• Quantum mechanical states of two, three, or more bodies
• Binding in reduced dimensions, 1D and 2D bound states
• Long-range interactions in mixed geometries such as arrays of planes or tubes
• Strong short-range interactions in 1D

• Top-down approach - Bound states on top of a background
• Bottom-up approach - Ab initio methods with increasing particle numbers

• Mean-field many-body dynamics using few-body dynamics as a guide
• 1D many-body methods such as DMRG or matrix product states