Ellipticity Weakens Chameleon Screening

Abstract

The chameleon mechanism enables a long range fifth force to be screened in dense environments when non-trivial self interactions of the field cause its mass to increase with the local density. To date, chameleon fifth forces have mainly been studied for spherically symmetric sources, however the non-linear self interactions mean that the chameleon responds to changes in the shape of the source differently to gravity. In this work we focus on ellipsoidal departures from spherical symmetry and compute the full form of the chameleon force, comparing it's shape dependence to that of gravity. Enhancement of the chameleon force by up to 40% is possible when deforming a sphere to an ellipsoid of the same mass, with an ellipticity $\simeq 0.99$.

References in corpus (7)

• Dynamics of dark energy
• Evading Equivalence Principle Violations, Cosmological and other Experimental Constraints in Scalar Field Theories with a Strong Coupling to Matter
• f(R) Gravity and Chameleon Theories
• Gravity Resonance Spectroscopy Constrains Dark Energy and Dark Matter Scenarios
• Detecting Chameleons through Casimir Force Measurements
• Atomic Precision Tests and Light Scalar Couplings
• Chameleon dark energy models with characteristic signatures

Cited by in corpus (3)

• A Compendium of Chameleon Constraints
• A parametrisation of modified gravity on nonlinear cosmological scales
• Calculation of the critical overdensity in the spherical-collapse approximation