321 research outputs found
Cyclic Universe \`{a} la string theory
We shall present a model of the "cyclic universe" that can be constructed
only by assuming a minimal set of properties of string theory. We clarify our
viewpoint of the cyclic universe and show some attempts to mateliarize the idea
as field theoretical manner.Comment: Proceeding of International Workshop "Frontier of Quantum Physics"
February 17(Thu.)-19(Sat.) 200
Renormalizability of Quantum Gravity near Two Dimensions
We study the renormalizability of quantum gravity near two dimensions. Our
formalism starts with the tree action which is invariant under the volume
preserving diffeomorphism. We identify the BRS invariance which originates from
the full diffeomorphism invariance. We study the Ward-Takahashi identities to
determine the general structure of the counter terms. We prove to all orders
that the counter terms can be supplied by the coupling and the wave function
renormalization of the tree action. The bare action can be constructed to be
the Einstein action form which ensures the full diffeomorphism invariance.Comment: 26 pages, Latex file, No figure
Scaling Exponents in Quantum Gravity near Two Dimensions
We formulate quantum gravity in dimensions in such a way that
the conformal mode is explicitly separated. The dynamics of the conformal mode
is understood in terms of the oversubtraction due to the one loop counter term.
The renormalization of the gravitational dressed operators is studied and their
anomalous dimensions are computed. The exact scaling exponents of the 2
dimensional quantum gravity are reproduced in the strong coupling regime when
we take limit. The theory possesses the ultraviolet
fixed point as long as the central charge , which separates weak and
strong coupling phases. The weak coupling phase may represent the same
universality class with our Universe in the sense that it contains massless
gravitons if we extrapolate up to 2.Comment: 24 pages and 1 figure, UT-614, TIT/HEP-191 and YITP/U-92-05 (figures
added to the 1st version
A new mechanism of realizing inflationary universe with recourse to backreaction of quantized free fields -- Inflation without inflaton --
It is shown that the inflationary era in early universe is realized due to
the effect of backreaction of quantized matter fields. In fact we start by
quantizing a free scalar field in the Friedmann-Robertson-Walker space-time,
and the field is fluctuating quantum mechanically around the bottom of the mass
potential. We then obtain the vacuum expectation value of the energy density of
the scalar field as a functional of the scale factor of the universe. By
plugging it into the Einstein equation, a self-consistent equation is
established in which the matter fields determine the time evolution of the
universe. We solve this equation by setting few conditions and find the
following solution: the universe expands \`{a} la de Sitter with e-folding
number and then it turns to shrink with a decreasing Hubble
parameter which rapidly goes to zero.Comment: 25 pages, 5 figure
Conformal Invariance and Renormalization Group in Quantum Gravity Near Two Dimensions
We study quantum gravity in dimensions in such a way to preserve
the volume preserving diffeomorphism invariance. In such a formulation, we
prove the following trinity: the general covariance, the conformal invariance
and the renormalization group flow to Einstein theory at long distance. We
emphasize that the consistent and macroscopic universes like our own can only
exist for matter central charge . We show that the spacetime
singularity at the big bang is resolved by the renormalization effect and
universes are found to bounce back from the big crunch. Our formulation may be
viewed as a Ginzburg-Landau theory which can describe both the broken and the
unbroken phase of quantum gravity and the phase transition between them.Comment: 32 pages, TIT-HEP-256, KEK-TH-395, YITP/U-94-1
Scaling Behavior of Ricci Curvature at Short Distance near Two Dimensions
We study the renormalization of the Ricci curvature as an example of
generally covariant operators in quantum gravity near two dimensions. We find
that it scales with a definite scaling dimension at short distance. The Ricci
curvature singularity at the big bang can be viewed as such a scaling
phenomenon. The problem of the spacetime singularity may be resolved by the
scale invariance of the spacetime at short distance.Comment: 9pages, LaTe
副睾丸アデノマトイド腫瘍--日本語文献の概観
アデノマトイド腫蕩は副睾丸腫瘍中最も多くみられるものである。坂口により第1例が発表されて以来44例が報告されている。われわれは比較的筋性成分を豊富に含む45例目を報告する。このような例はアデノマイド腫瘍のうち約3%の割でみられるといわれている。われわれはまた本邦において報告された全文献の概観をも報告する。ABSTRACT: Adenomatoid tumors are the most frequently encountered tumor of the epididymis, and forty-four cases have been reported in Japan since the first case was reported by Sakaguchi. We report the 45th case with relatively abundant leiomyomatous content, a characteristic said to be found in about 3 per cent of adenomatoid tumors. We also report the results of a review of all relevant literature published in this country
CMB Fluctuations and String Compactification Scales
We propose a mechanism for the generation of temperature fluctuations of
cosmic microwave background. We consider a large number of fields, such as
Kaluza-Klein modes and string excitations. Each field contributes to the
gravitational potential by a small amount, but an observable level of
temperature fluctuations is achieved by summing up the contribution of
typically of order 10^{14} fields. Tensor fluctuations are hardly affected by
these fields. Our mechanism is based on purely quantum effects, and is
different from the "slow-roll" or "curvaton" scenario. Using the observed data,
we find constraints on the parameters of this model, such as the size of the
extra dimensions and the string scale. Our model predicts a particular pattern
of non-gaussianity with a small magnitude.Comment: 4 pages, 2 figures; v2: Corrected a mistake in eq. (11), which does
not affect the subsequent context. Added a comment on inflaton fluctuations
at the end of the paper. Final version to appear in Phys. Lett.
- …