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Small scale structure on cosmic strings

Description: I discuss our current understanding of cosmic string evolution, and focus on the question of small scale structure on strings, where most of the disagreements lie. I present a physical picture designed to put the role of the small scale structure into more intuitive terms. In this picture one can see how the small scale structure can feed back in a major way on the overall scaling solution. I also argue that it is easy for small scale numerical errors to feed back in just such a way. The intuitive discussion presented here may form the basis for an analytic treatment of the small structure, which I argue in any case would be extremely valuable in filling the gaps in our resent understanding of cosmic string evolution. 24 refs., 8 figs.
Date: October 30, 1989
Creator: Albrecht, A.
Partner: UNT Libraries Government Documents Department

Evolution of cosmic string networks

Description: We summarize our new results on cosmic strings. These results include: the application of non-equilibrium statistical mechanics to cosmic string evolution, a simple ''one scale'' model for the long strings which has a great deal of predictive power, results from large scale numerical simulations, and a discussion of the observational consequences of our results. An upper bond on G/mu/ of approximately 10/sup /minus/7/ emerges from the millisecond pulsar gravity wave bound. We discuss how numerical uncertainties affect this. Any changes which weaken the bound would probably also give the long strings the dominant role in producing observational consequences. 22 refs.
Date: June 1, 1989
Creator: Albrecht, A. & Turok, N.
Partner: UNT Libraries Government Documents Department

Phenomenological implications of the blown-up orbifolds

Description: We discuss the structure of the effective Lagrangian for the (2,2) Z/sub N/ orbifolds and the corresponding Calabi-Yau manifolds which are obtained by ''blowing-up'' the orbifold singularities. The method to ''blow-up'' such singularities is reviewed. Results are exact at the string tree-level. In particular, the question of generating an intermediate scale M/sub I/ in such models is addressed. It is shown that for Z/sub N/ orbifolds (except one) and the corresponding blown-up orbifolds which are compactified on any six-torus T/sup 6/ which can be obtained by continuously deforming T/sup 4/ circle times T/sup 2/, all the terms of the type (2727)/sup K/ are absent from the effective superpotential, thus questioning the mechanism for generating a large intermediate scale for such compactifications.
Date: May 1, 1987
Creator: Cvetic, M.
Partner: UNT Libraries Government Documents Department

Bordered surfaces, off-shell amplitudes, sewing, and string field theory

Description: These lectures will deal with the current status of the sewing problem. The rationale for this approach is that any nonperturbative string theory must reproduce the Polyakov path integral as a perturbation series. If our experience in ordinary field theory is a guide --- and admittedly it may not be --- the terms in such a perturbation series, like Feynman diagrams, are likely to be built up from simple ''vertices'' and ''propagators,'' which can themselves be represented as (off-shell) Polyakov amplitudes. Hence an understanding of how to put together simple components into more complicated world sheet amplitudes is likely to give us much-needed information about the structure of nonperturbative string theory. To understand sewing, we must first understand the building blocks, off-shell Polyakov amplitudes. This is the subject of my first lecture. Next, we will explore the sewing of conformal field theories at a fixed conformal structure, that is, the reconstruction of correlation functions for a fixed surface /Sigma/ from those on a pair of surfaces /Sigma//sub 1/ and /Sigma//sub 2/ obtained by cutting /Sigma/ along a closed curve. We will then look at the problem of sewing amplitudes, integrals of correlation functions over moduli space. This will necessitate an understanding of how to build the moduli space of a complicated surface from simpler moduli spaces. Finally, we will briefly examine vertices and string field theories. 48 refs., 10 figs.
Date: April 1, 1989
Creator: Carlip, S.
Partner: UNT Libraries Government Documents Department

Two loop partition function in (compactified) heterotic string vacua

Description: Two loop partition function for the heterotic string theory, compactified on any background preserving space-time supersymmetry at the string tree level, is explicitly calculated. This includes E/sub 8/ x E/sub 8/ or SO(32) heterotic string theory in ten dimensional flat space-time.
Date: October 1, 1987
Creator: Atick, J.J. & Sen, A.
Partner: UNT Libraries Government Documents Department

Gauge invariant actions for string models

Description: String models of unified interactions are elegant sets of Feynman rules for the scattering of gravitons, gauge bosons, and a host of massive excitations. The purpose of these lectures is to describe the progress towards a nonperturbative formulation of the theory. Such a formulation should make the geometrical meaning of string theory manifest and explain the many ''miracles'' exhibited by the string Feynman rules. There are some new results on gauge invariant observables, on the cosmological constant, and on the symmetries of interacting string field theory. 49 refs.
Date: June 1, 1986
Creator: Banks, T.
Partner: UNT Libraries Government Documents Department

