Related papers: An effective three-dimensional de Sitter cosmology…
In this paper we analyze the vacuum bosonic current associated with a massive charged scalar field propagating in a $(D+1)$-dimensional anti-de Sitter (AdS) bulk in the presence of an idealized carrying-magnetic-flux cosmic string and also…
We derive a map between Einstein spaces of positive and negative curvature, including scalar matter. Starting from a space of positive curvature with some dimensions compactified on a sphere and analytically continuing the number of compact…
We generalize the swampland criterion forbidding stable non-supersymmetric AdS vacua and propose a new swampland conjecture forbidding stable non-supersymmetric "locally AdS" warped throats. The conjecture is motivated by the properties of…
This paper extends the recent investigation of the string theory landscape in hep-th/0605266, where it was found that the decay rate of dS vacua to a collapsing space with a negative vacuum energy can be quite large. The parts of space that…
In recent years, there has been considerable interest in theories formulated in anti-de Sitter (AdS) spacetime. However, AdS spacetime fails to be globally hyperbolic, so a classical field satisfying a hyperbolic wave equation on AdS…
We consider a cosmology with a non-compact nonlinear sigma model.The target space is of de-Sitter type and four scalar fields are introduced.The potential is absent but cosmological constant term $\Lambda$ is added. One of the scalar fields…
A new swampland criterion has recently been proposed. As a consequence, it forbids the existence of de Sitter solutions in a low energy effective theory of a quantum gravity. However, there exist classical de Sitter solutions of…
The late-time behavior of our universe is one of accelerated expansion, or that of a de Sitter space, and therefore motivates us to look for time-dependent backgrounds. Finding such backgrounds in string theory has always been a challenging…
In our previous paper [1,2], we proposed a probabilistic argument to explain the reason why the cosmological constant is very small in $4D$. We can ask a question: if the behavior of tunneling exponent $B$ can be generalized to…
We construct four-dimensional de Sitter space as an excited state, rather than as a vacuum configuration, in type IIB, heterotic SO(32), and heterotic E_8 \times E_8 string theories. This framework provides a mechanism to evade vacuum-based…
We present a model in which a 3-brane is embedded in a warped 5-dimensional background with a dilaton and a Kalb-Ramond 2-form. We show that it is possible to find static solutions of the form of charged dS/AdS-like black hole which could…
We expand on the braneworld-black hole de Sitter model introduced in \cite{Rasulian} which is a proposal for constructing an effective de Sitter spacetime with no explicit dependence on brane tension or bulk cosmological constant. In this…
Negative mass makes perfect physical sense as long as the dominant energy condition is satisfied by the corresponding energy-momentum tensor. Heretofore, only {\it configurations} of negative mass had been found…
We study, using Mean Curvature Flow methods, 3+1 dimensional cosmologies with a positive cosmological constant, matter satisfying the dominant and the strong energy conditions, and with spatial slices that can be foliated by 2-dimensional…
Exact and explicit string solutions in de Sitter spacetime are found. (Here, the string equations reduce to a sinh-Gordon model). A new feature without flat spacetime analogy appears: starting with a single world-sheet, several (here two)…
Consistent uplifting of AdS vacua in string theory often requires extra light degrees of freedom in addition to those of a (Kaehler) modulus. Here we consider the possibility that de Sitter and Minkowski vacua arise due to hidden sector…
Flux compactifications that give three- or four-dimensional Anti de Sitter vacua with a parametrically small negative cosmological constant are claimed to be ubiquitous in String Theory. However, the 1+1 and 2+1 dimensional CFT duals to…
In this thesis we study embedding formalisms for $\mathcal{N}$-extended anti-de Sitter (AdS) superspaces in four and five dimensions. Specifically, building on earlier work in the four-dimensional case, we develop bi-supertwistor…
We find explicitly the induced graviton propagator on de Sitter branes embedded in various five-dimensional spacetimes; de Sitter branes in AdS and Minkowski space are particular cases. By studying the structure of the momentum-space…
In this paper we construct the 5D uplift of 4D gravitational waves in de Sitter cosmology for the brane world scenario based on a nucleated bubble in AdS5. This makes it possible to generalize the connection between the dark bubbles and…