  Cosmic filaments are the largest collapsing structure in the Universe.
Recently both observations and simulations inferred that cosmic filaments have
coherent angular momenta (spins). Here we use filament finders to identify the
filamentary structures in cosmological simulations and study their physical
origins, which are well described by the primordial tidal torque of their
Lagrangian counterpart regions -- protofilaments. This initial angular momenta
statistically preserve their directions to low redshifts. We further show that
a spin reconstruction method can predict the spins of filaments and potentially
relate their spins to the initial conditions of the Universe. This correlation
provides a new way of constraining and obtaining additional information of the
initial perturbations of the Universe.
