The end may be hastened by magnetic monopoles

Abstract

In an open Universe, or even in just a long-lived Universe (as predicted in inflationary Universe models^1–3), the ultimate demise of matter is a certainty. Stars, of course, have only a fleeting existence as they must eventually exhaust their nuclear fuels (in ∼10¹⁰ yr for a 1 M_⊙ star). In 10¹⁴ yr or so new star formation will have ceased, and only neutron stars, white dwarfs, planetary-sized objects (such as Jupiter and Earth) and black holes will remain⁴. In the simplest grand unified theories (GUTs) the proton lifetime is but 0(10³⁰ yr), so that after this time neutron stars, white dwarfs, and planets will cease to exist. (Due to gravitational effects alone the proton lifetime is expected to be 0(10⁴⁶ yr) or less.) Although they could outlive the other three, black holes will also eventually disappear, evaporating through the Hawking process⁵ in a time ≃10⁶⁴(M/M_⊙)³ yr. I point out here that the existence of just a tiny flux of superheavy magnetic monopoles, say F≃F₋₂₁ × 10⁻²¹ cm⁻² sr⁻¹ s⁻¹, will, due to monopole-catalysed nucleon decay^6,7, hasten the demise of matter. Due to the monopoles that collect inside them, the lifetime of a neutron star will be ≃10¹¹F^−½₋₂₁ yr, of a white dwarf ≃10¹⁴F^−½₋₂₁ yr, and of an Earth-like planet ≃10¹⁸F^−½₋₂₁ yr.