Osaka Journal of Mathematics Articles (Project Euclid)
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The latest articles from Osaka Journal of Mathematics on Project Euclid, a site for mathematics and statistics resources.en-usCopyright 2010 Cornell University LibraryEuclid-L@cornell.edu (Project Euclid Team)Thu, 05 Aug 2010 15:41 EDTTue, 22 Mar 2011 10:05 EDThttp://projecteuclid.org/collection/euclid/images/logo_linking_100.gifProject Euclid
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Quotients of bounded homogeneous domains by cyclic groups
http://projecteuclid.org/euclid.ojm/1277298908
<strong>Christian Miebach</strong><p><strong>Source: </strong>Osaka J. Math., Volume 47, Number 2, 331--352.</p><p><strong>Abstract:</strong><br/>
Let $D$ be a bounded homogeneous domain in $\mathbb{C}^{n}$
and let $\varphi$ be an automorphism of $D$ which generates
a discrete subgroup $\Gamma$ of $\Aut_{\mathcal{O}}(D)$. It
is shown that the complex space $D/\Gamma$ is Stein.
</p>projecteuclid.org/euclid.ojm/1277298908_Thu, 05 Aug 2010 15:41 EDTThu, 05 Aug 2010 15:41 EDTMorphism complexes of sets with relationshttp://projecteuclid.org/euclid.ojm/1455892633<strong>Takahiro Matsushita</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 1, 267--285.</p><p><strong>Abstract:</strong><br/>
Let $r$ be a positive integer. An $r$-set is a pair $X= (V(X),
R(X))$ consisting of a set $V(X)$ with a subset $R(X)$ of
the direct product $V(X)^{r}$. The object of this paper is
to investigate the Hom complexes of $r$-sets, which were introduced
for graphs in the context of the graph coloring problem.
In the first part, we introduce simplicial sets which we call
singular complexes, and show that singular complexes and Hom
complexes are naturally homotopy equivalent. The second part
is devoted to the generalization of $\times$-homotopy theory
established by Dochtermann. We show the folding theorem for
hypergraphs which was partly proved by Iriye and Kishimoto.
</p>projecteuclid.org/euclid.ojm/1455892633_20160219093715Fri, 19 Feb 2016 09:37 ESTErratum to the article ``Beurling's theorem for nilpotent Lie groups'' Osaka J. Math. 48 (2011), 127--147http://projecteuclid.org/euclid.ojm/1455892634<strong>Kais Smaoui</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 1, 285--289.</p>projecteuclid.org/euclid.ojm/1455892634_20160219093715Fri, 19 Feb 2016 09:37 ESTErratum to the article ``Zero mean curvature surfaces in Lorentz--Minkowki 3-space which change type across a light-like line'' Osaka J. math. 52 (2015), 285--297http://projecteuclid.org/euclid.ojm/1455892635<strong>S. Fujimori</strong>, <strong>Y.W. Kim</strong>, <strong>S.-E. Koh</strong>, <strong>W. Rossman</strong>, <strong>H. Shin</strong>, <strong>M. Umehara</strong>, <strong>K. Yamada</strong>, <strong>S.-D. Yang</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 1, 289--293.</p>projecteuclid.org/euclid.ojm/1455892635_20160219093715Fri, 19 Feb 2016 09:37 ESTA model of the Borel construction on the free loopspacehttp://projecteuclid.org/euclid.ojm/1461781788<strong>Jan Spaliński</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 293--309.</p><p><strong>Abstract:</strong><br/>
Let $X$ be a CW-complex with basepoint. We obtain a simple
description of the Borel construction on the free loopspace
of the suspension of $X$ as a wedge of the classifying space
of the circle and the homotopy colimit of a diagram consisting
of products of a number of copies of $X$ and the standard topological
$n$-simplex. This is obtained by filtering the cyclic bar
construction on the James model of the based loopspace by word
length in order to express the homotopy type of the free loopspace
as a colimit of powers of $X$ and standard cyclic sets. It
is shown that this colimit is in fact a homotopy colimit and
commutativity of homotopy colimits is used to describe the
Borel construction.
