  A new framework for computing the Similarity Renormalization Group (SRG)
evolution of three-nucleon forces (3NF) in momentum representation is
presented. The use of antisymmetric three-particle hyperspherical momentum
states ensures unitary evolutions within certain basis truncations, much like
antisymmetric harmonic oscillator SRG evolutions. Additionally, in each partial
wave the $T_{\mbox{rel}}$-SRG regulator is exactly represented, similar to
recent 3NF momentum representation evolutions. Unitary equivalence is
demonstrated for the triton using several chiral two- plus three-nucleon
interactions. This method allows for a clean visualization of the evolution of
the three-nucleon forces, which manifests the SRG decoupling pattern and
low-momentum universality.
