63,555 research outputs found
The low energy expansion of the one-loop type II superstring amplitude
The one-loop four-graviton amplitude in either of the type II superstring
theories is expanded in powers of the external momenta up to and including
terms of order s^4 log s R^4, where R^4 denotes a specific contraction of four
linearized Weyl tensors and s is a Mandelstam invariant. Terms in this series
are obtained by integrating powers of the two-dimensional scalar field theory
propagator over the toroidal world-sheet as well as the moduli of the torus.
The values of these coefficients match expectations based on duality relations
between string theory and eleven-dimensional supergravity.Comment: harvmac (b), 25 pages, 3 eps figures. v2: Factors of 2 corrected.
Conclusion unchange
D-Instanton Corrections as (p,q)-String Effects and Non-Renormalization Theorems
We discuss higher derivative interactions in the type IIB superstring in ten
dimensions. From the fundamental string point of view, the non-perturbative
corrections are due to D-instantons. We argue that they can alternatively be
understood as arising from -strings. We derive a non-renormalization
theorem for eight-derivative bosonic interactions, which states that terms
involving either NS-NS or R-R fields occur at tree-level and one-loop only. By
using the symmetry of M-theory on , we show that in order for
the possible interactions in M-theory to have a
consistent perturbative expansion in nine dimensions, must be odd. Thus,
only terms can be present in M-theory and their string
theory counterparts arise at and loops. Finally, we treat an example
of fermionic term.Comment: 24 pages, latex, additional arguments for the perturbative form of
the eight-derivative interaction
Demonstration of the range over which the Langley Research Center digital computer charring ablation program (CHAP) can be used with confidence: Comparisons of CHAP predictions and test data for three ablation materials
Comparisons of ablation calculations with the charring ablation computer code and ablation test data are presented over a wide range of environmental conditions in air for three materials: low-density nylon phenolic, Avcoat 5026-39HC/G, and a filled silicon elastomer. Heat fluxes considered range from over 500 Btu/sq ft-sec to less than 50 Btu/sq ft-sec. Pressures range from 0.5 atm to .004 atm. Enthalpies range from about 2000 Btu/lb to 18000 Btu/lb. Predictions of recession, pyrolysis penetration, and thermocouple responses are considered. Recession predictions for nylon phenolic are good as steady state is approached, but strongly transient cases are underpredicted. Pyrolysis penetrations and thermocouple responses are very well predicted. Recession amounts for Avcoat and silicone elastomer are less well predicted, although high heat flux cases near steady state are fairly satisfactory. Pyrolysis penetrations and thermocouple responses are very well predicted
Supersymmetry Constraints on Type IIB Supergravity
Supersymmetry is used to derive conditions on higher derivative terms in the
effective action of type IIB supergravity. Using these conditions, we are able
to prove earlier conjectures that certain modular invariant interactions of
order alpha' **3 relative to the Einstein-Hilbert term are proportional to
eigenfunctions of the Laplace operator on the fundamental domain of SL(2,Z). We
also discuss how these arguments generalize to terms of higher order in alpha',
as well as to compactifications of supergravity.Comment: 31 pages, harvmac (b); minor correction
Relativistic effects and angular dependence in the reaction antiproton-proton -> pi^- pi^+
We present a new fit to the LEAR data on antiproton-proton -> pi^- pi^+
differential cross sections and analyzing powers motivated by relativistic
considerations. Within a quark model describing this annihilation we argue,
since the pions are highly energetic, that relativistic effects cannot be
neglected. The intrinsic pion wave functions are Lorentz transformed to the
center of mass frame. This change in quark geometry gives rise to additional
angular dependence in the transition operators and results in a relative
enhancement of higher J \ge 2 partial wave amplitudes. The fit to the data is
improved significantly.Comment: Revtex 4, 7 pages, 5 figures. Continuation and results of a previous
paper: nucl-th/040305
Spin-Statistics Violations in Superstring Theory
I describe how superstring theory may violate spin-statistics in an
experimentally observable manner. Reviewing the basics of superstring
interactions and how to utilize these to produce a statistical phase, I then
apply these ideas to two specific examples. The first is the case of heterotic
worldsheet linkings, whereby one small closed string momentarily enlarges
sufficiently to pass over another, producing such a statistical phase. The
second is the braneworld model with noncommutative geometry, whereby matter
composed of open strings may couple to a background in which spacetime
coordinates do not commute, modifying the field (anti)commutator algebra. I
conclude with ways to sharpen and experimentally test these exciting avenues to
possibly verify superstring theory.Comment: 18 pages, 3 figures; v2: references added and typos correcte
Combinatorics of Boundaries in String Theory
We investigate the possibility that stringy nonperturbative effects appear as
holes in the world-sheet. We focus on the case of Dirichlet string theory,
which we argue should be formulated differently than in previous work, and we
find that the effects of boundaries are naturally weighted by .Comment: 12 pages, 2 figures, LaTe
Connection between the Loop Variable Formalism and the Old Covariant Formalsm for the Open Bosonic String
The gauge invariant loop variable formalism and old covariant formalism for
bosonic open string theory are compared in this paper. It is expected that for
the free theory, after gauge fixing, the loop variable fields can be mapped to
those of the old covariant formalism in bosonic string theory, level by level.
This is verified explicitly for the first two massive levels. It is shown that
(in the critical dimension) the fields, constraints and gauge transformations
can all be mapped from one to the other. Assuming this continues at all levels
one can give general arguments that the tree S-matrix (integrated correlation
functions for on-shell physical fields) is the same in both formalisms and
therefore they describe the same physical theory (at tree level).Comment: Latex file, 24 page
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