</p>projecteuclid.org/euclid.ojm/1461781788_20160427142958Wed, 27 Apr 2016 14:29 EDTInertia groups and smooth structures of ($n-1$)-connected $2n$-manifoldshttp://projecteuclid.org/euclid.ojm/1461781789<strong>Kasilingam Ramesh</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 309--321.</p><p><strong>Abstract:</strong><br/>
Let $M^{2n}$ denote a closed ($n-1$)-connected smoothable
topological $2n$-manifold. We show that the group $\mathcal{C}(M^{2n})$
of concordance classes of smoothings of $M^{2n}$ is isomorphic
to the group of smooth homotopy spheres $\bar{\Theta}_{2n}$
for $n=4$ or $5$, the concordance inertia group $I_{c}(M^{2n})=0$
for $n=3$, $4$, $5$ or $11$ and the homotopy inertia group
$I_{h}(M^{2n})=0$ for $n=4$. On the way, following Wall's approach
[16] we present a new proof of the main result in [9], namely,
for $n=4$, $8$ and $H^{n}(M^{2n};\mathbb{Z})\cong \mathbb{Z}$,
the inertia group $I(M^{2n})\cong \mathbb{Z}_{2}$. We also
show that, up to orientation-preserving diffeomorphism, $M^{8}$
has at most two distinct smooth structures; $M^{10}$ has exactly
six distinct smooth structures and then show that if $M^{14}$
is a $\pi$-manifold, $M^{14}$ has exactly two distinct smooth
structures.
</p>projecteuclid.org/euclid.ojm/1461781789_20160427142958Wed, 27 Apr 2016 14:29 EDTOn some properties of Galois groups of unramified extensionshttp://projecteuclid.org/euclid.ojm/1461781790<strong>Mamoru Asada</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 321--331.</p><p><strong>Abstract:</strong><br/>
Let $k$ be an algebraic number field of finite degree and
$k_{\infty}$ be the maximal cyclotomic extension of $k$. Let
$\tilde{L}_{k}$ and $L_{k}$ be the maximal unramified Galois
extension and the maximal unramified abelian extension of $k_{\infty}$
respectively. We shall give some remarks on the Galois groups
$\mathrm{Gal}(\tilde{L}_{k}/k_{\infty})$, $\mathrm{Gal}(L_{k}/k_{\infty})$
and $\mathrm{Gal}(\tilde{L}_{k}/k)$. One of the remarks is concerned
with non-solvable quotients of $\mathrm{Gal}(\tilde{L}_{k}/k_{\infty})$
when $k$ is the rationals, which strengthens our previous result.
</p>projecteuclid.org/euclid.ojm/1461781790_20160427142958Wed, 27 Apr 2016 14:29 EDTMountain pass theorem with infinite discrete symmetryhttp://projecteuclid.org/euclid.ojm/1461781791<strong>Noé Bárcenas</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 331--351.</p><p><strong>Abstract:</strong><br/>
We extend an equivariant mountain pass theorem, due to Bartsch,
Clapp and Puppe for compact Lie groups to the setting of infinite
discrete groups satisfying a maximality condition on their
finite subgroups.
</p>projecteuclid.org/euclid.ojm/1461781791_20160427142958Wed, 27 Apr 2016 14:29 EDTOn genera of Lefschetz fibrations and finitely presented groupshttp://projecteuclid.org/euclid.ojm/1461781792<strong>Ryoma Kobayashi</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 351--377.</p><p><strong>Abstract:</strong><br/>
It is known that every finitely presented
group is the fundamental group of the total space of a Lefschetz
fibration. In this paper, we give another proof which improves
the result of Korkmaz. In addition, Korkmaz defined the genus
of a finitely presented group. We also evaluate upper bounds
for genera of some finitely presented groups.
</p>projecteuclid.org/euclid.ojm/1461781792_20160427142958Wed, 27 Apr 2016 14:29 EDTBuchstaber invariant, minimal non-simplices and relatedhttp://projecteuclid.org/euclid.ojm/1461781793<strong>Anton Ayzenberg</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 377--397.</p><p><strong>Abstract:</strong><br/>
Buchstaber invariant is a numerical characteristic of a simplicial
complex (or a polytope), measuring the degree of freeness of
the torus action on the corresponding moment-angle complex.
Recently an interesting combinatorial theory emerged around
this invariant. In this paper we answer two questions, considered
as conjectures in [2], [11]. First, Buchstaber invariant of
a convex polytope $P$ equals $1$ if and only if $P$ is a pyramid.
