RESEARCH ANNOUNCEMENTS——Strong Discreteness of Subgroups of SL（2, Гn）

As in [1,6], let Гn be the n-dimensional Clifford group, i.e., the set of all elements in n-dimensional Clifford algebra An, which can be expressed as a finite product of non-zero-vertors and SL(2, Гn) denote the group of n-dimensional Clifford matrices A=(α b c d)which satisfy:     

Strong Discreteness of Subgroups of SL(2,Гn)

As in [1,6], let Гn be the n-dimensional Clifford group, i.e., the set of all elements in n-dimensional Clifford algebra An, which can be expressed as a finite product of non-zero-vectors and SL(2, Гn)denote the group of n-dimensional Clifford matrices A= (a c b d) which satisfy:     

有限域上仿射m面诱导的图Ⅱ

Let AG(n,Fq) be the n-dimensional affine space over Fq,where Fq is a finite field with q elements. Denote by Г(m) the graph induced by m-flats of AG(n,Fq). For any two adjacent vertices E and F of Гr(m) ,Г(m) (E)∩ Г(m) (F) is studied. In particular,sizes of maximal cliques in Г(m) are determined and it is shown that Г(m) is not edge-regular when m＜n-1.     

The Poincaré Series of Relative Invariants of Finite Pseudo-Reflection Groups

Let F be a field with characteristic 0,V=F~n the n-dimensional vector space over F and let G be a finite pseudo-reflection group which acts on V.Let χ:G→F~* be a 1-dimensional representation of G.In this article we show that X(g)=(detg)~α(0≤α≤r-1),where g∈G and r is the order of g.In addition,we characterize the relation between the relative invariants and the invariants of the group G,and then we use Molien's Theorem of invariants to compute the Poincaré series of relative invariants.     

The Integral of Mean Curvatures on the Tube Hypersurfaces

The calculation on the tube hypersurfaces is very interesting and important,especially H.Weyl gave a formula of the volume of tubes which contains a seriesof curvature invariants of submanifolds. Let N be an oriented compact n-dimensional submanifold in the m-dimensional     

Exact Estimates of N widths and One-sided N-widths For a Set of Convolution Classes of Periodic Functions

Let E~ ( ,H_n)_q be the one-sided approximation by n-dimensional subspacein metric L_q to the set of functions and d_m~ ( H_n)_q be the one-sidedn-widths of in L_q. Let     

A Family of Non-quasiprimitive Graphs Constructed From PSU3（q） Where q Is Odd

Let Г be a simple connected graph and let G be a group of automorphisms of Г. Г is said to be （G, 2）-arc transitive if G is transitive on the 2-arcs of Г. It has been shown that there exists a family of non-quasiprimitive （PSU3（q）, 2）-arc transitive graphs where q = 2^3m with m an odd integer. In this paper we investigate the case where q is an odd prime power.     

STRONG SOLUTIONS AND PATHWlSE CONTROL FOR NON-LINEAR STOCHASTIC SYSTEM WITH POISSON JUMPS IN N-DIMENSIONAL SPACE

The existence of a pathwise unique strong solution for the stochastic differentialequation(S.D.E.)with Poisson jumps in n-dimensional space without continuityassumption on drift coefficient,which even can be greater than linear growth,andwithout Lipschitz condition on diffusion coefficients is obtained.Then the existence of apathwise stochastic optimal Bang-Bang control for a very much non-linear systemwithPoisson jumps in n-dimensional space is derived.The result is also applied to obtain amaximum likelihood estimate(MLE) of parameter for some continuous,S.D.E.withnon-Lipschitz oeffieients in n-dimensional space.     

E1ementary Bifurcations of Non—Critical but N0n—Hyperbolic Invariant Tori

Consider the time-periodic peturbations of n-dimensional autonomous systems with non-hyperbolic but non-critical closed orbits in the phase space.The elementary bifurcations,such as the saddle-node,transcritical,pitchfork bifurcation to a non-hyperbolic but non-critical invariant torus of the unperturbed systems in the extended phase space(x,t),are sutdied.Some conditions which depend only on ithe original systems and can be used to determine the bifurcation structures of these problems are obtained.The theory is applied to two concrete examples.     

有限伪反射群的相对不变式的 Poincar\'e级数

Let F be a field with characteristic 0, V = Fn the n-dimensional vector space over F and let G be a finite pseudo-reflection group which acts on V . Let χ ： G→ F＊ be a 1- dimensional representation of G. In this article we show that χ（g） = （detg）α（0 ≤ α ≤ r - 1）, where g ∈ G and r is the order of g. In addition, we characterize the relation between the relative invariants and the invariants of the group G, and then we use Molien’s Theorem of invariants to compute the Poincar′e series of relative invariants.     

