Abstract
In this paper we compute the sizes ofequilateral and orthogonal shape bispectrum for the generalLorentz invariant single-field inflation. The stability offield theory implies a non-negative square of sound speedwhich leads to a consistency relation between the sizes oforthogonal and equilateral shape bispectrum, namelyfNLorth. ⩽ −0.054fNLequil.. In particular,for the single-field Dirac-Born-Infeld (DBI) inflation, theconsistency relation becomes fNLorth. = 0.070fNLequil. ⩽ 0. These consistency relations arealso valid in the mixed scenario where the quantumfluctuations of some other light scalar fields contributeto a part of total curvature perturbation on thesuper-horizon scale and may generate a local formbispectrum. A distinguishing prediction of the mixedscenario is τNLloc. > ((6/5)fNLloc.)2.Comparing these consistency relations to WMAP 7yr data,there is still a big room for the Lorentz invariantinflation, but DBI inflation has been disfavored at morethan 68% CL.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
