In spin systems, the existence of a spectral gap has far-reaching
consequences. So-called "frustration-free" spin systems form a
subclass that is special enough to make the spectral gap problem
amenable and, at the same time, broad enough to include...
With the discovery of a binary neutron star coalescence in
gravitational waves, and the discovery of an associated short
gamma-ray burst, and the discovery of an associated optical
afterglow, we have finally entered the era of
gravitational-wave...
