Cosmological Frontiers in Fundamental Physics 2013
I will overview the progress of 21cm cosmology, with emphasis on intensity mapping. Current and future experiments have the potential for precision measurements of dark energy, neutrino mass, and gravitational waves.
This talk will present an effective description of single field dark energy/modified gravity models, which encompasses most existing proposals. The starting point is a generic Lagrangian expressed in terms of the lapse and of the extrinsic and intrinsic curvature tensors of the uniform scalar field hypersurfaces. By expanding this Lagrangian up to quadratic order, one can describe the homogeneous background and the dynamics of linear perturbations.
The AdS/CFT correspondence provides new insights and tools to answer
previously inaccessible questions in quantum gravity. Among the most
interesting is whether it is possible to describe a cosmological
"bounce" in a mathematically complete and consistent way. In the
talk, I'll discuss joint work with M. Smolkin, developing the dual description
of the simplest possible 4d M-theory cosmology in the stringy regime, employing
the full quantum dynamics of its dual CFT. I'll also present evidence that the
Ghost-free bimetric theories can be used to describe gravitational interactions in the presence of an extra neutral massive
spin-2 field that can modify gravity in non-trivial ways. They also
provide a natural framework for a possible non-linear extension of
partially masslessness known to arise in linear Fierz-Pauli theory.
This talk will describe bimetric theories and a procedure that
identifies a unique bimetric action as a candidate for a nonlinear
partially massless theory. We then show that in the low curvature
I will describe a cosmological model where primordial inflation is driven by a 'solid', defined as a system of three derivatively coupled scalar fields obeying certain symmetries and spontaneously breaking a certain subgroup of these. The symmetry breaking pattern differs drastically from that of standard inflationary models: time translations are unbroken. This prevents our model from fitting into the standard effective field theory description of adiabatic perturbations, with crucial consequences for the dynamics of cosmological perturbations.
In the standard model neutrinos are assumed to have streamed across the Universe since they last scattered at the weak decoupling epoch when the temperature of the standard-model plasma was ~MeV. The shear stress of free-streaming neutrinos imprints itself gravitationally on the Cosmic Microwave Background (CMB) and makes the CMB a sensitive probe of neutrino scattering. Yet, the presence of nonstandard physics in the neutrino sector may alter this standard chronology and delay neutrino free-streaming until a much later epoch.