2015/10/15 by Hmidi, Taoufik, Mateu, Joan · 3 citations
#Analysis of PDEs (math.AP) #FOS: Mathematics
paper · doi:10.48550/arxiv.1510.04657
In this paper we study the existence of doubly-connected rotating patches for Euler equations when the classical non-degeneracy conditions are not satisfied. We prove the bifurcation of the V-states with two-fold symmetry, however for higher m-fold symmetry with m≥3 the bifurcation does not occur. This answers to a problem left open in \citeH-F-M-V. Note that, contrary to the known results for simply-connected and doubly-connected cases where the bifurcation is pitchfork, we show that the degenerate bifurcation is actually transcritical. These results are in agreement with the numerical observations recently discussed in \citeH-F-M-V. The proofs stem from the local structure of the quadratic form associated to the reduced bifurcation equation.