Do monopoles keep white dwarfs hot?

Although theoretical cooling curves predict large numbers of faint white dwarfs (Mbol ≥ 16), none have been observed singly or even inferred as the missing objects in binary systems. The author suggests magnetic monopole-catalyzed nucleon decay as a mechanism for keeping white dwarfs hot (Mbol < 16). At the same time the observed luminosities of old white dwarfs (L = 10⁻⁴L_sun;) place an upper limit on the product of monopole flux times cross section for catalysis, (F/cm⁻²s⁻¹sr⁻¹)(σv/10⁻²⁸cm²) ≤ 2×10⁻¹⁸.