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    Resolvable Mendelsohn designs and finite Frobenius groups

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    We prove the existence and give constructions of a (p(k)βˆ’1)(p(k)-1)-fold perfect resolvable (v,k,1)(v, k, 1)-Mendelsohn design for any integers v>kβ‰₯2v > k \ge 2 with v≑1mod  kv \equiv 1 \mod k such that there exists a finite Frobenius group whose kernel KK has order vv and whose complement contains an element Ο•\phi of order kk, where p(k)p(k) is the least prime factor of kk. Such a design admits Kβ‹ŠβŸ¨Ο•βŸ©K \rtimes \langle \phi \rangle as a group of automorphisms and is perfect when kk is a prime. As an application we prove that for any integer v=p1e1…ptetβ‰₯3v = p_{1}^{e_1} \ldots p_{t}^{e_t} \ge 3 in prime factorization, and any prime kk dividing pieiβˆ’1p_{i}^{e_i} - 1 for 1≀i≀t1 \le i \le t, there exists a resolvable perfect (v,k,1)(v, k, 1)-Mendelsohn design that admits a Frobenius group as a group of automorphisms. We also prove that, if kk is even and divides piβˆ’1p_{i} - 1 for 1≀i≀t1 \le i \le t, then there are at least Ο†(k)t\varphi(k)^t resolvable (v,k,1)(v, k, 1)-Mendelsohn designs that admit a Frobenius group as a group of automorphisms, where Ο†\varphi is Euler's totient function.Comment: Final versio
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