Anisotropic inverse harmonic mean curvature flow

We study the evolution of convex hypersurfaces H（., t） with initial H（., 0） = 0H0 at a rate equal to H - f along its outer normal, where H is the inverse of harmonic mean curvature of H（., t）, H0 is a smooth, closed, and uniformly convex hypersurface. We find a θ^＊ 〉 0 and a sufficient condition about the anisotropic function f, such that if θ 〉 θ^＊, then H（.,t） remains uniformly convex and expands to infinity as t →∞ and its scaling, H（-, t）e^-nt, converges to a sphere. In addition, the convergence result is generalized to the fully nonlinear case in which the evolution rate is log H - log f instead of H - f.     

On minimal non- -groups

A finite group G is called an J N J-group if every proper subgroup H of G is either subnormal in G or self-normalizing. We determinate the structure of non-J N J-groups in which all proper subgroups are J N J- groups.     

Wavelet transform and radon transform on the quaternion Heisenberg group

Let Q be the quaternion Heisenberg group,and let P be the affine automorphism group of Q.We develop the theory of continuous wavelet transform on the quaternion Heisenberg group via the unitary representations of P on L2(Q).A class of radial wavelets is constructed.The inverse wavelet transform is simplified by using radial wavelets.Then we investigate the Radon transform on Q.A Semyanistyi–Lizorkin space is introduced,on which the Radon transform is a bijection.We deal with the Radon transform on Q both by the Euclidean Fourier transform and the group Fourier transform.These two treatments are essentially equivalent.We also give an inversion formula by using wavelets,which does not require the smoothness of functions if the wavelet is smooth.In addition,we obtain an inversion formula of the Radon transform associated with the sub-Laplacian on Q.     

Characterization of compact quantum group

Given a C^＊-algebra A and a comultiplication Ф on A, we show that the pair （A, Ф） is a compact quantum group if and only if the associated multiplier Hopf ^＊-algebra （A, ФA） is a compact Hopf ^＊-algebra.     

Topological spaces compact with respect to a set of filters

If is a family of filters over some set I, a topological space X is sequencewise -compact if for every I-indexed sequence of elements of X there is such that the sequence has an F-limit point. Countable compactness, sequential compactness, initial κ-compactness, [λ; µ]-compactness, the Menger and Rothberger properties can all be expressed in terms of sequencewise -compactness for appropriate choices of . We show that sequencewise -compactness is preserved under taking products if and only if there is a filter such that sequencewise -compactness is equivalent to F-compactness. If this is the case, and there exists a sequencewise -compact T ₁ topological space with more than one point, then F is necessarily an ultrafilter. The particular case of sequential compactness is analyzed in detail.     

Some remarks on projective generators and injective cogenerators

In this paper,we give a relationship between projective generators(resp.,injective cogenerators) in the category of R-modules and the counterparts in the category of complexes of R-modules.As a consequence,we get that complexes of W-Gorenstein modules are actually W-Gorenstein complexes whenever W is a subcategory of R-modules satisfying W⊥W,where W is the subcategory of exact complexes with all cycles in W.We also study when all cycles of a W-Gorenstein complexes are W-Gorenstein modules.     

Variations on ω-boundedness

Let be a property (or, equivalently, a class) of topological spaces. A space X is called -bounded if every subspace of X with (or in) has compact closure. Thus, countable-bounded has been known as ω-bounded and (σ-compact)-bounded as strongly ω-bounded. In this paper we present a systematic study of the interrelations of these two known “boundedness” concepts with -boundedness where is one of the further countability properties weakly Lindelöf, Lindelöf, hereditarily Lindelöf, and ccc.     

On the class of groups with pronormal hall π-subgroups

Given a set π of prime numbers, we define the class of all finite groups in which Hall π-subgroups exist and are pronormal by analogy with the Hall classes , , and . We study whether is closed under the main class-theoretic closure operations. In particular, we establish that is a saturated formation.     

