Covariant loop calculus for the neveu-schwarz string

We derive the g-loop, N-string amplitude (density) of the (closed) NS-string in an explicit parametrization of super moduli space for a subset of 2^g even spinstructures.     

Evaluation of the one loop string path integral

We evaluate Polyakov's path integral for the sum over all closed surfaces with the topology of a torus, in the critical dimensiond = 26. The result is applied to the partition function and cosmological constant of the free bosonic string, and to tachyon scattering amplitudes.     

A group theoretic method for string loop diagram

The new approach to arbitrary string scattering proposed by the authors is used to compute the planar tadpole operator, including its measure, for the open bosonic string. The Virasoro gauge identities play a crucial role and are found to contain in general anomalous terms for open strings.     

On loop corrections to string theory effective actions

We make some comments concerning the structure of loop corrections to the effective action (EA) for massless fields of a string. The singular part of the α′→0 limit of the one-loop EA in the open (super)string theory is studied and is shown to be in correspondence with the ultraviolet divergent part of the one-loop effective action in the (super) Yang-Mills theory. In particular, we reproduce the known result about the absence of Λ^D−4 F_μν² one-loop infinities in D = 26 Yang-Mills theory starting from the open Bose string theory. We also discuss the path integral representation for EA (EA = generalized partition function for the σ-model) and use it to compute the open string theory EA on the disc and the annulus.     

A phenomenological treatment of dual loop contributions to inclusive reactions

A phenomenological B₆ type amplitude is constructed which contains Regge singularities of twisted loop graphs such as ordinary trajectories, Regge cuts and Pomeron trajectories. With this amplitude possible implications of the different one and two-loop graphs for single particle distributions are derived for different kinematical regions including the fixed angle limit. The results emphasize the importance of dual loop contributions to single particle distributions.     

Covariant string amplitudes on exotic topologies to one loop

Rules are provided for the calculation of string amplitudes on all exotic topologies to one loop. These topologies include the real projective plane, the disk, the annulus, the Möbius strip, the torus and the Klein bottle. The rules are valid for bosonic strings, superstrings, and heterotic strings either in their critical dimensions or toroidally compactified, and they are applicable to amplitudes with arbitrary external bosonic and fermionic states, including mixed open- and closed-string transitions. The modular invariance of the torus amplitudes is discussed.     

Simplicial vs. continuum string theory and loop equations

We derive loop equations in a scalar matrix field theory. We discuss their solutions in terms of simplicial string theory—the theory describing embeddings of two-dimensional simplicial complexes into the spacetime of the matrix field theory. This relation between the loop equations and the simplicial string theory gives further arguments that favor one of the statements of the paper hep-th/0407018. The statement is that there is an equivalence between the partition function of the simplicial string theory and the functional integral in a continuum string theory—the theory describing embeddings of smooth two-dimensional world-sheets into the spacetime of the matrix field theory in question.     

N-string vertex and loop calculation in the bosonic string

We construct a BRST invariant twisted propagator and discuss different forms of the N-string vertex. We then use them for constructing loop diagrams in the bosonic string.     

Coset representation of closed loop space in string field theory

By taking analogy with Minkowski space, we construct a closed loop space CM which is an infinite-dimensional coset space and discuss some of its consequences.     

Some exact solutions in string cosmology

Some Bianchi-type string-cosmological models are presented here. The physical implications of the models are briefly discussed     

Some spatially homogeneous string cosmological models

The Einstein field equations of massive strings are solved completely with and without a source free magnetic field for the Bianchi type I metric in a different basic form. Some physical properties of the models are studied.     

Some phenomenological consequences of the super higgs effect

To the combined system of supergravity ofN=1 and the Higgs multiplet (a scalar multiplet) is coupled a complex scalar multiplet as a simplified representative of the matter. An order-of-magnitude estimate is attempted on the masses and the couplings of the gravitino and other fields.     

Extended holomorphic anomaly and loop amplitudes in open topological string

Open topological string amplitudes on compact Calabi–Yau threefolds are shown to satisfy an extension of the holomorphic anomaly equation of Bershadsky, Cecotti, Ooguri and Vafa. The total topological charge of the D-brane configuration must vanish in order to satisfy tadpole cancellation. The boundary state of such D-branes is holomorphically captured by a Hodge theoretic normal function. Its Griffiths' infinitesimal invariant is the analogue of the closed string Yukawa coupling and plays the role of the terminator in a Feynman diagram expansion for the topological string with D-branes. The holomorphic anomaly equation is solved and the holomorphic ambiguity is fixed for some representative worldsheets of low genus and with few boundaries on the real quintic.     

Modification of the loop filter design for a plucked string instrument

A modified loop filter design method for plucked string instruments is introduced. Previous loop filter designs do not properly represent the frequency-dependent damping of a silk stringed instrument. To solve this problem, the modified method evaluates how many harmonics are required and which portion of the sound should be chosen to effectively replicate the instrument. Then, the most reasonable filter parameters are determined based on the frequency signal-to-noise ratio of the synthesized sound.