Enhanced effects of violation of the fundamental symmetries, variation of the fundamental constants and dark matter field in thorium clock.

Thorium clock based on 8 eV transition in   ²²⁹Th nucleus has very high projected accuracy and strongly enhanced sensitivity to the effects of violation of the Lorentz invariance and Einstein equivalence principle, variation of the fundamental constants  and dark matter field. Sensitivity to the variation of the fine structure  constant alpha is expressed in terms of the difference between the charge radii  between the excited and ground states. This gives the enhancement factor  K=8000. This enhancement is also relevant to the dark matter search since interaction with dark matter leads to oscillating alpha.

    A different mechanism  related to the octupole deformation in the  ²²⁹Th nucleus enhances  time reversal invariance violating moments  such as the nuclear Schiff moment and atomic electric dipole moment. This allows one to test unification theories predicting CP violation and search for axion dark matter in experiments with thorium molecules.

     Probability of electronic transition excitation in thorium atom and ions exceeds probability of nuclear 8 eV  transition excitation by many orders of magnitude. Therefore, the electronic bridge mechanism may be used to excited the nuclear transition. The excitation is transferred from electronic shells to nucleus by the hyperfine interaction.  

Another candidate for nuclear clock may be 76 eV transition in ²³⁵U.      

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