# CSM

## Seminar

### Exact valence bond entanglement entropy in the XXZ and related spin chains

Seminar Room 1, Newton Institute

#### Abstract

Valence bond entanglement entropy has recently been proposed as an alternative to the well-known von Neumann entropy, measuring the information density in the ground state of spin chains. It is the mean value of the number N of valence bonds (spin singlets) connecting a subsystem of length L >> 1 to the remainder of the chain. We determine exactly the complete probability distribution of N in the XXZ spin chain, as well as in other related spin chains. At the combinatorial point (bond percolation) we conjecture exact expressions of that same distribution for finite values of L and the chain length.

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