6,770 research outputs found
Short Distance Contributions to Graviton-Graviton Scattering: Matrix Theory versus Supergravity
We study graviton scattering in the presence of higher dimensional operators
- particularly, R^4 - arising from loop effects. We find that the results do
not correspond to any known terms in the effective action of Matrix Theory,
thus lending support to the idea that the finite N Matrix Theory has no simple
relation to supergravity with large compactification radii.Comment: 13 pages, LaTeX file with 3 Postscript figures. Uses epsf.tex and
fps.sty macros. Revisions of v2: some comments in the end of section 3 have
been remove
Type IIB Conjectures
We propose (and ) invariant conjectures for all couplings of Type IIB strings on (and ),
generalizing conjectures of Green and Gutperle (and Kiritsis and Pioline) for
the coupling. A strong check for our conjectures is that on at weak
coupling, they reproduce the multiloop scattering amplitudes which had been
previously computed using N=2 strings in the N=4 topological formalism.
Applications to string production in a background field,
generalizing Schwinger's computation for pair production in constant field,
are suggested.Comment: Added three reference
A Note on Effective Lagrangians in Matrix Theory
We study the relation between the effective Lagrangian in Matrix Theory and
eleven dimensional supergravity. In particular, we provide a relationship
between supergravity operators and the corresponding terms in the
post-Newtonian approximation of Matrix Theory.Comment: 7 pages, use harvmac. References adde
Effects of D-instantons
Scattering of fundamental states of type IIB supergravity and superstring
theory is discussed at low orders in perturbation theory in the background of a
D-instanton. The integration over fermionic zero modes in both the low energy
supergravity and in the string theory leads to explicit nonperturbative terms
in the effective action. These include a single instanton correction to the
known tree-level and one-loop interactions. The `spectrum' of
multiply-charged D-instantons is deduced by T-duality in nine dimensions from
multiply-wound world-lines of marginally-bound D-particles. This, and other
clues, lead to a conjectured SL(2,Z) completion of the terms which
suggests that they are not renormalized by perturbative corrections in the
zero-instanton sector beyond one loop. The string theory unit-charged
D-instanton gives rise to point-like effects in fixed-angle scattering, raising
unresolved issues concerning distance scales in superstring theory.Comment: 31 pages, 6 figures, Latex, Reference added, corrected coefficients
in expansion of generalized Eisenstein series in equation 66 now agree with
hep-th/970414
Anomalies and large N limits in matrix string theory
We study the loop expansion for the low energy effective action for matrix
string theory. For long string configurations we find the result depends on the
ordering of limits. Taking before we find free strings.
Reversing the order of limits however we find anomalous contributions coming
from the large limit that invalidate the loop expansion. We then embed the
classical instanton solution into a long string configuration. We find the
instanton has a loop expansion weighted by fractional powers of . Finally we
identify the scaling regime for which interacting long string configurations
have a well defined large limit. The limit corresponds to large "classical"
strings and can be identified with the "dual of the 't Hooft limit,
.Comment: 13 pages, 1 figure, harvmac.tex, notational errors corrected,
references added. Trivial error in section 5 corrected with the result that
the domain of validity of the loop expn. is slightly modifie
High Energy Scattering and D-Pair Creation in Matrix String Theory
In this paper we use the matrix string approach to begin a study of high
energy scattering processes in M-theory. In particular we exhibit an
instanton-type configuration in 1+1 super-Yang-Mills theory that can be
interpreted as a non-perturbative description of a string interaction. This
solution is used to describe high energy processes with non-zero longitudinal
momentum exchange, in which an arbitrary number of eigenvalues get transferred
between the two scattering states. We describe a direct correspondence between
these semi-classical SYM configurations and the Gross-Mende saddle points. We
also study in detail the pair production of D-particles via a one-loop
calculation which in the 1+1D gauge theory language is described by the
(perturbative) transition between states with different electric flux. Finally,
we discuss a possible connection between these calculations in which D-particle
production gives important corrections to the Gross-Mende process.Comment: 44 pages, harvmac; minor reference and equation correction
Evidence flow graph methods for validation and verification of expert systems
The results of an investigation into the use of evidence flow graph techniques for performing validation and verification of expert systems are given. A translator to convert horn-clause rule bases into evidence flow graphs, a simulation program, and methods of analysis were developed. These tools were then applied to a simple rule base which contained errors. It was found that the method was capable of identifying a variety of problems, for example that the order of presentation of input data or small changes in critical parameters could affect the output from a set of rules
Boundaries in M-Theory
We formulate boundary conditions for an open membrane that ends on the
fivebrane of {\cal M}-theory. We show that the dynamics of the
eleven-dimensional fivebrane can be obtained from the quantization of a ``small
membrane'' that is confined to a single fivebrane and which moves with the
speed of light. This shows that the eleven-dimensional fivebrane has an
interpretation as a -brane of an open supermembrane as has recently been
proposed by Strominger and Townsend. We briefly discuss the boundary dynamics
of an infinitely extended planar membrane that is stretched between two
parallel fivebranesComment: 16 pages, phyzz
PP-Waves, M-Theory and Fluxes
We study a new type of warped compactifications of M-theory on eight
manifolds for which nowhere vanishing covariantly constant spinors of
indefinite chirality on the internal manifold can be found. We derive the
constraints on the fluxes and the warp factor following from supersymmetry and
the equations of motion. We show, that the lift of Type IIB PP-waves to
M-theory is a special type of solution of this general class of models. We
comment on the relation between the Type IIB version of such compactifications
as a dual description of the Polchinski-Strassler solution describing a
four-dimensional confining gauge theory.Comment: 22 Pages, TEX, no figures. Final version appearing in Nuclear Physics
Equations of Motion and Galilei Invariance in D-Particle Dynamics
As a continuation of our previous work on the multi-body forces of
D-particles in supergravity and Matrix theory, we investigate the problem of
motion. We show that the scattering of D-particles including recoil derived in
Matrix theory is precisely reproduced by supergravity with the discrete
light-cone prescription up to the second order in 11 dimensional Newton
constant. An intimate connection of recoil and Galilei invariance in
supergravity is pointed out and elucidated.Comment: 19 pages, no figures, LaTe
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