Related papers: On Negative Energies, Strings, Branes, and Branewo…
In the early Universe matter was crushed to high densities, in a manner similar to that encountered in gravitational collapse to black holes. String theory suggests that the large entropy of black holes can be understood in terms of…
In String Theory compactification, branes are often invoked to get the desired form of the radion effective potential. Current popular way of doing this assumes that the introduction of branes will not modify the background geometry in an…
A new braneworld in the sourced-Taub background is proposed. The gravity field equations in the internal source region and external vacuum region are investigated, respectively. We find that the equation of state for the effective dark…
These notes give an introductory review on brane cosmology. This subject deals with the cosmological behaviour of a brane-universe, i.e. a three-dimensional space, where ordinary matter is confined, embedded in a higher dimensional…
The ultraviolet cutoff on a quantum field theory can be interpreted as a condensate of the affine curvature such that while the maximum of the affine action gives the power-law corrections, its minimum leads to the emergence of gravity.…
We consider Type 0B D3-branes placed at conical singularities and analyze in detail the conifold singularity. We study the non supersymmetric gauge theories on their worldvolume and their conjectured dual gravity descriptions. In the…
We investigate quantum field theory in a bulk space with boundary, which represents a 3-brane. Both flat and anti-de Sitter backgrounds are considered. The basic idea is to keep local commutativity only on the brane, giving up this…
In this paper we consider some constraints on brane-world cosmologies. In the first part we analyze different behaviors for the expansion of our universe by imposing constraints on the speed of sound. In the second part, we study the nature…
We conjecture a general upper bound on the strength of gravity relative to gauge forces in quantum gravity. This implies, in particular, that in a four-dimensional theory with gravity and a U(1) gauge field with gauge coupling g, there is a…
We look at the various aspects of treating general relativity as a quantum theory. It is briefly studied how to consistently quantize general relativity as an effective field theory. A key achievement here is the long-range low-energy…
Dark bubble cosmology is an alternative paradigm to compactification, which can circumvent issues of moduli stabilization and scale separation. In this paper we investigate how electromagnetic fields can be incorporated in this framework.…
Models with extra dimensions have attracted much interest recently because they may provide the solution for long standing problems in physics. One interesting and very attractive idea is that our visible universe is confined to a…
All the models of elementary particles and their interactions derived from String Theory involve a compact six-dimensional internal space. Its volume and shape should be fixed or stabilized, since otherwise massless scalar fields (moduli)…
The quantum corrections to the counting of statistical entropy for the 5+1-dimensional extremal black string in type-IIB supergravity with two observers are studied using anomalous Wess-Zumino actions for the corresponding intersecting…
In this Thesis, we focus on the study of the low energy approximation to non-critical string theories. We present an exhaustive study of their solutions, which are divided in three cases: vacuum, NSNS charged, and RR charged solutions. In…
Recent developments in string theory have led to 5-dimensional warped spacetime models in which standard-model fields are confined to a 3-brane (the observed universe), while gravity can propagate in the fifth dimension. Gravity is…
The Higgs branches of the world-volume theories for multiple M5 branes on an $A_k$ or $D_k$-type ALE space are known to host a variety of fascinating properties, such as the small $E_8$ instanton transition or the discrete gauging…
Braneworld scenarios appear in dynamical string tension theories, where string tension is positive between two surfaces separated by a short distance and at the two surfaces themselves the string tensions become infinite, therefore…
We consider field theories with sixteen supersymmetries, which includes U(N) Yang-Mills theories in various dimensions, and argue that their large N limit is related to certain supergravity solutions. We study this by considering a system…
I briefly summarize a recent research program aiming to probe the landscape of low-energy phases of string theory from a global perspective. Borrowing conceptual lessons from the swampland program, I will discuss how the effective theories…