Related papers: A Note on Nonperturbative Instability in String Th…

In this thesis we discuss some nonperturbative and noncommutative aspects of string theory. We present low-energy background field solutions corresponding to various D-branes (and their bound states) and intersecting branes in flat and…

In arXiv:1907.07688 Balthazar, Rodriguez and Yin (BRY) computed the one instanton contribution to the two point scattering amplitude in two dimensional string theory to first subleading order in the string coupling. Their analysis left…

We study the origin of turbulence on the string worldsheet with boundaries laid in anti de Sitter (AdS) spacetime. While the classical motion of a single closed string in AdS is integrable, it has recently been recognized that weak…

We investigate the possibility that stringy nonperturbative effects appear as holes in the world-sheet. We focus on the case of Dirichlet string theory, which we argue should be formulated differently than in previous work, and we find that…

As of today there exist consistent, gauge-invariant string field theories describing all string theories: bosonic open and closed strings, open superstrings, heterotic strings and type II strings. The construction of these theories require…

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…

We use the boundary state formalism to study, from the closed string point of view, superpositions of branes and anti-branes which are relevant in some non-perturbative string dualities. Treating the tachyon instability of these systems as…

We consider how the time-dependent decay process of an unstable D-brane should be described in the full (quantum) open-closed string theory. It is argued that the system, starting from the unstable D-brane configuration, will evolve in time…

We suggest that the boundary cosmological constant \zeta in c<1 unitary string theory be regarded as the one-dimensional complex coordinate of the target space on which the boundaries of world-sheets can live. From this viewpoint we…

New non-perturbative interactions in the effective action of two dimensional string theory are described. These interactions are due to ``stringy" instantons

We review some recent developments in string theory, emphasizing the importance of vacuum instabilities, their relation to the density of states, and the role of space-time fermions in non-critical string theory. We also discuss the…

We present a pedagogical review of the stable non-BPS states in string theory which have recently attracted some attention in the literature. In particular, following the analysis of A. Sen, we discuss in detail the case of the stable…

In this paper we present time dependent solution of the open bosonic string field theory describing the motion of the tachyon on unstable D-brane.

In the first lecture, we discuss basic aspects of worldsheet and penta-brane instantons as well as (unoriented) D-brane instantons, which is our main focus here, and threshold corrections to BPS-saturated couplings. The second lecture is…

The boundary state associated with the rolling tachyon solution on an unstable D-brane contains a part that decays exponentially in the asymptotic past and the asymptotic future, but it also contains other parts which either remain constant…

For a superstring theory in four spacetime dimensions, we propose a modification of the Born-Infeld action that possesses a well-defined tensionless limit. We interpret this as describing the effective target space dynamics of null strings…

In this paper we investigate the tachyon instability of open bosonic string theory applying methods of boundary conformal field theory. We consider compactifications on maximal tori of various simple Lie algebras with a specific background…

D-instanton amplitudes suffer from various infrared divergences associated with tachyonic or massless open string modes, leading to ambiguous contribution to string amplitudes. It has been shown previously that string field theory can…

String Theory is a hot topic of physics and mathematics. For the former, it stands as a huge sandbox where the formulation of difficult problems can be simplified and their hard computations carried out. For the latter, it stands as a…

We discuss construction of classical time dependent solutions in open string (field) theory, describing the motion of the tachyon on unstable D-branes. Despite the fact that the string field theory action contains infinite number of time…