Related papers: Gravitational production of sterile neutrinos
We investigate the production of gravitinos in a cosmological background. Gravitinos can be produced during preheating after inflation due to a combined effect of interactions with an oscillating inflaton field and absence of conformal…
We develop the Bogolyubov coefficient formalism for gravitational production of fermions with time-dependent mixing, which allows us to study a prototype neutrino system. The neutrino masses and mixings depend on the scalar field values,…
The discovery of neutrino masses suggests the likely existence of gauge singlet fermions that participate in the neutrino mass generation via the seesaw mechanism. The masses of the corresponding degrees of freedom can range from well below…
We investigate the gravitational particle production from vacuum for a minimally coupled fermionic spectator field during a single-field inflationary phase. We observe that metric perturbations arising from the quantum fluctuations of a…
We investigate non-perturbative production of fermionic dark matter in the early universe. We study analytically the gravitational production mechanism accompanied by the coupling of fermions to the background inflaton field. The latter…
The success of primordial nucleosynthesis imposes stringent bounds on the abundance of gravitational relics. This is particularly true for gravitinos, which - for models with gravitationally mediated supersymmetry breaking - are expected to…
We revisit the gravitational production of massive Dirac fermions in inflationary cosmology with a focus on clarifying the analytic computation of the particle number density in both the large and the small mass regimes. For the case in…
Effects of gravitational interaction are generally neglected in particle physics. A first order formulation of gravity is presented to include gravity in Quantum Mechanical Lagrangian of fermions. It is seen that fermions minimally coupled…
We investigate the particle production from thermal gravitational annihilation in the very early universe, which is an important contribution for particles that might not be in thermal equilibrium or/and only have gravitational interaction,…
We consider the simplest possibility for a model of particle dark matter in which dark matter has only gravitational interaction with the standard model sector. Even in such a case, it is known that the gravitational particle production in…
The minimal coupling of massless fermions to gravity does not allow for their gravitational production solely based on the expansion of the Universe. We argue that this changes in presence of realistic and potentially detectable stochastic…
keV scale sterile neutrinos are excellent warm dark matter candidates. In the early Universe, these can be produced from oscillations and scatterings of active neutrinos. However, in the absence of any new physics, this mechanism is in…
We study gravitational creation of light fermions in the presence of classical scalar metric perturbations about a flat Friedmann-Lemaitre- Robertson-Walker (FLRW) background. These perturbations can be large during preheating, breaking the…
Sterile neutrinos, fermions with no standard model couplings [SU(2) singlets], are predicted by most extensions of the standard model, and may be the dark matter. I describe the nonthermal production and linear perturbation evolution in the…
We consider the cosmological production of fermionic dark matter during inflation and a post-inflationary radiation dominated era. This fermion \emph{only interacts gravitationally}, has a mass $m$ much smaller than the Hubble scale during…
A recent study shows that gravitational scattering of dark matter, in the form of massive objects with mass $m \sim 10^3-10^4M_{\odot}$, could provide a possible solution to alleviate the small-scale structure problems of cold dark matter.…
Weyl fermions of spin $\frac12$ minimally coupled to Einstein's gravity in 4 dimensions cannot be produced purely gravitationally in an expanding Universe at tree level. Surprisingly, as we showed in a recent letter [1], this changes at…
In the purely gravitational dark matter scenario, the dark matter particle does not have any interaction except for gravitational one. We study the gravitational particle production of dark matter particle in such a minimal setup and show…
Sterile neutrinos produced through oscillations are a well motivated dark matter candidate, but recent constraints from observations have ruled out most of the parameter space. We analyze the impact of new interactions on the evolution of…
We describe a scenario where the smallness of neutrino masses is related to a global symmetry that is only violated by quantum gravitational effects. The coupling of neutrinos to gauge singlet right-handed fermions is attributed to symmetry…