Energy Radiation by Cosmic Superstrings in Brane Inflation

The dominant method of energy loss by a loop of cosmic D-strings in models of warped brane inflation is studied. It is shown that the energy loss via Ramond-Ramond field radiation can dominate by many orders of magnitude over the energy radiation via gravitational wave emission. The ratio of these two energy loss mechanisms depends on the energy scale of inflation, the mass scale of string theory and whether it is a single-throat or a multi-throat inflationary scenario. This can have important consequences for the detection of cosmic superstrings in the near future. It is argued that the bounds from cosmic microwave background anisotropies and big bang nucleosynthesis are the dominant cosmological sources to constrain the physical parameters of the network of cosmic superstrings, whereas the role of the gravitational wave-based experiments may be secondary.Comment: 8 pages, no figure, added references, minor change

Dynamics of D3-D7 Brane Inflation in Throats

Dynamics of D3-branes in models of warped D3-D7 inflationary set up is studied where perturbative $\alpha'$ correction to the K\"ahler potential and the nonperturbative corrections to the superpotential are included. It is shown that a dS minimum can be obtained without introducing anti-branes. Some specific configurations of D7-branes embedding were studied. After stabilizing the angular directions, it is shown that the resulting D3-D7 potential of the radial position of the D3-brane is too steep to allow slow-roll inflation. Depending on D7-branes embedding and the stabilized angular directions, the mobile D3-brane can move either towards the tip of the throat or towards the D7-branes.Comment: minor changes, to appear in JHE

Loop Corrections in Gravitational Wave Spectrum in Single Field Inflation

We study the one-loop corrections in power spectrum of long gravitational waves induced from small scale modes in the models of single field inflation undergoing a phase of ultra-slow-roll (USR). We show that the spectrum of long tensor perturbations are largely unaffected by the loop corrections from the short scalar modes. In particular, the spectrum of long tensor perturbations is insensitive to the sharpness of the transition from the USR phase to the final slow-roll phase. This is in contrast to the case of scalar power spectrum in which the loop corrections can be large for a sharp transition while it is slow-roll suppressed in a mild transition. We study the tensor-scalar-scalar bispectrum in the squeezed limit and demonstrate that the Maldacena consistency condition does hold.Comment: 19 pages, 1 figur