Primordial Gravitational Waves and the Swampland
  The swampland conjectures seek to distinguish effective field theories which
can be consistently embedded in a theory of quantum gravity from those which
can not (and are hence referred to as being in the swampland). We consider two
such conjectures, known as the Swampland Distance and de Sitter Conjectures,
showing that taken together they place bounds on the amplitude of primordial
gravitational waves generated during single field slow-roll inflation. The
bounds depend on two parameters which for reasonable estimates restrict the
tensor-to-scalar ratio to be within reach of future surveys.
