Are there significant gravitational corrections to the unification scale?

Abstract

Higher dimension operators may be induced in the lagrangian of a unified theory by gravity. We find that ctr( G μv G μv H)/ M Planck can lead to substantial corrections to the unification scale. For ordinary SU(5) a second solution unifying at 10 17 GeV can exist which has no observable proton decay but an unacceptable value of sin 2 θ w. Analogous effects in supersymmetry, however, can lead to enormous corrections. We find that supersymmetric SU(5) can unify anywhere between 5 × 10 16 < M X < 10 18 GeV with an acceptable sin 2 θ wfor | c| ⩽ 1.0.