Superstrings and solitons (original) (raw)

Macroscopic superstrings as interpolating solitons

Physics Letters B, 1994

It is known that, in string sigma-model metric, the 'extreme' fivebrane solution of D=10 supergravity interpolates between D=10 Minkowski spacetime and a supersymmetric S 3 compactification to a linear dilaton vacuum. We show here that, in fivebrane sigma-model metric, the extreme string solution of D=10 supergravity interpolates between Minkowski spacetime and a hitherto unknown supersymmetric S 7 compactification of d=10 supergravity to a three-dimensional anti-de Sitter generalization of the linear dilaton vacuum, which may be invariantly characterized in terms of conformal Killing vectors. The dilaton field diverges near the string core but this divergence may be eliminated by re-interpreting the string solution as the extreme membrane solution of 11-dimensional supergravity. We show that the latter has an analytic extension through a regular degenerate event horizon to an interior region containing a curvature singularity. We obtain analogous results for other extended object solutions of supergravity theories. * If d = 1 the potential A is a one-form and there arises the possibility of a Kaluza-Klein interpretation of it as an off-diagonal component of the (D + 1)-metric. This allows other values of D, e.g. D = 4, but these cases are rather dissimilar to the D = 10 macroscopic superstring and will not be discussed here.

Supersymmetric String Solitons

1991

These notes are based on lectures given by C. Callan and J. Harvey at the 1991 Trieste Spring School on String Theory and Quantum Gravity. The subject is the construction of supersymmetric soliton solutions to superstring theory. A brief review of solitons and instantons in supersymmetric theories is presented. Yang-Mills instantons are then used to construct soliton solutions to heterotic string theory of various types. The structure of these solutions is discussed using low-energy field theory, sigma-model arguments, and in one case an exact construction of the underlying superconformal field theory.

Theoretical and Phenomenological Aspects of Superstring Theories

1998

Introduction CHAPTER 2 2 Compactification on Orbifolds 2.1 Toroidal Compactifications 2.2 General Theory of Orbifold Compactifications 2.3 Duality Symmetries CHAPTER 3 3 Aspects of Threshold Corrections to Low Energy Effective string Theories compactified on Orbifolds 1 where the invariant integral is given by ds 2 = −g µν (x)dx µ dx ν. 2 For n = 0 we have the point particle, for n = 1 we have the string, while for n = 2 we have the membrane and so on. . .. 3 See the footnote following 3.31. 4 Unoriented open and closed strings with N = 1 supersymmetry. 5 The ten dimensional N = 1 supergravity coupled to matter has anomalies coming from hegagon diagrams.

Superstrings with spontaneously broken supersymmetry and their effective theories

Nuclear Physics B, 1989

We discuss superstring models with spontaneous breaking of N = 1, 2 or 4 space-time supersymmetry, via coordinate-dependent compactifications from five to four dimensions. We provide a description of the supersymmetry breaking mechanism in the formulation with complex world-sheet fermions, and we reinterpret it in terms of special deformations of the lorentzian charge lattice. Considering a representative string model with spontaneously broken N = 1 supersymmetry and massless chiral fermions, we show that the knowledge of the spectrum of states and of the flat directions completely specifies its low-energy effcctive lagrangian, which turns out to be a new no-scale supergravity model. We outline the qualitative difference between these models and other scenarios of gaugino (gravitino) condensation or general non-pcrturbative phenomena.

Supersymmetry and dual string solitons

Physics Letters B, 1995

We present new classes of string-like soliton solutions in (N = 1 ; D = 10), (N = 2 ; D = 6) and (N = 4 ; D = 4) heterotic string theory. Connections are made between the solution-generating subgroup of the T-duality group of the compactication and the number of spacetime supersymmetries broken. Analogous solutions are also noted in (N = 1; 2; D = 4) compactications, where a dierent form of supersymmetry breaking arises.

