Symbol Δτ

The passage around this formula

The shared $M_0$$c^2$$\Delta$$\tau$/$\hbar$ term, common to both arms, is an overall phase and drops out of any interference signal — consistent with the rule that only relative phase between branches is ever observable. What survives is a clock-visible term set entirely by the internal-energy difference, first proposed as an observable interferometric signature of general-relativistic proper time by Zych, Costa, Pikovski, and Brukner [ 10 ] , and later reframed explicitly as a quantum analogue of the twin paradox by Loriani and collaborators [ 11 ] .

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