# Tensor Non-Gaussianity Search: Current Status and Future Prospects

## TL;DR

This paper reviews the current status and future prospects of detecting tensor non-Gaussianities in the CMB, emphasizing the importance of B-mode polarization data for improving detection sensitivity and guiding future surveys.

## Contribution

It summarizes existing methods for tensor non-Gaussianity detection and forecasts the potential improvements with upcoming CMB B-mode polarization measurements.

## Key findings

- No significant tensor non-Gaussianity detected so far.
- Adding B-mode polarization data greatly enhances detection limits.
- Established bispectrum estimation methods support future CMB B-mode surveys.

## Abstract

Primordial gravitational waves (GWs) are said to be a smoking gun in cosmic inflation, while, even if they are detected, the specification of their origins are still required for establishing a true inflationary model. Testing non-Gaussianity in the tensor-mode anisotropies of the cosmic microwave background (CMB) is one of the most powerful ways to identify sources of GW signals. In this paper, we review studies searching for tensor non-Gaussianities employing the CMB bispectrum and forecast future developments. No significant signal has so far been found from temperature and E-mode polarization data, while orders-of-magnitude improvements in detection limits can be achieved by adding the information of B-mode polarization. There is already an established methodology for bispectrum estimation, which encourages a follow-up investigation with next-decadal CMB B-mode surveys.