Category Archives: Physics

Information geometry (part 3/3)

Insofar as quantum mechanics can be regarded as an extension of (classical) probability theory, most of the concepts developed in the previous two parts of this sequence can be extended to quantum information theory as well, thus giving rise to … Continue reading

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Boundary conditions in AdS/CFT

The issue of boundary conditions in AdS/CFT has confused me for years; not because it’s intrinsically complicated, but because most of the literature simply regurgitates a superficial explanation for the standard prescription which collapses at the first inquiry. Typically, the … Continue reading

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Tomita-Takesaki in Rindler space

Rindler space provides a convenient example to elucidate some basic properties of AQFT — specifically Tomita-Takesaki theory — in what is arguably the case of greatest interest to high-energy theorists. We shall begin by introducing a few fundamental objects in … Continue reading

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Information geometry (part 2/3)

In the previous post, we introduced the -connection, and alluded to a dualistic structure between and . In particular, the cases are intimately related to two important families of statistical models, the exponential or e-family with affine connection , and … Continue reading

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Information geometry (part 1/3)

Information geometry is a rather interesting fusion of statistics and differential geometry, in which a statistical model is endowed with the structure of a Riemannian manifold. Each point on the manifold corresponds to a probability distribution function, and the metric … Continue reading

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Disjoint representations and particle ontology

There is a beautiful paper by Clifton and Halvorson [1], which discusses the ontology of particles in quantum field theory using the famous example of Minkowski vs. Rindler quantizations of a free bosonic field. What is especially nice about this … Continue reading

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The Reeh-Schlieder Theorem

The Reeh-Schlieder theorem is perhaps the most notorious result in algebraic quantum field theory, simultaneously one of the least intuitive and most fundamental. Denote the vacuum sector of Hilbert space, which consists of all states that can be created from … Continue reading

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General covariance, diffeomorphism invariance, and background independence

My attempts to understand the significance of diffeomorphism invariance in general relativity have been hampered by the confusion surrounding active vs. passive transformations, invariance vs. (general) covariance, background independence, etc. This post comprises my ambitious attempt to settle the matter … Continue reading

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Decoherence with holography

I recently read an interesting paper [1] that uses holography to study decoherence in strongly-coupled systems. It relies on the fact that, in the case of a linear coupling between the subsystem and the environment, the Feynman-Vernon influence functional — … Continue reading

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General relativity or gravitons?

Question: How is the existence of a graviton consistent with the GR paradigm of gravity as a purely geometrical effect? Answer: Ontologically, it’s not! Gravitons are predicated on a quantum field-theoretic formulation of gravity, while spacetime curvature is the corresponding … Continue reading

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