A Species or Weak-Gravity Bound for Large $N$ Gauge Theories Coupled to Gravity

Understand

Causality constrains the gravitational interactions of massive higher spin particles in both AdS and flat spacetime.

• We explore the extent to which these constraints apply to composite particles, explaining why they do not rule out macroscopic objects or hydrogen atoms.
• However, we find that they do apply to glueballs and mesons in confining large $N$ gauge theories.
• Assuming such theories contain massive bound states of general spin, we find parametric bounds in $(3+1)$ spacetime dimensions of the form $N\lesssim \frac{M_{Pl}}{\Lambda_{\text{QCD}}}$ relating $N$, the QCD scale, and the Planck scale.