Large Spin-2 Signals at the Cosmological Collider

Xi, Tao; Xianyu, Zhong-Zhi

doi:10.48550/arxiv.2203.06349

“…Therefore we should in general consider interactions that break the dS boosts. In particular, a recently studied class of models with chemical-potentialenhanced CC signals explicitly break the dS boosts [22,27,32,36,44]. The chemical potential originates from the dim-5 axion-type couplings between the inflaton field and a massive particle with nonzero spin [32,36].…”

Section: Dissecting Cosmological Collider Signalsmentioning

confidence: 99%

“…In this work, we shall demonstrate the use of phase information with several examples of nonlocal signals (to be explained below) at both the tree level and the 1-loop level, mediated by either massive scalars or massive vector bosons. For signals from spin-1 gauge bosons, we pay special attention to a possible parity-violating chemical potential, which is a known source of large signals [22,27,32,36,41,44].…”

Section: Introductionmentioning

confidence: 99%

Phase Information in Cosmological Collider Signals

Qin,

Xianyu

2022

Preprint

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Massive particles produced during the cosmic inflation can imprint in the primordial non-Gaussianities as characteristic oscillating functions of various momentum ratios, known as cosmological collider signals. We initiate a study of the phase of the oscillating signals which can be unambiguously defined and measured. The phase can provide useful new information about the spin and the couplings of the intermediate heavy particles that cannot be obtained from the signal frequency and angular dependences alone. We also present new analytical results for full nonlocal signals from two typical 1-loop processes, enabling precise determination of the signal phase away from the squeezed limit.

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“…In this work, we shall demonstrate the use of phase information with several examples of nonlocal signals (to be explained below) at both the tree level and the 1-loop level, mediated by either massive scalars or massive vector bosons. For signals from spin-1 gauge bosons, we pay special attention to a possible parity-violating chemical potential, which is a known source of large signals [22,29,34,38,44,48].…”

Section: Introductionmentioning

confidence: 99%

“…Therefore we should in general consider interactions that break the dS boosts. In particular, a recently studied class of models with chemical-potential-enhanced CC signals explicitly break the dS boosts [22,29,34,38,48]. 4 The chemical potential originates from the dim-5 axion-type couplings…”

mentioning

confidence: 99%

Phase information in cosmological collider signals

Zhehan

¹

,

Xianyu

²

2022

J. High Energ. Phys.

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Massive particles produced during the cosmic inflation can imprint in the primordial non-Gaussianities as characteristic oscillating functions of various momentum ratios, known as cosmological collider signals. We initiate a study of the phase of the oscillating signals which can be unambiguously defined and measured. The phase can provide useful new information about the spin and the couplings of the intermediate heavy particles that cannot be obtained from the signal frequency and angular dependences alone. We also present new analytical results for full nonlocal signals from two typical 1-loop processes, enabling precise determination of the signal phase away from the squeezed limit.

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“…Chern-Simons gravity [38,39] and the Nieh-Yah term in teleparallel gravity [40] can generate parity violation in the spin-2 sector. For strictly massive spin-1 and spin-2 fields, it also possible to construct dimension-5 operators that give large parity-violating signals [41][42][43][44][45]. Aside from inflation, sources of parity-violation can also come from cosmic strings [46,47].…”

Section: Introductionmentioning

confidence: 99%

Parity-Violating Trispectrum from Chern-Simons Gravity

Creque-Sarbinowski¹,

Alexander²,

Kamionkowski³

et al. 2023

Preprint

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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.

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Large Spin-2 Signals at the Cosmological Collider

Cited by 4 publications

References 84 publications

Phase Information in Cosmological Collider Signals

Phase Information in Cosmological Collider Signals

Phase information in cosmological collider signals

Parity-Violating Trispectrum from Chern-Simons Gravity

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