Abstract
Several novel approaches have been proposed to resolve the problem of time by relating it to change. We argue using quantum information theory that the Hamiltonian constraint in quantum gravity cannot probe change, so it cannot be used to obtain a meaningful notion of time. This is due to the absence of quantum Fisher information with respect to the quantum Hamiltonian of a time-reparametization invariant system. We also observe that the inability of this Hamiltonian to probe change can be related to its inability to discriminate between states of such a system. However, if the time-reparametization symmetry is spontaneously broken due to the formation of quantum cosmological time crystals, these problems can be resolved, and it is possible for time to emerge in quantum gravity.
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Acknowledgements
S.B. was supported by the Estonian Research Council grants PRG356 “Gauge Gravity” and by the European Regional Development Fund through the Center of Excellence TK133 “The Dark Side of the Universe”. J.Q.Q. acknowledges the nancial support of the Ramsay Fellowship. S.B. also acknowledges JSPS Postdoctoral Fellowships for Research in Japan and KAKENHI Grant-in-Aid for Scientific Research No. JP21F21789.
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Wani, S.S., Quach, J.Q., Faizal, M. et al. A Quantum Informational Approach to the Problem of Time. Found Phys 52, 25 (2022). https://doi.org/10.1007/s10701-022-00540-6
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DOI: https://doi.org/10.1007/s10701-022-00540-6