Expand all Collapse all | Results 1 - 25 of 46 |
1. CMB Online first
Essential Commutants of Semicrossed Products Let $\alpha\colon G\curvearrowright M$ be a spatial action of countable
abelian group on a "spatial" von Neumann algebra $M$ and $S$ be its
unital subsemigroup with $G=S^{-1}S$. We explicitly compute the
essential commutant and the essential fixed-points, modulo the
Schatten $p$-class or the compact operators, of the w$^*$-semicrossed
product of $M$ by $S$ when $M'$ contains no non-zero compact
operators. We also prove a weaker result when $M$ is a von Neumann
algebra on a finite dimensional Hilbert space and
$(G,S)=(\mathbb{Z},\mathbb{Z}_+)$, which extends a famous result due
to Davidson (1977) for the classical analytic Toeplitz operators.
Keywords:essential commutant, semicrossed product Categories:47L65, 47A55 |
2. CMB 2014 (vol 57 pp. 264)
On Semisimple Hopf Algebras of Dimension $pq^n$ Let $p,q$ be prime numbers with $p^2\lt q$, $n\in \mathbb{N}$, and $H$ a
semisimple Hopf algebra of dimension $pq^n$ over an algebraically
closed field of characteristic $0$. This paper proves that $H$ must
possess one of the following structures: (1) $H$ is semisolvable;
(2) $H$ is a Radford biproduct $R\# kG$, where $kG$ is the group
algebra of group $G$ of order $p$, and $R$ is a semisimple Yetter--Drinfeld
Hopf algebra in ${}^{kG}_{kG}\mathcal{YD}$ of dimension $q^n$.
Keywords:semisimple Hopf algebra, semisolvability, Radford biproduct, Drinfeld double Category:16W30 |
3. CMB 2013 (vol 57 pp. 375)
A Problem on Edge-magic Labelings of Cycles Kotzig and Rosa defined in 1970 the concept of edge-magic labelings as
follows: let $G$ be a simple $(p,q)$-graph (that is, a graph of order $p$
and size $q$ without loops or multiple edges). A bijective function $f:V(G)\cup
E(G)\rightarrow \{1,2,\ldots,p+q\}$ is an edge-magic labeling of $G$ if
$f(u)+f(uv)+f(v)=k$, for all $uv\in E(G)$. A graph that admits an edge-magic
labeling is called an edge-magic graph, and $k$ is called the magic sum
of the labeling. An old conjecture of Godbold and Slater sets that all
possible theoretical magic sums are attained for each cycle of order $n\ge
7$. Motivated by this conjecture, we prove that for all $n_0\in \mathbb{N}$,
there exists $n\in \mathbb{N}$, such that the cycle $C_n$ admits at least
$n_0$ edge-magic labelings with at least $n_0$ mutually distinct magic
sums. We do this by providing a lower bound for the number of magic sums
of the cycle $C_n$, depending on the sum of the exponents of the odd primes
appearing in the prime factorization of $n$.
Keywords:edge-magic, valence, $\otimes_h$-product Category:05C78 |
4. CMB 2013 (vol 57 pp. 245)
Assouad-Nagata Dimension of Wreath Products of Groups Consider the wreath product $H\wr G$, where $H\ne 1$ is finite and $G$ is finitely generated.
We show that the Assouad-Nagata dimension $\dim_{AN}(H\wr G)$ of $H\wr G$
depends on the growth of $G$ as follows:
\par If the growth of $G$ is not bounded by a linear function, then $\dim_{AN}(H\wr G)=\infty$,
otherwise $\dim_{AN}(H\wr G)=\dim_{AN}(G)\leq 1$.
Keywords:Assouad-Nagata dimension, asymptotic dimension, wreath product, growth of groups Categories:54F45, 55M10, 54C65 |
5. CMB 2013 (vol 57 pp. 821)
Real Hypersurfaces in Complex Two-Plane Grassmannians with Reeb Parallel Structure Jacobi Operator In this paper we give a characterization of a real hypersurface of
Type~$(A)$ in complex two-plane Grassmannians ${ { {G_2({\mathbb
C}^{m+2})} } }$, which means a
tube over a totally geodesic $G_{2}(\mathbb C^{m+1})$ in
${G_2({\mathbb C}^{m+2})}$, by
the Reeb parallel structure Jacobi operator ${\nabla}_{\xi}R_{\xi}=0$.
