A classification of pseudo-Anosov homeomorphisms I: the geometric type is a complete conjugacy invariant

Every pseudo-Anosov homeomorphism $f$ admits infinitely many Markov partitions. A $\mathit{\text{geometric}}\mathit{\text{Markov}}\mathit{\text{partition}}$ is a Markov partition $\mathcal{R}$ in which each rectangle is equipped with a vertical orientation. To each pair $(f,\mathcal{R})$, consisting of a pseudo-Anosov homeomorphism $f$ and a geometric Markov partition $\mathcal{R}$, there is a naturally associated combinatorial object called its $\mathit{\text{geometric}}\mathit{\text{type}}$ $\mathbf{T}(f,\mathcal{R})$. We prove, using symbolic dynamics, that two pseudo-Anosov homeomorphisms are topologically conjugate via an orientation-preserving homeomorphism if and only if they admit geometric Markov partitions with the same geometric type. This result lays the groundwork for the algorithmic classification we will develop in subsequent work.