid state physics. By summing infinite
series of diagrams, we derive a complex free energy whose imaginary part is
related to the relaxation time of the system. Summation of another series
yields two--point correlation function whose correlation length is essentially
given by the Jeans wavelength of the system.Comment: 4 pages including 2 eps figures, RevTe