Nelson is known for a number of theories, including: • The Nelson–Barr mechanism, a proposed solution to the
strong CP problem. The theory was developed independently by Nelson and
Stephen Barr in 1984. Nelson was a doctoral student at Harvard at the time. • The theory of spontaneous
violation of CP (charge conjugation and parity symmetry), which may explain the origin of the asymmetry observed between matter and anti-matter. • The theory of
Bose–Einstein condensation of
kaon mesons in dense matter, which predicts strangeness in neutron stars. • The basic mechanism for
electroweak baryogenesis, which may explain the origin of matter in the universe. • The theory of gauge-mediated
supersymmetry breaking, which accounts for how supersymmetry at short distances might be compatible with the absence of observed flavor-symmetry violation at long distances. • The
little Higgs theory, which may explain why the Higgs boson must be relatively light. • The theory of "accelerons", which relates neutrino masses to the
cosmological dark energy responsible for the relatively recent acceleration of the expansion of the universe. == Personal life ==