Torsion in superstrings

Description: String theories on a background manifold with torsion are discussed. Candidate vacuum configurations are discussed for ten-dimensional superstrings. These are compactified on M/sub 4/ x K, where M/sub 4/ is four-dimensional and K is some compact six-dimensional manifold. Solutions with non-zero torsion on K are emphasized. The compactification problem is approached both from the effective field theory point of view and directly using string considerations. The construction of string theories in curved space with torsion is then discussed. Particular emphasis is put on the constraints on space-time supersymmetry in the Green-Schwarz approach. Two-dimensional non-linear sigma models are used to describe the propagation of strings in background geometries with torsion. (LEW)
Date: September 1, 1985
Creator: Bars, I.; Nemeschansky, D. & Yankielowicz, S.
Partner: UNT Libraries Government Documents Department

Torsion and geometrostasis in covariant superstrings

Description: The covariant action for freely propagating heterotic superstrings consists of a metric and a torsion term with a special relative strength. It is shown that the strength for which torsion flattens the underlying 10-dimensional superspace geometry is precisely that which yields free oscillators on the light cone. This is in complete analogy with the geometrostasis of two-dimensional sigma-models with Wess-Zumino interactions. 13 refs.
Date: January 1, 1985
Creator: Zachos, C.
Partner: UNT Libraries Government Documents Department

Vacuum energy of M/sup 4/ x S/sup M/ x S/sup N/ in even dimensions

Description: We obtain an expression for the one loop effective potential coming from quantum fluctuations of scalars and spin-1/2 fermions in a higher-dimensional manifold of product form M/sup 4/ x S/sup M/ x S/sup N/. In contrast to previous calculations, we consider the case in which the total number of dimensions is even, since this is the relevant case for superstring compactification. A detailed calculation for a ten-dimensional spacetime with two internal 3-spheres is performed, and an approximate static solution for the geometry is found, with the two internal radii being of the order of the Planck length for a sufficiently large number of matter fields. We study the stability of this solution and make some remarks on the possible cosmological implications of our results.
Date: January 1, 1987
Creator: Gleiser, M.; Jetzer, P. & Rubin, M.A.
Partner: UNT Libraries Government Documents Department

Supermanifolds and super Riemann surfaces

Description: The theory of super Riemann surfaces is rigorously developed using Rogers' theory of supermanifolds. The global structures of super Teichmueller space and super moduli space are determined. The super modular group is shown to be precisely the ordinary modular group. Super moduli space is shown to be the gauge-fixing slice for the fermionic string path integral.
Date: September 1, 1986
Creator: Rabin, J.M.
Partner: UNT Libraries Government Documents Department

Superstring spectroscopy

Description: The basic elements of string theory are presented after a brief review of the main properties of string theories, particularly the supersymmetric version. Lessons are provided on the basic quantized string, zero-point energy, the bosonic string, compactification on a torus, the superstring, the heterotic string, field compactification on an orbifold, and string compactification on an orbifold. 35 refs., 17 figs. (LEW)
Date: December 1, 1986
Creator: Peskin, M.E.
Partner: UNT Libraries Government Documents Department

String mediated phase transitions

Description: It is demonstrated from first principles how the existence of string like structures can cause a system to undergo a phase transition. In particular, we concentrate on the role of topologically stable cosmic string in the restoration of spontaneously broken symmetries. We discuss how the thermodynamic properties of strings alter when stiffness and nearest neighbor string-string interactions are included. 25 refs., 5 figs.
Date: November 1, 1988
Creator: Copeland, E.; Haws, D.; Rivers, R. & Holbraad, S.
Partner: UNT Libraries Government Documents Department

Comment on String-Dominated Universe(SDU)

Description: Theoretical prejudice favors the flat(k=0) cosmology, and the inflationary Universe scenario implements this prejudice in a natural way. For the k=0 model ..cap omega.. (defined as rho total/rho critical; rho total = rho NR + rho vac + rho R + rho S) = 1. However, observational data suggests: ..cap omega../sub OBS/ approx. = 0.2' +- 0.1', where +- 0.1 indicates the range of values reported. This discrepancy is known as the ..cap omega..-problem. A number of solutions have been suggested: ..cap omega../sub OBS/ is determined by assuming that light (i.e., galaxies) traces mass - perhaps this assumption is not valid; ..cap omega../sub OBS/ is not sensitive to a smoothly-distributed component of mass density - perhaps most of the mass density resides in a smooth component. Candidates for the smooth component include: relativistic particles (rho/sub R/), a relic cosmological term (rho/sub vac/), and in a recent letter Vilenkin has suggested fast-moving strings (rho/sub S/).
Date: September 1, 1984
Creator: Turner, M.S.
Partner: UNT Libraries Government Documents Department

