Conjugated trees with minimum general Randi? index

The general Randi? index R_α(G) is the sum of the weights (d_G(u)d_G(v))^α over all edges uv of a (molecular) graph G, where α is a real number and d_G(u) is the degree of the vertex u of G. In this paper, for any real number α≤−1, the minimum general Randi? index R_α(T) among all the conjugated trees (trees with a Kekulé structure) is determined and the corresponding extremal conjugated trees are characterized. These trees are also extremal over all the conjugated chemical trees.     

Vacuum states on compressible Navier-Stokes equations with general density-dependent viscosity and general pressure law

In this paper,we study the one-dimensional motion of viscous gas with a general pres- sure law and a general density-dependent viscosity coefficient when the initial density connects to the vacuum state with a jump.We prove the global existence and the uniqueness of weak solutions to the compressible Navier-Stokes equations by using the line method.For this,some new a priori estimates are obtained to take care of the general viscosity coefficientμ(ρ)instead ofρ~θ.     

Explicit construction of general multivariate Padé approximants to an Appell function

Properties of Padé approximants to the Gauss hypergeometric function ₂F₁(a,b;c;z) have been studied in several papers and some of these properties have been generalized to several variables in [6]. In this paper we derive explicit formulae for the general multivariate Padé approximants to the Appell function F₁(a,1,1;a+1;x,y)=_i,j=0(axⁱy^j/(i+j+a)), where a is a positive integer. In particular, we prove that the denominator of the constructed approximant of partial degree n in x and y is given by , where the integer m, which defines the degree of the numerator, satisfies mn+1 and m+a2n. This formula generalizes the univariate explicit form for the Padé denominator of ₂F₁(a,1;c;z), which holds for c>a>0 and only in half of the Padé table. From the explicit formulae for the general multivariate Padé approximants, we can deduce the normality of a particular multivariate Padé table. AMS subject classification 41A63, 41A21     

∃-Free groups as groups with length function

It is shown that there exists a length function with values in a finitely generated group relative to which G is a -free group in any finitely generated group G.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 44, No. 6, pp. 813–822, June, 1992.     

On some general Hilbert’s inequalities with non-conjugate parameters

A generalized discrete Hilbert’s and Hardy-Hilbert’s inequality with non-conjugate parameters can be established by means of Euler-Maclaurin summation formula. We derive some general results for homogeneous functions and compare our results with some previously known from the literature. We also obtain the improvements on some earlier results.     

Witten’s perturbation on strata with general adapted metrics

Let M be a stratum of a compact stratified space A. It is equipped with a general adapted metric g, which is slightly more general than the adapted metrics of Nagase and Brasselet–Hector–Saralegi. In particular, g has a general type, which is an extension of the type of an adapted metric. A restriction on this general type is assumed, and then, g is called good. We consider the maximum/minimum ideal boundary condition, \(d_{\mathrm{max/min}}\), of the compactly supported de Rham complex on M, in the sense of Brüning–Lesch. Let \(H^*_{\mathrm{max/min}}(M)\) and \(\Delta _{\mathrm{max/min}}\) denote the cohomology and Laplacian of \(d_{\mathrm{max/min}}\). The first main theorem states that \(\Delta _{\mathrm{max/min}}\) has a discrete spectrum satisfying a weak form of the Weyl’s asymptotic formula. The second main theorem is a version of Morse inequalities using \(H_{\mathrm{max/min}}^*(M)\) and what we call rel-Morse functions. An ingredient of the proofs of both theorems is a version for \(d_{\mathrm{max/min}}\) of the Witten’s perturbation of the de Rham complex. Another ingredient is certain perturbation of the Dunkl harmonic oscillator previously studied by the authors using classical perturbation theory. The condition on g to be good is general enough in the following sense. Assume that A is a stratified pseudomanifold, and consider its intersection homology \(I^{\bar{p}}H_*(A)\) with perversity \(\bar{p}\); in particular, the lower and upper middle perversities are denoted by \(\bar{m}\) and \(\bar{n}\), respectively. Then, for any perversity \(\bar{p}\le \bar{m}\), there is an associated good adapted metric on M satisfying the Nagase isomorphism \(H^r_{\mathrm{max}}(M)\cong I^{\bar{p}}H_r(A)^*\) (\(r\in \mathbb {N}\)). If M is oriented and \(\bar{p}\ge \bar{n}\), we also get \(H^r_{\mathrm{min}}(M)\cong I^{\bar{p}}H_r(A)\). Thus our version of the Morse inequalities can be described in terms of \(I^{\bar{p}}H_*(A)\).     

