Quark spin in the proton

The proton spin puzzle has challenged our understanding of QCD for the last 20 years. We survey new developments in theory and experiment. The proton spin puzzle seems to be telling us about the interplay of valence quarks with chiral dynamics and the complex vacuum structure of QCD.Comment: 8 pages, presented at the Conference in Honour of Murray Gell-Mann's 80th Birthday: Quantum Mechanics, Elementary Particles, Quantum Cosmology and Complexity, NTU, Singapore, 24th-26th February 201

Neutrinos from spin dynamics

We conjecture that neutrino physics might correspond to the spontaneous magnetisation phase of an Ising-like spin model interaction coupled to neutrino chirality which operates at scales close to the Planck mass. We argue that this scenario leads to a simple extension of the Standard Model with no additional parameters that dynamically generates parity violation and spontaneous symmetry breaking for the gauge bosons which couple to the neutrino. The neutrino mass in the model ~ (the electroweak scale)^2 / 2M where M is the scale of the ``spin-spin'' interaction. For the ground state of the model the free energy density corresponding to the cosmological constant is ~ the neutrino mass, consistent with observation.Comment: 9 page