6 research outputs found
Discrepancy of Products of Hypergraphs
For a hypergraph , its ―fold symmetric product is . We give several upper and lower bounds for the -color discrepancy of such products. In particular, we show that the bound proven for all in [B. Doerr, A. Srivastav, and P. Wehr, Discrepancy of Cartesian products of arithmetic progressions, Electron. J. Combin. 11(2004), Research Paper 5, 16 pp.] cannot be extended to more than colors. In fact, for any and such that does not divide , there are hypergraphs having arbitrary large discrepancy and . Apart from constant factors (depending on and ), in these cases the symmetric product behaves no better than the general direct product , which satisfies
Discrepancy of products of hypergraphs
For a hypergraph H = (V, E), its d–fold symmetric product is ∆ d H = (V d, {E d |E ∈ E}). We give several upper and lower bounds for the c-color discrepancy of such products. In particular, we show that the bound disc( ∆ d H, 2) ≤ disc(H, 2) proven for all d in [B. Doerr, A. Srivastav, and P. Wehr, Discrepancy of Cartesian products of arithmetic progressions, Electron. J. Combin. 11(2004), Research Paper 5, 16 pp.] cannot be extended to more than c = 2 colors. In fact, for any c and d such that c does not divide d!, there are hypergraphs having arbitrary large discrepancy and disc( ∆ d H, c) = Ωd(disc(H, c) d). Apart from constant factors (depending on c and d), in these cases the symmetric product behaves no better than the general direct product H d, which satisfies disc(H d, c) = Oc,d(disc(H, c) d)