In this scheme, Tomimatsu and Sato found that the space-time in their solution
has ring singularities outside the event horizon, that is, there exist naked singularities. They thus suggested that the naked singularity may act as an active energy
source of gravitational waves.
Sato Katsuhiko, moved from Kyoto University to the University of Tokyo, was
one of the pioneers of the theory of an inflation universe in the early 1980s (Sato
1981).
The big-bang theory, posited by G. Gamow, was widely accepted and its standard
theory on the origin of our universe was constructed in the 1970s. In those years,
elementary-particle physics was also markedly advanced, and this new physics
pointed out several difficulties lying in the standard big-bang theory, particularly
on the origin of the large-scale homogeneity, and on the small-scale inhomogeneous
structure of the universe. In order to overcome these difficulties, Sato Katsuhiko
proposed a model of the universe exponentially expanding at its very-early phase
(Sato 1981). In the same year, Alan Guth of the Stanford University presented the
similar model and coined the name the inflation universe. This naming has been
widely accepted.
According to the inflationary universe model, the universe underwent extreme
supercooling. As the result, the universe approaches to a false vacuum, which is a
very peculiar state of matter, the energy density of the vacuum remains constant even
as the universe expands, and gravity works as the repulsion. The gravitational
repulsion would produce a very rapid expansion as compared to the expansion of
the standard model. This is the inflation period, which occurred in approximately
between 10
À34 to 10
À32 s after the big-bang explosion. The scale factor of expansion
reached as high as 3 Â 10
43 in R (/ e
t/T ), accompanied by strong cooling and
reheating. Thereafter, the false vacuum changed to a stable vacuum. Comparison of
the evolution of standard big-bang and inflation models are schematically shown in
Fig. 7.44.
The inflation theory became confirmed by the observations of cosmic background
radiation by COBE satellite launched in 1989 by NASA. In the inflationary epoch,
the state of matter is supposed to be in quantum fluctuation. After the inflationary
period, the fluctuations are imprinted in the cosmic microwave background. The
whole sky map obtained by COBE indicated general homogeneity of the universe
and its small-scale fluctuation. The amplitude of fluctuation is of the order of 10
À5
and this can be supposed to be the remnant of quantum fluctuation. These features
are well explained by the inflation cosmology.
7.10 Theoretical Astrophysics
7.10.1 Age of Cosmic Gas Dynamics
In August 1948, a symposium on cosmical aerodynamics was held in Paris under the
co-sponsors of the IAU and IUTAM (International Union of Theoretical and Applied
Mechanics). The purpose of the Symposium was to introduce to each other the gas
232
7 Postwar Development of Astrophysics, 1946–2000 (Part II: Astrophysics)
has ring singularities outside the event horizon, that is, there exist naked singularities. They thus suggested that the naked singularity may act as an active energy
source of gravitational waves.
Sato Katsuhiko, moved from Kyoto University to the University of Tokyo, was
one of the pioneers of the theory of an inflation universe in the early 1980s (Sato
1981).
The big-bang theory, posited by G. Gamow, was widely accepted and its standard
theory on the origin of our universe was constructed in the 1970s. In those years,
elementary-particle physics was also markedly advanced, and this new physics
pointed out several difficulties lying in the standard big-bang theory, particularly
on the origin of the large-scale homogeneity, and on the small-scale inhomogeneous
structure of the universe. In order to overcome these difficulties, Sato Katsuhiko
proposed a model of the universe exponentially expanding at its very-early phase
(Sato 1981). In the same year, Alan Guth of the Stanford University presented the
similar model and coined the name the inflation universe. This naming has been
widely accepted.
According to the inflationary universe model, the universe underwent extreme
supercooling. As the result, the universe approaches to a false vacuum, which is a
very peculiar state of matter, the energy density of the vacuum remains constant even
as the universe expands, and gravity works as the repulsion. The gravitational
repulsion would produce a very rapid expansion as compared to the expansion of
the standard model. This is the inflation period, which occurred in approximately
between 10
À34 to 10
À32 s after the big-bang explosion. The scale factor of expansion
reached as high as 3 Â 10
43 in R (/ e
t/T ), accompanied by strong cooling and
reheating. Thereafter, the false vacuum changed to a stable vacuum. Comparison of
the evolution of standard big-bang and inflation models are schematically shown in
Fig. 7.44.
The inflation theory became confirmed by the observations of cosmic background
radiation by COBE satellite launched in 1989 by NASA. In the inflationary epoch,
the state of matter is supposed to be in quantum fluctuation. After the inflationary
period, the fluctuations are imprinted in the cosmic microwave background. The
whole sky map obtained by COBE indicated general homogeneity of the universe
and its small-scale fluctuation. The amplitude of fluctuation is of the order of 10
À5
and this can be supposed to be the remnant of quantum fluctuation. These features
are well explained by the inflation cosmology.
7.10 Theoretical Astrophysics
7.10.1 Age of Cosmic Gas Dynamics
In August 1948, a symposium on cosmical aerodynamics was held in Paris under the
co-sponsors of the IAU and IUTAM (International Union of Theoretical and Applied
Mechanics). The purpose of the Symposium was to introduce to each other the gas
232
7 Postwar Development of Astrophysics, 1946–2000 (Part II: Astrophysics)