L. Plaskota
The exponent of discrepancy of sparse grids is at least $2.1933$
Abstract.  
We study bounds on the exponents of sparse grids for
$L_2$-discrepancy and average case $d$-dimensional integration with
respect to the Wiener sheet measure. Our main result is that the
minimal exponent of sparse grids is for these problems bounded from
below by $2.1933$. This shows that sparse grids provide a rather
poor exponent since, due to Wasilkowski and Wozniakowski,
the minimal exponent of L_2-discrepancy of arbitrary point sets
is at most $1.4778$. The proof of the latter is however
non-constructive. The best known constructive upper bound is still
obtained by a particular sparse grid and equal to $2.4526...$