Abstract
The trace anomaly of conformal matter implies the existence of massless scalar poles in physical amplitudes involving the stress-energy tensor. These poles may be described by a local effective action with massless scalar fields, which couple to classical sources, contribute to gravitational scattering processes, and can have long range gravitational effects at macroscopic scales. In an effective field theory approach, the effective action of the anomaly is an infrared relevant term that should be added to the Einstein-Hilbert action of classical General Relativity to take account of macroscopic quantum effects. The additional scalar degrees of freedom contained in this effective action may be understood as responsible for both the Casimir effect in flat spacetime and large quantum backreaction effects at the horizon scale of cosmological spacetimes. These effects of the trace anomaly imply that the cosmological vacuum energy is dynamical, and its value depends on macroscopic boundary conditions at the cosmological horizon scale, rather than sensitivity to the extreme ultraviolet Planck scale.
Highlights
Invited Talk at the Ninth Conference on Quantum Field Theory under the Influence of External Conditions
In an effective field theory approach, the effective action of the anomaly is an infrared relevant term that should be added to the Einstein-Hilbert action of classical General Relativity to take account of macroscopic quantum effects
The additional scalar degrees of freedom contained in this effective action may be understood as responsible for both the Casimir effect in flat spacetime and large quantum backreaction effects at the horizon scale of cosmological spacetimes
Summary
In classical General Relativity, the requirement that the field eqs. involve no more than two derivatives of the metric tensor allows for the possible addition of a constant term, the cosmological term Λ, to Einstein’s eqs. In the case of cosmology it is usually taken for granted that any effects of boundary conditions can be neglected It is not obvious what should play the role of the conducting plates in determining the magnitude of ρv in the universe, and the magnitude of any effect of quantum zero point energy on the curvature of space has remained unclear from Pauli’s original estimate down to the present. In recent years this has evolved from a question of fundamental importance in theoretical physics to a central one of observational cosmology as well.
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