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Theories of gravity for which gravitons can be treated as massive particles have presently been studied as realistic modifications of General Relativity, and can be tested with cosmological observations. In this work, we study the ability…
We consider the cosmological consequences of a special scalar-tensor-vector theory of gravity, known as MOG (for MOdified Gravity), proposed to address the dark matter problem. This theory introduces two scalar fields $G(x)$ and $\mu(x)$,…
The inverse Compton scattering of ultrarelativistic electrons accelerated at the pulsar wind termination shock is believed to be responsible for TeV gamma-ray signal recently reported from the binary system PSR B1259-63/SS2883. While this…
We review the No-Scale F-SU(5) model with extra TeV-scale vector-like flippon multiplets and associated collider phenomenology relating to the search for supersymmetry at the LHC. The model framework possesses the rather unique capacity to…
We describe a model in which the fundamental scale M_\star of the theory which unifies gravity and quantum mechanics is in the TeV range, but without requiring additional spacetime dimensions. The weakness of gravity at low energies is due…
The Standard Model of particle physics is assumed to be a low-energy effective theory with new physics theoretically motivated to be around TeV scale. The dissertation presents theories with new physics beyond the Standard Model at the TeV…
Recently modified gravitational theories which mimic the behaviour of dark matter, the so-called "Mimetic Dark Matter", have been proposed. We study the consistency of such theories with respect to the absence of ghost instability and…
We propose to use multiple-imaged gravitational lenses to set limits on gravity theories without dark matter, specificly TeVeS (Bekenstein 2004), a theory which is consistent with fundamental relativistic principles and the phenomenology of…
With the continuous upgrade of detectors, more and more gravitational wave (GW) events were captured by the LIGO Scientific Collaboration and Virgo Collaboration (LVC), which offers a new avenue to test General Relativity and explore the…
We follow a low-energy effective theory approach to identify the general class of theories that describes a vector field (of unconstrained norm) coupled to gravity. The resulting set may be regarded as a generalization of the conventional…
Since the discovery of the accelerated expansion of the present Universe, significant theoretical developments have been made in the area of modified gravity. In the meantime, cosmological observations have been providing more high-quality…
We study observational bounds in a class of scalar-tensor gravity theories recently proposed. Either an upper or lower bound on a conformal factor in these theories is derived from null observation in composition dependent fifth force…
We review and extend the Gauge Vectors-Tensor gravity: a covariant theory of gravity composed of a metric and gauge fields, leading to simple second order partial differential equations of motion, whose Newtonian and strong limits coincide…
The recent observations of neutron star mergers have changed our perspective on scalar- tensor theories of gravity, favouring models where gravitational waves travel at the speed of light. In this work we consider a scalar-tensor set-up…
The validity of MOND and TeVeS models of modified gravity has been recently tested by using lensing techniques, with the conclusion that a non-trivial component in the form of dark matter is needed in order to match the observations. In…
Most current models of Lorentz symmetry violation (LSV) at the Planck scale involve power-like extrapolations of the Lorentz-beaking term down to accelerator and even much lower energies. It is therefore assumed that no intermediate energy…
We study cosmological tensor perturbations generated during de Sitter inflation in the conformal gravity with mass parameter $m^2=2H^2$. It turns out that tensor power spectrum is scale-invariant.
A new vector-tensor model of classical gravity, which contains coupling between the field strength of the vector field and the curvature tensors in six dimensions, is proposed. Cosmological solutions of the scale factors in this model with…
A nonlocal quantum gravity theory is presented which is finite and unitary to all orders of perturbation theory. Vertex form factors in Feynman diagrams involving gravitons suppress graviton and matter vacuum fluctuation loops by…
We consider a special class of the tetrad theory of gravitation which can be considered as a viable alternative gravitational theories. We investigate cosmological models based on those theories by examining the possibility of fitting the…