Cosmology

Extending the EFT of Inflation by adding marginal operators in unitary gauge that can affect the equation of motion for scalar perturbations, we unravel new inflationary models in which the dispersion relations is a sixth order polynomial. In particular we focus on the healthy marginal operators that do not infiltrate ghosts into the equations of motion and allow for gravity to decouple from the Goldstone boson above some energy scale. Various scenarios can arise depending on the parameters in the original theory. In particular, one can consider scenarios in which the mode becomes tachyonic while still it is inside the horizon. More conservatively, one can consider models in which the group velocity of the propagation becomes negative. In these inflationary models, the amplitude of scalar power spectrum gets a modulation factor, which in majority of the cases is much bigger than one.  We also show that these marginal operators leave the tensor perturbations intact, and hence the form of tensor power spectrum remains resilient even in the marginally extended EFT of inflation.  Due to the enhancement of the scalar power spectrum,  the tensor-to-scalar ratio is suppressed by a huge factor..

The Dark Energy Survey (DES) is a five-year, 5000 sq. deg. observing program using the Dark Energy Camera on the 4m Blanco telescope at CTIO. I will describe the cosmological analysis of large-scale structure in the Universe using 1321 sq. deg. of data taken in the first year of DES operations. The analysis combines unprecedented measurements of weak gravitational lensing and the clustering of galaxies over the redshift range 0.2 to 1.3 to derive the most precise such cosmological constraints to date. These DES results from the low-redshift Universe are consistent with those from the cosmic microwave background (CMB) and support the standard cosmological model, LCDM. In the coming years, DES will produce significantly tighter constraints on cosmology through similar and additional analyses using observations over more than three times the sky-area and more than twice the integrated exposure time per object as these results.