Title: A strengthened inequality of Alon-Babai-Suzuki's conjecture on set systems with restricted intersections modulo p,
Abstract: Let $K=\{k_1,k_2,\ldots,k_r\}$ and $L=\{l_1,l_2,\ldots,l_s\}$ be disjoint
subsets of $\{0,1,\ldots,p-1\}$, where $p$ is a prime and
$A=\{A_1,A_2,\ldots,A_m\}$ be a family of subsets of $[n]$ such that
$|A_i|\pmod{p}\in K$ for all $A_i\in A$ and $|A_i\cap A_j|\pmod{p}\in L$ for
$i\ne j$. In 1991, Alon, Babai and Suzuki conjectured that if $n\geq
s+\max_{1\leq i\leq r} k_i$, then $|A|\leq {n\choose s}+{n\choose
s-1}+\cdots+{n\choose s-r+1}$. In 2000, Qian and Ray-Chaudhuri proved the
conjecture under the condition $n\geq 2s-r$. In 2015, Hwang and Kim verified
the conjecture of Alon, Babai and Suzuki.
In this paper, we will prove that if $n\geq 2s-2r+1$ or $n\geq s+\max_{1\leq
i\leq r}k_i$, then \[ |A|\leq{n-1\choose s}+{n-1\choose s-1}+\cdots+{n-1\choose
s-2r+1}. \] This result strengthens the upper bound of Alon, Babai and Suzuki's
conjecture when $n\geq 2s-2$.