Phase Information in Cosmological Collider Signals

Qin, Zhehan; Xianyu, Zhong-Zhi

doi:10.48550/arxiv.2205.01692

Cited by 1 publication

(2 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hence, the ratio of the two trispectra encodes direct information about the spin of the graviton, in line with similar findings of Ref. [101] for massive particles in oscillatory cosmological collider signals. Massive spin-2 particles with zero chemical potential have five degrees of freedom, while those with a chemical potential have three [44].…”

Section: With Standard Dcssupporting

confidence: 89%

“…1 has four boundary scalar modes and two bulk graviton modes, the trispectrum is always proportional to two factors of the scalar primordial power spectra and one factor of the primordial tensor power spectrum. The specific angular dependence arises for massless spin-2 particles in de Sitter space and corresponds to associated Legendre polynomials (as opposed to spherical harmonic functions in flat-space) [101]. As shown in Ref.…”

Section: B Without Dcsmentioning

confidence: 87%

See 1 more Smart Citation

Parity-Violating Trispectrum from Chern-Simons Gravity

Creque-Sarbinowski¹,

Alexander²,

Kamionkowski³

et al. 2023

Preprint

View full text Add to dashboard Cite

A potential source for parity violation in the Universe is inflation. The simplest inflationary models have two fields: the inflaton and graviton, and the lowest-order parity-violating coupling between them is dynamical Chern-Simons (dCS) gravity with a decay constant f . Here, we show that dCS imprints a parity-violating signal in primordial scalar perturbations. Specifically, we find that, after dCS amplifies one graviton helicity due to a tachyonic instability, the graviton-mediated correlation between two pairs of scalars develops a parity-odd component. This correlation, the primordial scalar trispectrum, is then transferred to the corresponding curvature correlator and thus is imprinted in both large-scale structure (LSS) and the cosmic microwave background (CMB). We find that the parity-odd piece has roughly the same amplitude as its parity-even counterpart, scaled linearly by the degree of gravitational circular polarization Πcirc ∼ √ ε[H 2 /(M Pl f )] ≤ 1, with ε the slow-roll parameter, H the inflationary Hubble scale, and the upper bound saturated for purely circularlypolarized gravitons. We also find that, in the collapsed limit, the ratio of the two trispectra contains direct information about the graviton's spin. In models beyond standard inflationary dCS, e.g. those with multiple scalar fields or superluminal scalar sound speed, there can be a large enhancement factor F 10 6 to the trispectrum. We find that an LSS survey that contains N modes linear modes would place an nσ constraint on Πcircr of ∼ 0.04 (n/3)(10 6 /F )(10 6 /N modes ) 1/2 from the parity-odd galaxy trispectrum, for tensor-to-scalar ratio r. We also forecast for several spectroscopic and 21-cm surveys. This constraint implies that, for high-scale single-field inflation parameters, LSS can probe very large dCS decay constants f 4 × 10 9 GeV(3/n)(F/10 6 ) N modes /10 6 1/2 . Our result is the first example of a massless particle yielding a parity-odd scalar trispectrum through spin-exchange.

show abstract

Section: With Standard Dcssupporting

confidence: 89%

Section: B Without Dcsmentioning

confidence: 87%