How symmetry hides in a spin chain
A quantum chain is like a string of lights, where the bulbs are the spins of particles. Ideally, all bulbs glow in sync, following a common rhythm: that's symmetry. But if you cut off a piece of the string, the rhythm can get out of step: within that segment, symmetry is broken.
Physicists study a chain of strongly interacting particles (the XYZ model).