Bound state by definition is a state when particles are bounded together, so then "many-body bound state" would be bound state for a system of many bodies. Then I have several puzzles:
is the state when many particles are confined in a box or some traps could be viewed as many-body bound state?
But usually bound state is due to interactions between themselves not to external potentials. So is it just a favor of definition, so then trivial?
is solid/liquid state a many-body bound state?
I am just wondering why few people would say that. The problem may be that: here a solid/liquid state is actually a phase, not a single quantum state. So then is a solid/liquid at zero temperature, meaning that it is in a single quantum state, could be viewed as a many-body bound state?
Thanks to @ACuriousMind, I find that my "definition" of bound state seems to be a circular-type. I just refer to its literal meaning. To be accurate, say by wiki:
In physics, a bound state describes a system where a particle is subject to a potential such that the particle has a tendency to remain localised in one or more regions of space. The potential may be either an external potential, or may be the result of the presence of another particle.
If the external potential could be included, then particles in a box or in a trap could also be viewed as in bound state. Any reason to object?