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Author Archives: rojefferson
Hilbert space factorization and quantum gravity
There’s a fundamental problem in gauge theory known as Hilbert space factorization. This has its roots in the issue of how local quantities (e.g., operators) are defined in quantum field theory, and has consequences for everything from entanglement and holographic … Continue reading
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Quantum 101
Reference: John Preskill’s notes on Quantum Information and Computation. In quantum mechanics, a state is a complete description of a physical system. Mathematically, it is given by a ray (an equivalence class of vectors) in Hilbert space, , which is … Continue reading
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Generalized gravitational entropy
The derivation of RyuTakayanagi (RT) put forward by Lewkowycz and Maldacena (LM) is essentially an extension of the (boundary) replica trick into the bulk. The basic idea of the replica trick is that entanglement entropy is generally hard to calculate, … Continue reading
Hawking pairs and ontic toys
The most widely known picture of Hawking radiation involves the creation of a particleantiparticle pair at the horizon. At face value, this seems natural enough: we know from QFT that the vacuum is hardly vacuum at all, but instead a … Continue reading
Posted in Philosophy, Physics
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Action integrals and partition functions
There’s a marvelous — and by now quite wellknown — paper (paywalled) by Gibbons and Hawking, in which they compute the entropy of black holes from what is essentially a purely geometrical argument. This relies on the fact that the … Continue reading
Posted in Physics
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