Scale invariance of the primordial tensor power spectrum

Abstract

Future cosmic microwave background polarization experiments will search for evidence of primordial tensor modes at large angular scales, in the multipole range 4 ≤ ≤ 50. Because in that range there is some mild evidence of departures from scale invariance in the power spectrum of primordial curvature perturbations, one may wonder about the possibility of similar deviations appearing in the primordial power spectrum of tensor modes. Here we address this issue and analyze the possible presence of features in the tensor spectrum resulting from the dynamics of primordial fluctuations during inflation. We derive a general, model independent, relation linking features in the spectra of curvature and tensor perturbations. We conclude that even with large deviations from scale invariance in the curvature power spectrum, the tensor spectrum remains scale invariant for all observational purposes.

Constraints on inflation with LSS surveys: features in the primordial power spectrum

“…steps and bumps in the potential) [7][8][9][10][11][12][13][14][15][16][17]; (2) multi-field models of inflation with a meandering inflationary trajectory [18][19][20][21][22][23][24][25][26][27][28][29][30][31]; (3) particle production during inflation for a brief period of time [32][33][34][35][36][37][38]; (4) P (X)-models with features in the kinetic terms of the inflaton field [39]; (5) string models of inflation [40][41][42][43]; (6) string and gauge theory models involving axions [44][45][46]. In addition, efforts have been made to study the appearance of features in the spectra in a model independent manner [47][48][49][50]…”

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