581 research outputs found
Maverick Examples Of Coset Conformal Field Theories
We present coset conformal field theories whose spectrum is not determined by
the identification current method. In these ``maverick'' cosets there is a
larger symmetry identifying primary fields than under the identification
current. We find an A-D-E classification of these mavericks. }Comment: 16pages , reportSWAT-93-0
Advanced Techniques for Multiparton Loop Calculations: A Minireview
We present an overview of techniques developed in recent years for the
efficient calculation of one-loop multiparton amplitudes, in particular those
relying on unitarity and collinear factorization.Comment: 5 pages, LaTeX/aipproc, presented at DIS '97, Chicago, IL, April
14-18, 199
Alternative Compactification of Superstring Related Theories
The aim of this work is to consider the recently introduced ten dimensional Superstring theories and, by considering the low energy field theory limit, consider possible compactification schemes where the original ten dimensions split up into four observed space time dimensions and six highly curved, compactified dimensions. We shall attempt to find solutions which satisfy the classical equations of motion and then, using these solutions, we shall try to obtain schemes which give a spectrum of particles which is compatible with the observed spectrum. We shall, by considering situations where we allow nonzero torsion on the compactified 6-D manifold, investigate possibilities other than the Calabi-Yau spaces which are usually considered. In Chapter 0 we give a (very biased) review of particle physics and in Chapter 1 we give a little Superstring formalism. In Chapter 2 we discuss the low energy limit of Superstring theories and decide upon the lagrangian which we shall subsequently use. The two types of internal manifold which we shall consider are group manifolds and Coset spaces. We consider these because they provide a natural ansatz for a non-zero torsion. In Chapter 3 we attempt to find solutions to the equations of motion when the internal manifold is a group space and in Chapter 4 we discuss the consequence of any such solutions. In Chapters 5 and 6 we do the same for Non-Symmetric Coset Spaces and in Chapter 7 we look at Symmetric Coset Spaces. In Chapter 8 we return to the issue of what the low energy field theory should be
Identities amongst the Two Loop Partial Amplitudes of Yang-Mills theory
We characterise possible identities among the two-loop partial amplitudes of
gluon scattering in Yang-Mills theory. We use known amplitudes in an exhaustive
search to identify potential new relations. We find two candidate relations
which may extend to all- amplitudes
Counterterms in type I Supergravities
We compute the one-loop divergences of D=10, N=1 supergravity and of its
reduction to D=8. We study the tensor structure of the counterterms appearing
in D=8 and D=10 and compare these to expressions previously found in the low
energy expansion of string theory. The infinities have the primitive Yang-Mills
tree amplitude as a common factor.Comment: 26 pages, Latex, 4 eps figure
Perturbative expansion of N<8 Supergravity
We characterise the one-loop amplitudes for N=6 and N=4 supergravity in four
dimensions. For N=6 we find that the one-loop n-point amplitudes can be
expanded in terms of scalar box and triangle functions only. This
simplification is consistent with a loop momentum power count of n-3, which we
would interpret as being n+4 for gravity with a further -7 from the N=6
superalgebra. For N=4 we find that the amplitude is consistent with a loop
momentum power count of n, which we would interpret as being n+4 for gravity
with a further -4 from the N=4 superalgebra. Specifically the N=4 amplitudes
contain non-cut-constructible rational terms.Comment: 13 pages. v2 adds analytic expression for rational parts of 5-pt
1-loop N=4 SUGRA amplitude; v3 normalisations clarifie
Obtaining One-loop Gravity Amplitudes Using Spurious Singularities
The decomposition of a one-loop scattering amplitude into elementary
functions with rational coefficients introduces spurious singularities which
afflict individual coefficients but cancel in the complete amplitude. These
cancellations create a web of interactions between the various terms. We
explore the extent to which entire one-loop amplitudes can be determined from
these relationships starting with a relatively small input of initial
information, typically the coefficients of the scalar integral functions as
these are readily determined. In the context of one-loop gravity amplitudes, of
which relatively little is known, we find that some amplitudes with a small
number of legs can be completely determined from their box coefficients. For
increasing numbers of legs, ambiguities appear which can be determined from the
physical singularity structure of the amplitude. We illustrate this with the
four-point and N=1,4 five-point (super)gravity one-loop amplitudes.Comment: Minor corrections. Appendix adde
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