Entanglement spectrum in one-dimensional systems

Understand

We derive the distribution of eigenvalues of the reduced density matrix of a block of length l in a one-dimensional system in the scaling regime.

• The resulting "entanglement spectrum" is described by a universal scaling function depending only on the central charge of the underlying conformal field theory.
• This prediction is checked against exact results for the XX chain.
• We also show how the entanglement gap closes when l is large.