Search results for " Algebra"
showing 10 items of 2082 documents
Trace and density results on regular trees
2019
We give characterizations for the existence of traces for first order Sobolev spaces defined on regular trees.
Comments on an article of Slinn
1989
The discussion of the relationship between concentration fluctuations and residence times is certainly highly welcomed, because it can spread the news of how a simple analytical equation eases the often needed estimate of residence times for trace substances, gases and aerosols in size ranges. However, the treatment by Slinn (1988a) might confuse potential users. To ease the following clarification, I will use Slinn’s notation with C being a concentration and C the mean concentration, whether averaged over the exponentially decaying concentration in time or in distance downwind of a finite-area source. DOI: 10.1111/j.1600-0889.1989.tb00142.x
An Outline of Morpho-Constructional Analysis
1991
A concept of morpho-constructional analysis is outlined which describes functions of organic features in terms of transformation of energy input into effect output on the strength of physical principles. The dependence of effect outputs on constructional parameters, such as geometrical configurations and material properties, is illustrated in a vector model. It shows that performances of organisms, on principle, can be provided in equivalent manner by different constructional solutions. Options exist in regards to (1) how constructional parameters can be provided by an organism, (2) how particular effects or performances can be produced, and (3) how organizational units can be constrained b…
On the coupling between agent internal and agent/ environmental dynamics: Development of spatial representations in evolving autonomous robots
2008
In this article we describe how a population of evolving robots can autonomously develop forms of spatial representation which allow them to self-localize and to discriminate different locations of their environment by integrating sensory-motor information over time. The evolving robots also display a remarkable ability to generalize their skill in new environmental conditions that they have never experienced before. The analysis of the obtained results indicates that the evolved robots come up with simple and robust solutions that exploit quasi-periodic limit cycle dynamics emerging from the coupling between the robot/environmental dynamics and a robot's internal dynamics. More specifical…
Highly transitive actions of free products
2013
We characterize free products admitting a faithful and highly transitive action. In particular, we show that the group $\PSL_2(\Z)\simeq (\Z/2\Z)*(\Z/3\Z)$ admits a faithful and highly transitive action on a countable set.
Algebraic (2, 2)-transformation groups
2009
This paper contains the more significant part of the article with the same title that will appear in the Volume 12 of Journal of Group Theory (2009). In this paper we determine all algebraic transformation groups $G$, defined over an algebraically closed field $\sf k$, which operate transitively, but not primitively, on a variety $\Omega$, provided the following conditions are fulfilled. We ask that the (non-effective) action of $G$ on the variety of blocks is sharply 2-transitive, as well as the action on a block $\Delta$ of the normalizer $G_\Delta$. Also we require sharp transitivity on pairs $(X,Y)$ of independent points of $\Omega$, i.e. points contained in different blocks.
A generalized transitive closure for relational queries
1988
We augment relational algebra with a generalized transitive closure operator that allows for the efficient evaluation of a subclass of recursive queries. The operator is based on a composition operator which is as general as possible when the operator is required to be associative and when only relational algebra operators are used in its definition. The closure of such a composition can be computed using the well-known efficient algorithms designed for the computation of the usual transitive closure. Besides the case in which complete materialization of recursive relations are required, our strategy also yields an efficient solution in the case in which a selection is applied to the closur…
Towards efficient inductive synthesis: Rapid construction of local regularities
2006
Given several input/output examples of some function we can state the problem: what is the “simplest” function which complies with these examples. This problem is well studied and is known to be very hard in the general case. In this paper we address a special case of the problem, when the target function can be expressed as a simple composition of known functions. We propose a new inductive synthesis algorithm for this case and show that it is efficient enough to synthesize complex geometry formulas.
A relational model for unstructured documents
1987
The logical structure of a document is usually a tree in which the order of the nodes is important at least at some level of the tree. We call a document unstructured if its structure is a single-level ordered tree. The purpose of this paper is to present a many-sorted algebra for handling unstructured documents. The documents in the model are represented by relations. An algebra for handling documents of one type can be extended to an algebra for handling documents of several types. Further, an algebra for handling documents can be extended by the relational algebra for handling documents and relations in a common algebra. The model of this paper can be regarded as a part of a general docu…
Anàlisi de la interpretació dels termes literals per alumnes de secundària
2012
Tal com diu Freudenthal (2001), el llenguatge algebraic és un llenguatge formal amb una estructura clara que permet expressar les relacions amb precisió i simplicitat. Al contrari que el llenguatge vernacle que pot resultar ambigu ja que, en nombroses ocasions, es fa ús de termes que poden tindre una multiplicitat de significats, fet que provoca una inevitable incertesa. Així i tot, els estudiants que s’inicien en l’àlgebra troben dificultats quan a l’enteniment d’aquesta rama de la matemàtica, potser degut a problemes de comprensió i/o interpretació de la seua estructura i llenguatge o al canvi de concepció que ha de produir-se al passar de l’estudi de l’aritmètica al de l’àlgebra, entre a…