Second, there exist two simplicial complexes with isomorphic
bigraded $\mathrm{Tor}$-algebras, which have different Buchstaber invariants.
In the proofs of both statements we essentially use the result
of N. Erokhovets, relating Buchstaber invariant of simplicial
complex $K$ to the distribution of minimal non-simplices of
$K$. Gale duality is used in the proof of the first statement.
Taylor resolution of a Stanley--Reisner ring is used for the
second.
</p>projecteuclid.org/euclid.ojm/1461781793_20160427142958Wed, 27 Apr 2016 14:29 EDTSummation formula inequalities for eigenvalues of the perturbed harmonic oscillatorhttp://projecteuclid.org/euclid.ojm/1461781794<strong>Pedro Freitas</strong>, <strong>James B. Kennedy</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 397--417.</p><p><strong>Abstract:</strong><br/>
We derive explicit inequalities for sums of eigenvalues of
one-dimensional Schrödinger operators on the whole line.
In the case of the perturbed harmonic oscillator, these bounds
converge to the corresponding trace formula in the limit as
the number of eigenvalues covers the whole spectrum.
</p>projecteuclid.org/euclid.ojm/1461781794_20160427142958Wed, 27 Apr 2016 14:29 EDTA logarithmically improved regularity criterion of smooth solutions for the 3D Boussinesq equationshttp://projecteuclid.org/euclid.ojm/1461781795<strong>Zhuan Ye</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 417--425.</p><p><strong>Abstract:</strong><br/>
In this note, we consider the three-dimensional (3D) incompressible
Boussinesq equations. We obtain the logarithmically improved
regularity criterion of smooth solutions in terms of the velocity
field. This result improves some previous works.
</p>projecteuclid.org/euclid.ojm/1461781795_20160427142958Wed, 27 Apr 2016 14:29 EDTAlmost relative injective moduleshttp://projecteuclid.org/euclid.ojm/1461781796<strong>Surjeet Singh</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 425--439.</p><p><strong>Abstract:</strong><br/>
The concept of a module $M$ being
almost $N$-injective, where $N$ is some module, was introduced
by Baba (1989). For a given module $M$, the class of modules
$N$, for which $M$ is almost $N$-injective, is not closed under
direct sums. Baba gave a necessary and sufficient condition
under which a uniform, finite length module $U$ is almost $V$-injective,
where $V$ is a finite direct sum of uniform, finite length
modules, in terms of extending properties of simple submodules
of $V$. Let $M$ be a uniform module and $V$ be a finite direct
sum of indecomposable modules. Some conditions under which
$M$ is almost $V$-injective are determined, thereby Baba's
result is generalized. A module $M$ that is almost $M$-injective
is called an almost self-injective module. Commutative indecomposable
rings and von Neumann regular rings that are almost self-injective
are studied. It is proved that any minimal right ideal of a
von Neumann regular, almost right self-injective ring, is injective.
This result is used to give an example of a von Neumann regular
ring that is not almost right self-injective.
</p>projecteuclid.org/euclid.ojm/1461781796_20160427142958Wed, 27 Apr 2016 14:29 EDTPrime component-preservingly amphicheiral link with odd minimal crossing numberhttp://projecteuclid.org/euclid.ojm/1461781797<strong>Teruhisa Kadokami</strong>, <strong>Yoji Kobatake</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 439--463.</p><p><strong>Abstract:</strong><br/>
For every odd integer $c\ge 21$, we raise an example of a
prime component-preservingly amphicheiral link with the minimal
crossing number $c$. The link has two components, and consists
of an unknot and a knot which is ($-$)-amphicheiral with odd
minimal crossing number. We call the latter knot a Stoimenow
knot . We also show that the Stoimenow knot is not invertible
by the Alexander polynomials.
</p>projecteuclid.org/euclid.ojm/1461781797_20160427142958Wed, 27 Apr 2016 14:29 EDTRepresentation type of finite quiver Hecke algebras of type $C^{(1)}_{l}$http://projecteuclid.org/euclid.ojm/1461781798<strong>Susumu Ariki</strong>, <strong>Euiyong Park</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 463--489.</p><p><strong>Abstract:</strong><br/>
We give a graded dimension formula described in terms of combinatorics
of Young diagrams and a simple criterion to determine the representation
type for the finite quiver Hecke algebras of type $C_{l}^{(1)}$.