Keywords:real hypersurfaces, complex two-plane Grassmannians, Hopf hypersurface, Reeb parallel, structure Jacobi operator Categories:53C40, 53C15 |
6. CMB 2013 (vol 57 pp. 401)
Curvature of $K$-contact Semi-Riemannian Manifolds In this paper we characterize $K$-contact semi-Riemannian manifolds
and Sasakian semi-Riemannian manifolds in terms of
curvature. Moreover, we show that any conformally flat $K$-contact
semi-Riemannian manifold is Sasakian and of constant sectional
curvature $\kappa=\varepsilon$, where $\varepsilon =\pm 1$ denotes
the causal character of the Reeb vector field. Finally, we give some
results about the curvature of a $K$-contact Lorentzian manifold.
Keywords:contact semi-Riemannian structures, $K$-contact structures, conformally flat manifolds, Einstein Lorentzian-Sasaki manifolds Categories:53C50, 53C25, 53B30 |
7. CMB 2013 (vol 57 pp. 598)
Interpolation of Morrey Spaces on Metric Measure Spaces In this article, via the classical complex interpolation method
and some interpolation methods traced to Gagliardo,
the authors obtain an interpolation theorem for
Morrey spaces on quasi-metric measure spaces, which generalizes
some known results on ${\mathbb R}^n$.
Keywords:complex interpolation, Morrey space, Gagliardo interpolation, CalderÃ³n product, quasi-metric measure space Categories:46B70, 46E30 |
8. CMB 2012 (vol 57 pp. 326)
On Zero-divisors in Group Rings of Groups with Torsion Nontrivial pairs of zero-divisors in group rings are
introduced and discussed. A problem on the existence of nontrivial
pairs of zero-divisors in group rings of free Burnside groups of odd
exponent $n \gg 1$ is solved in the affirmative. Nontrivial pairs of
zero-divisors are also found in group rings of free products of groups
with torsion.
Keywords:Burnside groups, free products of groups, group rings, zero-divisors Categories:20C07, 20E06, 20F05, , 20F50 |
9. CMB 2012 (vol 57 pp. 97)
Rationality and the Jordan-Gatti-Viniberghi decomposition We verify
our earlier conjecture
and use it to prove that the
semisimple parts of the rational Jordan-Kac-Vinberg decompositions of
a rational vector all lie in a single rational orbit.
Keywords:reductive group, $G$-module, Jordan decomposition, orbit closure, rationality Categories:20G15, 14L24 |
10. CMB 2012 (vol 57 pp. 80)
Semicrossed Products of the Disk Algebra and the Jacobson Radical We consider semicrossed products of the disk algebra with respect to
endomorphisms defined by finite Blaschke products. We characterize the Jacobson radical
of these operator algebras. Furthermore, in the case the finite Blaschke product is elliptic,
we show that the semicrossed product contains no nonzero quasinilpotent
elements. However, if the finite Blaschke product is hyperbolic or parabolic with positive hyperbolic step,
the Jacobson radical is nonzero and a proper subset of the set of quasinilpotent elements.
Keywords:semicrossed product, disk algebra, Jacobson radical Categories:47L65, 47L20, 30J10, 30H50 |
11. CMB 2012 (vol 56 pp. 647)
On Induced Representations Distinguished by Orthogonal Groups Let $F$ be a local non-archimedean field of characteristic zero. We
prove that a representation of $GL(n,F)$ obtained from irreducible
parabolic induction of supercuspidal representations is distinguished
by an orthogonal group only if the inducing data is distinguished by
appropriate orthogonal groups. As a corollary, we get that an
irreducible representation induced from supercuspidals that is
distinguished by an orthogonal group is metic.
Keywords:distinguished representation, parabolic induction Category:22E50 |
12. CMB 2012 (vol 56 pp. 870)
Note on Kasparov Product of $C^*$-algebra Extensions Using the Dadarlat isomorphism, we give a characterization for the
Kasparov product of $C^*$-algebra extensions. A certain relation
between $KK(A, \mathcal q(B))$ and $KK(A, \mathcal q(\mathcal k B))$ is also considered when
$B$ is not stable and it is proved that $KK(A, \mathcal q(B))$ and
$KK(A, \mathcal q(\mathcal k B))$ are not isomorphic in general.
