Two nonisomorphic flows with the same very weak Bernoulli partition on a base

We build two flows with the same very weak Bernoulli partition on a base that are not isomorphic even after time scaling. Both flows are built under functions which take constant values on each of the atoms of the partiton. Moreover the values of each function are independent over the rationals.     

Invariant submanifolds for systems of vector fields of constant rank

Given a system of vector fields on a smooth manifold that spans a plane field of constant rank, we present a systematic method and an algorithm to find submanifolds that are invariant under the flows of the vector fields. We present examples of partition into invariant submanifolds, which further gives partition into orbits. We use the method of generalized Frobenius theorem by means of exterior differential systems.     

A special family of ergodic flows and their\bar d - limits

A flow built under a step function with a multi-step Markov partition on the base is a direct product of a Bernoulli flow with a finite rotation. A of the flows in this family cannot have two irrationally related rotation factors. of this family is shown to consist of all direct products of Bernoulli flows and flows of rational pure point spectrum with respect to some number.     

Deformation in locally convex topological linear spaces

We are concerned with a deformation theory in locally convex topological linear spaces. A special "nice" partition of unity is given. This enables us to construct certain vector fields which are locally Lipschitz continuous with respect to the locally convex topology. The existence, uniqueness and continuous dependence of flows associated to the vector fields are established. Deformations related to strongly indefinite functionals are then obtained. Finally, as applications, we prove some abstract critical point theorems.     

Supersonic flow past triangular wings with ribs on their surface PMM vol. 31, no. 6, 1967, pp. 1050–1056

Various types of partitions are a common feature of lifting surfaces. These partitions can take the form of stiffening ribs, deflectors for preventing secondary flows or flow separation, etc. The presence of partitions has a marked effect on the character of flow and on the values of the aerodynamic parameters. Flow past such wings cannot be computed in the general case. Wings of a special type are amenable to simple solution, however, and this will be considered below. One special case of interaction between a partition and an infinite wing is also considered in [1].     

Brunn-Minkowski inequalities for contingency tables and integer flows

We establish approximate log-concavity for a wide family of combinatorially defined integer-valued functions. Examples include the number of non-negative integer matrices (contingency tables) with prescribed row and column sums (margins), as a function of the margins and the number of integer feasible flows in a network, as a function of the excesses at the vertices. As a corollary, we obtain approximate log-concavity for the Kostant partition function of type A. We also present an indirect evidence that at least some of the considered functions might be genuinely log-concave.     

Numerical model for tsunami generation by subaerial landslides

A discretization method based on stabilized space–time finite elements is presented for the numerical analysis of three–fluid flows of immiscible and incompressible fluids. Signed distance functions are used to assign the material properties to each spatial point in the domain. The motion and the change in topology of fluid–fluid interfaces are implicitly described by the level–set method. Strong and weak discontinuities in the fields of the physical state variables are captured by locally enriched approximations based on the partition–of–unity concept. An interior penalty method enforces interfacial conservation of mass and momentum. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mathematical expressions for the transit time of merchandise through a liner shipping network

Recent publications on the design of liner shipping networks are limited in their treatment of the level of service (LoS) experienced by shippers. We propose the use of inventory holding costs—a function of merchandise transit time—as a proxy for LoS. We assume the existence of a two-tier optimization model, where fleet deployment, vessel routing, and vessel speed are determined in the higher tier. Merchandise flows and transshipment quantities are determined in the lower tier. We partition the total merchandise transit time into time spent in open waters, time spent during port calls, and time spent dwelling in the terminal yard. Using the notions of service frequency and service phase, we develop mathematical expressions for the three aforementioned quantities within the lower tier of the optimization model. We arrive at a bilinear expression for overall inventory holding costs that is suitable for liner shipping network design.     

Description of π-partition of a diffeomorphism with invariant measure

For a diffeomorphism of a smooth compact Riemann manifold, retaining a measure equivalent to Riemann volume, a special invariant partition is constructed on a set where at least one value of the characteristic Lyapunov indicators is nonzero. This partition possesses properties analogous to the properties of partition into global condensing sheets for Y-diffeomorphisms while, as the complement to this set, there is partition into points. It is proven that the measurable hull of this partition coincides with the π-partition of a diffeomorphism.     

A partition relation for partially ordered sets

We introduce a partition relation which is an alternate for measuring how badly the ordinary partition relation fails, we develop its corresponding partition calculus and we determine its status for various typical partially ordered sets.     

Vertex transversals that dominate

For any graph, there is a largest integer k such that given any partition of the vertex set with at most k elements in each class of the partition, there is transversal of the partition that is a dominating set in the graph. Some basic results about this parameter, the partition domination number, are obtained. In particular, it is shown that its value is 2 for the two-dimensional infinite grid, and that determining whether a given vertex partition admits a dominating transversal is NP-complete, even for a graph which is a simple path. The existence of various dominating transversals in certain partitions in regular graphs is studied as well. © 1996 John Wiley & Sons, Inc.     

