Semiclassical limit problems with concurrent use of several clocks in quantum cosmology

@article{Alexandre2021SemiclassicalLP,
  title={Semiclassical limit problems with concurrent use of several clocks in quantum cosmology},
  author={Bruno Alexandre and Jo{\~a}o Magueijo},
  journal={Physical Review D},
  year={2021}
}
We revisit a recent proposal for a definition of time in quantum cosmology, to investigate the effects of having more than one possible type of clock “at the same time”. We use as test tube an extension of Einstein gravity with a massless scalar field in which the gravitational coupling GN is only a constant on-shell, mimicking the procedure for Λ in unimodular gravity. Hence we have two “simultaneous” clocks in the theory: a scalar field clock, and the conjugate of GN . We find that attempts… 

Possible quantum effects at the transition from cosmological deceleration to acceleration

The recent transition from decelerated to accelerated expansion can be seen as a reflection (or “bounce”) in the connection variable, defined by the inverse comoving Hubble length ( b = ˙ a ,

Connection between cosmological time and the constants of nature

We examine in greater detail the proposal that time is the conjugate of the constants of nature. Fundamentally distinct times are associated with different constants, a situation often found in

Quantum resolution of the cosmological singularity

We study a quantum Hot Big Bang with matter characterized by a constant of motion m , whose conjugate defines time. A superposition in m suggests a natural, conserved inner product. For two quantum

Quantum resolution of the cosmological singularity without new physics

We study a quantum Hot Big Bang in the connection representation, with a matter constant of motion m whose conjugate defines time. Superpositions in m induce a unitary inner product. The wavefunction

References

SHOWING 1-10 OF 33 REFERENCES

Unitarity, clock dependence and quantum recollapse in quantum cosmology

We continue our analysis of a quantum cosmology model describing a flat Friedmann–Lemaître–Robertson–Walker Universe filled with a (free) massless scalar field and an arbitrary perfect fluid. For

Singularity resolution depends on the clock

We study the quantum cosmology of a flat Friedmann–Lemaître–Robertson–Walker Universe filled with a (free) massless scalar field and a perfect fluid that represents radiation or a cosmological

Probabilities in Quantum Cosmological Models: A Decoherent Histories Analysis Using a Complex Potential

In the quantization of simple cosmological models (minisuperspace models) described by the Wheeler-DeWitt equation, an important step is the construction, from the wave function, of a probability

A note on classical and quantum unimodular gravity

We discuss unimodular gravity at a classical level, and in terms of its extension into the UV through an appropriate path integral representation. Classically, unimodular gravity is locally a gauge

A Universe that Does Not Know the Time

In this paper, we propose that cosmological time is a quantum observable that does not commute with other quantum operators essential for the definition of cosmological states, notably the

Complexifier coherent states for quantum general relativity

Recently, substantial amount of activity in quantum general relativity (QGR) has focused on the semiclassical analysis of the theory. In this paper, we want to comment on two such developments: (1)

Partial and complete observables for Hamiltonian constrained systems

We will pick up the concepts of partial and complete observables introduced by Rovelli in Conceptional Problems in Quantum Gravity, Birkhäuser, Boston (1991); Class Quant Grav, 8:1895 (1991); Phys

Losing the trace to find dynamical Newton or Planck constants

We show that promoting the trace part of the Einstein equations to a trivial identity results in the Newton constant being an integration constant. Thus, in this formulation the Newton constant is a

Thermal time and Tolman–Ehrenfest effect: ‘temperature as the speed of time’

The notion of thermal time has been introduced as a possible basis for a fully general-relativistic thermodynamics. Here we study this notion in the restricted context of stationary spacetimes. We