MERONS AND THOMAS PRECESSION

In a recent study of Thomas precession of electron spin in the context of the Dirac equation, Shankar and Mathur identify the non-Abelian Be rry potential (arising from Kramers degeneracy) with the meron. We poi nt out that there is a global mathematical subtlety which prevents suc h an identification. We go on to clarify the physical context in which merons do arise as Berry potentials.