Quantum Indefinite Spacetime
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Date
2017
Authors
Jia, Ding
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
We combine the principle of superposition from quantum theory and the
principle of dynamical causal structure from general relativity to attack
fundamental questions in quantum gravity. We generalize the concept of
entanglement to parties whose causal relation is quantum indefinite. The
generalized notion of entanglement gives meaning to timelike and more generally
spacetime entanglement in quantum theory both with and without
indefinite causal structure. Using this generalization, we identify quantum
gravitational
uctuations of causal structure as a possible mechanism that
regularizes the otherwise divergent entanglement. We give the name "quantum
indefinite spacetime" to the model of spacetime incorporating quantum
gravitational causal
uctuations.
Quantum indefinite spacetime sheds new light on black hole information
problem as we argue that quantum gravitational causal
uctuations allow
positive information communication capacity to the outside of the black
holes. The new generalized notion of entanglement offers additional support
from the black hole thermodynamics perspective.
Towards the end of the thesis we make a preliminary proposal that the
quantum
uctuating entanglement regularization may explain the apparent
accelerated expansion of the universe without introducing dark energy or
cosmological constant.
All these results and proposals are obtained on the basis of jointly applying
quantum and general relativistic principles, but without making tentative
postulates about the microscopic degrees of freedom of quantum spacetime.
We hope to convey the message that this more conservative approach
can offer firrm answers to several questions in quantum gravity. Moreover,
other approaches to quantum gravity should incorporate features of quantum indefinite spacetime if they assume the same principles.