Antenna Factorization in Strongly-Ordered Limits

When energies or angles of gluons emitted in a gauge-theory process are small and strongly ordered, the emission factorizes in a simple way to all orders in perturbation theory. I show how to unify the various strongly-ordered soft, mixed soft-collinear, and collinear limits using antenna factorization amplitudes, which are generalizations of the Catani--Seymour dipole factorization function.Comment: 21 pages, 8 figures; final Phys Rev version, corrected definition of multiple-emission recosnstruction functions for strongly-ordered limit, added appendix with new form of double-emission antenna function valid in strongly-ordered limi

New QCD Results from String Theory

We discuss new results in QCD obtained with string-based methods. These methods were originally derived from superstring theory and are significantly more efficient than conventional Feynman rules. This technology was a key ingredient in the first calculation of the one-loop five-gluon amplitude. We also present a conjecture for a particular one-loop helicity amplitude with an arbitrary number of external gluons.Comment: talk presented by Z.B. at Strings 1993, May 24-29, Berkeley CA, 16 page

The Five Gluon Amplitude and One-Loop Integrals

We review the conventional field theory description of the string motivated technique. This technique is applied to the one-loop five-gluon amplitude. To evaluate the amplitude a general method for computing dimensionally regulated one-loop integrals is outlined including results for one-loop integrals required for the pentagon diagram and beyond. Finally, two five-gluon helicity amplitudes are given.Comment: (talk presented at DPF92), LaTeX, 6 pages, CERN-Th.6733/92, SLAC-PUB-6012, UCLA/92/TEP/4

QCD and QED Corrections to Light-by-Light Scattering

We present the QCD and QED corrections to the fermion-loop contributions to light-by-light scattering, gamma gamma to gamma gamma, in the ultrarelativistic limit where the kinematic invariants are much larger than the masses of the charged fermions.Comment: 17 pages, 3 figure files, JHEP styl

All-Orders Singular Emission in Gauge Theories

I present a class of functions unifying all singular limits for the emission of soft or collinear gluons in gauge-theory amplitudes at any order in perturbation theory. Each function is a generalization of the antenna functions of ref. [1]. The helicity-summed interferences these functions are thereby also generalizations to higher orders of the Catani--Seymour dipole factorization function.Comment: 5 pages, 1 figur

Classical String in Curved Backgrounds

The Mathisson-Papapetrou method is originally used for derivation of the particle world line equation from the covariant conservation of its stress-energy tensor. We generalize this method to extended objects, such as a string. Without specifying the type of matter the string is made of, we obtain both the equations of motion and boundary conditions of the string. The world sheet equations turn out to be more general than the familiar minimal surface equations. In particular, they depend on the internal structure of the string. The relevant cases are classified by examining canonical forms of the effective 2-dimensional stress-energy tensor. The case of homogeneously distributed matter with the tension that equals its mass density is shown to define the familiar Nambu-Goto dynamics. The other three cases include physically relevant massive and massless strings, and unphysical tahyonic strings.Comment: 12 pages, REVTeX 4. Added a note and one referenc

FACTORS DETERMINING FSA GUARANTEED LOAN LOSS CLAIM ACTIVITY IN THE U.S. FOR 1990-1997

The study identifies farm operator and economic characteristics explaining variation in FSA guaranteed loan loss claims rates. Regression models using state-level data are estimated. Debt-to-asset ratios, interest rates, off-farm income and bank loan-to-asset ratios explain FO loss rates. Farm size and bank loan-to-asset ratios are important to OL loss rates.Agricultural Finance,

Generalizing Boolean Satisfiability I: Background and Survey of Existing Work

This is the first of three planned papers describing ZAP, a satisfiability engine that substantially generalizes existing tools while retaining the performance characteristics of modern high-performance solvers. The fundamental idea underlying ZAP is that many problems passed to such engines contain rich internal structure that is obscured by the Boolean representation used; our goal is to define a representation in which this structure is apparent and can easily be exploited to improve computational performance. This paper is a survey of the work underlying ZAP, and discusses previous attempts to improve the performance of the Davis-Putnam-Logemann-Loveland algorithm by exploiting the structure of the problem being solved. We examine existing ideas including extensions of the Boolean language to allow cardinality constraints, pseudo-Boolean representations, symmetry, and a limited form of quantification. While this paper is intended as a survey, our research results are contained in the two subsequent articles, with the theoretical structure of ZAP described in the second paper in this series, and ZAP's implementation described in the third