Onsager's Mean Field Theory of Vortex Flows with Singular Sources: Blow-Up and Concentration without Quantization
Daniele Bartolucci, Paolo Cosentino, Lina Wu
TL;DR
This work extends Onsager's mean-field theory to include a fixed singular vortex of strength $\sigma$ at the origin, formulating canonical and microcanonical variational principles with a singular weight $H_{\lambda}(x)$ and establishing a sharp blow-up threshold $\lambda_{\sigma}$. It proves the equivalence of the CVP and MVP for a class of domains, develops a minimal mass framework that yields a lower bound on the concentration mass and introduces a novel blow-up regime—blow-up with concentration without quantization—where the concentrated mass varies in a real interval and depends on the singularity strength. The authors derive refined non-quantized bubbling profiles, prove existence of entropy-maximizing densities, and analyze high-energy limits, including a detailed Type I disk example that yields explicit entropy asymptotics and confirms the domain-type classification. Together, these results provide a comprehensive variational and asymptotic description of vortex flows with singular sources, bridging classical quantized blow-up with non-quantized concentration phenomena and suggesting geophysical applications related to principal vortex structures.
Abstract
Motivated by the Onsager statistical mechanics description of turbulent Euler flows with point singularities, we make a first step in the generalization of the mean field theory in [Caglioti, Lions, Marchioro, Pulvirenti; Comm. Math. Phys. (1995)]. On one side we prove the equivalence of statistical ensembles, on the other side we are bound to the analysis of a new blow up phenomenon, which we call "blow up and concentration without quantization", where the mass associated with the concentration is allowed to take values in a full interval of real numbers. This singular behavior may be regarded as lying between the classical blow up-concentration-quantization and the blow up without concentration phenomenon first proposed in [Lin, Tarantello; C.R. Math. Acad. Sci. Paris (2016)]. A careful analysis is needed to generalize known pointwise estimates in this non standard context, resulting in a complete description of the allowed asymptotic profiles.