</p>projecteuclid.org/euclid.ojm/1461781798_20160427142958Wed, 27 Apr 2016 14:29 EDTNonlinear elliptic equations with singular reactionhttp://projecteuclid.org/euclid.ojm/1461781799<strong>Nikolaos S. Papageorgiou</strong>, <strong>George Smyrlis</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 489--515.</p><p><strong>Abstract:</strong><br/>
We study a nonlinear elliptic equation with a singular term
and a continuous perturbation. We look for positive solutions.
We prove three multiplicity theorems producing at least two
positive solutions. The first multiplicity theorem concerns
equations driven by a nonhomogeneous in general differential
operator. Also, two of the theorems have a superlinear perturbation
(but without the Ambrosetti--Rabinowitz condition), while the
third has a sublinear perturbation. Our approach is variational
together with suitable truncation and comparison techniques.
</p>projecteuclid.org/euclid.ojm/1461781799_20160427142958Wed, 27 Apr 2016 14:29 EDTCotton tensor and conformal deformations of three-dimensional Ricci flowhttp://projecteuclid.org/euclid.ojm/1461781800<strong>Yoshihiro Umehara</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 515--535.</p><p><strong>Abstract:</strong><br/>
In this paper, we study the deformation of the three-dimensional
conformal structures by the Ricci flow. We drive the evolution
equation of the Cotton--York tensor and the $L^{1}$-norm of
it under the Ricci flow. In particular, we investigate the
behavior of the $L^{1}$-norm of the Cotton--York tensor under
the Ricci flow on three-dimensional simply-connected Riemannian
homogeneous spaces which admit compact quotients. For a non-homogeneous
case, we also investigate the behavior of the $L^{1}$-norm
for the product metric of the Rosenau solution for the Ricci
flow on $S^{2}$ and the standard metric of $S^{1}$.
</p>projecteuclid.org/euclid.ojm/1461781800_20160427142958Wed, 27 Apr 2016 14:29 EDTAbundance theorem for semi log canonical surfaces in positive characteristichttp://projecteuclid.org/euclid.ojm/1461781801<strong>Hiromu Tanaka</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 2, 535--567.</p><p><strong>Abstract:</strong><br/>
We prove the abundance theorem for semi log canonical surfaces
in positive characteristic.
</p>projecteuclid.org/euclid.ojm/1461781801_20160427142958Wed, 27 Apr 2016 14:29 EDTOn instability of global path properties of symmetric Dirichlet forms under Mosco-convergencehttp://projecteuclid.org/euclid.ojm/1470413979<strong>Kohei Suzuki</strong>, <strong>Toshihiro Uemura</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 567--590.</p><p><strong>Abstract:</strong><br/>
We give sufficient conditions for Mosco convergences for the
following three cases: symmetric locally uniformly elliptic
diffusions, symmetric Lévy processes, and symmetric
jump processes in terms of the $L^1(\mathbb{R}^{d};dx)$-local
convergence of the (elliptic) coefficients, the characteristic
exponents and the jump density functions, respectively. We
stress that the global path properties of the corresponding
Markov processes such as recurrence/transience, and conservativeness/explosion
are not preserved under Mosco convergences and we give several
examples where such situations indeed happen.
</p>projecteuclid.org/euclid.ojm/1470413979_20160805121946Fri, 05 Aug 2016 12:19 EDTFactorial $P$- and $Q$-Schur functions represent equivariant quantum Schubert classeshttp://projecteuclid.org/euclid.ojm/1470413980<strong>Takeshi Ikeda</strong>, <strong>Leonardo C. Mihalcea</strong>, <strong>Hiroshi Naruse</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 591--619.</p><p><strong>Abstract:</strong><br/>
We find presentations by generators and relations for the
equivariant quantum cohomology rings of the maximal isotropic
Grassmannians of types B, C and D, and we find polynomial representatives
for the Schubert classes in these rings. These representatives
are given in terms of the same Pfaffian formulas which appear
in the theory of factorial $P$- and $Q$-Schur functions. After
specializing to equivariant cohomology, we interpret the resulting
presentations and Pfaffian formulas in terms of Chern classes
of tautological bundles.
