Search results for "Combinatorics"
showing 10 items of 1770 documents
Finite groups which are products of pairwise totally permutable subgroups
1998
Finite groups which are products of pairwise totally permutable subgroups are studied in this paper. The -residual, -projectors and -normalizers in such groups are obtained from the corresponding subgroups of the factor subgroups under suitable hypotheses.
On 2-groups with no abelian subgroups of rank four
1975
Wedge filling and interface delocalization in finite Ising lattices with antisymmetric surface fields
2003
Theoretical predictions by Parry et al. for wetting phenomena in a wedge geometry are tested by Monte Carlo simulations. Simple cubic $L\ifmmode\times\else\texttimes\fi{}L\ifmmode\times\else\texttimes\fi{}{L}_{y}$ Ising lattices with nearest neighbor ferromagnetic exchange and four free $L\ifmmode\times\else\texttimes\fi{}{L}_{y}$ surfaces, at which antisymmetric surface fields $\ifmmode\pm\else\textpm\fi{}{H}_{s}$ act, are studied for a wide range of linear dimensions $(4l~Ll~320,30l~{L}_{y}l~1000),$ in an attempt to clarify finite size effects on the wedge filling transition in this ``double-wedge'' geometry. Interpreting the Ising model as a lattice gas, the problem is equivalent to a li…
Convergence of Markov Chains
2020
We consider a Markov chain X with invariant distribution π and investigate conditions under which the distribution of X n converges to π as n→∞. Essentially it is necessary and sufficient that the state space of the chain cannot be decomposed into subspaces that the chain does not leave, or that are visited by the chain periodically; e.g., only for odd n or only for even n.
Maslov Anomaly and the Morse Index Theorem
2001
Our starting point is again the phase space integral $$\displaystyle{ \text{e}^{\text{i}\hat{\varGamma }[\tilde{M}]} =\int \mathcal{D}\chi ^{a}\,\text{e}^{\text{i}S_{\text{fl}}[\chi,\tilde{M}]} }$$ (31.1) with periodic boundary conditions χ(0) = χ(T) and $$\displaystyle{ S_{\text{fl}}[\chi,\tilde{M}] = \frac{1} {2}\int _{0}^{T}dt\,\bar{\chi }_{ a}(t)\left [ \frac{\partial } {\partial t} -\tilde{M}(t)\right ]_{\phantom{a}b}^{a}\chi ^{b}(t)\;. }$$ (31.2) Here we have indicated that Sfl and \(\hat{\varGamma }\) depend on ηcl a and A i only through \(\tilde{M}_{\phantom{a}b}^{a}\): $$\displaystyle{ \tilde{M}(t)_{\phantom{a}b}^{a} =\omega ^{ac}\partial _{ c}\partial _{b}\mathcal{H}{\bigl (\eta _…
Orientation matters
2008
The optimal communication spanning tree (OCST) problem is a well known $\mathcal{NP}$-hard combinatorial optimization problem which seeks a spanning tree that satisfies all given communication requirements for minimal total costs. It has been shown that optimal solutions of OCST problems are biased towards the much simpler minimum spanning tree (MST) problem. Therefore, problem-specific representations for EAs like heuristic variants of edge-sets that are biased towards MSTs show high performance.In this paper, additional properties of optimal solutions for Euclidean variants of OCST problems are studied. Experimental results show that not only edges in optimal trees are biased towards low-…
Optional Sampling Sätze
2020
In Kapitel 9 haben wir den Stabilitatssatz fur Martingale kennengelernt, der besagt, dass Martingale durch die Anwendung gewisser Spielstrategien wieder in Martingale uberfuhrt werden. Wir untersuchen in diesem Kapitel ahnliche Stabilitatseigenschaften fur zufallig gestoppte Martingale zeigen. Um die Aussagen auch fur Submartingale und Supermartingale zu bekommen, geben wir im ersten Abschnitt einen Zerlegungssatz fur adaptierte Prozesse an. Im zweiten Abschnitt kommen dann die Optional Sampling und Optional Stopping Satze.
Nullstellen bei Lösungen der Differentialgleichung y(n) + gy(n−1)+ fy = 0
1990
On closures of discrete sets
2018
The depth of a topological space $X$ ($g(X)$) is defined as the supremum of the cardinalities of closures of discrete subsets of $X$. Solving a problem of Mart\'inez-Ruiz, Ram\'irez-P\'aramo and Romero-Morales, we prove that the cardinal inequality $|X| \leq g(X)^{L(X) \cdot F(X)}$ holds for every Hausdorff space $X$, where $L(X)$ is the Lindel\"of number of $X$ and $F(X)$ is the supremum of the cardinalities of the free sequences in $X$.
The complex of words and Nakaoka stability
2005
We give a new simple proof of the exactness of the complex of injective words and use it to prove Nakaoka's homology stability for symmetric groups. The methods are generalized to show acyclicity in low degrees for the complex of words in "general position". Hm(§ni1;Z) = Hm(§n;Z) for n=2 > m where §n denotes the permutation group of n elements. An elementary proof of this fact has not been available in the literature. In the first section the complex C⁄(m) of abelian groups is studied which in de- gree n is freely generated by injective words of length n. The alphabet consists of m letters. The complex C⁄(m) has the only non vanishing homology in degree m (Theorem 1). This is a result of F.…