  Quasiparticles are low-energy excitations with important roles in condensed
matter physics. An intriguing example is provided by Majorana fermions,
quasiparticles which are identical to their antiparticles. Despite being
implicated in neutrino oscillations and topological superconductivity, their
experimental realisations remain scarce. Here we propose a purely classical
realisation of Majorana fermions, in terms of 3-dimensional disclination lines
in active nematics. Activity is required to overcome the elastic cost
associated with these excitations, so they can appear in steady state. We
combine topology and simulations to show that active nematics under confinement
spontaneously create in their interior topologically charged disclination lines
and loops, akin to Majorana quasiparticles with finite momentum. Within an
elongated channel, we find a phenomenology similar to that of the Kitaev chain,
as local Majorana-like excitations appear near surfaces, while a non-local
system-spanning helical disclination line can arise along the centre. In
unconfined active turbulence, Majorana-like charged loops are instead
exceedingly rare, suggesting that boundaries are crucial to generate these
quasiparticles, as in quantum condensed matter. We suggest that 3-dimensional
active disclinations can be used to probe the physics of Majorana spinors at a
much larger scale than traditionally considered, potentially facilitating the
experimental observation of their dynamics.
