We propose that the mechanism responsible for the ``collapse of the wave
function" (or "decoherence" in its broadest meaning) in quantum mechanics is
the nonlinearities already present in the theory via nonabelian gauge
interactions. Unlike all other models of spontaneous collapse, our proposal is,
to the best of our knowledge, the only one which does not introduce any new
elements into the theory. Indeed, unless the gauge interaction nonlinearities
are not used for exactly this purpose, one must then explain why the violation
of the superposition principle which they introduce does not destroy quantum
mechanics. A possible experimental test of the model would be to compare the
coherence lengths for, e.g., electrons and photons in a double-slit experiment.
The electrons should have a finite coherence length, while photons should have
a much longer (in principle infinite) coherence length.Comment: 7 pages, LaTe
