Surgery for partially hyperbolic dynamical systems I. Blow-ups of invariant submanifolds

We suggest a method to construct new examples of partially hyperbolic diffeomorphisms. We begin with a partially hyperbolic diffeomorphism $f\colon M\to M$whichleavesinvariantasubmanifold$N\subset M$\mathrm{.}Weassumethat$N$isanAnosovsubmanifoldfor$f$,thatis,therestriction$f|_N$ is an Anosov diffeomorphism and the center distribution is transverse to $TN\subset TM$. By replacing each point in $N$ with the projective space (real or complex) of lines normal to $N$ we obtain the blow-up $\widehat{M}$. Replacing $M$ with $\widehat{M}$ amounts to a surgery on the neighborhood of $N$ which alters the topology of the manifold. The diffeomorphism $f$ induces a canonical diffeomorphism $\hat f\colon \hat M\to \hat M$. We prove that under certain assumptions on the local dynamics of $f$ at $N$ the diffeomorphism $\widehat{f}$ is also partially hyperbolic. We also present some modifications such as the connected sum construction which allows to “paste together” two partially hyperbolic diffeomorphisms to obtain a new one. Finally, we present several examples to which our results apply.