@mathematical_research_goal (1).md @mathematical_audit_prompt_v3 (1).md I am attaching `mathematical_research_goal.md`. Read that file completely and treat it as the governing research procedure. The authoritative mathematical problem is the complete LaTeX source between the two TARGET_PROBLEM markers below. PROJECT_WINDOW_BUDGET: 6 hours \<TARGET_PROBLEM_BEGIN> \paragraph{Problem (global existence for general vortex-sheet data).}\
Let $\mathcal M(\mathbb R^2)$ denote the space of finite signed\
Radon measures, equipped with the total variation norm, and set\
\\[\
  K(x)=\frac{(-x_2,x_1)}{2\pi|x|^2}.\
\\]\
For every\
\\[\
  \omega_0\in\mathcal M(\mathbb R^2)\cap H^{-1}(\mathbb R^2),\
  \qquad u_0=K\*\omega_0,\
\\]\
with no sign restriction on $\omega_0$, does there exist a global\
weak solution of the incompressible Euler equations\
\\[\
  u\in C_w([0,\infty);\
  L^2\_{\mathrm{loc}}(\mathbb R^2;\mathbb R^2))\
\\]\
with $u(0)=u_0$ and $\operatorname{div}u=0$, whose vorticity\
$\omega(t):=\partial_1u_2(t)-\partial_2u_1(t)$ satisfies\
\\[\
\begin{gathered}\
  \omega(t)\in\mathcal M(\mathbb R^2),\
  \qquad u(t)=K\*\omega(t)\
  \qquad\text{for every }t\geq0,\\\\\
  \sup\_{0\leq t\leq T}\\|\omega(t)\\|\_{\mathcal M}<\infty\
  \qquad\text{for every }T>0?\
\end{gathered}\
\\]\
Here the Euler equations are required in the sense that\
\\[\
  \int_0^T\\!\\!\int\_{\mathbb R^2}\
  \bigl(u\cdot\partial_t\varphi\
  +(u\otimes u):\nabla\varphi\bigr)\\,dx\\,dt\
  +\int\_{\mathbb R^2}u_0\cdot\varphi(0,\cdot)\\,dx=0\
\\]\
for every $T>0$ and every divergence-free\
$\varphi\in C_c^\infty([0,T)\times\mathbb R^2;\mathbb R^2)$.\
The notation $C_w$ means weak continuity in $L^2$ on every\
bounded spatial subdomain. \<TARGET_PROBLEM_END> This is a bounded mathematical research project, not a request for an immediate literature-status answer. Begin the procedure in `mathematical_research_goal.md` now. As the first persistence action, create and maintain `checkpoint.md`. Copy the exact marked problem into that checkpoint before beginning heavy route work. Do not terminate except under a stopping condition permitted by `mathematical_research_goal.md`.