Abstract:
On the infinite-dimensional torus
$\mathbb{T}^{\infty} = E/2\pi\mathbb{Z}^{\infty}$,
where $E$ is an infinite-dimensional real Banach space,
$\mathbb{Z}^{\infty}$is an abstract integer lattice, a special class
of diffeomorphisms $\mathrm{Diff}(\mathbb{T}^{\infty})$ is considered.
This class consists of the mappings
$G\colon \mathbb{T}^{\infty} \to \mathbb{T}^{\infty}$
such that the differentials $DG$ and $D(G^{-1})$
are uniformly bounded and uniformly continuous on $\mathbb{T}^{\infty}$.
For diffeomorphisms from $\mathrm{Diff}(\mathbb{T}^{\infty})$, we establish
the validity of the so-called cone criterion, which is a classical result
of finite-dimensional hyperbolic theory (that is, the hyperbolicity criterion
formulated in terms of fields of invariant horizontal and vertical cones).