Related papers: A different kind of four dimensional brane for str…
We consider brane cosmologies within the context of five-dimensional actions with O(a') higher curvature corrections. The actions are compatible with bulk string amplitude calculations from heterotic string theory. We find wrapped solutions…
We describe cosmic D--term strings as D3 branes wrapped on a resolved conifold. The matter content that gives rise to D--term strings is shown to describe the world--volume theory of a space--filling D3 brane transverse to the conifold…
The Hamiltonian analysis of Polyakov action is reviewed putting emphasis in two topics: Dirac observables and gauge conditions. In the case of the closed string it is computed the change of its action induced by the gauge transformation…
We study the behavior of D-branes at distances far shorter than the string length scale~$l_s$. We argue that short-distance phenomena are described by the IR behavior of the D-brane world-volume quantum theory. This description is valid…
We study the cosmology induced on a brane probing a warped throat region in a Calabi-Yau compactification of type IIB string theory. For the case of a BPS D3-brane probing the Klebanov-Strassler warped deformed conifold, the cosmology…
We investigate braneworld cosmology based on the D-brane initiated in our previous paper. The brane is described by a Born-Infeld action and the gauge field is contained. The higher order corrections of an inverse string tension will be…
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…
The brane world scenario is a new approach to resolve the problem on how to compactify the higher dimensional spacetime to our 4-dimensional world. One of the remarkable features of this scenario is the higher dimensional effects in…
We present Poincare invariant domain wall (``3-brane'') solutions to some 5-dimensional effective theories which can arise naturally in string theory. In particular, we find theories where Poincare invariant solutions exist for arbitrary…
Some shortcomings in regard to our lack of conceptual understanding of string theory are displayed and prescription to untangle them is proposed. String theory should be a fundamental dynamics of four dimensional symmetric space-times.…
The Lorentz harmonic formulation of D-dimensional bosonic p-brane theory with $D\geq (p+1)(p+2)/2$ coupled to an antisymmetric tensor field of rank d=(p+1) provides the dynamical ground for the description of d=(p+1) dimensional Gravity. It…
We reconstruct the tachyon effective action for unstable D-branes in superstring theory by examining its behaviour near exactly marginal deformations, where the ambigous higher derivative terms can be eliminated. We then compare this action…
The dynamics of extended objects, such as strings and membranes, has attracted more attention in the past decades since the fundamental objects introduced in high-energy physics are no longer pointlike. Their motion is generally quite…
A couple of issues concerning the effective dynamics of D-branes in string theory are discussed. Primarily, I am concerned with linearization of the actions by introduction of non-propagating fields and a full super- and kappa-symmetric…
The Brownian motion of a number of quantum states in a compact one-dimensional space is studied via the Wiener fractal measure, and it is shown that the derived path-integral measure coincides precisely with the Polyakov path-integral…
We consider evolution of compact extra dimensions in cosmology and try to see whether wrapped branes can prevent the expansion of the internal space. Some difficulties of Brandenberger and Vafa mechanism for decompactification are pointed…
Over the last few years, string theory has changed profoundly. Most importantly, novel duality relations have emerged which involve gauge theories of brane excitations on one side and various closed string backgrounds on the other. In this…
We evaluate a 5-dimensional Randall Sundrum type metric in the Lagrangian of the Einstein-Chern-Simons gravity, and then we derive an action and its corresponding field equations, for a 4-dimensional brane embedded in the 5-dimensional…
We construct a string theory realization of the 4+1d quantum Hall effect recently discovered by Zhang and Hu. The string theory picture contains coincident D4-branes forming an S^4 and having D0-branes (i.e. instantons) in their…
The recent interest in modified theories of gravity, involving some type of non-minimal coupling to the Ricci scalar, and the calculation of cosmological observables in the Einstein or the Jordan frame, motivate the formulation of these…