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Representation of groups by automorphisms of normal topological spaces
Computer Research and Modeling, 2009, v. 1, no. 3, pp. 243249Views (last year): 1.The famous fact [3, 5] of existence of an exact representation for any finite group in the form of the full automorphism group of a finite graph was generalize in [4]. For an arbitrary group exact representation exists in the form of the full automorphism group of Kolmogorov topological space (weak type of separability T_{0}). For a finite group a finite space may be chosen, thus allowing to restore a finite graph with the same number of vertices and having the same automorphism group. Such topological spaces and graphs are called topological imprints and graph imprints of a group (Timprints and Gimprints, respectively). The question of maximum type of separability of a topological space for which Timprint can be obtained for any group is open. The author proves that the problem can be solved for the class of normal topology (maximal type of separability T_{4}+T_{0}). Special finite Timprint for a symmetric group may be obtained as a discrete topology; for any other group minimal cardinality of normal Timprint is countable. There is a generic procedure to construct a Timprint for any group. For a finite group this procedure allows finite space partitioning into subspaces having Gimprint of the original group as their connectivity graphs.

Uniform graph embedding into metric spaces
Computer Research and Modeling, 2012, v. 4, no. 2, pp. 241251The task of embedding an infinity countable graph into continuous metric space is considered. The concept of uniform embedding having no accumulation point in a set of vertex images and having all graph edge images of a limited length is introduced. Necessary and sufficient conditions for possibility of uniform embedding into spaces with Euclid and Lorenz metrics are stated in terms of graph structure. It is proved that tree graphs with finite branching have uniform embedding into space with absolute Minkowski metric.
Keywords: metric space, infinite graph, factor graph, Minkowski metric, Lorenz metric, Euclid metric. 
Scientific and pedagogical schools founded by A. S. Kholodov
Computer Research and Modeling, 2018, v. 10, no. 5, pp. 561579Views (last year): 42.In the science development an important role the scientific schools are played. This schools are the associations of researchers connected by the common problem, the ideas and the methods used for problems solution. Usually Scientific schools are formed around the leader and the uniting idea.
The several sciences schools were created around academician A. S. Kholodov during his scientific and pedagogical activity.
This review tries to present the main scientific directions in which the bright science collectives with the common frames of reference and approaches to researches were created. In the review this common base is marked out. First, this is development of the group of numerical methods for hyperbolic type systems of partial derivatives differential equations solution — grid and characteristic methods. Secondly, the description of different numerical methods in the undetermined coefficients spaces. This approach developed for all types of partial equations and for ordinary differential equations.
On the basis of A. S. Kholodov’s numerical approaches the research teams working in different subject domains are formed. The fields of interests are including mathematical modeling of the plasma dynamics, deformable solid body dynamics, some problems of biology, biophysics, medical physics and biomechanics. The new field of interest includes solving problem on graphs (such as processes of the electric power transportation, modeling of the traffic flows on a road network etc).
There is the attempt in the present review analyzed the activity of scientific schools from the moment of their origin so far, to trace the connection of A. S. Kholodov’s works with his colleagues and followers works. The complete overview of all the scientific schools created around A. S. Kholodov is impossible due to the huge amount and a variety of the scientific results.
The attempt to connect scientific schools activity with the advent of scientific and educational school in Moscow Institute of Physics and Technology also becomes.

The task of integral geometry with measure induction
Computer Research and Modeling, 2011, v. 3, no. 1, pp. 3137A new statement of Integral Geometry problem where the image of function in each point is taken as an integral with respect to measure which depends on the point is suggested. Such Measure System is named Measure Induction. It is shown that an inversion formula exists for class of measures having a unit atom in corresponding
point and limited on whole space. Previously obtained results for average on systems of measurement dissections and for weight average on graphs are generalized. 
Using collective of agents for exploration of graph
Computer Research and Modeling, 2013, v. 5, no. 4, pp. 525532Problem of exploration finite undirected graphs by a collective of agents is considered in this work. Two agentsresearchers simultaneously move on graph, they read and change marks of graph elements, transfer the information to the agentexperimenter (it builds explored graph representation). It was constructed an algorithm linear (from amount of the graph’s nodes) time complexity, quadratic space complexity and communication complexity, that is equal to O(n^{2}·log(n)). Two agents (which move on graph) need two different colors (in total three colors) for graph exploration. An algorithm is based on depthfirst traversal method.
Keywords: graph exploration, collective of agents.Views (last year): 4. Citations: 2 (RSCI). 
Representation of an invariant measure of irreducible discretetime Markov chain with a finite state space by a set of opposite directed trees
Computer Research and Modeling, 2015, v. 7, no. 2, pp. 221226Views (last year): 1.A problem of finding of an invariant measure of irreducible discretetime Markov chain with a finite state space is considered. There is a unique invariant measure for such Markov chain that can be multiplied by an arbitrary constant. A representation of a Markov chain by a directed graph is considered. Each state is represented by a vertex, and each conditional transition probability is represented by a directed edge. It is proved that an invariant measure for each state is a sum of $n^{n−2}$ nonnegative summands, where $n$ is a cardinality of state space. Each summand is a product of $n − 1$ conditional transition probabilities and is represented by an opposite directed tree that includes all vertices. The root represents the considered state. The edges are directed to the root. This result leads to methods of analyses and calculation of an invariant measure that is based on a graph theory.

