New exotics in the double beta decay contributions zoo
  We discuss the potential of neutrinoless double beta decay for testing Lorentz invariance and the weak equivalence principle as well as contributions from dilaton exchange gravity in the neutrino sector. While neutrino oscillation bounds constrain the region of large mixing of the weak and gravitational eigenstates, we obtain new constraints on violations of Lorentz invariance and the equivalence principle from neutrinoless double beta decay, applying even in the case of no mixing. Double beta decay thus probes a totally unconstrained region in the parameter space. 
H.V. Klapdor-Kleingrothaus, H. P\"as, U. Sarkar