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This paper elaborates on an intrinsically quantum approach to gravity, which begins with a general framework for quantum mechanics and then seeks to identify additional mathematical structure on Hilbert space that is responsible for gravity and other phenomena. A key principle in this approach is that of correspondence: this structure should reproduce spacetime, general relativity, and quantum field theory in a limit of weak gravitational fields. A central question is that of "Einstein separability," and asks how to define mutually independent subsystems, e.g. through localization. Familiar definitions involving tensor products or operator subalgebras do not clearly accomplish this in gravity, as is seen in the correspondence limit. Instead, gravitational behavior, particularly gauge-invariance, suggests a network of Hilbert subspaces related via inclusion maps. Any such localization structure is also expected to place strong constraints on evolution, which are also supplemented by the constraint of unitarity.
An interesting conclusion is that gravity comes before entanglement in the structures - which means that entanglement can't cause gravity.Greg Bernhardt said:
Quantum-first gravity, also known as quantum gravity, is a theoretical framework that attempts to unify the theories of general relativity and quantum mechanics. It aims to explain the fundamental nature of space, time, and matter at the smallest scales.
Steve Giddings is a theoretical physicist who has made significant contributions to the field of quantum gravity. His research focuses on understanding the quantum aspects of black holes and the information paradox. He has also proposed several approaches to resolving the challenges of quantizing gravity.
Classical gravity, described by Newton's law of gravitation, is a theory that explains how objects with mass interact with each other. Quantum-first gravity, on the other hand, takes into account the principles of quantum mechanics and attempts to describe gravity at a much smaller scale, such as the Planck length.
One of the main challenges in developing a theory of quantum gravity is reconciling the principles of general relativity and quantum mechanics. These two theories are fundamentally different and have not yet been successfully unified. Additionally, there is currently no experimental evidence to support any specific theory of quantum gravity.
If a theory of quantum gravity is successfully developed, it could have far-reaching implications in our understanding of the universe. It could potentially help explain the behavior of black holes, the origin of the universe, and the nature of space and time. It could also have practical applications in fields such as astrophysics and cosmology.