Computer research of the holomorphic dynamics of exponential and linearexponential maps
Computer Research and Modeling, 2018, v. 10, no. 4, pp. 383405Views (last year): 51. Citations: 1 (RSCI).The work belongs to the direction of experimental mathematics, which investigates the properties of mathematical objects by the computing facilities of a computer. The base is an exponential map, its topological properties (Cantor's bouquets) differ from properties of polynomial and rational complexvalued functions. The subject of the study are the character and features of the Fatou and Julia sets, as well as the equilibrium points and orbits of the zero of three iterated complexvalued mappings: $f:z \to (1+ \mu) \exp (iz)$, $g : z \to \big(1+ \mu z  z^*\big) \exp (iz)$, $h : z \to \big(1+ \mu (z  z^* )\big) \exp (iz)$, with $z,\mu \in \mathbb{C}$, $z^* : \exp (iz^*) = z^*$. For a quasilinear map g having no analyticity characteristic, two bifurcation transitions were discovered: the creation of a new equilibrium point (for which the critical value of the linear parameter was found and the bifurcation consists of “fork” type and “saddle”node transition) and the transition to the radical transformation of the Fatou set. A nontrivial character of convergence to a fixed point is revealed, which is associated with the appearance of “valleys” on the graph of convergence rates. For two other maps, the monoperiodicity of regimes is significant, the phenomenon of “period doubling” is noted (in one case along the path $39\to 3$, in the other along the path $17\to 2$), and the coincidence of the period multiplicity and the number of sleeves of the Julia spiral in a neighborhood of a fixed point is found. A rich illustrative material, numerical results of experiments and summary tables reflecting the parametric dependence of maps are given. Some questions are formulated in the paper for further research using traditional mathematics methods.

Development of network computational models for the study of nonlinear wave processes on graphs
Computer Research and Modeling, 2019, v. 11, no. 5, pp. 777814In various applications arise problems modeled by nonlinear partial differential equations on graphs (networks, trees). In order to study such problems and various extreme situations arose in the problems of designing and optimizing networks developed the computational model based on solving the corresponding boundary problems for partial differential equations of hyperbolic type on graphs (networks, trees). As applications, three different problems were chosen solved in the framework of the general approach of network computational models. The first was modeling of traffic flow. In solving this problem, a macroscopic approach was used in which the transport flow is described by a nonlinear system of secondorder hyperbolic equations. The results of numerical simulations showed that the model developed as part of the proposed approach well reproduces the real situation various sections of the Moscow transport network on significant time intervals and can also be used to select the most optimal traffic management strategy in the city. The second was modeling of data flows in computer networks. In this problem data flows of various connections in packet data network were simulated as some continuous medium flows. Conceptual and mathematical network models are proposed. The numerical simulation was carried out in comparison with the NS2 network simulation system. The results showed that in comparison with the NS2 packet model the developed streaming model demonstrates significant savings in computing resources while ensuring a good level of similarity and allows us to simulate the behavior of complex globally distributed IP networks. The third was simulation of the distribution of gas impurities in ventilation networks. It was developed the computational mathematical model for the propagation of finely dispersed or gas impurities in ventilation networks using the gas dynamics equations by numerical linking of regions of different sizes. The calculations shown that the model with good accuracy allows to determine the distribution of gasdynamic parameters in the pipeline network and solve the problems of dynamic ventilation management.

The error accumulation in the conjugate gradient method for degenerate problem
Computer Research and Modeling, 2021, v. 13, no. 3, pp. 459472In this paper, we consider the conjugate gradient method for solving the problem of minimizing a quadratic function with additive noise in the gradient. Three concepts of noise were considered: antagonistic noise in the linear term, stochastic noise in the linear term and noise in the quadratic term, as well as combinations of the first and second with the last. It was experimentally obtained that error accumulation is absent for any of the considered concepts, which differs from the folklore opinion that, as in accelerated methods, error accumulation must take place. The paper gives motivation for why the error may not accumulate. The dependence of the solution error both on the magnitude (scale) of the noise and on the size of the solution using the conjugate gradient method was also experimentally investigated. Hypotheses about the dependence of the error in the solution on the noise scale and the size (2norm) of the solution are proposed and tested for all the concepts considered. It turned out that the error in the solution (by function) linearly depends on the noise scale. The work contains graphs illustrating each individual study, as well as a detailed description of numerical experiments, which includes an account of the methods of noise of both the vector and the matrix.

Modeling of disassembly processes of complex products
Computer Research and Modeling, 2022, v. 14, no. 3, pp. 525537The work is devoted to modeling the processes of disassembling complex products in CADsystems. The ability to dismantle a product in a given sequence is formed at the early design stages, and is implemented at the end of the life cycle. Therefore, modern CADsystems should have tools for assessing the complexity of dismantling parts and assembly units of a product. A hypergraph model of the mechanical structure of the product is proposed. It is shown that the mathematical description of coherent and sequential disassembly operations is the normal cutting of the edge of the hypergraph. A theorem on the properties of normal cuts is proved. This theorem allows us to organize a simple recursive procedure for generating all cuts of the hypergraph. The set of all cuts is represented as an AND/ORtree. The tree contains information about plans for disassembling the product and its parts. Mathematical descriptions of various types of disassembly processes are proposed: complete, incomplete, linear, nonlinear. It is shown that the decisive graph of the AND/ORtree is a model of disassembling the product and all its components obtained in the process of dismantling. An important characteristic of the complexity of dismantling parts is considered — the depth of nesting. A method of effective calculation of the estimate from below has been developed for this characteristic.
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