The spacetime supersymmetric formulation of the string

Physics Reports, 1990

The superparticle in background supergravitational 1. Introduction 223 fields 258 2. Classical superparticles and the twistor transform 225 3. The superstring in curved superspace 269 2.1. Constrained dynamics of massless particles 225 3.1. The superstring action 270 2.2. A first look at the superparticle 228 3.2. The constraints in "flat" superspace 276 2.3. Superspace 229 3.3. The first-class constraints in curved space 277 2.4. Constrained dynamics of the superparticle 234 4. Recent developments 280 2.5. The superparticle in background Yang-Mills fields 239 Appendix A. Gamma matrices 282 2.6. Constraint equations and the super-Yang-Mills equa-Al. The Dirac algebra 282 tions of motion 247 A.2. Fierz identities 284 2.7. The ten-dimensional twistor transform 252 References 286

Towards a Non-Supersymmetric String Phenomenology

2015

Over the past three decades, considerable effort has been devoted to studying the rich and diverse phenomenologies of heterotic strings exhibiting spacetime supersymmetry. Unfortunately, during this same period, there has been relatively little work studying the phenomenologies associated with their non-supersymmetric counterparts. The primary reason for this relative lack of attention is the fact that strings without spacetime supersymmetry are generally unstable, exhibiting large one-loop dilaton tadpoles. In this paper, we demonstrate that this hurdle can be overcome in a class of tachyon-free four-dimensional string models realized through coordinate-dependent compactifications. Moreover, as we shall see, it is possible to construct models in this class whose low-lying states resemble the Standard Model (or even potential unified extensions thereof)-all without any light superpartners, and indeed without supersymmetry at any energy scale. The existence of such models thus opens the door to general studies of non-supersymmetric string phenomenology, and in this paper we proceed to discuss a variety of theoretical and phenomenological issues associated with such non-supersymmetric strings. On the theoretical side, we discuss the finiteness properties of such strings, the general characteristics of their mass spectra, the magnitude and behavior of their one-loop cosmological constants, and their interpolation properties. By contrast, on the phenomenological side, the properties we discuss are more model-specific and include their construction techniques, their natural energy scales, their particle and charge assignments, and the magnitudes of their associated Yukawa couplings and scalar masses.

Phenomenological survey of a minimal superstring standard model

… of the seventh international symposium particles, …, 2000

We discuss a heterotic-string solution in which the observable sector effective field theory just below the string scale reduces to that of the MSSM, with the standard observable gauge group being just SU

Superstring Phenomenology-A Personal Perspective 1

2013

In the first part of this paper I review the construction of the realistic free fermionic models, as well as current attempts to study aspects of these models in the nonperturbative framework of M– and F–theories. I discuss the recent demonstration of a Minimal Superstring Standard Model, which contains in the observable sector, below the string scale, solely the MSSM charged spectrum, and provides further support to the assertion that the true string vacuum is connected to the Z2×Z2 orbifold in the vicinity of the free fermionic point in the Narain moduli space. In the second part I review the recent formulation of quantum mechanics from an equivalence postulate, which offers a new perspective on the synthesis of gravity and quantum mechanics, and contemplate possible relations with string theory and beyond.

Navigating into the realm of Non-Supersymmetric String Theories

2016

For more than two decades, remarkable progress has been made in the construction of supersymmetric Standard Model-like theories from the heterotic string theory. In particular, considerable effort has been invested in studying the abundant phenomenological features of heterotic strings exhibiting N = 1 spacetime supersymmetry. At the same time, their non-supersymmetric counterparts have received little attention on the grounds that strings which do not exhibit spacetime supersymmetry admit large one-loop dilaton tadpoles, and are therefore unstable. Nonetheless, in this epoch of data acquisition from high-luminosity experiments, the observational absence of supersymmetry is striking. Consequently, non-supersymmetric theories receive a profound interest in the particle physics community. In this thesis, a class of non-supersymmetric, tachyon-free, four-dimensional string models is constructed via a string generalisation of Scherk-Schwarz compactification. Such models demonstrate grea...