On groups of type Φ

We define a group G to be of type Φ if it has the property that for every -module G, proj. G < ∞ iff proj. H G < ∞ for every finite subgroup H of G. We conjecture that the type Φ is an algebraic characterization of those groups G which admit a finite dimensional model for , the classifying space for the family of the finite subgroups of G. We also conjecture that the type Φ is equivalent to spli being finite, where spli is the supremum of the projective lengths of the injective -modules. Here we prove certain parts of these conjectures. The project is cofounded by the European Social Fund and National Resources–EPEAK II–Pythagoras. Received: 21 June 2006     

Besicovitch cylindrical transformation with a Hölder function

For any γ ∈ (0, 1) and ε > 0, we construct a cylindrical cascade with a γ-Hölder function over some rotation of the circle. This transformation has the Besicovitch property; i.e., it is topologically transitive and has discrete orbits. The Hausdorff dimension of the set of points of the circle that have discrete orbits is greater than 1 ? γ ? ε.     

An analysis of single-index model with monotonic link function

The single-index model with monotonic link function is investigated. Firstly, it is showed that the link function h（.） can be viewed by a graphic method. That is, the plot with the fitted response y on the horizontal axis and the observed y on the vertical axis can be used to visualize the link function. It is pointed out that this graphic approach is also applicable even when the link function is not monotonic. Note that many existing nonparametric smoothers can also be used to assess h（.）. Therefore, the I-spline approximation of the link function via maximizing the covariance function with a penalty function is investigated in the present work. The consistency of the criterion is constructed. A small simulation is carried out to evidence the efficiency of the approach proposed in the paper.     

Conjugated tricyclic graphs with the maximum zeroth-order general Randić index

Let G be a simple connected graph and α be a given real number. The zeroth-order general Randi? index of G is defined as ⁰ R _α (G)=∑ _v∈V(G)[d _G (v)] ^α , where d _G (v) denotes the degree of the vertex v of G. In this paper, for any α>2, we give sharp upper bounds of the zeroth-order general Randi? index ⁰ R _α of all conjugated tricyclic graphs with 2m vertices.     

Second derivative general linear methods with inherent Runge–Kutta stability

In this paper, we find some relationships among the coefficients matrices of second derivative general linear methods (SGLMs) which are sufficient conditions, but not necessary, to ensure the methods have Runge–Kutta stability (RKS) property. Considering these conditions, we construct some A– and L–stable SGLMs with inherent RKS of orders up to five. Also, some numerical experiments for the constructed methods in variable stepsize environment are given.     

A general vectorial Ekeland’s variational principle with a P-distance

In this paper, by using p-distances on uniform spaces, we establish a general vectorial Ekeland variational principle （in short EVP）, where the objective function is defined on a uniform space and taking values in a pre-ordered real linear space and the perturbation involves a p-distance and a monotone function of the objective function. Since p-distances are very extensive, such a form of the perturbation in deed contains many different forms of perturbations appeared in the previous versions of EVP. Besides, we only require the objective function has a very weak property, as a substitute for lower semi-continuity, and only require the domain space （which is a uniform space） has a very weak type of completeness, i.e., completeness with respect to a certain p-distance. Such very weak type of completeness even includes local completeness when the uniform space is a locally convex topological vector space. From the general vectorial EVP, we deduce a general vectorial Caristi＇s fixed point theorem and a general vectorial Takahashi＇s nonconvex minimization theorem. Moreover, we show that the above three theorems are equivalent to each other. We see that the above general vectorial EVP includes many particular versions of EVP, which extend and complement the related known results.     

On Φ-Derivation in Banach Algebras

Using Bre?ar and ?emrl approach, we give a proof of the extended Jacobson density theorem for Φ-derivations. Further, some applications on Banach algebras will be given. Precisely, for d being a continuous Φ-derivation on a given Banach algebra ?, we show that: d(?) ? rad (?) ? [b,[a, d(a)]] ∈ rad (?) for all a, b ∈ ? and d leaves invariant all maximal ideals of codimension one?for every a ∈ ? there exists a positive integer n such that (d(a)) ⁿ is quasi-nilpotent ? [d, Φ](?) ? rad (?) and d ²(a) ∈ rad (?) for all a ∈ ?. Finally, we characterize all pairs d, δ of continuous Φ-derivations such that dδ(a) is quasi-nilpotent for all a ∈ ? and [d, δ](?), [d, Φ](?), [δ,Φ](?) are subsets of rad (?).     

Complex valued neural network with Möbius activation function

In this work, we propose a new type of activation function for a complex valued neural network (CVNN). This activation function is a special Möbius transformation classified as reflection. It is bounded outside of the unit disk and has partial continuous derivatives but not differentiable since it does not satisfy the Cauchy–Riemann equalities. However, the fixed points set of this function is a circle. Therefore, we employ this function to a specific complex valued Hopfield neural network (CVHNN) and increase the number of fixed points of the CVHNN. Using of this activation function leads us also to guarantee the existence of fixed points of the CVHNN. It is shown that the fixed points are all asymptotically stable states of the CVHNN which indicates that the information capacity is enlarged.