Related papers: Constraints on Extra Time Dimensions
We show that the electron in the Riemann-Cartan spacetime with extra dimensions has a finite size that is much larger than the experimental upper limit on its radius. Thus the Arkani-Hamed-Dimopoulos-Dvali and Randall-Sundrum models of the…
In the Kaluza-Klein (KK) scenario with n large extra dimensions where gravity propagates in the 4+n dimensional bulk of spacetime while gauge and matter fields are confined to a four dimensional subspace, the light graviton KK modes can be…
In the present work we analize the behavior of 5-dimensional gravitational waves propagating on a Kaluza-Klein background and we face separately the two cases in which respectively the waves are generated before and after the process of…
The incorporation of an adequate discrete expansion to the formalism of the special relativity that does not allow gravitational acceleration unravels unexplored phenomena. This extension takes into account consequences of a small variation…
It is found the exact solution of the Poisson equation for the multidimensional space with topology $M_{3+d}=\mathbb{R}^3\times T^d$. This solution describes smooth transition from the newtonian behavior $1/r_3$ for distances bigger than…
String theory suggests modifications of our spacetime such as extra dimensions and the existence of a mininal length scale. In models with addidional dimensions, the Planck scale can be lowered to values accessible by future colliders.…
Models predicting the existence of extra spatial dimensions offer compelling and novel solutions to outstanding problems of the Standard Model. In such models, our universe exists on a 4 dimensional brane embedded in a larger dimensional…
The metric of a perturbed Robertson-Walker spacetime is characterized by three functions: a scale-factor giving the expansion history and two potentials which generalize the single potential of Newtonian gravity. The Newtonian potential…
We suggest the possibility that in ADD type brane-world scenarios, the higher KK excitations of the graviton may decay to lower ones owing to a breakdown of the conservation of extra dimensional ``momenta'' and study its implications for…
General relativity describes the gravitational field geometrically and in a self-interacting way because it couples to all forms of energy, including its own. Both features make finding a quantum theory difficult, yet it is important in the…
A novel theory of Quantum Gravity is presented in which the real gravitons manifest themselves as holes in space. In general, these holes propagate at the speed of light through an expanding universe with boundary denoted by U, which is…
Recent criticism of higher-dimensional extensions of Einstein's theory is considered. This may have some justification as regards string theory, but is misguided as applied to five-dimensional theories with a large extra dimension. Such…
We address the issue of whether extra dimensions could have an infinite volume and yet reproduce the effects of observable four-dimensional gravity on a brane. There is no normalizable zero-mode graviton in this case, nevertheless correct…
Additional U(1) gauge symmetries and corresponding vector bosons, called hidden photons, interacting with the regular photon via kinetic mixing are well motivated in extensions of the Standard Model. Such extensions often exhibit extra…
I argue that the true quantum gravity scale cannot be much larger than the Planck length, because if it were then the quantum gravity-induced fluctuations in $\Lam$ would be insufficient to produce the observed cosmic ``dark energy''. If…
A satisfactory theory of quantum gravity may necessitate a drastic modification of our perception of space-time, by giving it a foamy structure at distances comparable to the Planck length. It is argued in this essay that the experimental…
We give an overview of the issue of anomalies in field theories with extra dimensions. We start by reviewing in a pedagogical way the computation of the standard perturbative gauge and gravitational anomalies on non-compact spaces, using…
The field equations of a generalized $f(R)$ type gravity model, in which there is an arbitrary coupling between matter and geometry, are obtained. The equations of motion for test particles are derived from a variational principle in the…
It is generally expected that quantum gravity affects the structure of space-time by introducing stochastic fluctuations in the geometry, and, ultimately, in the measurements of four-distances and four-momenta.These fluctuations may induce…
In this lecture I address the issue of possible large distance modification of gravity and its observational consequences. Although, for the illustrative purposes we focus on a particular simple generally-covariant example, our conclusions…