scholarly journals Cyclic partitions of complete uniform hypergraphs

10.37236/390 ◽  
2010 ◽  
Vol 17 (1) ◽  
Author(s):  
Artur Szymański ◽  
A. Paweł Wojda

By $K^{(k)}_n$ we denote the complete $k$-uniform hypergraph of order $n$, $1\le k \le n-1$, i.e. the hypergraph with the set $V_n=\{ 1,2,...,n\}$ of vertices and the set $V_n \choose k$ of edges. If there exists a permutation $\sigma$ of the set $V_n$ such that $\{ E,\sigma (E),..., \sigma^{q-1}(E) \}$ is a partition of the set $V_n \choose k$ then we call it cyclic $q$-partition of $K^{(k)}_n$ and $\sigma$ is said to be a $(q,k)$-complementing. In the paper, for arbitrary integers $k,q$ and $n$, we give a necessary and sufficient condition for a permutation to be $(q,k)$-complementing permutation of $K^{(k)}_n$. By $\tilde{K}_n$ we denote the hypergraph with the set of vertices $V_n$ and the set of edges $2^{V_n} - \{ \emptyset , V_n \}$. If there is a permutation $\sigma$ of $V_n$ and a set $E \subset 2^{V_n} - \{ \emptyset , V_n \}$ such that $\{ E, \sigma (E),..., \sigma^{p-1}(E) \}$ is a $p$-partition of $ 2^{V_n} - \{ \emptyset , V_n \}$ then we call it a cyclic $p$-partition of $K_n$ and we say that $\sigma$ is $p$-complementing. We prove that $\tilde{K}_n$ has a cyclic $p$-partition if and only if $p$ is prime and $n$ is a power of $p$ (and $n > p$). Moreover, any $p$-complementing permutation is cyclic.


2013 ◽  
Vol Vol. 15 no. 2 (Combinatorics) ◽  
Author(s):  
Shonda Gosselin ◽  
Andrzej Szymański ◽  
Adam Pawel Wojda

Combinatorics International audience A \em cyclic q-partition of a hypergraph (V,E) is a partition of the edge set E of the form \F,F^θ,F^θ², \ldots, F^θ^q-1\ for some permutation θ of the vertex set V. Let Vₙ = \ 1,2,\ldots,n\. For a positive integer k, Vₙ\choose k denotes the set of all k-subsets of Vₙ. For a nonempty subset K of V_n-1, we let \mathcalKₙ^(K) denote the hypergraph ≤ft(Vₙ, \bigcup_k∈ K Vₙ\choose k\right). In this paper, we find a necessary and sufficient condition on n, q and k for the existence of a cyclic q-partition of \mathcalKₙ^(V_k). In particular, we prove that if p is prime then there is a cyclic p^α-partition of \mathcalK^(Vₖ)ₙ if and only if p^α + β divides n, where β = \lfloor \logₚ k\rfloor. As an application of this result, we obtain two sufficient conditions on n₁,n₂,\ldots,n_t, k, α and a prime p for the existence of a cyclic p^α-partition of the complete t-partite k-uniform hypergraph \mathcal K^(k)_n₁,n₂,\ldots,n_t.



2003 ◽  
Vol 17 (3) ◽  
pp. 257-266 ◽  
Author(s):  
Mark H. Taylor ◽  
F. Todd DeZoort ◽  
Edward Munn ◽  
Martha Wetterhall Thomas

This paper introduces an auditor reliability framework that repositions the role of auditor independence in the accounting profession. The framework is motivated in part by widespread confusion about independence and the auditing profession's continuing problems with managing independence and inspiring public confidence. We use philosophical, theoretical, and professional arguments to argue that the public interest will be best served by reprioritizing professional and ethical objectives to establish reliability in fact and appearance as the cornerstone of the profession, rather than relationship-based independence in fact and appearance. This revised framework requires three foundation elements to control subjectivity in auditors' judgments and decisions: independence, integrity, and expertise. Each element is a necessary but not sufficient condition for maximizing objectivity. Objectivity, in turn, is a necessary and sufficient condition for achieving and maintaining reliability in fact and appearance.



Author(s):  
Thomas Sinclair

The Kantian account of political authority holds that the state is a necessary and sufficient condition of our freedom. We cannot be free outside the state, Kantians argue, because any attempt to have the “acquired rights” necessary for our freedom implicates us in objectionable relations of dependence on private judgment. Only in the state can this problem be overcome. But it is not clear how mere institutions could make the necessary difference, and contemporary Kantians have not offered compelling explanations. A detailed analysis is presented of the problems Kantians identify with the state of nature and the objections they face in claiming that the state overcomes them. A response is sketched on behalf of Kantians. The key idea is that under state institutions, a person can make claims of acquired right without presupposing that she is by nature exceptional in her capacity to bind others.



Physics ◽  
2021 ◽  
Vol 3 (2) ◽  
pp. 352-366
Author(s):  
Thomas Berry ◽  
Matt Visser

In this paper, Lorentz boosts and Wigner rotations are considered from a (complexified) quaternionic point of view. It is demonstrated that, for a suitably defined self-adjoint complex quaternionic 4-velocity, pure Lorentz boosts can be phrased in terms of the quaternion square root of the relative 4-velocity connecting the two inertial frames. Straightforward computations then lead to quite explicit and relatively simple algebraic formulae for the composition of 4-velocities and the Wigner angle. The Wigner rotation is subsequently related to the generic non-associativity of the composition of three 4-velocities, and a necessary and sufficient condition is developed for the associativity to hold. Finally, the authors relate the composition of 4-velocities to a specific implementation of the Baker–Campbell–Hausdorff theorem. As compared to ordinary 4×4 Lorentz transformations, the use of self-adjoint complexified quaternions leads, from a computational view, to storage savings and more rapid computations, and from a pedagogical view to to relatively simple and explicit formulae.



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