The Swampland program aims to distinguish effective theories which can be completed into
quantum gravity in the ultraviolet from those which cannot. This article forms an introduction …

Axions comprise a broad class of particles that can play a major role in explaining the
unknown aspects of cosmology. They are also well-motivated within high energy physics …

We review applications of string theory to cosmology, from primordial times to the present-
day accelerated expansion. Starting with a brief overview of cosmology and string …

The Swampland program aims to determine the constraints that an effective field theory must
satisfy to be consistent with a UV embedding in a quantum gravity theory. Different …

In this review we present a thoroughly comprehensive survey of recent work on modified
theories of gravity and their cosmological consequences. Amongst other things, we cover …

We review in detail a number of approaches that have been adopted to try and explain the
remarkable observation of our accelerating universe. In particular we discuss the arguments …

It has been notoriously difficult to construct a meta-stable de Sitter (dS) vacuum in string
theory in a controlled approximation. This suggests the possibility that meta-stable dS …

Gravitational waves (GWs) have a great potential to probe cosmology. We review early
universe sources that can lead to cosmological backgrounds of GWs. We begin by …

After a decade and a half of research motivated by the accelerating universe, theory and
experiment have reached a certain level of maturity. The development of theoretical models …

The recently introduced swampland criterion for de Sitter [17] can be viewed as a
(hierarchically large) bound on the smallness of the slow roll parameter 𝜖 V. This leads us to …