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The recently proposed map [5] between the hydrodynamic equationsgoverning the two-dimensional triangular cold-bosonic breathers [1] andthe high-density zero-temperature triangular free-fermionic clouds, bothtrapped harmonically, perfectly explains the former phenomenon butleaves uninterpreted the nature of the initial(t=0)singularity. This singularity is a density discontinuity that leads, inthe bosonic case, to an infinite force at the cloud edge. The map itselfbecomes invalid at times t<0 t < 0 .A similar singularity appears at t = T/4 t = T / 4 ,where Tis the period of the harmonic trap, with the Fermi-Bose map becominginvalid at t > T/4 t > T / 4 . Here, we first map—using the scale invariance of the problem—thetrapped motion to an untrapped one. Then we show that in the newrepresentation, the solution [5] becomes, along a ray in the directionnormal to one of the three edges of the initial cloud, a freelypropagating one-dimensional shock wave of a class proposed by Damski in[7]. There, for a broad class of initial conditions, the one-dimensionalhydrodynamic equations can be mapped to the inviscid Burgers’ equation,which is equivalent to a nonlinear transport equation. Morespecifically, under the Damski map, thet=0singularity of the original problem becomes, verbatim, the initialcondition for the wave catastrophe solution found by Chandrasekhar in1943 [9]. At t=T/8 t = T / 8 ,our interpretation ceases to exist: at this instance, all threeeffectively one-dimensional shock waves emanating from each of the threesides of the initial triangle collide at the origin, and the 2D-1Dcorrespondence between the solution of [5] and the Damski-Chandrasekharshock wave becomes invalid.