  Sketching and streaming algorithms are in the forefront of current research
directions for cut problems in graphs. In the streaming model, we show that
$(1-\epsilon)$-approximation for Max-Cut must use $n^{1-O(\epsilon)}$ space;
moreover, beating $4/5$-approximation requires polynomial space. For the
sketching model, we show that $r$-uniform hypergraphs admit a
$(1+\epsilon)$-cut-sparsifier (i.e., a weighted subhypergraph that
approximately preserves all the cuts) with $O(\epsilon^{-2} n (r+\log n))$
edges. We also make first steps towards sketching general CSPs (Constraint
Satisfaction Problems).
