On the Tzitzeica–Johnson configuration

Working in the context of Hilbert’s axiomatic system, we prove that the generic Tzitzeica–Johnson configuration presents an equivalent to the determination of the metric of an absolute plane.     

On the girth and diameter of generalized Johnson graphs

Let $v>k>i$ be non-negative integers. The generalized Johnson graph, $J(v,k,i)$, is the graph whose vertices are the $k$-subsets of a $v$-set, where vertices $A$ and $B$ are adjacent whenever $|A\cap B|=i$. In this article, we derive general formulas for the girth and diameter of $J(v,k,i)$. Additionally, we provide a formula for the distance between any two vertices $A$ and $B$ in terms of the cardinality of their intersection.     

On residuals in generalized Johnson SB regressions

An important challenge in the class of generalized Johnson S_B regression models is to define residuals which are capable of identifying departures from the model assumptions, as well as to assess the overall goodness-of-fit of the model. On this regard, we propose a new residual for this class of models, and numerically evaluate its behaviour relative to the deviance residual initially proposed for this class of regression models. Monte Carlo simulation experiments and empirical applications using real and simulated data are provided. Overall, the results favour the residual we propose.     

On a conjecture of C. Johnson

Given a pair of n×n matricesA and B, one may form a polynomial P(A,B,λ) which generalizes the characteristic polynomial of BP(B,λ). In particular, when A=I (identity), P(A, B,λ) = P(B,λ), the characteristic polynomial of B. C. Johnson has conjectured [1] (among other things) that when A and B are hermitian and A is positive definite, then P(A,B,λ) has real roots. The case n=2 can be done by hand. In this paper we verify the conjecture for n=3.     

Nonbinary quantum error-correcting codes from algebraic curves

We give a new exposition and proof of a generalized CSS construction for nonbinary quantum error-correcting codes. Using this we construct nonbinary quantum stabilizer codes with various lengths, dimensions, and minimum distances from algebraic curves. We also give asymptotically good nonbinary quantum codes from a Garcia–Stichtenoth tower of function fields which are constructible in polynomial time.     

On structures of modular adjacency algebras of Johnson schemes

In this paper, we consider algebras over a field of characteristic p, which are generated by adjacency algebras of Johnson schemes. If the algebra is semisimple, the structure is the same as that of the well-known Bose-Mesner algebras. We determine the structure of the algebra when it is not semisimple.     

Nonbinary convolutional codes derived from group character codes

New families of unit memory as well as multi-memory nonbinary convolutional codes are constructed algebraically in this paper. These convolutional codes are derived from the class of group character codes. The proposed codes have basic generator matrices, consequently, they are noncatastrophic. Additionally, the new code parameters are better than the ones available in the literature.     

On the fourth Johnson homomorphism of the automorphism group of a free group

In this paper we consider the Johnson homomorphism of the automorphism group of a free group with respect to the lower central series of the IA-automorphism group of a free group. In particular, we determine the rational cokernel of the fourth Johnson homomorphism, and show that there appears a new obstruction for the surjectivity of the Johnson homomorphism. Furthermore we characterize this obstruction using trace maps.     

Nonbinary quantum codes derived from finite geometries

The paper gives explicit parameters for several infinite families of q-ary quantum stabilizer codes. These codes are derived from combinatorial designs which arise from finite projective and affine geometries.     

On the Discriminant Scheme of Homogeneous Polynomials

In this paper, the discriminant scheme of homogeneous polynomials is studied in two particular cases: the case of a single homogeneous polynomial and the case of a collection of n ? 1 homogeneous polynomials in \({n\geqslant 2}\) variables. In both situations, a normalized discriminant polynomial is defined over an arbitrary commutative ring of coefficients by means of the resultant theory. An extensive formalism for this discriminant is then developed, including many new properties and computational rules. Finally, it is shown that this discriminant polynomial is faithful to the geometry: it is a defining equation of the discriminant scheme over a general coefficient ring k, typically a domain, if \({2\neq 0}\) in k. The case where 2 = 0 in k is also analyzed in detail.     

可列无限等可能概型概率场的讨论

假设有某试验,对每次试验而言有可列无限个试验结果,由于某种对称性,每个结果的出现又有一定的均匀性.对这种概型本文称之谓可列无限等可能慨型,这种概型的问题其概率场是什么?这是个颇有趣的问题,本文将针对这一问题进行一定的探讨.本文将针对从全体正整数中随机取数的问题的一种特殊的子集类构成事件域,并在其上合理地定义概率,从而建立概率场.     

关于Reissner-Mindlin板问题的线性格式

本文给出Ｒｅｉｓｓｎｅｒ－Ｍｉｎｄｌｉｎ板问题的线性格式[1]中的汽泡函数的最优选取。     

Regular weights and the Johnson scheme

This work addresses existence of weighted coherent configurations (cc’s) in the special case of the Johnson schemes,J(n, k). Many examples of weighted cc’s occur in the context of a permutation representation of a group which affords the cc. We determine the ranks of the weighted Johnson schemes which arise in this “group case” in connection with the alternating groupA _n . The association schemeJ(n, 2) has rank 3, with the triangular graphT(n) as one of its graphs. Conditions on feasible parameters for regular, full rank weights onT(n) are established. We describe two infinite families of such feasible parameters. Research supported by the Department of Education and the Rackham Graduate School of the University of Michigan as part of Ph.D. thesis written under the direction of D. G. Higman.     

Connection between the Kadomtsev-Petviashvili and Johnson equations

The equivalence of the Kadomtsev-Petviashvili and Johnson equations is established in the class of rapidly decreasing Cauchy data. As an illustration of the isomorphism cited the Hamiltonian structure of the Johnson equation is studied.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 150, pp. 70–75, 1986.We thank M. A. Sall' for helpful discussions.     

Spectrum of Johnson graphs

In this paper we prove new bounds on the second eigenvalue of Johnson graphs. We then apply these bounds to obtain new results on the modularity of Johnson graphs and their random subgraphs, hamiltonicity of Johnson graphs and thresholds of the appearance of the Hamilton cycles and giant components. Furthermore, we provide general bounds on vertex connectivity and the stability of the modularity for $(n,d,\lambda )$-graphs.     

The Terwilliger algebra of the Johnson schemes

One of the classical families of association schemes is known as the Johnson schemes J(n,d). In this paper we compute the Terwilliger algebra associated to them when 3d?n. We give its decomposition into simple ideals and the decomposition of its standard module into irreducible submodules.