  The condensation of Cooper pairs, originating from the Fermi-surface
instability due to a weakly attractive interaction between two fermions, opened
a new frontier for exploring many-body physics in interdisciplinary contexts.
In this work, we discuss the possible condensation of Cooper triples, which are
three-body counterparts of Cooper pairs for three-component fermions with a
three-body attraction. Although each composite trimer-like state obeys the
Fermi-Dirac statistics, its aggregate can form a condensate at zero
center-of-mass momentum in the presence of the internal degrees of freedom
associated with the relative momenta of constituent particles of momenta close
to the Fermi surface. Such condensation can be regarded as bosonization in
infinite-component fermions. We propose a variational wave function for the
condensate of Cooper triples in analogy with the Bardeen-Cooper-Schrieffer
ground state and obtain the ground-state energy.