</p>projecteuclid.org/euclid.ojm/1470413980_20160805121946Fri, 05 Aug 2016 12:19 EDTSome remarks on the homogeneous Boltzmann equation with the fractional Laplacian termhttp://projecteuclid.org/euclid.ojm/1470413981<strong>Shota Sakamoto</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 621--636.</p><p><strong>Abstract:</strong><br/>
We study the homogeneous Boltzmann equation with the fractional
Laplacian term. Working on the Fourier side we solve the resulting
integral equation, and improve a previous result by Y.-K. Cho.
We replace the initial data space with a certain space $\mathcal{M}^{\alpha}$
introduced by Morimoto, Wang, and Yang. This space precisely
captures the Fourier image of probability measures with bounded
fractional moments, providing a more natural initial condition.
We show existence of a unique global solution, in addition
to the expected maximal growth estimates and stability estimates.
As a consequence we obtain a continuous density solution of
the original equation.
</p>projecteuclid.org/euclid.ojm/1470413981_20160805121946Fri, 05 Aug 2016 12:19 EDTRussell's hypersurface from a geometric point of viewhttp://projecteuclid.org/euclid.ojm/1470413982<strong>Isac Hedén</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 637--644.</p><p><strong>Abstract:</strong><br/>
The famous Russell hypersurface is a smooth complex affine
threefold which is diffeomorphic to a euclidean space but not
algebraically isomorphic to the three dimensional affine space.
This fact was first established by Makar-Limanov, using algebraic
minded techniques. In this article, we give an elementary argument
which adds a greater insight to the geometry behind the original
proof and which also may be applicable in other situations.
</p>projecteuclid.org/euclid.ojm/1470413982_20160805121946Fri, 05 Aug 2016 12:19 EDTE-polynomials of $\mathrm{SL}(2, \mathbb{C})$-character varieties of complex curves of genus $3$http://projecteuclid.org/euclid.ojm/1470413983<strong>Javier Martí nez</strong>, <strong>Vicente Muñoz</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 645--681.</p><p><strong>Abstract:</strong><br/>
We compute the E-polynomials of the moduli spaces of representations
of the fundamental group of a complex curve of genus $g=3$
into $\mathrm{SL}(2, \mathbb{C})$, and also of the moduli space of
twisted representations. The case of genus $g=1, 2$ has already
been done in [12]. We follow the geometric technique introduced
in [12], based on stratifying the space of representations,
and on the analysis of the behaviour of the E-polynomial under
fibrations.
</p>projecteuclid.org/euclid.ojm/1470413983_20160805121946Fri, 05 Aug 2016 12:19 EDTCompact homogeneous locally conformally Kähler manifoldshttp://projecteuclid.org/euclid.ojm/1470413984<strong>Keizo Hasegawa</strong>, <strong>Yoshinobu Kamishima</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 683--703.</p><p><strong>Abstract:</strong><br/>
In this paper we show as main results two structure theorems
of a compact homogeneous locally conformally Kähler
(or shortly l.c.K.) manifold, a holomorphic structure theorem
asserting that it has a structure of holomorphic principal
fiber bundle over a flag manifold with fiber a $1$-dimensional
complex torus, and a metric structure theorem asserting that
it is necessarily of Vaisman type. We also discuss and determine
l.c.K. reductive Lie groups and compact locally homogeneous
l.c.K. manifolds of reductive Lie groups.
</p>projecteuclid.org/euclid.ojm/1470413984_20160805121946Fri, 05 Aug 2016 12:19 EDTRight-angled Artin groups and finite subgraphs of curve graphshttp://projecteuclid.org/euclid.ojm/1470413985<strong>Sang-Hyun Kim</strong>, <strong>Thomas Koberda</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 705--716.</p><p><strong>Abstract:</strong><br/>
We show that for a sufficiently simple surface $S$, if a right-angled
Artin group $A(\Gamma)$ embeds into $\mathrm{Mod}(S)$ then
$\Gamma$ embeds into the curve graph $\mathcal{C}(S)$ as an
induced subgraph. When $S$ is sufficiently complicated, there
exists an embedding $A(\Gamma) \to \mathrm{Mod}(S)$ such that
$\Gamma$ is not contained in $\mathcal{C}(S)$ as an induced
subgraph.
