Entanglement entropy of the random<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>s</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math>Heisenberg chain

Random spin chains at quantum critical points exhibit an entanglement entropy\nbetween a segment of length L and the rest of the chain that scales as log_2 L\nwith a universal coefficient. Since for pure quantum critical spin chains this\ncoefficient is fixed by the central charge of the associated conformal field\ntheory, the universal coefficient in the random case can be understood as an\neffective central charge. In this paper we calculate the entanglement entropy\nand effective central charge of the spin-1 random Heisenberg model in its\nrandom-singlet phase and also at the critical point at which the Haldane phase\nbreaks down. The latter is the first entanglement calculation for an\ninfinite-randomness fixed point that is not in the random-singlet universality\nclass. Our results are consistent with a c-theorem for flow between\ninfinite-randomness fixed points. The formalism we use can be generally applied\nto calculation of quantities that depend on the RG history in s&gt;=1 random\nHeisenberg chains.\n