Higher Spin Supersymmetry at the Cosmological Collider: Sculpting SUSY Rilles in the CMB (1907.05829v3)

Abstract: We study the imprint of higher spin supermultiplets on cosmological correlators, namely the non-Gaussianity of the cosmic microwave background. Supersymmetry is used as a guide to introduce the contribution of fermionic higher spin particles, which have been neglected thus far in the literature. This necessarily introduces more than just a single additional fermionic superpartner, since the spectrum of massive, higher spin supermultiplets includes two propagating higher spin bosons and two propagating higher spin fermions, which all contribute to the three point function. As an example we consider the half-integer superspin $\textsf{Y}=s+1/2$ supermultiplet, which includes particles of spin values $j=s+1,~j=s+1/2,~j=s+1/2$ and $j=s$. We compute the curvature perturbation 3-point function for higher spin particle exchange and find that the known $P_{s}(\cos \theta)$ angular dependence is accompanied by superpartner contributions that scale as $P_{s+1}(\cos \theta)$ and $\sum_{m}P^{m}_{s} (\cos \theta)$, with $P_{s}$ and $P_{s} ^m$ defined as the Legendre and Associated Legendre polynomials respectively. We also compute the tensor-scalar-scalar 3-point function, and find a complicated angular dependence as an integral over products of Legendre and associated Legendre polynomials.

Higher Spin Supersymmetry at the Cosmological Collider: Sculpting SUSY Rilles in the CMB

The paper "Higher Spin Supersymmetry at the Cosmological Collider: Sculpting SUSY Rilles in the CMB" focuses on the investigation of higher spin supermultiplet imprints on cosmological correlators, particularly the non-Gaussianity of the Cosmic Microwave Background (CMB). The authors explore how supersymmetry may introduce contributions from fermionic higher spin particles, which have been largely ignored in prior literature. This paper strives to incorporate fermionic components into the analysis of cosmological collider physics and highlights how supersymmetry dictates the interaction structure of higher spin fermions with the primordial curvature perturbation.

Overview of the Approach

The paper develops a framework to evaluate the theoretical impact of fermionic higher spin particles on the non-Gaussianity observed in the CMB. The analysis considers a fermionic half-integer superspin supermultiplet $s + 1/2$ and a bosonic integer superspin supermultiplet $s$. The interaction of these higher spin particles with the scalar curvature perturbation field is studied to predict contributions to the 3-point function $\langle \zeta \zeta \zeta \rangle$.

Numerical Results and Angular Dependence

The researchers compute the curvature perturbation 3-point function for higher spin particle exchange, revealing it is accompanied by angular dependence related to Legendre and associated Legendre polynomials. The known $P_s(\cos \theta)$ dependence of spin-$s$ bosons is supplemented by contributions from superpartner particles scaling as $P_{s+1}(\cos \theta)$ and $\sum_m P_s^m(\cos \theta)$. These results underscore the potential sensitivity of non-Gaussian features even to fields heavier than the Hubble scale during inflation, promoting the concept of 'Cosmological Collider Physics'.

Implications

Supersymmetrizing the cosmological collider incorporates both bosonic and fermionic particles, contributing distinct angular dependencies to the correlators. The paper proposes angular patterns in the non-Gaussianity that are distinctly indicative of underlying higher spin supersymmetry. This pushes the boundaries of current understanding regarding the particle content of the early universe, potentially offering new avenues for detecting signals at cosmic scales.

Beyond theoretical implications, these results offer predictions that could be valuable in observational cosmology. The non-Gaussianity might serve as a unique probe of new degrees of freedom that are otherwise inaccessible.

Future Developments

This paper lays foundational work for future studies into supergravity extensions and more comprehensive models describing interactions between higher spin particles and cosmological structures during inflation. This may include probing primordial gravitational waves or further refining constraints on the mass and interaction strengths of higher-spin states within the inflationary context. Future research could unify findings in string theory and establish stronger observational methods to detect such subtle cosmological signals.

In conclusion, by investigating the role of higher spin supermultiplets and their associated angular dependencies in the non-Gaussianity of the CMB, this paper provides a significant theoretical contribution to our understanding of particle physics at cosmological scales. As experimental techniques and observational tools advance, such theoretical models could help affirm or refine our current models of the early universe, guiding further exploration into the interplay between cosmology and particle physics.