</p>projecteuclid.org/euclid.ojm/1470413985_20160805121946Fri, 05 Aug 2016 12:19 EDTA note on the exponential decay for the nonlinear Schrödinger equationhttp://projecteuclid.org/euclid.ojm/1470413986<strong>Fábio Natali</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 717--729.</p><p><strong>Abstract:</strong><br/>
We prove new results about exponential decay rates associated
with the two dimensional Schrödinger equation with critical
nonlinearity and localized damping. Our article improve incomplete
previous results established in [4].
</p>projecteuclid.org/euclid.ojm/1470413986_20160805121946Fri, 05 Aug 2016 12:19 EDTPartially ordered sets of non-trivial nilpotent $\pi$-subgroupshttp://projecteuclid.org/euclid.ojm/1470413987<strong>Nobuo Iiyori</strong>, <strong>Masato Sawabe</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 731--750.</p><p><strong>Abstract:</strong><br/>
In this paper, we introduce a subposet $\mathcal{L}_{\pi}(G)$
of a poset $\mathcal{N}_{\pi}(G)$ of all non-trivial nilpotent
$\pi$-subgroups of a finite group $G$. We examine basic properties
of subgroups in $\mathcal{L}_{\pi}(G)$ which contain the notion
of both radical $p$-subgroups and centric $p$-subgroups of
$G$. It is shown that $\mathcal{L}_{\pi}(G)$ is homotopy equivalent
to $\mathcal{N}_{\pi}(G)$. As examples, we investigate in detail
the case where symmetric groups.
</p>projecteuclid.org/euclid.ojm/1470413987_20160805121946Fri, 05 Aug 2016 12:19 EDTFacets of secondary polytopes and chow stability of toric varietieshttp://projecteuclid.org/euclid.ojm/1470413988<strong>Naoto Yotsutani</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 751--765.</p><p><strong>Abstract:</strong><br/>
Chow stability is one notion of Mumford's geometric invariant
theory for studying the moduli space of polarized varieties.
Kapranov, Sturmfels and Zelevinsky detected that Chow stability
of polarized toric varieties is determined by its inherent
secondary polytope , which is a polytope whose vertices
correspond to regular triangulations of the associated polytope
[7]. In this paper, we give a purely convex-geometrical proof
that the Chow form of a projective toric variety is $H$-semistable
if and only if it is $H$-polystable with respect to the standard
complex torus action $H$. This essentially means that
Chow semistability is equivalent to Chow polystability for
any (not-necessaliry-smooth) projective toric varieties.
</p>projecteuclid.org/euclid.ojm/1470413988_20160805121946Fri, 05 Aug 2016 12:19 EDTSeifert surgery on knots via Reidemeister torsion and Casson--Walker--Lescop invariant IIhttp://projecteuclid.org/euclid.ojm/1470413989<strong>Teruhisa Kadokami</strong>, <strong>Noriko Maruyama</strong>, <strong>Tsuyoshi Sakai</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 767--773.</p><p><strong>Abstract:</strong><br/>
For a knot $K$ with $\Delta_{K}(t)\doteq t^{2}-3t+1$ in a
homology $3$-sphere, let $M$ be the result of $2/q$-surgery
on $K$. We show that an appropriate assumption on the Reidemeister
torsion of the universal abelian covering of $M$ implies $q=\pm
1$, if $M$ is a Seifert fibered space.
</p>projecteuclid.org/euclid.ojm/1470413989_20160805121946Fri, 05 Aug 2016 12:19 EDTA pairwise independent random sampling method in the ring of $p$-adic integershttp://projecteuclid.org/euclid.ojm/1470413990<strong>Hiroshi Kaneko</strong>, <strong>Hisaaki Matsumoto</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 775--798.</p><p><strong>Abstract:</strong><br/>
For the ring of $p$-adic integers, $p$ being a fixed prime,
any sequence which plays a similar role to Weyl's irrational
rotation has not been proposed yet. We will see that a modified
$p$-adic van der Corput sequence provides us with a reasonable
counterpart of Weyl's irrational rotation in the ring. We will
present a similar random Weyl sampling on the ring to the one
proposed by Sugita and Takanobu. In the process of establishing
the counterpart, a sampling method based on a function with
naturally extended domain to the field of $p$-adic numbers
in terms of the additive characters will be mentioned.
