Abstract. We consider singular solutions of the L 2 -critical biharmonic nonlinear Schrödinger equation. We prove that the blowup rate is bounded by a quartic-root, the solution approaches a quasi-self-similar profile, and a finite amount of L 2 -norm, which is no less than the critical power, concentrates into the singularity. We also prove the existence of a ground-state solution. We use asymptotic analysis to show that the blowup rate of peak-type singular solutions is slightly faster than that of a quartic-root, and the self-similar profile is given by the ground-state standing wave. These findings are verified numerically (up to focusing levels of 10 8 ) using an adaptive grid method. We also use the spectral renormalization method to compute the ground state of the standing-wave equation, and the critical power for collapse, in one, two, and three dimensions.

We present new singular solutions of the biharmonic nonlinear Schrödinger equationThese solutions collapse with the quasi self-similar ring profile ψQ B , whereis the ring width that vanishes at singularity, rmax(t) ∼ r0L α (t) is the ring radius, and α = 4−σThe blowup rate of these solutions is 1 3+α for 4/d ≤ σ < 4, and slightly faster than 1/4 for σ = 4. These solutions are analogous to the ring-type solutions of the nonlinear Schrödinger equation.

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