74 research outputs found
Instability of Massive Scalar Fields in Kerr-Newman Spacetime
We investigate the instability of charged massive scalar fields in
Kerr-Newman spacetime. Due to the super-radiant effect of the background
geometry, the bound state of the scalar field is unstable, and its amplitude
grows in time. By solving the Klein-Gordon equation of the scalar field as an
eigenvalue problem, we numerically obtain the growth rate of the amplitude of
the scalar field. Although the dependence of the scalar field mass and the
scalar field charge on this growth rate agrees with the result of the analytic
approximation, the maximum value of the growth rate is three times larger than
that of the analytic approximation. We also discuss the effect of the electric
charge on the instability of the scalar field.Comment: 15 pages, 10 figures. Accepted for publication in Prog.Theor.Phy
Fate of Inhomogeneity in Schwarzschild-deSitter Space-time
We investigate the global structure of the space time with a spherically
symmetric inhomogeneity using a metric junction, and classify all possible
types. We found that a motion with a negative gravitational mass is possible
although the energy condition of the matter is not violated. Using the result,
formation of black hole and worm hole during the inflationary era is discussed.Comment: 6page
The separate universe and the back reaction of long wavelength fluctuations
We investigate the backreaction of cosmological long wavelength perturbations
on the evolution of the Universe. By applying the renormalization group method
to a Friedmann-Robertson-Walker universe with long wavelength fluctuations, we
demonstrate that the renormalized solution with the backreaction effect is
equivalent to that of the separate universe. Then, using the effective
Friedmann equation, we show that only non-adiabatic mode of long wavelength
fluctuations affects the expansion law of the spatially averaged universe.Comment: 10 pages. to be published in Phys. Rev.
Evolution of Cosmological Perturbation in Reheating Phase of the Universe
The evolution of the cosmological perturbation during the oscillatory stage
of the scalar field is investigated. For the power law potential of the
inflaton field, the evolution equation of the Mukhanov's gauge invariant
variable is reduced to the Mathieu equation and the density perturbation grows
by the parametric resonance.Comment: 10 pages, 1 figure
- …