Landau-Ginzburg topological theories in the framework of GKM and equivalent hierarchies

We consider the deformations of monomial solutions to the Generalized Kontsevich Model [1, 2] and establish the relation between the flows generated by these deformations with those of N=2 Landau-Ginzburg topological theories. We prove that the partition function of a generic Generalized Kontsevich Model can be presented as a product of some quasiclassical factor and non-deformed partition function which depends only on the sum of Miwa transformed and flat times. This result is important for the restoration of explicit p-q symmetry in the interpolation pattern between all the (p,q)-minimal string models with c<1 and for revealing its integrable structure in p-direction, determined by deformations of the potential. It also implies the way in which supersymmetric Landau-Ginzburg models are embedded into the general context of GKM. From the point of view of integrable theory these deformations present a particular case of what is called equivalent hierarchies.Published in Teoreticheskaya i Matematicheskaya Fizika, Vol. 95, No. 2, pp. 280–292, May, 1993.     

A unified approach to known and unknown cases of Berge's conjecture

Berge's elegant dipath partition conjecture from 1982 states that in a dipath partition P of the vertex set of a digraph minimizing , there exists a collection C^k of k disjoint independent sets, where each dipath P∈P meets exactly min{|P|, k} of the independent sets in C. This conjecture extends Linial's conjecture, the Greene–Kleitman Theorem and Dilworth's Theorem for all digraphs. The conjecture is known to be true for acyclic digraphs. For general digraphs, it is known for k=1 by the Gallai–Milgram Theorem, for k?λ (where λis the number of vertices in the longest dipath in the graph), by the Gallai–Roy Theorem, and when the optimal path partition P contains only dipaths P with |P|?k. Recently, it was proved (Eur J Combin (2007)) for k=2. There was no proof that covers all the known cases of Berge's conjecture. In this article, we give an algorithmic proof of a stronger version of the conjecture for acyclic digraphs, using network flows, which covers all the known cases, except the case k=2, and the new, unknown case, of k=λ?1 for all digraphs. So far, there has been no proof that unified all these cases. This proof gives hope for finding a proof for all k.     

AN UPPER BOUND ON AVERAGE TOUCHING NUMBER OF A VORONOI PARTITION

A Voronoi partition is decided bythe configurations of N centerepoints in n dimensional Euclidean space. The total number of nearest neighbor points for a given centerpoint in the partition is called its touching number. It is shown that the average touching number for all points in a Voronoi partition is not greater than the n dimensional kissing number, that is, the maximum uumber of unit spheres that can touch a given unit sphere without overlapping.     

Maximal Multiplicative Properties of Partitions

Extending the partition function multiplicatively to a function on partitions, we show that it has a unique maximum at an explicitly given partition for any n ≠ 7. The basis for this is an inequality for the partition function which seems not to have been noticed before.     

Graphs with unique maximal clumpings

A partition of the vertices of a graph is called a clumping if, for vertices in distinct partition classes, adjacency depends only on the partition classes, not on the specific vertices. We give a simple necessary and sufficient condition for a finite graph to have a unique maximal clumping. We also investigate the extent to which this and related results generalize to infinite graphs.     

Conditions for graphs to be path partition optimal

The path partition number of a graph is the minimum number of edges we have to add to turn it into a Hamiltonian graph, and the separable degree is the minimum number of edges we have to add to turn it into a 2-connected graph. A graph is called path partition optimal if its path partition number is equal to its separable degree. We study conditions that guarantee path partition optimality. We extend several known results on Hamiltonicity to path partition optimality, in particular results involving degree conditions and induced subgraph conditions.     

图的k-单圈划分中的优化问题

图的划分问题曾引起图论界的广泛关注，在文献[4]中讨论了k-单圈划分，本文进一步研究基于k-单圈划分的优化问题，即在一个赋权图中求一个最小权可k-单圈划分的支撑子图，以及对一个不存在k-单圈划分支撑子图的图，如何添最少的边使得它有k-单圈划分的支撑子图。     

Local and parallel finite element algorithm based on the partition of unity method for the incompressible MHD flow

Based on the partition of unity method (PUM), a local and parallel finite element method is designed and analyzed for solving the stationary incompressible magnetohydrodynamics (MHD). The key idea of the proposed algorithm is to first solve the nonlinear system on a coarse mesh, divide the globally fine grid correction into a series of locally linearized residual problems on some subdomains derived by a class of partition of unity, then compute the local subproblems in parallel, and obtain the globally continuous finite element solution by assembling all local solutions together by the partition of unity functions. The main feature of the new method is that the partition of unity provide a flexible and controllable framework for the domain decomposition. Finally, the efficiency of our theoretical analysis is tested by numerical experiments.