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Solar constraints on new couplings between electromagnetism and gravity

S. K. Solanki·O. Preuss·M. P. Haugan·A. Gandorfer·H. P. Povel·P. Steiner·K. Stucki·P. N. Bernasconi·D. Soltau
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Abstract

The unification of quantum field theory and general relativity is a fundamental goal of modern physics. In many cases, theoretical efforts to achieve this goal introduce auxiliary gravitational fields, ones in addition to the familiar symmetric second-rank tensor potential of general relativity, and lead to nonmetric theories because of direct couplings between these auxiliary fields and matter. Here, we consider an example of a metric-affine gauge theory of gravity in which torsion couples nonminimally to the electromagnetic field. This coupling causes a phase difference to accumulate between different polarization states of light as they propagate through the metric-affine gravitational field. Solar spectropolarimetric observations are reported and used to set strong constraints on the relevant coupling constant k: k^2 < (2.5 km)^2.

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S. K. Solanki, O. Preuss, M. P. Haugan, A. Gandorfer, H. P. Povel, P. Steiner, K. Stucki, P. N. Bernasconi, D. Soltau. 2004-02-12. Solar constraints on new couplings between electromagnetism and gravity. https://doi.org/10.1103/physrevd.69.062001

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