Universally sparse hypergraphs with applications to coding theory
C Shangguan, I Tamo - 2019 IEEE International Symposium on …, 2019 - ieeexplore.ieee.org
2019 IEEE International Symposium on Information Theory (ISIT), 2019•ieeexplore.ieee.org
For fixed integers r≥ 2, e≥ 2, v≥ r+ 1, an r-uniform hypergraph is called G r (v, e)-free if the
union of any e distinct edges contains at least v+ 1 vertices. Let G r (n, v, e) denote the
maximum number of edges in a G r (v, e)-free r-uniform hypergraph on n vertices. Brown,
Erdós and Sós showed in 1973 that there exist constants c 1, c 2 depending only on r, e, v
such that c1n er-v/e-1≤ fr (n, v, e)≤ c2n [er-v/e-1] For e-1| er-v, the lower bound matches the
upper bound up to a constant factor; whereas for e-1 t er-v, it is a notoriously hard problem to …
union of any e distinct edges contains at least v+ 1 vertices. Let G r (n, v, e) denote the
maximum number of edges in a G r (v, e)-free r-uniform hypergraph on n vertices. Brown,
Erdós and Sós showed in 1973 that there exist constants c 1, c 2 depending only on r, e, v
such that c1n er-v/e-1≤ fr (n, v, e)≤ c2n [er-v/e-1] For e-1| er-v, the lower bound matches the
upper bound up to a constant factor; whereas for e-1 t er-v, it is a notoriously hard problem to …
For fixed integers r ≥ 2, e ≥ 2, v ≥ r + 1, an r-uniform hypergraph is called G r (v, e)-free if the union of any e distinct edges contains at least v+1 vertices. Let G r (n, v, e) denote the maximum number of edges in a G r (v, e)-free r-uniform hypergraph on n vertices. Brown, Erdós and Sós showed in 1973 that there exist constants c 1 , c 2 depending only on r, e, v such that c1n er-v/e-1 ≤ f r (n,v,e) ≤ c2n [er-v/e-1] For e - 1|er - v, the lower bound matches the upper bound up to a constant factor; whereas for e - 1 t er - v, it is a notoriously hard problem to determine the correct exponent of n. Our main result is an er-v improvement f r (n, v, e) = Ω(n e-1 (log n) 1 e-1 ) for any r, e, v satisfying gcd(e - 1, er - v) = 1. Moreover, the hypergraph we constructed is not only gr(v, e)-free but also universally G r (ir - Γ (i-1)(-1er-v) 1 + i)-free for every 2 <; i <; e. Interestingly, e our new lower bound provides improved constructions for several seemingly unrelated topics in Coding Theory, namely, Parent-Identifying Set Systems, uniform Combinatorial Batch Codes and optimal Locally Recoverable Codes.
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