Restoring time dependence into quantum cosmology. (English) Zbl 1266.83180
Summary: Mini superspace cosmology treats the scale factor \(a(t)\), the lapse function \(n(t)\) and an optional dilation field \(\phi(t)\) as canonical variables. While pre-fixing \(n(t)\) means losing the Hamiltonian constraint, pre-fixing \(a(t)\) is serendipitously harmless at this level. This suggests an alternative to the Hartle-Hawking approach, where the pre-fixed \(a(t)\) and its derivatives are treated as explicit functions of time, leaving \(n(t)\) and a now mandatory \(\phi(t)\) to serve as canonical variables. The naive gauge pre-fix \(a(t) =\) const. is clearly forbidden, causing evolution to freeze altogether; so pre-fixing the scale factor, say \(a(t) = t\), necessarily introduces explicit time dependence into the Lagrangian. Invoking Dirac’s prescription for dealing with constraints, we construct the corresponding mini superspace time-dependent total Hamiltonian and calculate the Dirac brackets, characterized by \(\{n,\phi\}_D\neq 0\), which are promoted to commutation relations in the quantum theory.
MSC:
83F05 | Relativistic cosmology |
83C45 | Quantization of the gravitational field |
83D05 | Relativistic gravitational theories other than Einstein’s, including asymmetric field theories |
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