E. Regos (Budapest):
Casimir Effect: Running Newton Constant or Cosmological Term
Abstract:
We argue that the instability of Euclidean Einstein gravity is an indication that the
vacuum is non perturbative and contains a condensate of the metric tensor in a manner reminiscent of YangMills
theories. As a simple step toward the characterization of such a vacuum the value of the oneloop effective
action is computed for Euclidean de Sitter spaces as a function of the curvature when the unstable conformal
modes are held fixed. Two phases are found, one where the curvature is large and an IR Landau pole suggests
confinement of gravitons and another one which appears to be weakly coupled and tends to be flat. The induced
cosmological constant is positive or negative in the strongly or weakly curved phase, respectively. The relevance
of the Casimir effect in understanding the UV sensitivity of gravity is pointed out.
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