Related papers: On the gravitational seesaw in higher-derivative g…
We investigate 4-dim gauge theories and gravitational theories with nonpolynomial actions containing an infinite series in covariant derivatives of the fields representing the expansion of a transcendental entire function. A class of entire…
A discussion of an extended class of higher-derivative classical theories of gravity is presented. A procedure is given for exhibiting the new propagating degrees of freedom, at the full non-linear level, by transforming the…
Just like light, gravitational waves (GWs) are deflected and magnified by gravitational fields as they propagate through the Universe. However, their low frequency, phase coherence and feeble coupling to matter allow for distinct lensing…
We propose a class of multidimensional higher derivative theories of gravity without extra real degrees of freedom besides the graviton field. The propagator shows up the usual real graviton pole and extra complex conjugates poles that do…
We consider the problem of Newtonian singularity in the wide class of higher derivative gravity models, including the ones which are renormalizable and super-renormalizable at the quantum level. The simplest version of the singularity-free…
A discussion of the number of degrees of freedom, and their dynamical properties, in higher derivative gravitational theories is presented. The complete non-linear sigma model for these degrees of freedom is exhibited using the method of…
The linear seesaw mechanism provides a simple way to generate neutrino masses. In addition to Standard Model particles, it includes quasi-Dirac leptons as neutrino mass mediators, and a leptophilic scalar doublet seeding small neutrino…
The seesaw model of heavy and light Majorana neutrinos and its low-energy effective theory are studied, when the number of heavy neutrinos is equal to or less than the number of light lepton generations. We establish a general relationship…
We analyze the sensitivity of galaxy and weak-lensing surveys to detect preferred directions in the gravitational interaction. We consider general theories of gravity involving additional vector degrees of freedom with non-vanishing spatial…
General Relativity (GR) describes gravitation well at the energy scales which we have so far been able to achieve or detect. However, we do not know whether GR is behind the physics governing stronger gravitational field regimes, such as…
We present a general method which can be used for geometrical and physical interpretation of an arbitrary spacetime in four or any higher number of dimensions. It is based on the systematic analysis of relative motion of free test…
Recent theoretical developments have shown that extra spacetime dimensions can lower the fundamental GUT, Planck, and string scales. However, recent evidence for neutrino oscillations suggests the existence of light non-zero neutrino…
The prediction of small neutrino masses through the Seesaw Mechanism and their subsequent measurement suggests that the natural cut-off of the Standard Model is very high indeed. The recent neutrino data must be interpreted as a reflection…
Traditional seesaw mechanisms provide an elegant theoretical framework for explaining the small yet non-zero masses of neutrinos. Nevertheless, they face significant experimental challenges, primarily because the energy scale associated…
Neutrinos stand out among elementary particles through their unusually small masses. Various seesaw mechanisms attempt to explain this fact. In this work applying insights from matrix theory we are in a position to treat variants of seesaw…
In Gravity Unified Theories all operators that are consistent with the local gauge and discrete symmetries are expected to arise in the effective low-energy theory. Given the absence of multiplets like 126 of SO(10) in string models, and…
Various phenomenological consequences of seesaw theories for the generation of the fermion mass hierarchy of the Standard Model have been analyzed, with an emphasis on models in which the light-active neutrino masses are derived from…
Theories of modified gravity attempt to reconcile physics at the largest and the smallest scales by explaining the accelerated expansion of our universe without introducing the cosmological constant. One class of such theories, known as…
We consider the Standard Model extended by right-handed neutrinos to explain massive neutrinos through the seesaw mechanism. The new fermion can be observed when it has a sufficiently small mass and large mixings to left-handed neutrinos.…
We recalculate the beta functions of higher derivative gravity in four dimensions using the one--loop approximation to an Exact Renormalization Group Equation. We reproduce the beta functions of the dimensionless couplings that were known…