A violation of the Equivalence Principle (EP), which hypothesizes the equality of inertial mass and gravitational mass, is indicated by current theories in modern physics.
Some interesting points concerning the violation of the equivalence principle and violation of diffeomorphism invariance in connection with emergent gravity were discussed in[43, 44] and references therein.
A violation of the Equivalence Principle will appear as a difference in the electrostatic forces necessary to maintain both masses on the same orbit.
But there is reason to suspect that gravitational energy is a special case, that measurements of sufficient accuracy might expose a violation of the equivalence principle when energy is stored in a gravity field.
The differential accelerometer is spun about an horizontal axis at a frequency in the range 0.5 1 Hz in order to modulate, during the free fall, the signal from a possible violation of the Equivalence Principle.
Despite its technical difficulty, lunar laser ranging is capable of exquisite precision, and Murphy thinks it's possible that his measurements--the most accurate measurements ever of the moon's path around Earth, if all goes well--may be precise enough to reveal a violation of the equivalence principle.
If it will detect a signal to the expected level, it will be impossible to establish with certainty whether it is due to the well known classical radiometer effect or else to a violation of the equivalence principle which would invalidate General Relativity.
They would add their effects to those of gravity and lead, because of their composition-dependence, to apparent violations of the Equivalence Principle, possibly at a detectable level.
Finally, it was observed that nonstandard Lagrangians result in the violation of the weak equivalence principle.
It's a difficult challenge, but then Murphy and his colleagues are pursuing powerful prey: They seek to expose violations of the principle of equivalence, the core concept of Einstein's General Theory of Relativity.
Up to now an experimental proof of a violation of the Weak Principle of Equivalence (WEP) has been missing.
