COSMOS-e′-GTachyon (from String Theory)

Specific role of various non-standard (non-canonical and non-minimal) effective interactions and its cosmological consequences was not very well understood within the framework of (string) inflation. To address this issue, in this talk, we discuss the details of cosmological inflationary paradigm in presence of such non-canonical interactions from generalized tachyon (GTachyon) living on the world volume of a non-BPS string theory. First, we start with a brief introduction to inflation, its cosmological consequences and observational limits. Then we show that the tachyon effective action is considered here is getting modified compared to the original action as appearing in non-BPS string theory. One can quantify the amount of the modification via a power q instead of 1/2 in the effective action. Using this theoretical set up we study single field inflation from various types of tachyonic effective potentials, using which we further constrain the general index q and other stringy parameters-Regge slope α', string coupling constant gs and mass scale of tachyon Ms, from the recently observed Planck 2015 data. We also put further stringent constraints from the temperature anisotropy and polarization spectra, which shows that our analysis confronts well with the Planck 2015 data. For completeness, we also provide the results for assisted and multi field Gtachyon inflation in the end part of the talk to give a comparison between all the field configurations.