Exploring degeneracies in modified gravity with weak lensing

TL;DR

This paper derives a new expression for the weak lensing convergence power spectrum under modified gravity theories, enabling analysis of how different gravitational parameters influence weak lensing signals and their degeneracies.

Contribution

It introduces a novel formulation separating general relativistic and theory-specific effects in weak lensing, facilitating the study of parameter degeneracies in modified gravity models.

Findings

Derived a new integral expression for the convergence power spectrum.

Identified degeneracies between gravitational parameters in weak lensing.

Separated theory-independent and -dependent effects explicitly.

Abstract

By considering linear-order departures from general relativity, we compute a novel expression for the weak lensing convergence power spectrum under alternative theories of gravity. This comprises an integral over a 'kernel' of general relativistic quantities multiplied by a theory-dependent 'source' term. The clear separation between theory-independent and -dependent terms allows for an explicit understanding of each physical effect introduced by altering the theory of gravity. We take advantage of this to explore the degeneracies between gravitational parameters in weak lensing observations.