Multipoles of the relativistic galaxy bispectrum

Understand

Above the equality scale the galaxy bispectrum will be a key probe for measuring primordial non-Gaussianity which can help differentiate between different inflationary models and other theories of the early universe.

• On these scales a variety of relativistic effects come into play once the galaxy number-count fluctuation is projected onto our past lightcone.
• By decomposing the Fourier-space bispectrum into invariant multipoles about the observer's line of sight we examine in detail how the relativistic effects contribute to these.
• We show how to perform this decomposition analytically, which is significantly faster for subsequent computations.