Test of Special Relativity and Equivalence Principle from Neutrinoless   Double Beta Decay
  We generalize the formalism for testing Lorentz invariance and the equivalence principle in the neutrino sector. While neutrino oscillation bounds constrain the region of large mixing of the the weak and gravitational eigenstates, we obtain new constraints on violations of Lorentz invariance and the equivalence principle from neutrinoless double beta decay. These bounds apply even in the case of no mixing and thus probe a totally unconstrained region in the parameter space. 
H.V. Klapdor--Kleingrothaus, H. P\"as, U. Sarkar