scholarly journals Inequivalence of Skew Hadamard Difference Sets and Triple Intersection Numbers Modulo a Prime

10.37236/3762 ◽  
2013 ◽  
Vol 20 (4) ◽  
Author(s):  
Koji Momihara

Recently, Feng and Xiang found a new construction of skew Hadamard difference sets in elementary abelian groups. In this paper, we introduce a new invariant for equivalence of skew Hadamard difference sets, namely triple intersection numbers modulo a prime, and discuss inequivalence between Feng-Xiang skew Hadamard difference sets and the Paley difference sets. As a consequence, we show that their construction produces infinitely many skew Hadamard difference sets inequivalent to the Paley difference sets.


10.37236/9058 ◽  
2020 ◽  
Vol 27 (3) ◽  
Author(s):  
Koji Momihara

A major conjecture on the existence of abelian skew Hadamard difference sets is: if an abelian group $G$ contains a skew Hadamard difference set, then $G$ must be elementary abelian. This conjecture remains open in general. In this paper, we give a recursive construction for skew Hadamard difference sets in abelian (not necessarily elementary abelian) groups. The new construction can be considered as a result on the aforementioned conjecture: if there exists a counterexample to the conjecture, then there exist infinitely many counterexamples to it.



10.37236/5157 ◽  
2015 ◽  
Vol 22 (2) ◽  
Author(s):  
Ante Ćustić ◽  
Vedran Krčadinac ◽  
Yue Zhou

We study tilings of groups with mutually disjoint difference sets. Some necessary existence conditions are proved and shown not to be sufficient. In the case of tilings with two difference sets we show the equivalence to skew Hadamard difference sets, and prove that they must be normalized if the group is abelian. Furthermore, we present some constructions of tilings based on cyclotomy and investigate tilings consisting of Singer difference sets.



2006 ◽  
Vol 113 (7) ◽  
pp. 1526-1535 ◽  
Author(s):  
Cunsheng Ding ◽  
Jin Yuan


2008 ◽  
Vol 50 (1) ◽  
pp. 93-105 ◽  
Author(s):  
Guobiao Weng ◽  
Lei Hu








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