Let $G$ be an abelian group, $R$ a commutative ring of prime characteristic $p$ with identity and $R_tG$ a commutative twisted group ring of $G$ over $R$. Suppose $p$ is a fixed prime, $G_p$ and $S(R_tG)$ are the $p$-components of $G$ and of the unit group $U(R_tG)$ of $R_tG$, respectively. Let $R^*$ be the multiplicative group of $R$ and let $f_\alpha (S)$ be the $ \alpha $-th Ulm-Kaplansky invariant of $S(R_tG)$ where $\alpha $ is any ordinal. In the paper the invariants $f_n(S)$, $ n\in \mathbb{N}\cup \lbrace 0\rbrace $, are calculated, provided $G_p=1$. Further, a commutative ring $R$ with identity of prime characteristic $p$ is said to be multiplicatively $p$-perfect if $(R^*)^p = R^*$. For these rings the invariants $f_\alpha (S)$ are calculated for any ordinal $\alpha $ and a description, up to an isomorphism, of the maximal divisible subgroup of $S(R_tG)$ is given.
Různé přístupy к teoretickému popisu jazyka je třeba porovnávat jak co do empirického rozsahu popisného rámce, tak co do kvalit a stupně dodržování jejich principů. Důležité je diskutoval věcně o možnosti spojení jednotlivých dílčích řešení do bezrozporných celků a o možnostech, jak co nejekonomičtěji zachytit jádro (centrum) jazykového systému.
A subgroup $H$ of a group $G$ is said to be complemented in $G$ if there exists a subgroup $K$ of $G$ such that $G=HK$ and $H\cap K=1$. In this paper we determine the structure of finite groups with some complemented primary subgroups, and obtain some new results about $p$-nilpotent groups.
In this work, a complete moment convergence theorem is obtained for weighted sums of asymptotically almost negatively associated (AANA) random variables without assumption of identical distribution under some mild moment conditions. As an application, the complete convergence theorems for weighted sums of negatively associated (NA) and AANA random variables are obtained. The result not only generalizes the corresponding ones of Sung \cite{15} and Huang et al. \cite{16}, but also improves them.
In this article, a general problem of sequential statistical inference for general discrete-time stochastic processes is considered. The problem is to minimize an average sample number given that Bayesian risk due to incorrect decision does not exceed some given bound. We characterize the form of optimal sequential stopping rules in this problem. In particular, we have a characterization of the form of optimal sequential decision procedures when the Bayesian risk includes both the loss due to incorrect decision and the cost of observations.
The knowledge of causal relations provides a possibility to perform predictions and helps to decide about the most reasonable actions aiming at the desired objectives. Although the causal reasoning appears to be natural for the human thinking, most of the traditional statistical methods fail to address this issue. One of the well-known methodologies correctly representing the relations of cause and effect is Pearl's causality approach. The paper brings an alternative, purely algebraic methodology of causal compositional models. It presents the properties of operator of composition, on which a general methodology is based that makes it possible to evaluate the causal effects of some external action. The proposed methodology is applied to four illustrative examples. They illustrate that the effect of intervention can in some cases be evaluated even when the model contains latent (unobservable) variables.
In the paper the fundamentaì pгopeгties of discrete dynamical systems generated by an a-condensing mapping (a is the Kuratowski measure of noncompactness) are studied. The results extend and deepen those obtained by M. A. Krasnoseľskij and A. V. Lusnikov in [21]. They are aìso applied to study a mathematical rдodel for spreading of an infectious disease investigated by P.Takáč in [35], [36].
Some results concerning congruence relations on partially ordered quasigroups (especially, Riesz quasigroups) and ideals of partially ordered loops are presented. These results generalize the assertions which were proved by Fuchs in [5] for partially ordered groups and Riesz groups.
For an ordered $k$-decomposition $\mathcal D = \lbrace G_1, G_2,\dots , G_k\rbrace $ of a connected graph $G$ and an edge $e$ of $G$, the $\mathcal D$-code of $e$ is the $k$-tuple $c_{\mathcal D}(e) = (d(e, G_1), d(e, G_2),\ldots , d(e, G_k))$, where $d(e, G_i)$ is the distance from $e$ to $G_i$. A decomposition $\mathcal D$ is resolving if every two distinct edges of $G$ have distinct $\mathcal D$-codes. The minimum $k$ for which $G$ has a resolving $k$-decomposition is its decomposition dimension $\dim _d(G)$. A resolving decomposition $\mathcal D$ of $G$ is connected if each $G_i$ is connected for $1 \le i \le k$. The minimum $k$ for which $G$ has a connected resolving $k$-decomposition is its connected decomposition number $\mathop {\mathrm cd}(G)$. Thus $2 \le \dim _d(G) \le \mathop {\mathrm cd}(G) \le m$ for every connected graph $G$ of size $m \ge 2$. All nontrivial connected graphs of size $m$ with connected decomposition number 2 or $m$ have been characterized. We present characterizations for connected graphs of size $m$ with connected decomposition number $m-1$ or $m-2$. It is shown that each pair $s, t$ of rational numbers with $ 0 < s \le t \le 1$, there is a connected graph $G$ of size $m$ such that $\dim _d(G)/m = s$ and $\mathop {\mathrm cd}(G) / m = t$.
Let P denote the well-known class of Caratheodory functions of the form p(z) = 1+ciz-i , z e A = {z ∈ ℂ: \z\ < 1}, with positive real part in the unit disc and let H(M) stand for the class of holomorphic functions commonly bounded by M in A. In 1992, J. Fuka and Z. J. Jakubowski began an investigation of families of mappings p ∈ P fulfilling certain additional boundary conditions on the unit circle T. At first, the authors examined the class P(B, b; α) of functions defined by conditions given by the upper limits for two disjoint open arcs of T. After that, such boundary conditions given, in particular, by the nontangential limits, were assumed for different subsets of the unit circle. In parallel, G. Adamczyk started to search for properties of families, contained in H(M) and satisfying certain similar conditions on T. The present article belongs to the above series of papers. In the first section we will consider subclasses of V of functions satisfying some inequalities on several arcs of T, whereas in Sections 2 and 3-families of mappings f ∈ H(M) with conditions given for measurable subsets of the unit circle T.