85 research outputs found
Area-Preserving Structure of Massless Matter-Gravity Fields in 1+1 Dimensions
We derive anomalous Ward identities in two different approaches to the
quantization of massless matter-gravity fields in 1+1 dimensions.Comment: 5 pages, LaTex. (Contribution to the Proceedings of the XXXIV
Internationale Universit\"atswochen f\"ur Kern- und Teilchenphysik.
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
Singular Vectors and Topological Theories from Virasoro Constraints via the Kontsevich-Miwa Transform
We use the Kontsevich-Miwa transform to relate the different pictures
describing matter coupled to topological gravity in two dimensions: topological
theories, Virasoro constraints on integrable hierarchies, and a DDK-type
formalism. With the help of the Kontsevich-Miwa transform, we solve the
Virasoro constraints on the KP hierarchy in terms of minimal models dressed
with a (free) Liouville-like scalar. The dressing prescription originates in a
topological (twisted N=2) theory. The Virasoro constraints are thus related to
essentially the N=2 null state decoupling equations. The N=2 generators are
constructed out of matter, the `Liouville' scalar, and ghosts. By a
`dual' construction involving the reparametrization ghosts, the DDK
dressing prescription is reproduced from the N=2 symmetry. As a by-product we
thus observe that there are two ways to dress arbitrary or
matter theory, that allow its embedding into a topological theory. By th e
Kontsevich-Miwa transform, which introduces an infinite set of `time' variables
, the equations ensuring the vanishing of correlators that involve
BRST-exact primary states, factorize through the Virasoro generators expressed
in terms of the . The background charge of these Virasoro generators is
determined by the topological central charge.Comment: 62p. LaTeX, CERN-TH.6752, IMAFF-92/8, revised (minor corrections,
typos) easy-fontversio
Scaling laws in hadronic processes and string theory
We propose a possible scheme for getting the known QCD scaling laws within
string theory. In particular, we consider amplitudes for exclusive scattering
of hadrons at large momentum transfer, hadronic form factors and distribution
functions.Comment: 13 pages, 2 figures, a comment and a reference added, a final version
to appear in Physical Review
Solving Virasoro Constraints on Integrable Hierarchies via the Kontsevich-Miwa Transform
We solve Virasoro constraints on the KP hierarchy in terms of minimal
conformal models. The constraints we start with are implemented by the Virasoro
generators depending on a background charge . Then the solutions to the
constraints are given by the theory which has the same field content as the
David-Distler-Kawai theory: it consists of a minimal matter scalar with
background charge , dressed with an extra `Liouville' scalar. The
construction is based on a generalization of the Kontsevich parametrization of
the KP times achieved by introducing into it Miwa parameters which depend on
the value of . Under the thus defined Kontsevich-Miwa transformation, the
Virasoro constraints are proven to be equivalent to a master equation depending
on the parameter . The master equation is further identified with a
null-vector decoupling equation. We conjecture that constraints on
the KP hierarchy are similarly related to a level- decoupling equation. We
also consider the master equation for the -reduced KP hierarchies. Several
comments are made on a possible relation of the generalized master equation to
{\it scaled} Kontsevich-type matrix integrals and on the form the equation
takes in higher genera.Comment: 23pp (REVISED VERSION, 10 April 1992
Coherent \pi^0 threshold production from the deuteron at Q^2 = 0.1 GeV^2/c^2
First data on coherent threshold \pi^0 electroproduction from the deuteron
taken by the A1 Collaboration at the Mainz Microtron MAMI are presented. At a
four-momentum transfer of q^2=-0.1 GeV^2/c^2 the full solid angle was covered
up to a center-of-mass energy of 4 MeV above threshold. By means of a
Rosenbluth separation the longitudinal threshold s wave multipole and an upper
limit for the transverse threshold s wave multipole could be extracted and
compared to predictions of Heavy Baryon Chiral Perturbation Theory.Comment: 7 pages, 7 figures, latex2
Higher string functions, higher-level Appell functions, and the logarithmic ^sl(2)_k/u(1) CFT model
We generalize the string functions C_{n,r}(tau) associated with the coset
^sl(2)_k/u(1) to higher string functions A_{n,r}(tau) and B_{n,r}(tau)
associated with the coset W(k)/u(1) of the W-algebra of the logarithmically
extended ^sl(2)_k conformal field model with positive integer k. The higher
string functions occur in decomposing W(k) characters with respect to level-k
theta and Appell functions and their derivatives (the characters are neither
quasiperiodic nor holomorphic, and therefore cannot decompose with respect to
only theta-functions). The decomposition coefficients, to be considered
``logarithmic parafermionic characters,'' are given by A_{n,r}(tau),
B_{n,r}(tau), C_{n,r}(tau), and by the triplet \mathscr{W}(p)-algebra
characters of the (p=k+2,1) logarithmic model. We study the properties of
A_{n,r} and B_{n,r}, which nontrivially generalize those of the classic string
functions C_{n,r}, and evaluate the modular group representation generated from
A_{n,r}(tau) and B_{n,r}(tau); its structure inherits some features of modular
transformations of the higher-level Appell functions and the associated
transcendental function Phi.Comment: 34 pages, amsart++, times. V2: references added; minor changes; some
nonsense in B.3.3. correcte
BRST Analysis of Physical States for 2D (Super) Gravity Coupled to (Super) Conformal Matter
We summarize some recent results on the BRST analysis of physical states of
2D gravity coupled to c<=1 conformal matter and the supersymmetric
generalization.Comment: 11 page
Considerations on rescattering effects for threshold photo- and electro-production of on deuteron
We show that for the S-state -production in processes and the rescattering effects due to the
transition: (or are cancelled
out due to the Pauli principle. The large values for these effects predicted in
the past may result from the fact that the spin structure of the corresponding
matrix element and the necessary antisymmetrization induced by the presence of
identical protons (or neutrons) in the intermediate state was not taken into
account accurately. One of the important consequences of these considerations
is that photo- and electro-production on deuteron near threshold can
bring direct information about elementary neutron amplitudes.Comment: Add a new sectio
A Matrix Model Dual of Type 0B String Theory in Two Dimensions
We propose that type 0B string theory in two dimensions admits a dual
description in terms of a one dimensional bosonic matrix model of a hermitian
matrix. The potential in the matrix model is symmetric with respect to the
parity-like Z_2 transformation of the matrix. The two sectors in the theory,
namely the NSNS and RR scalar sectors correspond to two classes of operators in
the matrix model, even and odd under the Z_2 symmetry respectively. We provide
evidence that the matrix model successfully reconstructs the perturbative
S-matrix of the string theory, and reproduces the closed string emission
amplitude from unstable D-branes. Following recent work in two dimensional
bosonic string, we argue that the matrix model can be identified with the
theory describing N unstable D0-branes in type 0B theory. We also argue that
type 0A theory is described in terms of the quantum mechanics of
brane-antibrane systems.Comment: Latex, 20 pages, typos corrected, explanations added, references
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