Langlands duality for representations of quantum groups

We establish a correspondence (or duality) between the characters and the crystal bases of finite-dimensional representations of quantum groups associated to Langlands dual semi-simple Lie algebras. This duality may also be stated purely in terms of semi-simple Lie algebras. To explain this duality, we introduce an “interpolating quantum group” depending on two parameters which interpolates between a quantum group and its Langlands dual. We construct examples of its representations, depending on two parameters, which interpolate between representations of two Langlands dual quantum groups.     

边赋权图对策Myerson值的和分解

2003年,Gómez等在考虑社会网络中心性度量时,引入了对称对策上Myerson值的和分解概念,本文将这一概念推广到边赋权图对策上,给出了相应于边赋权图对策的组内Myerson值和组间Myerson值。其中边的权表示这条边的两个端点之间的直接通讯容量,组内Myerson值衡量了每个参与者来自它所在联盟的收益,而组间Myerson值评估了参与者作为其他参与者中介所获取的收益。本文侧重分析了边赋权图对策的组内Myerson值和组间Myerson值的权稳定性和广义稳定性, 并给出了这两类值的刻画。     

On recognizing proportionality: Does the ability to solve missing value proportional problems presuppose the conception of proportional reasoning?

This paper investigates the relationship between the ability of middle school students to solve missing value proportional problems and their facility in differentiating proportional relationships from non-proportional relationships. Students in low- and high-proficiency groups in mathematics took a ratio-and-proportion test involving two typical missing value proportional (MVP) and two recognizing proportionality (RP) problems. The findings revealed that while the students generally performed better on MVP problems than on RP problems, the two groups differed in their performance on MVP problems, but not on RP problems. Moreover, of those students from both the groups who successfully solved the two MVP problems, a significantly greater proportion of students in the high-proficiency group were unsuccessful in solving either of the two RP problems than those in the low-proficiency group. An analysis of performance differences between items within the same student group showed that the effect of differences in the structural components of RP problems to some extent contradicted the previous findings on the effect of differences in the structural components of MVP problems. It is hoped that these findings can shed light on what might be missing in the teaching and learning of proportional reasoning.     

Juche in international trade

We show that in trade between two parties, one of whom has much greater endowment that the other, calculated by the Nash bargaining solution, tends to exploit the poorer party, as compared with the competitive equilibrium. This can be interpreted as saying that trade between a developed country and a developing nation, each acting on the basis of self-interest, will result in exploitation of the developing nation. This illustrates one aspect of the idea of Juche. We also show that if trade in two goods among two parties is extended to a third, one of the two parties will be worse off as a result under natural hypotheses. This can be interpreted as explaining why trade between a developing country and a developed country might make some groups in the developing country rich but other groups poor, a second aspect of Juche.     

Isomorphisms of Kac-Moody groups which preserve bounded subgroups

A subgroup of a Kac-Moody group is called bounded if it is contained in the intersection of two finite type parabolic subgroups of opposite signs. In this paper, we study the isomorphisms between Kac-Moody groups over arbitrary fields of cardinality at least 4, which preserve the set of bounded subgroups. We show that such an isomorphism between two such Kac-Moody groups induces an isomorphism between the respective twin root data of these groups. As a consequence, we obtain the solution of the isomorphism problem for Kac-Moody groups over finite fields of cardinality at least 4.     

Extracting informative variables in the validation of two-group causal relationship

The validation of causal relationship between two groups of multivariate time series data often requires the precedence knowledge of all variables. However, in practice one finds that some variables may be negligible in describing the underlying causal structure. In this article we provide an explicit definition of “non-informative variables” in a two-group causal relationship and introduce various automatic computer-search algorithms that can be utilized to extract informative variables based on a hypothesis testing procedure. The result allows us to represent a simplified causal relationship by using minimum possible information on two groups of variables.     

