Mass-concentration of low-regularity blow-up solutions to the focusing 2D modified Zakharov-Kuznetsov equation

We consider the focusing modified Zakharov-Kuznetsov (mZK) equation in two space dimensions. We prove that solutions which blow up in finite time in the $H^1({\mathbb{R}}^2)$ norm have the property that they concentrate a non-trivial portion of their mass (more precisely, at least the amount equal to the mass of the ground state) at blow-up time. For finite-time blow-up solutions in the $H^s({\mathbb{R}}^2)$ norm for $\frac{17}{18}<s<1$, we prove a slightly weaker result. Moreover, we prove that the stronger concentration result can be extended to the range $\frac{17}{18}<s\le 1$ under an additional assumption on the upper bound of the blow-up rate of the solution. The main tools used here are the $I$-method and a profile decomposition theorem for a bounded family of $H^1({\mathbb{R}}^2)$ functions.