Cosmological collider physics and the curvaton

Abstract

Primordial non-Gaussianity signatures of extremely heavy particles are reexamined within a simple alternative to the standard inflationary paradigm, in which the primordial fluctuations and the inflationary spacetime expansion are sourced by two different fields. The curvaton scenario provides an example of this in which the distinct roles are played by the curvaton and the inflaton fields, respectively. We study couplings of the curvaton to heavy particles with masses of order the inflationary Hubble scale, and show that they can lead to non-Gaussian signals orders of magnitude larger than those in standard inflation, consistent with explicit effective field theory control of inflationary dynamics. This brings various motivated particle physics signatures, such as loops of heavy gauge-charged scalars and fermions, within future observational reach. The curvaton paradigm can be viewed as a partial UV completion of effective field theories of only inflationary fluctuations in which large non-Gaussian signals of heavy particles have also been discussed, but in which inflationary dynamics is not explicitly derived.

On the inflationary massive field with a curved field manifold

“…As a next-to-leading order correction, usually the dim-6 operator in (3.2) is supposed to be sub-dominant. For instance, it contributes to the scalar bispectrum through loop diagrams, which turns out to be negligible [13,20]. But as discussed above (and also pointed out in Ref.…”

“…But as discussed above (and also pointed out in Ref. [20,36,74] previously), this operator may give nontrivial corrections to the isocurvature mass. One can interpret this effect by the right diagram in Fig.…”

“…From this point of view, one well-studied example is quasi-single field inflation (QSFI) [7][8][9][10][11][12], where the extra fields during inflation with mass of O(H) can leave unique signatures in the primordial bispectrum of curvature perturbation. This idea has been further developed into model-independent frameworks for probing primordial physics, such as the proposals of cosmological collider physics [13][14][15][16][17][18][19][20][21] and primordial standard clocks [22][23][24][25].…”

In search of large signals at the cosmological collider

“…(We will henceforth refer to this oscillatory shape the "signal.") Detecting such a signal at this so-called cosmological collider offers direct evidence of new physics particles and a tool of studying their properties [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Impact of transforming to conformal Fermi coordinates on quasisingle field non-Gaussianity

“…This cancellation is manifest in the de Sitter era before reheating takes place. Many inflationary models have been studied that can give rise to significant non-Gaussianities, see for example [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. One of the most studied and simplest of these is called quasisingle field inflation (QSFI).…”