240 research outputs found
DP-colorings of uniform hypergraphs and splittings of Boolean hypercube into faces
We develop a connection between DP-colorings of -uniform hypergraphs of
order and coverings of -dimensional Boolean hypercube by pairs of
antipodal -dimensional faces. Bernshteyn and Kostochka established that
the lower bound on edges in a non-2-DP-colorable -uniform hypergraph is
equal to for odd and for even . They proved that
these bounds are tight for . In this paper, we prove that the bound is
achieved for all odd .Comment: The previous versions of paper contains a significant erro
On unbalanced Boolean functions with best correlation immunity
It is known that the order of correlation immunity of a nonconstant
unbalanced Boolean function in variables cannot exceed ; moreover,
it is if and only if the function corresponds to an equitable
-partition of the -cube with an eigenvalue of the quotient matrix.
The known series of such functions have proportion , , or of
the number of ones and zeros. We prove that if a nonconstant unbalanced Boolean
function attains the correlation-immunity bound and has ratio of the
number of ones and zeros, then is divisible by . In particular, this
proves the nonexistence of equitable partitions for an infinite series of
putative quotient matrices. We also establish that there are exactly
equivalence classes of the equitable partitions of the -cube with quotient
matrix and classes, with . These
parameters correspond to the Boolean functions in variables with
correlation immunity and proportion and , respectively (the case
remains unsolved). This also implies the characterization of the
orthogonal arrays OA and OA.Comment: v3: final; title changed; revised; OA(512,11,2,6) discusse
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