The regularized expectation values of the field fluctuation ${〈{\phi }^2〉}_{\mathrm{reg}}$ of an arbitrary coupled, nonconformal massless scalar field in the spacetime of the electrically charged dilaton black hole in the Boulware, Unruh, and Hartle-Hawking vacua are evaluated. Their leading behaviors near the horizon and the spatial infinity are investigated. It is found that the result agrees with Page's approximation if the coupling constants are small.

• Received 20 May 1993

DOI:https://doi.org/10.1103/PhysRevD.48.5021