Realistic Clocks for a Universe Without Time

Rodolfo Gambini, Rafael A. Porto, Jorge A. Pullin

Ordinary quantum mechanics is formulated on the basis of the existence of an ideal classical clock external to the system under study. This is clearly an idealization. As emphasized originally by Salecker and Wigner and more recently by others, there exist limits in nature to how "classical" even the best possible clock can be. With realistic clocks, quantum mechanics ceases to be unitary and a fundamental mechanism of decoherence of quantum states arises. We estimate the rate of the universal loss of unitarity using optimal realistic clocks. In particular, we observe that the rate is rapid enough to eliminate the black hole information puzzle: all information is lost through the fundamental decoherence before the black hole can evaporate. This improves on a previous calculation we presented with a suboptimal clock in which only part of the information was lost by the time of evaporation.

Magdalena Zych

Tommaso Favalli

James B. Hartle

Nonrelativistic model quantum cosmologies are studied in which the basic time variable is the position of a clock indicator and the time parameter of the Schr\"odinger equation is an unobservable label. Familiar Schr\"odinger-Heisenberg quantum mechanics emerges if the clock is ideal---arbitrarily accurate for arbitrarily long times. More realistically, however, the usual formulation emerges only as an approximation appropriate to states of this model universe in which part of the system functions approximately as an ideal clock. It is suggested that the quantum kinematics of spacetime theories such as general relativity may be analogous to those of this model. In particular it is suggested that our familiar notion of time in quantum mechanics is not an inevitable property of a general quantum framework but an approximate feature of specific initial conditions.

Peter D. Collins, Euan J. Squires

Ramanathan, R.

An alternative to the current accepted model of expanding universe is presented. The proposal is anchored in the objective realist, stochastic formulation of quantum mechanics wherein the Planck constant plays the role of a diffusion constant which need not be an universal constant for all epochs. This underlying noise is charecterised by a very high initial value of the Planck constant which gradually decreased over the epochs gone by, finally reaching its present value .It is this decrease in the strength of the Planck constant that causes a spectral red shift with the passage of time .The compatibility of this proposal with some cosmological data is shown.Feasible spectroscopic measurement of a specific spectral line frequency done over a period of a few years can decisively either validate or invalidate the proposal in a terrestrially bound experiment. This proposal predicts a slowing down of atomic clocks by nearly 2. 10^-18 s with respect to every preceding second. A positive experimental outcome will validate the objective realist basis of quantum physics as advocated by Einstein and many others.