Signal of quark deconfinement in the timing structure of pulsar spin-down

The conversion of nuclear matter to quark matter in the core of a rotating neutron star alters its moment of inertia, so the epoch over which conversion takes place will be signaled in the spin-down characteristics of pulsars. An observable called the braking index should be easily measurable during the transition epoch and can have a value removed by orders of magnitude from the canonical value of 3 expected for magnetic dipole radiation. The duration of the transition epoch is governed by the slow loss of angular momentum to radiation and is further prolonged by the reduction in the moment of inertia caused by the phase change which can even introduce an era of spin-up. We estimate that about one in a hundred pulsars may be passing through this phase.