Strings and Supersymmetry as Tools for Perturbative QCD

We review techniques simplifying the analytic calculation of one-loop QCD amplitudes with many external legs, for use in next-to-leading-order corrections to multi-jet processes. We explain how a supersymmetry-inspired organization works well in conjunction with other tools, namely the color and helicity decompositions of amplitudes, and the constraints imposed by perturbative unitarity and collinear singularities. String theory seems most useful as a heuristic guide. Using these techniques, the complete set of one-loop five-parton QCD amplitudes, as well as certain sequences of special helicity amplitudes with an arbitrary number of external gluons, have been obtained.Comment: LaTex, 11 pages with 2 encapsulated figures in a uuencoded file. Presented at SUSY95, Paris, May, 199

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

Liophis ceii

Number of Pages: 2Integrative BiologyGeological Science

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

Exponentially Small Couplings between Twisted Fields of Orbifold String Theories

We investigate the natural occurence of exponentially small couplings in effective field theories deduced from higher dimensional models. We calculate the coupling between twisted fields of the Z_3 Abelian orbifold compactification of the heterotic string. Due to the propagation of massive Kaluza-Klein modes between the fixed points of the orbifold, the massless twisted fields located at these singular points become weakly coupled. The resulting small couplings have an exponential dependence on the mass of the intermediate states and the distance between the fixed points.Comment: 21 pages, 4 figure

Liophis jaegeri

Number of Pages: 4Integrative BiologyGeological Science

Sharing storage using dirty vectors

Consider a computation F with n inputs (independent variables) and m outputs (dependent variables) and suppose that we wish to evaluate the Jacobian of F. Automatic differentiation commonly performs this evaluation by associating vector storage either with the program variables (in the case of forward-mode automatic differentiation) or with the adjoint variables (in the case of reverse). Each vector component contains a partial derivative with respect to an independent variable, or a partial derivative of a dependent variable, respectively. The vectors may be full vectors, or they may be dynamically managed sparse data structures. In either case, many of these vectors will be scalar multiples of one another. For example, any intermediate variable produced by a unary operation in the forward mode will have a derivative vector that is a multiple of the derivative for the argument. Any computational graph node that is read just once during its lifetime will have an adjoint vector that is a multiple of the adjoint of the node that reads it. It is frequently wasteful to perform component multiplications explicitly. A scalar multiple of another vector can be replaced by a single multiplicative "scale factor" together with a pointer to the other vector. Automated use of this "dirty vector" technique can save considerable memory management overhead and dramatically reduce the number of floating-point operations required. In particular, dirty vectors often allow shared threads of computation to be reverse-accumulated cheaply. The mechanism permits a number of generalizations, some of which give efficient techniques for preaccumulation

The performance of gender with particular reference to the plays of Shakespeare.

An analytical history of the representation of gender on the English stage from Shakespeare to modern times is followed by a detailed examination of the National Theatre of Great Britain's production of `As You Like It' in 1967, the first production of a play by Shakespeare for over three hundred years in which the female parts were played by male actors. Subsequent cross-cast productions of Shakespeare's plays by Glasgow Citizen's Theatre, Prospect theatre Company, Lindsay Kemp, Theatre du Soleil and Goodman Theatre Chicago are discussed and the views of directors and critics of those productions analysed. The thesis then presents the results of a series of workshops with actors into the playing of gender and examines, by means of an experiment employing Gender Schema Theory, how actors construct gender in a production of `Twelfth Night'. The final part of the thesis describes a controlled experiment into audience perception of gender using a scene from `Hamlet'. Theories are presented about the nature of the performance of gender on stage and the use of theatrical conventions, the relationship between social conventions and stage conventions, about the way in which an actor builds a character, the influence of biological sex on actors' creativity, and about audience participation

IMPACTS OF INCREASED CLIMATE VARIABILITY ON THE PROFITABILITY OF MIDWEST AGRICULTURE

Approximate profit functions are estimated using time-series, cross-sectional, county level data for 12 midwest states. Measures of climate variability are included in the profit functions. Simulated impacts of climate changes on profits are derived. Results show that inclusion of measures of climate variation are important for measuring the impact of changes in mean temperature and precipitation levels. Failure to account for the impact of differences in variability leads to an overestimate of damages. If global warming increases diurnal variation, such increases would have negative impacts on the profitability of midwest agriculture.climate change, climate variability, Midwest, profit function, Farm Management,