Corner contribution to the entanglement entropy of an O(3) quantum   critical point in 2+1 dimensions
  The entanglement entropy for a quantum critical system across a boundary with a corner exhibits a sub-leading logarithmic scaling term with a scale-invariant coefficient. Using a Numerical Linked Cluster Expansion, we calculate this universal quantity for a square-lattice bilayer Heisenberg model at its quantum critical point. We find, for this 2+1 dimensional O(3) universality class, that it is thrice the value calculated previously for the Ising universality class. This relation gives substantial evidence that this coefficient provides a measure of the number of degrees of freedom of the theory, analogous to the central charge in a 1+1 dimensional conformal field theory. 
Ann B. Kallin, E. M. Stoudenmire, Paul Fendley, Rajiv R. P. Singh,   Roger G. Melko
cond-mat.str-el cond-mat.stat-mech hep-th quant-ph