Swampland Bounds on Dark Sectors

Abstract

We use Swampland principles to theoretically disfavor regions of the parameter space of dark matter and other darkly charged particles that may exist. The Festina Lente bound, the analogue of the Weak-Gravity conjecture in de Sitter, places constraints on the mass and charge of dark particles, which here we show cover regions in parameter space that are currently allowed by observations. As a consequence, a broad set of new ultra-light particles are in the Swampland, independently of their cosmic abundance, showing the complementarity of Quantum Gravity limits with laboratory and astrophysical studies. In parallel, a Swampland bound on the UV cutoff associated to the axion giving a Stückelberg photon its longitudinal mode translates to a new constraint on the kinetic mixings and masses of dark photons. This covers part of the parameter space targeted by upcoming dark-photon direct-detection experiments. Moreover, it puts astrophysically interesting models in the Swampland, including freeze-in dark matter through an ultra-light dark photon, as well as radio models invoked to explain the 21-cm EDGES anomaly.

The Inflated Chern-Simons Number in Spectator Chromo-Natural Inflation

“…Since the additional axion θ relies on a substantially stronger conjecture than the original WGC, we will not pursue a more detailed exploration of its consequences here. The implications for chromo-natural inflation of a completely different set of conjectural Swampland constraints are discussed in [61].…”

Dark Matter decay to neutrinos

“…The parameter space of such nongravitational interactions is immense, and myriad portals are potentially available. Traditional searches for electroweak and supersymmetry-inspired WIMPs in the GeV-TeV mass range that scatter with or annihilate to quarks have expanded in the past decades to encompass light axionlike [3] and minicharged particles [4][5][6][7][8], sub-GeV nonthermal DM candidates [9,10], primordial black holes [11], and other exotic objects. In some of these scenarios, dark matter can be unstable and decay to Standard Model particles.…”

Confinement in de Sitter Space and the Swampland

“…Seemingly consistent low energy effective field theories (EFTs) can be severely constrained by the requirement of a successful embedding into a quantum theory of gravity such as string theory. An interconnected web of conjectures has been put forth under the swampland program [1] (see [2][3][4] for a review), and has provided new perspectives on several theoretical [5] as well as phenomenological [6][7][8][9][10] research directions. Some of the most powerful conjectures, even if seen amply in string theory examples, can be equally derived by elegant arguments using black holes (BH), e.g.…”