Dear mathoverflowers,
I would like to have a reference regarding the optimal constant in the Sobolev embedding
$$ \|u\|_{L^q}\leq C_{s,q}\|u\|_{\dot{H}^s}, $$
($H^s$ denotes the standard L^2 Sobolev space $W^{s,2}$)
for zero mean periodic functions. Can you help me? Thank you in advance.
PD: A reference on the slightly different embedding
$$ \|u\|_{L^q}\leq C_{s,q}\|u\|_{H^s} $$
is also appreciated :-).
