D-branes and boundary states in closed string theories

We review the boundary state description of D-branes in type I string theory and show that the only stable non-BPS configurations are the D-particle and the D-instanton. We also compute the gauge and gravitational interactions of the non-BPS D-particles and compare them with the interactions of the dual non-BPS states of the heterotic string, finding complete agreement.

In these lectures we review the basic ideas of perturbative and non-perturbative string theory. On the non-perturbative side we give an introduction to D-branes and string duality. The elementary concepts of non-BPS branes and noncommutative gauge theories are also discussed.

This thesis is devoted to the construction and study of D-branes in some curved space-times in string theory. On the one hand, those D-branes are described geometrically as submanifolds subject to Born-Infeld effective dynamics. On the other hand, they can be built microscopically using boundary conformal field theory. We use and compare those two approaches. We also improve them technically : we rewrite Born-Infeld dynamics in a gauge-invariant way, and formulate precise ana...

Recently a boundary string field theory that had been proposed some time ago, was used to calculate correctly the ratios of D-brane (both BPS and non-BPS) tensions. We discuss how this work is related to the boundary state formalism and open string closed string duality, and argue that the latter clarifies why the correct tension ratios are obtained in these recent calculations.

The first part of this thesis is a general introduction to the bosonic and fermionic string theory, to the concept of D brane and to string dualities. A discussion of anomalies cancellation closes the chapter. The second part of the thesis reviews the basics of orientifold and orbifold constructions and the Scherk-Schwarz mechanism of supersymmetry breaking. The last part starts with an introduction to standard cosmology and inflation. Alternatives to inflation inspired from ...

In this Ph.D. thesis we review and elaborate on a method to find the D-brane effective action, based on BPS equations. Firstly, both for the Yang-Mills action and the Born-Infeld action it is shown that these configurations are indeed BPS, i.e. solutions to these equations saturate a Bogomolny bound and leave some supersymmetry unbroken. Next, we use the BPS equations as a tool to construct the D-brane effective action and require that (a deformation of) these equations shoul...

This introductory part of the author's PhD compilation thesis discusses non-perturbative aspects of string theory, with focus on D-instantons which play key roles in the context of string phenomenology and dualities. By translating ideas from ordinary instanton calculus in field theory, D-instanton calculus is formulated and applied to supersymmetric gauge theories realized as world volume theories of spacefilling D-branes in non-trivial backgrounds. We show that, for configu...

This is a short arrangement of notes on D-branes, offered as an embellishment of five lectures which were presented at the 1998 Trieste Spring School entitled ``Non-Perturbative Aspects of String Theory and Supersymmetric Gauge Theory''. There is a good number of collections of pedagogical notes on D-branes in the literature, and since space here is limited, no attempt will be made to cover all of the introductory material again. Instead, the notes cover selected topics and t...

We review the recent developments in our understanding of non-BPS states and branes in string theory. The topics include 1) construction of unstable non-BPS D-branes in type IIA and type IIB string theories, 2) construction of stable non-BPS D-branes on various orbifolds and orientifolds of type II string theories, 3) description of BPS and non-BPS D-branes as tachyonic soliton solutions on brane-antibrane pair of higher dimension, and 4) study of the spectrum of non-BPS stat...

We determine all D-branes in the non-tachyonic 0'B orientifold, examine their world-volume anomalies and study orbifold compactifications. We find that the spectrum of the D-branes contains chiral fermions in the symmetric, antisymmetric and fundamental representations of (unitary) gauge groups on the branes. The cancellation of the world-volume anomalies requires Wess-Zumino terms which we determine explicitly. We examine a non-tachyonic compactification to 9D whose closed p...