In a previous paper we have considered the functional V (u) = 1 2 ∫ RN | grad u(x)| dx+ ∫ RN F (u(x)) dx subject to ∫ RN G(u(x)) dx = λ > 0 , where u(x) = (u1(x), . . . , uK(x)) belongs to H 1 K(R ) = H(R ) × · · · × H(R) (K times) and | grad u(x)| means ∑K i=1 | gradui(x)|. We have shown that, under some technical assumptions and except for a translation in the space variable x, any global min...

Material accreted onto a neutron star can stably burn in steady state only when the accretion rate is high (typically super-Eddington) or if a large flux from the neutron star crust permeates the outer atmosphere. For such situations we have analyzed the stability of nonradial oscillations, finding one unstable mode for pure helium accretion. This is a shallow surface wave which resides in the ...