Difference of observability between classical electromagnetic and gravitational gauge fields

Abstract

An analysis of the observability of the classical electromagnetic gauge field based in its quantum effects shows that this is physically determined up to equivalences. By contrast a similar analysis of the gravitational gauge field from Einstein's General Relativity theory shows that this field is univocally determined by the trajectories of material particles provided they feel only that gravitational field, and its proper gravitational and quantum effects are negligible. This difference of observability in both kinds of gauge fields is caused by the attachment of the gravitational field in the Einstein theory to the space-time, and this difference must be taken into account to formulate unified gauge theories with both kinds of fields.