Introduction to the theory of strings

Description: These lectures present, from an introductory perspective, some basic aspects of the quantum theory of strings. They treat (1) the kinematics, spectrum, and scattering amplitude of the bosonic string, (2) the spectrum and supersymmetry of Green-Schwarz superstring, and (3) the identification of the underlying gauge invariances of the string theory. 43 refs.
Date: October 1, 1985
Creator: Peskin, M.E.
Partner: UNT Libraries Government Documents Department

Supersymmetry breaking from superstrings

Description: The gauge hierarchy problem is briefly reviewed and a class of effective field theories obtained from superstrings is described. These are characterized by a classical symmetry, related to the space-time duality of string theory, that is responsible for the suppression of observable supersymmetry breaking effects. At the quantum level, the symmetry is broken by anomalies that provide the seed of observable supersymmetry breaking, and an acceptably large gauge hierarchy may be generated. 26 refs.
Date: May 1, 1990
Creator: Gaillard, M.K. (European Organization for Nuclear Research, Geneva (Switzerland) Lawrence Berkeley Lab., CA (USA))
Partner: UNT Libraries Government Documents Department

Resurrection of neutrinos as dark matter

Description: It is shown that new observations of large scale structure in the universe (voids, foam, and large-scale velocity fields) are best understood if the dominant matter of the universe is in the form of massive (9eV less than or equal to m/sub nu/ less than or equal to 35 eV) neutrinos. Cold dark matter, even with biasing, seems unable to duplicate the combination of these observations (although a fine-tuned loophole with cold matter and percolated explosions may also marginally work.) The previous fatal problems of galaxy formation with neutrinos can be remedied by combining them with either cosmic strings or explosive galaxy formation. The former naturally gives the scale-free correlation function for galaxies, clusters, and superclusters, and gives large, but not necessarily spherical voids. The latter naturally gives spherical voids, but requires fine tuning and percolation to get the large scales and the scale-free correlation function. 39 refs.
Date: May 1, 1986
Creator: Schramm, D.N.
Partner: UNT Libraries Government Documents Department

String driven inflation

Description: It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation. 17 refs., 1 fig.
Date: November 1, 1987
Creator: Turok, N.
Partner: UNT Libraries Government Documents Department

Anyons in a magnetic field: Landau levels and vertex operator representation

Description: We construct exact many-body eigenstates of both energy and angular momentum for the N-anyon problem in an external magnetic field. Such states span the full ground-state eigenspace and have a natural representation in terms of the Fubini-Veneziano vertex operators of string theory. 19 refs.
Date: January 1, 1991
Creator: Dunne, G.V.; Lerda, A. (Massachusetts Inst. of Tech., Cambridge, MA (USA)) & Trugenberger, C.A. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Fayet-Iliopoulos D terms in string theory

Description: One loop scalar masses induced by Fayet-Ilipoulos D terms in string theory are calculated directly in the heterotic string theory for an arbitrary compactification which preserves space-time supersymmetry at the string tree level. The result is shown to be a total derivative in the moduli space of a torus with two punctures, and hence receives contribution only from the boundary of this moduli space.
Date: June 1, 1987
Creator: Sen, A.
Partner: UNT Libraries Government Documents Department

String primer

Description: This is an elementary introduction to the classical and quantum mechanics of a single bosonic string, and to some aspects of its supersymmetric and heterotic extensions. 22 refs.
Date: March 1, 1986
Creator: Bachas, C.
Partner: UNT Libraries Government Documents Department

Strings and their compactification from the particle viewpoint

Description: A series of four lectures is given which deals with the particle formulation of string theory. An introductory lecture is given on where the idea of strings comes from and what strings are. An introduction is given to simple Lie algebras and their representations. Compactified strings and the heterotic theories are discussed, showing how infinite-dimensional Kac-Moody affine algebras can be spectrum generating algebras in (open) string theories. The spectrum of excited states of the heterotic string is examined, and comments are made on representations of affine algebras. Some aspects are shown of the algebraic structure of compactified closed bosonic strings. (LEW)
Date: January 1, 1986
Creator: Slansky, R.
Partner: UNT Libraries Government Documents Department

Open superstrings as the theory of everything

Description: We discuss the first examples of one-loop finite four-dimensional superstrings. These examples can be either space-time supersymmetric or not depending on the details of the models. 17 refs.
Date: January 1, 1990
Creator: Bern, Z. (Los Alamos National Lab., NM (USA)) & Dunbar, D.C. (Liverpool Univ. (UK). Dept. of Applied Mathematics and Theoretical Physics)
Partner: UNT Libraries Government Documents Department