Related papers: Transient weak gravity in scalar-tensor theories
It is shown that a certain sum rule for soft supersymmetry-breaking scalar masses, which has been recently found in a certain class of superstring models, is universal for gauge-Yukawa unified models. To explain this coincidence, we argue…
In scalar-tensor theories we revisit the issue of strong coupling of perturbations around stealth solutions, i.e.\ backgrounds with the same forms of the metric as in General Relativity but with non-trivial configurations of the scalar…
Recent observations of near supernova show that the acceleration expansion of Universe decreases. This phenomenon is called the transient acceleration. In the second part of work we consider the 3-component Universe composed of a scalar…
We propose a phenomenological model where the gravitational interaction between dark matter and baryons is suppressed on small, subgalactic scales. We describe the gravitational force by adding a Yukawa contribution to the standard…
We revisit the problem of phantom behaviour of effective dark energy in scalar-tensor gravity. The main focus is on the properties of the functions defining the model. We find that models with the present phantom behavior can be made…
Supersymmetric models with t-b-\tau Yukawa unification at M_{GUT} qualitatively predict a sparticle mass spectrum including first and second generation scalars at the 3--15 TeV scale, third generation scalars at the (few) TeV scale and…
Higher-order scalar-tensor theories having an instantaneous mode do not develop the Ostrogradsky instability even if a seemingly dangerous mode is present. Such theories satisfy only partially the degeneracy conditions that are usually…
Disformal theories of gravity are scalar-tensor theories where the scalar couples derivatively to matter via the Jordan frame metric. These models have recently attracted interest in the cosmological context since they admit accelerating…
Observations provide increasingly strong evidence that the universe is accelerating. This revolutionary advance in cosmological observations confronts theoretical cosmology with a tremendous challenge, which it has so far failed to meet.…
We propose a natural extension of Horava's model for quantum gravity, which is free from the notorious pathologies of the original proposal. The new model endows the scalar graviton mode with a regular quadratic action and remains…
A cosmological model is formulated in the context of a scalar-tensor theory of gravity in which the entire cosmic background evolution is due to a complex scalar field evolving in Minkowski spacetime, such that its (dimensional) modulus is…
Scalar-tensor theories of gravity modify General Relativity by introducing a scalar field that couples non-minimally to the metric tensor, while satisfying the weak-equivalence principle. These theories are interesting because they have the…
We consider a higher dimensional gravity theory with a negative kinetic energy scalar field and a cosmological constant. We find that the theory admits an exact cosmological solution for the scale factor of our universe. It has the feature…
A decade ago, it was shown that a wide class of scalar-tensor theories can pass very restrictive weak field tests of gravity and yet exhibit non-perturbative strong field deviations away from General Relativity. This phenomenon was called…
A phenomenon of weak transient chaos is discussed that is caused by sub-exponential divergence of trajectories in the basin of a non-chaotic attractor. Such a regime is not easy to detect, because conventional characteristics, such as the…
A viable alternative to the dark energy as a solution of the cosmic speed up problem is represented by Extended Theories of Gravity. Should this be indeed the case, there will be an impact not only on cosmological scales, but also at any…
The supersymmetric flavor, CP and Polonyi problems are hints that the fundamental scale of the soft supersymmetry breaking parameters may be above a TeV, in apparent conflict with naturalness. We consider the possibility that multi-TeV…
We study the Weak Gravity Conjecture in the presence of scalar fields. The Weak Gravity Conjecture is a consistency condition for a theory of quantum gravity asserting that for a U(1) gauge field, there is a particle charged under this…
These proceedings summarise some recent efforts in understanding a class of vector-tensor theories known as {\it bumblebee} models, which spontaneously break local Lorentz and diffeomorphism invariance. Using cosmological perturbation…
The best motivated alternatives to general relativity are scalar-tensor theories, in which the gravitational interaction is mediated by one or several scalar fields together with the usual graviton. The analysis of their various…