</p>projecteuclid.org/euclid.ojm/1470413990_20160805121946Fri, 05 Aug 2016 12:19 EDTBehavior of solutions for radially symmetric solutions for Burgers equation with a boundary corresponding to the rarefaction wavehttp://projecteuclid.org/euclid.ojm/1470413991<strong>Itsuko Hashimoto</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 799--811.</p><p><strong>Abstract:</strong><br/>
We investigate the large-time behavior of the radially symmetric
solution for Burgers equation on the exterior of a small ball
in multi-dimensional space, where the boundary data and the
data at the far field are prescribed. In a previous paper [1],
we showed that, for the case in which the boundary data is
equal to $0$ or negative, the asymptotic stability is the same
as that for the viscous conservation law. In the present paper,
it is proved that if the boundary data is positive, the asymptotic
state is a superposition of the stationary wave and the rarefaction
wave, which is a new wave phenomenon. The proof is given using
a standard $L^{2}$ energy method and the characteristic curve
method.
</p>projecteuclid.org/euclid.ojm/1470413991_20160805121946Fri, 05 Aug 2016 12:19 EDTOn deformations of isolated singularities of polar weighted homogeneous mixed polynomialshttp://projecteuclid.org/euclid.ojm/1470413992<strong>Kazumasa Inaba</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 813--842.</p><p><strong>Abstract:</strong><br/>
In the present paper, we deform isolated singularities of
$f\bar{g}$, where $f$ and $g$ are $2$-variable weighted
homogeneous complex polynomials, and show that there exists
a deformation of $f\bar{g}$ which has only indefinite
fold singularities and mixed Morse singularities.
</p>projecteuclid.org/euclid.ojm/1470413992_20160805121946Fri, 05 Aug 2016 12:19 EDT$p$-local stable splitting of quasitoric manifoldshttp://projecteuclid.org/euclid.ojm/1470413993<strong>Sho Hasui</strong>, <strong>Daisuke Kishimoto</strong>, <strong>Takashi Sato</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 843--854.</p><p><strong>Abstract:</strong><br/>
We show a homotopy decomposition of the $p$-localized suspension
$\Sigma M_{(p)}$ of a quasitoric manifold $M$ by constructing
power maps. As an application we investigate the $p$-localized
suspension of the projection $\pi$ from the moment-angle complex
onto $M$, from which we deduce its triviality for $p>\dim
M/2$. We also discuss non-triviality of $\pi_{(p)}$ and $\Sigma^{\infty}\pi$.
</p>projecteuclid.org/euclid.ojm/1470413993_20160805121946Fri, 05 Aug 2016 12:19 EDTGlobal solvability for double-diffusive convection system based on Brinkman--Forchheimer equation in general domainshttp://projecteuclid.org/euclid.ojm/1470413994<strong>Mitsuharu Ôtani</strong>, <strong>Shun Uchida</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 3, 855--872.</p><p><strong>Abstract:</strong><br/>
In this paper, we are concerned with the solvability of the
initial boundary value problem of a system which describes
double-diffusive convection phenomena in some porous medium
under general domains, especially unbounded domains. In previous
works where the boundedness of the space domain is imposed,
some global solvability results have been already derived.
However, when we consider our problem in general domains, some
compactness theorems are not available. Hence it becomes difficult
to follow the same strategies as before. Nevertheless, we can
assure the global existence of a unique solution via the contraction
method. Moreover, it is revealed that the global solvability
holds for higher space dimension and larger class of the initial
data than those assumed in previous works.
</p>projecteuclid.org/euclid.ojm/1470413994_20160805121946Fri, 05 Aug 2016 12:19 EDTMeasure-expansive homoclinic classeshttp://projecteuclid.org/euclid.ojm/1475601821<strong>Keonhee Lee</strong>, <strong>Manseob Lee</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 873--887.</p><p><strong>Abstract:</strong><br/>
Let $p$ be a hyperbolic periodic point of a diffeomorphism
$f$ on a compact $C^{\infty}$ Riemannian manifold $M$. In
this paper we introduce the notion of $C^{1}$ stably measure
expansiveness of closed $f$-invariant sets, and prove that
(i) the chain recurrent set $\mathcal{R}(f)$ of $f$ is $C^{1}$
stably measure expansive if and only if $f$ satisfies both
Axiom A and no-cycle condition, and (ii) the homoclinic class
$H_{f}(p)$ of $f$ associated to $p$ is $C^{1}$ stably measure
expansive if and only if $H_{f}(p)$ is hyperbolic.
