71 research outputs found
Bouncing of gravitons emitted from the brane to the bulk back to the brane
Solutions of geodesic equations describing propagation of gravitons in the
bulk are studied in a cosmological model with one extra dimension. Brane with
matter is embedded in the bulk. It is shown that in the period of early
cosmology gravitons emitted from the brane to the bulk under certain conditions
can return back to the brane. The model is discussed in two alternative
approaches: (i) brane with static metric moving in the AdS space, and (ii)
brane located at a fixed position in extra dimension with non-static metric.
Transformation of coordinates from the one picture to another is performed. In
both approaches conditions for gravitons emitted to the bulk to come back to
the brane are found.Comment: LaTeX2e, 12 pages. Refs. added. arXiv admin note: text overlap with
arXiv:1204.235
Nonabelian Fields in Exact String Solutions
Within the framework of "anomalously gauged" Wess-Zumino-Witten (WZW) models,
we construct solutions which include nonabelian fields. Both compact and
noncompact groups are discussed. In the case of compact groups, as an example
of background containing nonabelian fields, we discuss conformal theory on the
coset, which is the natural generalization of the 2D monopole
theory corresponding to the coset. In noncompact case, we
consider examples with and cosets.Comment: 15 pages, Late
String-Loop Corrected Magnetic Black Holes
We discuss the form of the string-loop-corrected effective action obtained by
compactification of the heterotic string theory on the manifold
or on its orbifold limit and the loop-corrected magnetic black hole solutions
of the equations of motion. Effective 4D theory has N=2 local supersymmetry.
Using the string-loop-corrected prepotential of the N=2 supersymmetric theory,
which receives corrections only from the string world sheets of torus topology,
we calculate the loop corrections to the tree-level gauge couplings and solve
the loop-corrected equations of motion. At the string-tree level, the effective
gauge couplings decrease at small distances from the origin, and in this region
string-loop corrections to the gauge couplings become important. A possibility
of smearing the singularity of the tree-level supersymmetric solution with
partially broken supersymmetry by quantum corrections is discussed.Comment: Improved version. Mixing of the dilaton with other moduli properly
taken into account. Explanatory notes adde
Quantum field theory with a fundamental length: A general mathematical framework
We review and develop a mathematical framework for nonlocal quantum field
theory (QFT) with a fundamental length. As an instructive example, we reexamine
the normal ordered Gaussian function of a free field and find the primitive
analyticity domain of its n-point vacuum expectation values. This domain is
smaller than the usual future tube of local QFT, but we prove that in
difference variables, it has the same structure of a tube whose base is the
(n-1)-fold product of a Lorentz invariant region. It follows that this model
satisfies Wightman-type axioms with an exponential high-energy bound which does
not depend on n, contrary to the claims in the literature. In our setting, the
Wightman generalized functions are defined on test functions analytic in the
complex l-neighborhood of the real space, where l is an n-independent constant
playing the role of a fundamental length, and the causality condition is
formulated with the use of an analogous function space associated with the
light cone. In contrast to the scheme proposed by Bruning and Nagamachi [J.
Math. Phys. 45 (2004) 2199] in terms of ultra-hyperfunctions, the presented
theory obviously becomes local as l tends to zero.Comment: 25 pages, v2: updated to match J. Math. Phys. versio
Non-Localizability and Asymptotic Commutativity
The mathematical formalism commonly used in treating nonlocal highly singular
interactions is revised. The notion of support cone is introduced which
replaces that of support for nonlocalizable distributions. Such support cones
are proven to exist for distributions defined on the Gelfand-Shilov spaces
, where . This result leads to a refinement of previous
generalizations of the local commutativity condition to nonlocal quantum
fields. For string propagators, a new derivation of a representation similar to
that of K\"{a}llen-Lehmann is proposed. It is applicable to any initial and
final string configurations and manifests exponential growth of spectral
densities intrinsic in nonlocalizable theories.Comment: This version is identical to the initial one whose ps and pdf files
were unavailable, with few corrections of misprint
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