Related papers: Superluminality in DHOST theory with extra scalar
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…
If cosmological perturbations in our Hubble sized volume are nongaussian, then they will be coupled to any larger perturbation modes outside our Hubble volume. This has important consequences for modeling inflation: the scalar power…
We consider two examples of solutions of the equations of motion of scalar field theories with higher derivatives. These are the cosmology of the rolling tachyon and static spherically symmetric solutions of the scalar field in flat space.…
We study the cosmological perturbations of the recently proposed extension of non-linear massive gravity with a scalar field. The added scalar field ensures a new symmetry on the field space of the theory. The theory has the property of…
We study the late cosmological evolution, from the nonrelativistic matter dominated era to the dark energy era, in modified gravity models described by Degenerate Higher-Order Scalar-Tensor (DHOST) theories. They represent the most general…
It continues to be alleged that superluminal influences of any sort would be inconsistent with special relativity for the following three reasons: (i) they would imply the existence of a distinguished' frame; (ii) they would allow the…
We present the superfield generalization of free higher spin equations in tensorial superspaces and analyze tensorial supergravities with GL(n) and SL(n) holonomy as a possible framework for the construction of a non-linear higher spin…
Dimension-five photon $(\gamma )$ scalar $(\phi)$ interaction terms usually appear in the bosonic sector of unified theories of electromagnetism and gravity. In these theories the three propagation eigenstates are different from the three…
Ghost inflation is a well-known framework in which cosmological fluctuations can generate enhanced primordial non-Gaussianity, typically of the equilateral type. In its original form, however, it is in tension with current observational…
We show that in the presence of a distance dependent Lorentz-violating time-like background one may find superluminal neutrinos at some high energy such as OPERA's scale. The similar behavior but approaching the subluminal branch is found…
We study perturbations of a scalar field cosmology in Horava-Lifshitz gravity, adopting the most general setup without detailed balance but with the projectability condition. We derive the generalized Klein-Gordon equation, which is…
We solve the general problem of mixing of electromagnetic and scalar or pseudoscalar fields coupled by axion-type interactions ${\cal L}_{int} =g_{\phi} \phi \epsilon_{\mu \nu \a \b}F^{\mu \nu}F^{\a \b} $. The problem depends on several…
We consider a general five-dimensional sigma-model coupled to gravity, with any number of scalars and general sigma-model metric and potential. We discuss in detail the problem of the boundary conditions for the scalar fluctuations, in the…
A recently proposed gedankenexperiment involving the (gravitational or electromagnetic) interaction between two objects--one placed in a state of quantum superposition of two locations--seems to allow for faster-than-light communication.…
It has recently been realized that many theories of physics beyond the Standard Model give rise to cosmological histories exhibiting extended epochs of cosmological stasis. During such epochs, the abundances of different energy components…
A scalar-tensor theory of gravity can be made not only to account for the current cosmic acceleration, but also to satisfy solar-system and laboratory constraints, by introducing a non-linear derivative interaction for the scalar field.…
This thesis contributes to the field of gravitational lensing (GL) and observational cosmology. We discuss the use of gravitational lensing as a tool in search of exotic objects in the Universe. In the next chapter the concordance of an…
In previous work, we showed that in loop quantum cosmology of scalar-tensor theory (STT) with the holonomy correction the background equations of motion in the Jordan frame have two branches, i.e., the $b_{+}$ branch and the $b_{-}$ branch.…
Extended Theories of Gravity with additional scalar degrees of freedom have recently acquired increasing interest due to the presence of a screening mechanism that allows suppressing at small scales (e.g., the Solar System scale) every…
Degenerate Higher Order Scalar Tensor (DHOST) theories are the most general scalar-tensor theories whose Lagrangian depends on the metric tensor and a single scalar field and its derivatives up to second order. They propagate only one…