Equicontinuity conjecture for derivative nonlinear Schrödinger flows

Let S\mathcal{S} denote the Schwartz class. For a set QSQ\subseteq\mathcal{S}, call QQ L2L^2-equicontinuous if its elements have uniformly small high-frequency tails, and let etJHqe^{tJ\nabla H}q denote the derivative nonlinear Schrödinger flow from initial data qq. Define

Q={etJHq:qQ and tR}.Q_* = \{ e^{tJ\nabla H} q: q\in Q \text{ and } t\in\mathbb{R}\}.

Equicontinuity conjecture. For any QSQ\subseteq\mathcal{S} that is L2L^2-bounded and equicontinuous, the set QQ_* is also L2L^2-equicontinuous.

This conjecture would rule out the concentration scenario associated with type-II blowup and is motivated by the fact that the mass is a coercive, scaling-critical conserved quantity. Local well-posedness is known for HsH^s data with s12s\geq\frac12, but global well-posedness at the L2L^2 level is not known.

Sources & referencesView supporting material

Primary source

Rowan Killip, Maria Ntekoume and Monica Visan, “On the well-posedness problem for the derivative nonlinear Schrödinger equation”, arXiv:2101.12274 (2021).

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