Sang Pyo Kim (群山大学、韓国)

Title:"Probing the vacuum structure of spacetime"


We explore the question of how to probe the vacuum structure of space
time by a massive scalar field through interaction with background
gravitons. Using the $\Gamma$-regularization for the in-/out-state
formalism, we find the effective action of a scalar field in a
conformally, asymptotically flat spacetime and a four-dimensional de
Sitter space, which is a gravitational analog of the Heisenberg-Euler
and Schwinger effective action for a charged scalar in a constant
electric field. The effective action is nonperturbative in that it sums
all one-loop diagrams with arbitrary number of external lines of
gravitons. The massive scalar field becomes unstable due to particle
production, the effective action has an imaginary part that determines
the decay rate of the vacuum, and the out-vacuum is unitarily
inequivalent to the in-vacuum.

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Last-modified: 2013-11-20 (水) 11:11:54 (1401d)