Related papers: The dangerous irrelevance of string theory
The tensionless limit of classical string theory may be formulated as a topological theory on the world-sheet. A vector density carries geometrical information in place of an internal metric. It is found that path-integral quantization…
String Theory includes a plethora of higher-spin excitations, which clearly lie behind its most spectacular properties, but whose detailed behavior is largely unknown. Conversely, string interactions contain much useful information on…
This article briefly summarizes the motivations for -- and recent progress in -- searching for cosmological configurations within string theory, with a focus on how much we might reasonably hope to learn about fundamental physics from…
Searching for space/time noncommutativity we reconsider open strings in a constant background electric field. The main difference between this situation and its magnetic counterpart is that here there is a critical electric field beyond…
Inflationary string cosmology backgrounds can amplify perturbations in a more efficient way than conventional inflationary backgrounds, because the perturbation amplitude may grow - instead of being constant - outside the horizon. If not…
I review several aspects of torsion in string-inspired cosmologies. In particular, I discuss its connection with fundamental, string-model independent, axion fields associated with the massless gravitational multiplet of the string. I argue…
In this work we raise the question whether nonsymmetric gravity and string theory are related. We start making the observation, that the gravitational field $ g_{\mu\nu}$ and the nonsymmetric gauge field $ A_{\mu\nu}$ arising in the low…
Appearance of cosmic strings in the early Universe is a common manifestation of new physics typically linked to some high energy scale. In this paper, we discuss a different situation, where a model underlying cosmic string formation is…
We argue that the light particles in string theory obey an effective quantum mechanics modified by the inclusion of a quantum-gravitational friction term, induced by unavoidable couplings to unobserved massive string states in the…
We argue that deriving an effective field theory from string theory requires a Wilsonian perspective with a physical cutoff. Employing proper time regularization we demonstrate the decoupling of states and contrast this with what happens in…
String theory has not even come close to a complete formulation after half a century of intense research. On the other hand, a number of features of the theory suggest that the theory, once completed, may be a final theory. It is argued in…
We present a minimal model for the Universe evolution fully extracted from effective String Theory. This model is by its construction close to the standard cosmological evolution, and it is driven selfconsistently by the evolution of the…
It is argued that string theory may pose new conceptual issues for the history and philosophy of science.
We argue that traditional methods of compactification of string theory make it very difficult to understand how the cosmological constant becomes zero. String inspired models can give zero cosmological constant after fine tuning but since…
The problem of dark energy arises due to its self-gravitating properties. Therefore explaining vacuum energy may become a question for the realm of quantum gravity, that can be addressed within string theory context. In this talk I…
String theory is the leading contemporary framework to explore the synthesis of quantum mechanics with gravity. String phenomenology aims to study string theory while maintaining contact with observational data. The fermionic $Z_2\times…
The gravitational fields of vacuumless global and gauge strings have been studied in Brans-Dicke theory under the weak field assumption of the field equations. It has been shown that both global and gauge string can have repulsive as well…
Cosmic strings are predicted by many field-theory models, and may have been formed at a symmetry-breaking transition early in the history of the universe, such as that associated with grand unification. They could have important…
Generic cosmological models in non-critical string theory have a time-dependent dilaton background at a late epoch. The cosmological deceleration parameter Q_0 is given by the square of the string coupling, g_s^2, up to a negative sign.…
There is evidence that string theory possesses a large discretuum of stable and/or metastable ground states, with zero or four supersymmetries in four dimensions. I discuss critically the nature of this evidence. Assuming this "landscape"…