The tensor-to-scalar ratio in punctuated inflation

Scalar spectra which exhibit a sharp drop in power at length scales corresponding to the Hubble radius today are known to lead to a better fit of the observed Cosmic Microwave Background (CMB) anisotropies, when compared to the conventional, featureless, power law spectrum. Recently, we have shown that scalar spectra with lower power on large scales naturally occur in punctuated inflation, i.e. the scenario wherein a brief period of rapid roll is sandwiched between two stages of slow roll inflation. In this work, we highlight a characteristic feature of the punctuated inflationary scenario that could lead to a potentially observable signature. With examples from the canonical scalar field as well as the tachyonic models, we illustrate that, in punctuated inflation, a drop in the scalar power on large scales is always accompanied by a rise in the tensor power and, hence, even a more pronounced increase in the tensor-to-scalar ratio that actually exceeds well beyond unity over a small range of scales. This translates to a rapid increase in the angular power spectrum, C l , of the B-mode polarization of the CMB at the low multipoles. Although, in the specific models of punctuated inflation that we study, the C l does not attain values that are observable, our work suggests that there could be models of punctuated inflation that fit the data well, and also predict observable levels of C l . PACS numbers: 98.80.Cq, 98.70.Vc, 04.30.-w The tensor-to-scalar ratio in punctuated inflation 2