Laboratory search for a quintessence field

Abstract

A cosmic scalar field evolving very slowly in time can account for the observed dark energy of the Universe. Unlike a cosmological constant, an evolving scalar field also has local spatial gradients due to gravity. If the scalar field has a minimal derivative coupling to electromagnetism, it will cause modifications of Maxwell's equations. In particular, in the presence of a scalar field gradient generated by Earth's gravity, regions with a magnetic field appear to be electrically charged and regions with a static electric field appear to contain electric currents. We propose experiments to detect such effects with sensitivity exceeding current limits on scalar field interactions from measurements of cosmological birefringence. If the scalar field has derivative couplings to fermions, it would also generate observable effects in precision spin precession experiments.