Keywords:extension, Kasparov product, $KK$-group Category:46L80 |
13. CMB 2011 (vol 56 pp. 306)
Real Hypersurfaces in Complex Projective Space Whose Structure Jacobi Operator is Lie $\mathbb{D}$-parallel |
Real Hypersurfaces in Complex Projective Space Whose Structure Jacobi Operator is Lie $\mathbb{D}$-parallel We prove the non-existence of real hypersurfaces in complex projective
space whose structure Jacobi operator is Lie $\mathbb{D}$-parallel and
satisfies a further condition.
Keywords:complex projective space, real hypersurface, structure Jacobi operator Categories:53C15, 53C40 |
14. CMB 2011 (vol 55 pp. 783)
Products and Direct Sums in Locally Convex Cones In this paper we define lower, upper, and symmetric completeness and
discuss closure of the sets in product and direct sums. In particular,
we introduce suitable bases for these topologies, which leads us to
investigate completeness of the direct sum and its components. Some
results obtained about $X$-topologies and polars of the neighborhoods.
Keywords:product and direct sum, duality, locally convex cone Categories:20K25, 46A30, 46A20 |
15. CMB 2011 (vol 56 pp. 203)
Productively LindelÃ¶f Spaces May All Be $D$ We give easy proofs that (a) the Continuum Hypothesis implies that if
the product of $X$ with every LindelÃ¶f space is LindelÃ¶f, then $X$ is
a $D$-space, and (b) Borel's Conjecture implies every Rothberger space
is Hurewicz.
Keywords:productively LindelÃ¶f, $D$-space, projectively $\sigma$-compact, Menger, Hurewicz Categories:54D20, 54B10, 54D55, 54A20, 03F50 |
16. CMB 2011 (vol 56 pp. 136)
On Constructing Ergodic Hyperfinite Equivalence Relations of Non-Product Type Product type equivalence relations are hyperfinite measured
equivalence relations, which, up to orbit equivalence, are generated
by product type odometer actions. We give a concrete example of a
hyperfinite equivalence relation of non-product type, which is the
tail equivalence on a Bratteli diagram.
In order to show that the equivalence relation constructed is not of
product type we will use a criterion called property A. This
property, introduced by Krieger for non-singular transformations, is
defined directly for hyperfinite equivalence relations in this paper.
Keywords:property A, hyperfinite equivalence relation, non-product type Categories:37A20, 37A35, 46L10 |
17. CMB 2011 (vol 55 pp. 586)
On Sha's Secondary Chern-Euler Class For a manifold with boundary, the restriction of Chern's transgression
form of the Euler curvature form over the boundary is closed. Its
cohomology class is called the secondary Chern-Euler class and was
used by Sha to formulate a relative PoincarÃ©-Hopf theorem under the
condition that the metric on the manifold is locally product near the
boundary. We show that the secondary Chern-Euler form is exact away
from the outward and inward unit normal vectors of the boundary by
explicitly constructing a transgression form. Using Stokes' theorem,
this evaluates the boundary term in Sha's relative PoincarÃ©-Hopf
theorem in terms of more classical indices of the tangential
projection of a vector field. This evaluation in particular shows
that Sha's relative PoincarÃ©-Hopf theorem is equivalent to the more
classical law of vector fields.
Keywords:transgression, secondary Chern-Euler class, locally product metric, law of vector fields Categories:57R20, 57R25 |
18. CMB 2011 (vol 54 pp. 456)
On Operator Sum and Product Adjoints and Closures We comment on domain conditions that regulate when the adjoint of the
sum or product of two unbounded operators is the sum or product of their
adjoints, and related closure issues. The quantum mechanical problem PHP
essentially selfadjoint for unbounded Hamiltonians is addressed, with new
results.
