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Computer Science 2010
How frequently is a system of 2-linear Boolean equations solvable?Abstract: We consider a random system of equations $x_i+x_j=b_{(i,j)} (\text{mod }2)$, $(x_u\in \{0,1\},\, b_{(u,v)}=b_{(v,u)}\in\{0,1\})$, with the pairs $(i,j)$ from $E$, a symmetric subset of $[n]\times [n]$. $E$ is chosen uniformly at random among all such subsets of a given cardinality $m$; alternatively $(i,j)\in E$ with a given probability $p$, independently of all other pairs. Also, given $E$, $\pr\{b_{e}=0\}=\pr\{b_e=1\}$ for each $e\in E$, independently of all other $b_{e^\prime}$. It is well known that, as $m$ passes through $n/2$ ($p$ passes through $1/n$, resp.), the underlying random graph $G(n,\#\text{edges}=m)$, ($G(n,\pr(\text{edge})=p)$, resp.) undergoes a rapid transition, from essentially a forest of many small trees to a graph with one large, multicyclic, component in a sea of small tree components. We should expect then that the solvability probability decreases precipitously in the vicinity of $m\sim n/2$ ($p\sim 1/n$), and indeed this probability is of order $(1-2m/n)^{1/4}$, for $m
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