- The paper shows that supersymmetric inflaton and partner interactions can produce observable non-Gaussianities in the squeezed bispectrum.
- It establishes a supersymmetric effective field theory to classify inflaton interactions and capture inflationary fluctuations with higher-derivative terms.
- The study reveals that future CMB and large-scale structure observations may detect distinctive SUSY-breaking signatures in primordial perturbations.
Signatures of Supersymmetry from the Early Universe
The paper "Signatures of Supersymmetry from the Early Universe" by Baumann and Green investigates the potential observational signatures of supersymmetry (SUSY) that could arise from the inflationary epoch of the universe. In particular, the authors explore how SUSY might manifest itself through the properties of scalar fields during inflation, and how these effects could leave imprints on the cosmic microwave background (CMB) in the form of non-Gaussianities in the primordial curvature perturbations.
Breaking of SUSY and Its Implications
Within the inflationary paradigm, scalar fields, particularly the inflaton, drive rapid expansion. SUSY is known to offer a framework that can protect such scalar fields from significant quantum corrections, thereby addressing the naturalness problem often associated with inflationary models. When SUSY is spontaneously broken, fields acquire masses of the order of the Hubble parameter during inflation. This breaking is inevitably linked to the vacuum energy driving inflation, suggesting that inflatons and other scalars naturally have partners whose masses are determined by the Hubble scale. This mechanism can yield observational signatures unique to the SUSY framework.
Key Findings and Theoretical Developments
Baumann and Green develop a supersymmetric effective theory of inflation to analyze this connection systematically. They classify interactions between the inflaton and additional fields, identifying those that naturally yield large non-Gaussianities protected by SUSY. The supersymmetric extensions of the effective field theory of inflation include higher-derivative terms, which play a crucial role in capturing the dynamics of inflationary fluctuations while preserving stability and causality.
The authors find that the presence of Hubble-scale secondary fields can lead to noticeable non-Gaussian features in the squeezed limit of the primordial curvature perturbation's bispectrum. Specifically, they show that in quasi-single-field inflation scenarios, the presence of a massive isocurvature partner field to the inflaton can enhance the squeezed limit signature in the bispectrum, acting as a probe for the supersymmetric nature of the inflationary model.
Observational Prospects and Future Directions
The squeezed limit of the three-point function, or bispectrum, of primordial perturbations offers a promising observational avenue to detect signs of SUSY. In single-field inflation, this limit leads to negligible effects, but the presence of additional fields with masses near the Hubble scale, as predicted by SUSY, can produce distinctive non-Gaussianity. Future CMB experiments, such as those analyzing the Planck satellite data, in conjunction with large-scale structure surveys, might be sensitive to these signatures. By probing the specific scaling of non-Gaussianity in the squeezed limit, researchers can potentially distinguish between SUSY-induced non-Gaussianities and those from alternative sources.
The work speculates that these observational probes might offer opportunities to investigate the SUSY breaking scale indirectly, providing empirical input into the nature of high-energy physics during the inflationary epoch. Further theoretical endeavors might focus on refining simulations and predictions regarding how such supersymmetric models impact the evolution of structures in the universe, providing a more nuanced understanding of the early universe dynamics.
Ultimately, the exploration undertaken by Baumann and Green in this paper paves the way for a more comprehensive understanding of how supersymmetry, a prevalent concept in high-energy physics, could have left its unmistakable mark in the cosmos. As experimental techniques advance, the authors’ framework might be pivotal in interpreting data within the context of SUSY-influenced cosmology, potentially elucidating some fundamental aspects of our universe's infancy.