Stringballs and Planckballs for Dark Matter

TL;DR

This paper explores the formation of gravitationally bound states in various theories beyond Einstein's gravity, proposing they could serve as dark matter candidates due to their unique formation conditions and properties.

Contribution

It explicitly demonstrates bound state formation in string theory and higher derivative theories, contrasting with Einstein gravity, and discusses their potential role as dark matter.

Findings

Bound states form at energies above the Planck scale in certain theories.

In higher derivative and nonlocal theories, bound states form below the Planck energy.

These bound states could be dark matter candidates or seeds for cosmic structure formation.

Abstract

As a follow up of the seminal work by Guiot, Borquez, Deur, and Werner on "Graviballs and Dark Matter", we explicitly show that contrary to Einstein's gravity, in string theory, local and nonlocal higher derivative theories, as well as general asymptotically-free or finite theories, gravitationally interacting bound states can form when the energy is larger than the Planck energy. On the other hand, in higher derivative or nonlocal theories with interaction governed by a dimensionless or a dimensionful coupling constant, the bound states form when the energy is smaller than the Planck energy. Such bound states are allowed because of the softness of the scattering amplitudes in the ultraviolet region. Indeed, in such theories, the potential is finite while the force is zero or constant in $r=0$. Finally, since the bound states that form in the early Universe may have an energy that ranges from the Planck mass to any arbitrarily large or small value, we argue that they can serve as dark matter candidates and/or as the seeds for the structure's formation at large scale in the Cosmos.