Eisenstein points on the Hilbert cuspidal eigenvariety

We present a comprehensive study of the geometry of Hilbert $p$-adic eigenvarieties at parallel weight one intersection points of their cuspidal and Eisenstein loci. The Galois theoretic approach presents genuine difficulties due to the lack of good deformation theory for pseudo-characters irregular at $p$ and reflects the rich local geometry at such points. We believe that our geometric results lead to deeper insight into the arithmetic of Hilbert automorphic forms and we produce several applications in Iwasawa theory to support that.