Finite difference simulation of elastic wave propagation through 3D heterogeneous multiscale media based on locally refined grids

To simulate the interaction of seismic waves with microheterogeneities (like cavernous/fractured reservoirs), a finite difference technique based on grids locally refined in time and space is used. These grids are used because the scales of heterogeneities in the reference medium and in the reservoir are different. Parallel computations based on domain decomposition of the target area into elementary subdomains in both the reference medium (a coarse grid) and the reservoir (a fine grid) are performed. Each subdomain is assigned to a specific processor unit, which forms two groups: one for the reference medium, and the other for the reservoir. The data exchange between the groups within a processor unit is performed by non-blocking iSend/iReceive MPI commands. The data exchange between the two groups is performed simultaneously with coupling the coarse and a fine grids, and is controlled by a specially chosen processor unit. The results of a numerical simulation for a realistic model of fracture corridors are presented and discussed.     

ISOMORPHISMS OF STABLE STEINBERG GROUPS

In [2] the author discussed the isomorphisms between two unstable Steinberg groups $St_m(A)$ and $St_n(R)$ over commutative rings. The aim,of the present paper is to determine the isomorphisms between two stable Steinberg groups St(A) and St(R), and the isomorphisms between the corresponding stable linear groups.     

Wreath products and representations of p-local finite groups

Given two finite p-local finite groups and a fusion preserving morphism between their Sylow subgroups, we study the question of extending it to a continuous map between their classifying spaces. The results depend on the construction of the wreath product of p-local finite groups which is also used to study p-local permutation representations.     

Comparison of relative risk,attributable risk and logistic response procedures for 2×2×2 andc 2×2×2 contingency tables

Summary A numerical evaluation was made on three different χ² statistics in order to compare mutagenic risk frequencies between two experimental groups in a 2×2×2 contingency table andc 2×2×2 contingency tables. The three methods involve 1) a relative risk approach, 2) an attributable risk approach and 3) a logistic response approach. A relatively large difference was observed among χ² statistics in the three approaches using actual data under the hypothesis that there is no difference between the two groups under scrutiny. With regard to approximate power, it appears that approaches 2) and 3) give fairly stable results. Approach 1) has greater power if there is a small difference in the control groups. It was confirmed that the approximate power of approach 1) is extremely large when the difference in the relative risk frequencies between the two groups under contrast is constant and each relative risk frequency is small. This paper was presented at the 48th annual meeting of Japan Statistical Association in Tokyo, Japan, 1980.     

Dimension Groups for Polynomial Odometers

Here we study a class of dynamical systems we call polynomial odometers. These are adic maps on regularly structured Bratteli diagrams and include the Pascal and Stirling adic maps as examples. We describe the dimension groups associated with these systems and use this to study spaces of invariant measures. For many, but not all, the space of invariant measures is affinely homeomorphic to the space of Borel probability measures on a closed interval in $\mathbb{R}$ , we call such polynomial odometers reasonable. We describe the possible isomorphisms between dimension groups for reasonable polynomial odometers, and use this to prove a version of a result of Giordano, Putnam and Skau for this situation. Namely, we show that there is an isomorphism between unital ordered groups associated with two reasonable polynomial odometers if and only if there is a special kind of orbit equivalence between the two.     

Effectiveness of Two Generative Learning Strategies in the Science Classroom

The purpose of this study was to assess the effectiveness of two generative learning strategies, concept mapping and laboratory experiments involving object manipulation, to determine if either one is more‐effective with individual learners or learning groups in a science classroom. Eighty sixth‐grade science‐students were randomly assigned to group or individual conditions and to one of two experimental treatments. Experimental treatments were changed between a first and second posttest. Long‐term retention was evaluated with a third, delayed posttest. Students starting with concept maps showed higher achievement on the delayed posttest than students beginning with the laboratory experiment. No difference was found between students working as individuals or in groups, but a significant interaction between generative learning strategy and grouping condition was revealed. Implications for sequencing generative learning strategies are discussed.     

Factor morphisms and centroids of locally nilpotent groups

For a class of locally nilpotent groups, we study interrelations between two known analogs of the concept of a ring centroid in the class of groups.     

Groups of even type which are not of even characteristic,I

In the ongoing revision of the classification of the finite simple groups there is a subdivision into two classes of groups, which reflects whether semisimple elements or unipotent elements are the primary focus of the investigation. While semisimple methods naturally lead to the definition of groups of even type, unipotent methods, notably the amalgam method, naturally lead to groups of even characteristic. This paper clarifies the relationship between the two definitions and thus makes the amalgam method available for use in the classification of groups of even type.     