Keywords:unbounded operators, adjoints of sums and products, quantum mechanics Category:47A05 |
19. CMB 2011 (vol 54 pp. 506)
On the Canonical Solution of the Sturm-Liouville Problem with Singularity and Turning Point of Even Order |
On the Canonical Solution of the Sturm-Liouville Problem with Singularity and Turning Point of Even Order In this paper, we are going to investigate the canonical property of solutions of
systems of differential equations having a singularity and turning
point of even order. First, by a replacement, we transform the system
to the Sturm-Liouville equation with turning point. Using of the
asymptotic estimates provided by Eberhard, Freiling, and Schneider
for a special fundamental system of solutions of the Sturm-Liouville
equation, we study the infinite product representation of solutions of the systems. Then we
transform the Sturm-Liouville equation with
turning point to the
equation with singularity, then we study the asymptotic behavior of its solutions. Such
representations are relevant to the inverse spectral problem.
Keywords:turning point, singularity, Sturm-Liouville, infinite products, Hadamard's theorem, eigenvalues Categories:34B05, 34Lxx, 47E05 |
20. CMB 2011 (vol 55 pp. 67)
An $E_8$ Correspondence for Multiplicative Eta-Products We describe an $E_8$ correspondence for the multiplicative
eta-products of weight at least $4$.
Keywords:We describe an E_{8} correspondence for the multiplicative eta-products of weight at leastÂ 4. Categories:11F20, 11F12, 17B60 |
21. CMB 2011 (vol 54 pp. 498)
On the Adjoint and the Closure of the Sum of Two Unbounded Operators We prove, under some conditions on the domains, that the adjoint of
the sum of two unbounded operators is the sum of their adjoints in
both Hilbert and Banach space settings. A similar result about the
closure of operators is also proved. Some interesting consequences
and examples "spice up" the paper.
Keywords:unbounded operators, sum and products of operators, Hilbert and Banach adjoints, self-adjoint operators, closed operators, closure of operators Category:47A05 |
22. CMB 2011 (vol 54 pp. 422)
Two Conditions on the Structure Jacobi Operator for Real Hypersurfaces in Complex Projective Space We classify real hypersurfaces in complex projective space whose
structure Jacobi operator satisfies two conditions at the same time.
Keywords:complex projective space, real hypersurface, structure Jacobi operator, two conditions Categories:53C15, 53B25 |
23. CMB 2011 (vol 54 pp. 472)
A Semiregularity Map Annihilating Obstructions to Deforming Holomorphic Maps We study infinitesimal deformations of holomorphic maps of
compact, complex, KÃ¤hler manifolds. In particular, we describe a
generalization of Bloch's semiregularity map that annihilates
obstructions to deform holomorphic maps with fixed codomain.
Keywords:semiregularity map, obstruction theory, functors of Artin rings, differential graded Lie algebras Categories:13D10, 14D15, 14B10 |
24. CMB 2011 (vol 54 pp. 283)
Surgery on $\widetilde{\mathbb{SL}} \times \mathbb{E}^n$-Manifolds We show that closed $\widetilde{\mathbb{SL}} \times \mathbb{E}^n$-manifolds
are topologically rigid if $n\geq 2$, and are rigid up to
$s$-cobordism, if $n=1$.
Keywords:topological rigidity, geometric structure, surgery groups Categories:57R67, 57N16 |
25. CMB 2010 (vol 54 pp. 141)
Linear Maps on $C^*$-Algebras Preserving the Set of Operators that are Invertible in $\mathcal{A}/\mathcal{I}$ |
Linear Maps on $C^*$-Algebras Preserving the Set of Operators that are Invertible in $\mathcal{A}/\mathcal{I}$
For $C^*$-algebras $\mathcal{A}$ of real rank zero, we describe
linear maps $\phi$ on $\mathcal{A}$ that are surjective up to ideals
$\mathcal{I}$, and $\pi(A)$ is invertible in $\mathcal{A}/\mathcal{I}$ if and only if
$\pi(\phi(A))$ is invertible in $\mathcal{A}/\mathcal{I}$, where $A\in\mathcal{A}$ and
$\pi:\mathcal{A}\to\mathcal{A}/\mathcal{I}$ is the quotient map. We also consider similar
linear maps preserving zero products on the Calkin algebra.
Keywords:preservers, Jordan automorphisms, invertible operators, zero products Categories:47B48, 47A10, 46H10 |