39752437
Cross section for hard processes involving two quarks and four gluons.
The cross section for hard processes involving two quarks and four gluons is given in a form suitable for fast numerical calculations.
14387997
N = 2 HETEROTIC SUPERSTRING AND ITS DUAL THEORY IN FIVE DIMENSIONS
Abstract We study quantum effects in five dimensions in heterotic superstring theory compactified on K 3 × S 1 and analyze the conjecture that its dual effective theory is eleven-dimensional supergravity compactified on a Calabi-Yau threefold. This theory is also equivalent to type II superstring theory compactified on the same Calabi-Yau manifold, in an appropriate large volume limit. In this limit the conifold singularity disappears and is replaced by a singularity associated to enhanced gauge symmetries, as naively expected from the heterotic description. Furthermore, we exhibit the existence of additional massless states which appear in the strong coupling regime of the heterotic theory and are related to a different type of singular points on Calabi-Yau threefolds.
62835109
Lectures on heterotic-type I duality
In the last couple of years, there has been remarkable progress in understanding non-perturbative aspects of string theories. The new ingredient is the discovery of various duality symmetries; these, in particular, invert the coupling constant and exchange perturbative states with non-perturbative solitonic excitations. Since inversion of the coupling involves the Planck constant ħ, duality symmetries can be realized only at the quantum level. Once the dual models are identified, non-perturbative dynamics of one model can be studied by means of the standard perturbative techniques in the other model.
120318508
Low-energy softly-broken supersymmetry
Abstract We consider supersymmetric low-energy lagrangians based on the gauge group SU(3) × SU(2) × U(1) × Ũ(1), where Ũ(1) is an additional axial group a la Fayet. Models with explicit soft breaking of supersymmetry are considered as an alternative to models with axial anomalies. We argue that soft breaking can be very efficient and illustrate this with a simple example in which the introduction of a negative mass squared term for only one scalar field leads to a phenomenologically interesting model.
120401055
Dilaton Couplings at Large Distances
Abstract The large-distance behaviour of dilaton couplings is studied within the framework of four-dimensional heterotic superstring theories. String loop corrections violate universality of dilaton and graviton couplings, increasing dilaton couplings at large distances. This implies a serious problem for string theories, unless a non-zero dilaton mass is generated.
120574302
Stability of supersymmetric ground state in chiral theories
Abstract The effective action for the scalar propagator is studied in supersymmetric chiral gauge theories. The form of the scalar potential ensures the stability of the supersymmetric ground state, even for large values of the coupling constant. It is found however, that the gluino condensation tends to destabilize the system. This may signal dynamical supersymmetry breaking.
38327098
Quantizing compact phase spaces: Irreducible representations from constrained dynamics.
We study the quantization of the coset space SU(3)/U(1){times}U(1), considered as an example of a compact phase space. We embed this system in the flat space {ital C}{sup 6} endowed with a Poisson-bracket structure, then quantize it as a constrained system, finding consistency only for isolated symplectic structures. The space of states for each admissible symplectic structure forms an irreducible representation of SU(3). In this way, we recover in the language of constrained dynamics some of the results of the Borel-Weil-Bott theorem and geometric quantization.
17862595
Role of zero modes in the canonical quantization of heavy-fermion QED in light-cone coordinates.
Four-dimensional heavy-fermion QED is studied in light-cone coordinates with (anti)periodic field boundary conditions. We carry out a consistent light-cone canonical quantization of this model using the Dirac algorithm for a system with first- and second-class constraints. To examine the role of the zero modes, we consider the quantization procedure in the zero mode and the nonzero-mode sectors separately. In both sectors we obtain the physical variables and their canonical commutation relations. The physical Hamiltonian is constructed via a step-by-step exclusion of the unphysical degrees of freedom. An example using this Hamiltonian in which the zero modes play a role is the verification of the correct Coulomb potential between two heavy fermions.
12568136
Correlations and renormalization in lattice gases.
An exact kinetic theory is formulated for lattice gases. This kinetic theory makes possible the calculation of corrections to the usual combined Boltzmann and Chapman-Enskog analysis of lattice gases due to the buildup of correlations. Cluster expansion methods are used to show that renormalized transport coefficients for lattice gases satisfying semidetailed balance can be calculated perturbatively by summing terms in an infinite series. A diagrammatic notation for the terms in this series is given, in analogy with the diagrammatic expansions of continuum kinetic theory and quantum field theory. A closed-form expression for the coefficients associated with the vertices of these diagrams is given. This method is applied to several standard lattice gases, and the results are shown to correctly predict observed deviations from the Boltzmann analysis.
33049133
Vacuum structure, zero modes, and the effective potential in light-cone quantization.
A Hamiltonian formalism for the calculation of the usual effective potential is presented in the context of scalar field theory. When applied in the context of light-cone quantization, we find contributions at [ital k][sup +]=0 which are missed by standard light-cone infrared regularizations. We present a (time-dependent) regularization of the Hamiltonian which correctly incorporates these contributions at the one-loop level. We briefly discuss the implications of these findings for the more general program of diagonalizing the light-cone Hamiltonian.
16060889
Varieties of vacua in classical supersymmetric gauge theories.
We give a simple description of the classical moduli space of vacua for supersymmetric gauge theories with or without a superpotential. The key ingredient in our analysis is the observation that the Lagrangian is invariant under the action of the complexified gauge group {ital G}{sup {ital c}}. From this point of view the usual {ital D}-flatness conditions are an artifact of the Wess-Zumino gauge. By using a gauge that preserves {ital G}{sup {ital c}} invariance we show that every constant matter field configuration that extremizes the superpotential is {ital G}{sup {ital c}} gauge equivalent (in a sense that we make precise) to a unique classical vacuum. This result is used to prove that in the absence of a superpotential the classical moduli space is the algebraic variety described by the set of all holomorphic gauge-invariant polynomials. When a superpotential is present, we show that the classical moduli space is a variety defined by imposing additional relations on the holomorphic polynomials. Many of these points are already contained in the existing literature. The main contribution of the present work is that we give a careful and self-contained treatment of limit points and singularities. {copyright} {ital 1996 The American Physical Society.}