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Register a new userSmooth and sharp creation of a pointlike source for a $(3+1)$-dimensional quantum field
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We analyse the smooth and sharp creation of a pointlike source for a quantised massless scalar field in $(3+1)$-dimensional Minkowski spacetime, as a model for the breakdown of correlations that has been proposed to occur at the horizon of an evaporating black hole. The creation is implemented by a time-dependent self-adjointness parameter at the excised spatial origin. In a smooth creation, the renormalised energy density $langle T_{00} rangle$ is well defined away from the source, but it is unbounded both above and below: the outgoing pulse contains an infinite negative energy, while a cloud of infinite positive energy lingers near the fully-formed source. In the sharp creation limit, $langle T_{00} rangle$ diverges everywhere in the timelike future of the creation event, and so does the response of an Unruh-DeWitt detector that operates in the timelike future of the creation event. The source creation is significantly more singular than the corresponding process in $1+1$ dimensions, analysed previously, and it may be sufficiently singular to break quantum correlations as proposed in a black hole spacetime.
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A complete quantum field theoretic study of charged and neutral particle creation in a rapidly/adiabatically expanding Friedman-Robertson-Walker metric for an O(4) scalar field theory with quartic interactions (admitting a phase transition) is given. Quantization is carried out by inclusion of quantum fluctuations. We show that the quantized Hamiltonian admits an su(1,1) invariance. The squeezing transformation diagonalizes the Hamiltonian and shows that the dynamical states are squeezed states. Allowing for different forms of the expansion parameter, we show how the neutral and charged particle production rates change as the expansion is rapid or adiabatic. The effects of the expansion rate versus the symmetry restoration rate on the squeezing parameter is shown.
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