  Physical systems in reduced dimensions exhibit intriguing properties. For
instance, the dependences of two-body and many-body physics on scattering
lengths are distinct from their counterparts in three dimensions. Whereas many
studies of ultracold atoms and molecules in reduced dimensions have been
focusing on closed systems, two-body losses may occur in such systems. Here, we
show that the two-body inelastic loss rate in reduced dimensions can be
expressed in universal relations that are governed by contacts. These universal
relations correlate the two-body decay rate with other physical observables at
arbitrary temperatures and interaction strengths. Our results will provide
experimentalists with a new protocol to study inelastic scatterings in both
few- and many-body systems in reduced dimensions.