On the positivity of high-degree Schur classes of an ample vector bundle

Let X be a smooth projective variety of dimension n,and let E be an ample vector bundle over X.We show that any Schur class of E,lying in the cohomology group of bidegree(n-1,n-1),has a representative which is strictly positive in the sense of smooth forms.This conforms the prediction of Griffiths conjecture on the positive polynomials of Chern classes/forms of an ample vector bundle on the form level,and thus strengthens the celebrated positivity results of Fulton and Lazarsfeld(1983)for certain degrees.     

Some pinching theorems for minimal submanifolds in \mathbb{S}^m (1) \times \mathbb{R}

Let Mn be an n-dimensional compact minimal submanifolds in Sm(1)×R.We prove two pinching theorems by the Ricci curvature and the sectional curvature pinching conditions respectively.In fact,we characterize the Clifford tori and Veronese submanifolds by our pinching conditions respectively.     

A decomposition theorem for G-groups

Some classical results about linear representations of a finite group G have been also proved for representations of G on non-abelian groups （G-groups）. In this paper we establish a decomposition theorem for irreducible G-groups which expresses a suitable irreducible G-group as a tensor product of two projective G-groups in a similar way to the celebrated theorem of Clifford for linear representations. Moreover, we study the non-abelian minimal normal subgroups of G in which this decomposition is possible.     

A ■_n-Related Family of Homotopy Elements in the Stable Homotopy of Spheres

To determine the stable homotopy groups of spheres π_*(S) is one of the central problems in homotopy theory. Let p be a prime greater than 5. The authors make use of the May spectral sequence and the Adams spectral sequence to prove the existence of a ■_n-related family of homotopy elements, β1ω_nγ_s, in the stable homotopy groups of spheres, where ■_n 3, 3≤s p-2 and the ■_n-element was detected by X. Liu.     

Characterizations of Best L_p(1≤p≤+ ∞) Approximation With Restricted Ranges of Derivatives

Let [a,b] be a compact set containing at least n + 1 points. If Φ_n = span(φ_1, φ_2,…, φ_n) is an n-dimensional subspace of L,[a, b] m φ_1~(s), φ_2~(s)…, φ_n~(s)exist (s≥0is an integer) and have a maximal linearly independent subset which is an extendedChebyshev system of order rs on [a,b], then write     

Elements of Small Orders in K_2FⅡ

In"Elements of small orders in K_2(F)"(Algebraic K-Theory,Lecture Notes in Math.,966,1982,1-6.),the author investigates elements of the form {a,Φ_n(a)} in the Milnor group K_2F of a field F,whereΦ_n(x)is the n-th cyclotomic polynomial.In this paper,these elements are generalized.Applying the explicit formulas of Rosset and Tate for the transfer homomorphism for K_2,the author proves some new results on elements of small orders in K_2F.     

Hermitian generalization of the Rarita-Schwinger operators

We introduce two new linear differential operators which are invariant with respect to the unitary group SU（n）. They constitute analogues of the twistor and the Rarita-Schwinger operator in the orthogonal case. The natural setting for doing this is Hermitian Clifford Analysis. Such operators are constructed by twisting the two versions of the Hermitian Dirac operator 6z_ and 6z_ and then projecting on irreducible modules for the unitary group. We then study some properties of their spaces of nullsolutions and we find a formulation of the Hermitian Rarita-Schwinger operators in terms of Hermitian monogenic polynomials.     

本刊英文版Vol.26(2010),No.3论文摘要(英文)

<正>A Decomposition Theorem for G-GroupsⅠ.LIZASOAIN Some classical results about linear representations of a finite group G have been also proved for representations of G on non-abelian groups(G-groups).In this paper we establish a decomposition theorem for irreducible G-groups which expresses a suitable irreducible G-group as a tensor product of two projective G-groups in a similar way to the celebrated theorem of Clifford for linear representations.Moreover,we study the non-abelian minimal normal subgroups of G in which this decomposition is possible.     

Г-CONVERGENCE OF INTEGRAL FUNCTIONALS DEPENDING ON VECTOR-VALUED FUNCTIONS OVER PARABOLIC DOMAINS

This paper studies Г-convergence for a sequence of parabolic functionals, F^e(u)=∫0^T∫f(x/e,t.Δ↓u) dxdt as ε→0, where the integrand f is nonconvex, and periodic on the first variable. The author obtains the representation formula of the Г-limit. The results in this paper support a conclusion which relates Г-convergence of parabolic functionals to the associated gradient flows and confirms one of De Giorgi‘s conjectures partially.     

Noetherian Skew Group Rings of F.C Groups

Let R *θG be the skew group ring with a F.C group G and the group homom-rphismθfrom G to Aut(R), the group of automorphisms of the ring R. In this paper,the necessary and sufficient condition such that R*θG will be Noetherian is given, which generalizes the results of I.G. connel.