Aspects of Nonlocality in Quantum Field Theory, Quantum Gravity and Cosmology

Abstract

This paper contains a collection of essays on nonlocal phenomena in quantum field theory, gravity and cosmology. Mechanisms of nonlocal contributions to the quantum effective action are discussed within the covariant perturbation expansion in field strengths and spacetime curvatures and the nonperturbative method based on the late time asymptotics of the heat kernel. Euclidean version of the Schwinger-Keldysh technique for quantum expectation values is presented as a special rule of obtaining the nonlocal effective equations of motion for the mean quantum field from the Euclidean effective action. This rule is applied to a new model of ghost free nonlocal cosmology which can generate the de Sitter stage of cosmological evolution at an arbitrary value of $\Lambda$ -- a model of dark energy with its scale played by the dynamical variable that can be fixed by a kind of a scaling symmetry breaking mechanism. This model is shown to interpolate between the superhorizon phase of gravity theory mediated by a scalar mode and the short distance general relativistic limit in a special frame which is related by a nonlocal conformal transformation to the original metric. The role of compactness and regularity of spacetime in the Euclidean version of the Schwinger-Keldysh technique is discussed.

30 pages, 1 figure, extended version of the paper to appear in Modern Physics Letters A, contains discussion of the effective action generated by late time heat kernel asymptotics and the discussion of regularity on compact Euclidean spacetimes with conical singularities

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Cited by in corpus (17)

• Non-Local Gravity Cosmology: an Overview
• Constraining Generalized Non-local Cosmology from Noether Symmetries
• Non-Local Gravity Wormholes
• Estimating the Parameters of Extended Gravity Theories with the Schwarzschild Precession of S2 Star
• General Relativistic Wormhole Connections from Planck-Scales and the ER = EPR Conjecture
• Non-Local Curvature and Gauss-Bonnet Cosmologies by Noether Symmetries
• Instabilities in tensorial nonlocal gravity
• The phase-space view of non-local gravity cosmology
• Non-Local Curvature Gravity Cosmology via Noether Symmetries
• Addressing Cosmological Tensions by Non-Local Gravity
• Testing non-local gravity by clusters of galaxies
• Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review
• Velocity distribution of elliptical galaxies in the framework of Non-local Gravity model
• Towards UV Finiteness of Infinite Derivative Theories of Gravity and Field Theories
• Topological defects in nonlocal field theories
• Testing non-local gravity through Ultra-Diffuse Galaxies kinematics
• On the impact of non-local gravity on compact stars