Contents

# Contents

## Examples

The hierarchy of bound states in quantum chromodynamics:

Here the last two steps go beyond QCD as they also involve electrons from quantum electrodynamics.

There are also bound states purely in QED:

Hypothetically:

brane intersections/bound states/wrapped branes/polarized branes

S-duality$\,$bound states:

intersecting$\,$M-branes:

## References

On bound states in QED and QCD:

• Paul Hoyer, Bound states – from QED to QCD, Lectures at “Mini-school on theoretical methods in particle physics” at the Higgs Centre for Theoretical Physics, University of Edinburgh on 30 September to 4 October 2013 (arXiv:1402.5005)

• Changyong Liu, On bound states in Quantum Field Theory (arXiv:1811.06457)

• Paul Hoyer, Journey to the Bound States (arXiv:2101.06721)