Multipoles of the relativistic galaxy bispectrum
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Date
2020
Journal Title
Journal ISSN
Volume Title
Publisher
IOP Publishing Ltd
Abstract
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. While all multipoles receive a contribution from the relativistic part, odd
multipoles arising from the imaginary part of the bispectrum have no Newtonian contribution,
making the odd multipoles a smoking gun for a relativistic signature in the bispectrum for
single tracers. The dipole and the octopole are significant on equality scales and above where
the Newtonian approximation breaks down. This breakdown is further signified by the fact
that the even multipoles receive a significant correction on very large scales.
Description
Keywords
Power spectrum, Redshift surveys, Cosmic web, Relativistic, Galaxy surveys
Citation
Clarkson, C. et al. (2020). Multipoles of the relativistic galaxy bispectrum. Journal of Cosmology and Astroparticle Physics, 2020(05)