Draining the Swampland

TL;DR

The paper explores the implications of the Swampland conjecture on inflationary models and particle phenomenology, suggesting it could challenge slow-roll inflation and influence dark matter theories.

Contribution

It analyzes how the Swampland conjecture constrains inflation and introduces the concept of a drainon scalar field affecting cosmological evolution.

Findings

Swampland conjecture challenges slow-roll inflation models.

Scalar fields, including drainons, can satisfy the conjecture and influence dark matter.

Potential tension between the conjecture and observed scalar power spectrum.

Abstract

We discuss some implications of the recently suggested Swampland conjecture $\frac{|\nabla V|}{V}\gtrsim c\sim 1$, together with a previous one $\Delta \phi \lesssim 1$. We list some implications for particle phenomenology and the Early Universe. The most intriguing implication of the conjecture could be a significant shift in allowed inflationary models, if not ruling out slow-roll (single field) inflation altogether. The tension of inflation and the conjecture does not only regard the amplitude of the tensor spectrum, but also its tilt, as $c\gtrsim 1$ implies both a yet unobserved tensor to scalar ratio, and an enhancement of the observed scalar power spectrum on large scales in discord with current data that favors a suppression on these scales. Scalar fields are abundant in theories of quantum gravity. Considering a second scalar field, its dynamics are dictated by the relation between its mass, $m$, and the Hubble parameter, $H$, at different epochs in the history of the Universe. This scalar field, a drainon, fulfills the conjecture draining up the swampland. For Inflation, this drainon requires a modest hierarchy compared to the inflaton. For the rest of the thermal history of the Universe, the drainon can be a coherently oscillating scalar field strengthening the case of Dark Matter candidates of that sort.