Routing protocol

Physics

Pure mathematics

Canonical ensemble

Computer network

Mathematics

Mathematical physics

Black hole (networking)

Boundary (topology)

Hyperbolic space

Link-state routing protocol

Microcanonical ensemble

Statistical physics

Statistics

Limit (mathematics)

Mathematical analysis

Philosophy

Amplitude

Monte Carlo method

Space (punctuation)

Theoretical physics

Computer science

Linguistics

Quantum mechanics

Routing (electronic design automation)

Observable

Hilbert space

Journal of High Energy Physics

A bstract In the AdS/CFT correspondence, amplitudes associated to connected bulk manifolds with disconnected boundaries have presented a longstanding mystery. A possible interpretation is that they reflect the effects of averaging over an ensemble of boundary theories. But in examples in dimension D ≥ 3, an appropriate ensemble of boundary theories does not exist. Here we sharpen the puzzle by identifying a class of “fixed energy” or “sub-threshold” observables that we claim do not show effects of ensemble averaging. These are amplitudes that involve states that are above the ground state by only a fixed amount in the large N limit, and in particular are far from being black hole states. To support our claim, we explore the example of D = 3, and show that connected solutions of Einstein’s equations with disconnected boundary never contribute to these observables. To demonstrate this requires some novel results about the renormalized volume of a hyperbolic three-manifold, which we prove using modern methods in hyperbolic geometry. Why then do any observables show apparent ensemble averaging? We propose that this reflects the chaotic nature of black hole physics and the fact that the Hilbert space describing a black hole does not have a large N limit.

No ensemble averaging below the black hole threshold