Let $\mathcal{M}$ be a compact Riemannian manifold and let $I=(0,1)$. I seek a trace theorem saying that functions $u \in H^1(\mathcal{M} \times I)$ have a well-defined trace at $\mathcal{M} \times \{0\}$ and $\mathcal{M} \times \{1\}$ in some fractional Sobolev space.
Furthermore, since the boundary of $\mathcal{M} \times I$ is disjoint, how does one think of the trace mapping? Can someone point out a reference? Thank you.