Minimum distance classification rules for high dimensional data

In this article, the problem of classifying a new observation vector into one of the two known groups Π_i,i=1,2, distributed as multivariate normal with common covariance matrix is considered. The total number of observation vectors from the two groups is, however, less than the dimension of the observation vectors. A sample-squared distance between the two groups, using Moore-Penrose inverse, is introduced. A classification rule based on the minimum distance is proposed to classify an observation vector into two or several groups. An expression for the error of misclassification when there are only two groups is derived for large p and n=O(p^δ),0<δ<1.     

The Interplay Between Gesture and Discourse as Mediating Devices in Collaborative Mathematical Reasoning:A Multimodal Approach

This article aims to identify the mathematical reasoning strategies expressed through gestures and speech used by two groups of sixth-grade pupils when solving a task related to the transition between two semiotic representations: figure and Cartesian diagram. The article also identifies the difficulties the pupils meet in the solution process. The analyses of the group dialogues focus particularly on the gesture dimension of deixis. The pupils in both groups have used the following deictic gestures: pointing, held-point, linear point-slide, and circular point-slide in their solution process, while repeated pointing has been identified only in one of the groups. These pointing gestures are related to the reasoning strategies: comparison of persons in the figure, coordination of two dimensions in the diagram, recapitulation and going to an extreme location. The pupils use the modalities of speech, gesture, and writing in order to solve the mathematical task. Their pointing gestures related to their use of reasoning strategies play a multifaceted role in developing collaborative mathematical reasoning in the two small groups.     

Automata and Square Complexes

We introduce a new geometric tool for analyzing groups of finite automata. To each finite automaton we associate a square complex. The square complex is covered by a product of two trees iff the automaton is bi-reversible. Using this method we give examples of free groups and of Kazhdan groups which are generated by the different states of one finite (bi-reversible) automaton. We also reprove the theorem of Macedońska, Nekrashevych, Sushchansky, on the connection between bi-reversible automata and the commensurator of a regular tree.     

General constructions of biquandles and their symmetries

Biquandles are algebraic objects with two binary operations whose axioms encode the generalized Reidemeister moves for virtual knots and links. These objects also provide set theoretic solutions of the well-known Yang-Baxter equation. The first half of this paper proposes some natural constructions of biquandles from groups and from their simpler counterparts, namely, quandles. We completely determine all words in the free group on two generators that give rise to (bi)quandle structures on all groups. We give some novel constructions of biquandles on unions and products of quandles, including what we refer as the holomorph biquandle of a quandle. These constructions give a wealth of solutions of the Yang-Baxter equation. We also show that for nice quandle coverings a biquandle structure on the base can be lifted to a biquandle structure on the covering. In the second half of the paper, we determine automorphism groups of these biquandles in terms of associated quandles showing elegant relationships between the symmetries of the underlying structures.     

Tandem queue with group arrivals and no intermediate buffer

We study a system with two single-server stations in series. There is an infinite buffer in front of the first station and no buffer between the two stations. The customers come in groups; the groups contain random numbers of customers and arrive according to a Poisson process. Assuming general service time distributions at the two stations, we derive the Laplace transform and the recursive formula for the moments of the total time spent in the tandem system (waiting time in the system) by an arbitrary customer. From the Laplace transform, we conclude that the optimal order of the servers for minimizing the waiting time in the system does not depend on the group size.     

Perfect state transfer on bi-Cayley graphs over abelian groups

The study of perfect state transfer on graphs has attracted a great deal of attention during the past ten years because of its applications to quantum information processing and quantum computation. Perfect state transfer is understood to be a rare phenomenon. This paper establishes necessary and sufficient conditions for a bi-Cayley graph having a perfect state transfer over any given finite abelian group. As corollaries, many known and new results are obtained on Cayley graphs having perfect state transfer over abelian groups, (generalized) dihedral groups, semi-dihedral groups and generalized quaternion groups. Especially, we give an example of a connected non-normal Cayley graph over a dihedral group having perfect state transfer between two distinct vertices, which was thought impossible.