Hausdorff dimensions of the Julia sets of reluctantly recurrent rational maps

In this paper, we consider a rational map f of degree at least two acting on Riemman sphere that is expanding away from critical points. Assuming that all critical points of f in the Julia set J(f) are reluctantly recurrent, we prove that the Hausdorff dimension of the Julia set J(f) is equal to the hyperbolic dimension, and the Lebesgue measure of Julia set is zero when the Julia set J(f) ≠ .     

Double Hilbert transform on

We introduce a space , where is the testing function space whose functions are infinitely differentiable and have bounded support, and is the space the double Hilbert transform acting on the testing function space. We prove that the double Hilbert transform is a homeomorphism from onto itself.     

Upper estimates for the approximation numbers of the generalized Laplace transform

A Laplace-transform-type operator acting in the Lebesgue spaces of real functions on the half-axis is considered. Sufficient conditions under which belongs to some Schattentype classes are found. Upper asymptotic estimates for the approximation numbers of are obtained.     

Commuting variety of Witt algebra

Let \(\mathfrak{g} = W_1 \) be the Witt algebra over an algebraically closed field k of characteristic p > 3; and let Open image in new window be the commuting variety of g. In contrast with the case of classical Lie algebras of P. Levy [J. Algebra, 2002, 250: 473–484], we show that the variety Open image in new window is reducible, and not equidimensional. Irreducible components of Open image in new window and their dimensions are precisely given. As a consequence, the variety Open image in new window is not normal.     

The s-Riesz transform of an s-dimensional measure in ℝ2 is unbounded for 1 < s < 2

In this paper, we prove that for s ∈ (1, 2) there exists no totally lower irregular finite positive Borel measure µ in ?² with such that ${\left\| {R\mu } \right\|_{{L^\infty }({m_2})}} < + \infty $ , where Rµ = µ*x/|x| ^s+1 and m ₂ is the Lebesgue measure in ?². Combined with known results of Prat and Vihtilä, this shows that for any s ∈ (0, 1) ∪ (1, 2) and any finite positive Borel measure in ?² with , we have ${\left\| {R\mu } \right\|_{{L^\infty }({m_2})}} = \infty $ .     

Compact differences of composition operators on weighted Dirichlet spaces

Here we consider when the difference of two composition operators is compact on the weighted Dirichlet spaces . Specifically we study differences of composition operators on the Dirichlet space and S ², the space of analytic functions whose first derivative is in H ², and then use Calderón’s complex interpolation to extend the results to the general weighted Dirichlet spaces. As a corollary we consider composition operators induced by linear fractional self-maps of the disk.     

On the isomorphic mapping of weighted spaces by an elliptic operator with degeneration on the domain boundary

We consider the first boundary value problem for a second-order elliptic equation with degeneration on the entire twice continuously differentiable boundary of a two-dimensional domain Ω; this problem has a generalized solution in the weighted space . We find conditions ensuring that the generalized solution belongs to the narrower space , which permits obtaining estimates for the convergence rate of an approximate finite-element solution to the exact solution in the norms of the spaces and L ₂(Ω).     

BGP-reflection functors and Lusztig’s symmetries of modified quantized enveloping algebras

Let U be a quantized enveloping algebra and  its modified form.Lusztig gives some symmetries on U and.In view of the realization of U by the reduced Drinfeld double of the Ringel-Hall algebra,one can apply the BGP-reflection functors to the double Ringel-Hall algebra to obtain Lusztig's symmetries on U and their important properties,for instance,the braid relations.In this paper,we define a modified form ■ of the Ringel-Hall algebra and realize the Lusztig's symmetries on  by applying the BGP-reflection functors to ■.     

Minimal graphs in over unbounded domains

We study the existence of minimal graphs in with prescribed boundary data, possibly infinite. We give necessary and sufficient conditions on the “lengths” of the sides of the inscribed polygons in an unbounded domain in ?², that yield solutions to the minimal surface equation with prescribed boundary data.     

Two Parameter Asymptotic Spectra

The two parameter eigenvalue problem in Hilbert space is discussed for selfadjoint operators T. with discrete spectrum and bounded symmetric V_jk satisfying “uniform right definiteness”. Then there are countably many eigenvalues in ?². Results are given relating the set of limit points of ) to a set defined entirely by the V_jk.