Large-N bounds on, and compositeness limit of, gauge and gravitational interactions

TL;DR

This paper demonstrates that in a large-N toy model of gauge and gravitational interactions with a UV cutoff, the couplings are bounded by powers of 1/N, suggesting a smooth compositeness limit with potential implications for fundamental physics.

Contribution

It establishes bounds on gauge and gravitational couplings in large-N models, showing the compositeness limit is smooth and applicable to realistic theories.

Findings

Gauge and gravitational couplings are bounded by powers of 1/N.

The compositeness limit can be smooth and physically relevant.

Implications for entropy bounds, string theory, and quintessence.

Abstract

In a toy model of gauge and gravitational interactions in $D \ge 4$ dimensions, endowed with an invariant UV cut-off $\Lambda$, and containing a large number $N$ of non-self-interacting matter species, the physical gauge and gravitational couplings at the cut-off, $\alpha_g \equiv g^2 \Lambda^{D-4}$ and $\alpha_G \equiv G_N \Lambda^{D-2}$, are shown to be bounded by appropriate powers of ${1\over N}$. This implies that the infinite-bare-coupling (so-called compositeness) limit of these theories is smooth, and can even resemble our world. We argue that such a result, when extended to more realistic situations, can help avoid large-N violations of entropy bounds, solve the dilaton stabilization and GUT-scale problems in superstring theory, and provide a new possible candidate for quintessence.