  We introduce the notion of branon jets, states of collinear flux tube
excitations. We argue for the analyticity, crossing and unitarity of the
multi-particle scattering of these jets and, through the S-matrix bootstrap,
place bounds on a set of finite energy multi-particle sum rules. Such bounds
define a matrioska of sorts with a smaller and smaller allowed regions as we
impose more constraints. The Yang-Mills flux tube, as well as other interesting
flux tube theories recently studied through lattice simulations, lie inside a
tiny island hundreds of times smaller than the most general space of allowed
two-dimensional theories.