</p>projecteuclid.org/euclid.ojm/1475601821_20161004132358Tue, 04 Oct 2016 13:23 EDTTautological sheaves: Stability, moduli spaces and restrictions to generalised Kummer varietieshttp://projecteuclid.org/euclid.ojm/1475601822<strong>Malte Wandel</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 889--910.</p><p><strong>Abstract:</strong><br/>
Results on stability of tautological sheaves on Hilbert schemes
of points are extended to higher dimensions and to the restriction
of tautological sheaves to generalised Kummer varieties. This
provides a big class of new examples of stable sheaves on
higher dimensional irreducible symplectic manifolds. Some
aspects of deformations of tautological sheaves are studied.
</p>projecteuclid.org/euclid.ojm/1475601822_20161004132358Tue, 04 Oct 2016 13:23 EDTOn Castelnuovo theory and non-existence of smooth isolated curves in quintic threefoldshttp://projecteuclid.org/euclid.ojm/1475601823<strong>Xun Yu</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 911--918.</p><p><strong>Abstract:</strong><br/>
We find some necessary conditions for a smooth irreducible
curve $C\subset \mathbb{P}^{4}$ to be isolated in a smooth
quintic threefold. As an application, we prove that Knutsen's
list of examples of smooth isolated curves in general quintic
threefolds is complete up to degree 9.
</p>projecteuclid.org/euclid.ojm/1475601823_20161004132358Tue, 04 Oct 2016 13:23 EDTIll-posedness issue for the drift diffusion system in the homogeneous Besov spaceshttp://projecteuclid.org/euclid.ojm/1475601824<strong>Tsukasa Iwabuchi</strong>, <strong>Takayoshi Ogawa</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 919--939.</p><p><strong>Abstract:</strong><br/>
We consider the ill-posedness issue for the drift-diffusion
system of bipolar type by showing that the continuous dependence
on initial data does not hold generally in the scaling invariant
Besov spaces. The scaling invariant Besov spaces are $\dot{B}_{p, \sigma}^{-2+ n/p} (\mathbb{R}^{n})$ with $1 \leq p, \sigma
\leq \infty$ and we show the optimality of the case $p = 2n$
to obtain the well-posedness and the ill-posedness for the
drift-diffusion system of bipolar type.
</p>projecteuclid.org/euclid.ojm/1475601824_20161004132358Tue, 04 Oct 2016 13:23 EDTQuasi-sure existence of Gaussian rough paths and large deviation principles for capacitieshttp://projecteuclid.org/euclid.ojm/1475601825<strong>H. Boedihardjo</strong>, <strong>X. Geng</strong>, <strong>Z. Qian</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 941--970.</p><p><strong>Abstract:</strong><br/>
We construct a quasi-sure version (in the sense of Malliavin)
of geometric rough paths associated with a Gaussian process
with long-time memory. As an application we establish a large
deviation principle (LDP) for capacities for such Gaussian
rough paths. Together with Lyons' universal limit theorem,
our results yield immediately the corresponding results for
pathwise solutions to stochastic differential equations driven
by such Gaussian process in the sense of rough paths. Moreover,
our LDP result implies the result of Yoshida on the LDP for
capacities over the abstract Wiener space associated with such
Gaussian process.
</p>projecteuclid.org/euclid.ojm/1475601825_20161004132358Tue, 04 Oct 2016 13:23 EDTThe homotopy fixed point sets of spheres actions on rational complexeshttp://projecteuclid.org/euclid.ojm/1475601826<strong>Yanlong Hao</strong>, <strong>Xiugui Liu</strong>, <strong>Qianwen Sun</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 971--981.</p><p><strong>Abstract:</strong><br/>
In this paper, we describe the homotopy type of the homotopy
fixed point sets of $S^{3}$-actions on rational spheres and
complex projective spaces, and provide some properties of
$S^{1}$-actions on a general rational complex.
</p>projecteuclid.org/euclid.ojm/1475601826_20161004132358Tue, 04 Oct 2016 13:23 EDTNotes on quadratic integers and real quadratic number fieldshttp://projecteuclid.org/euclid.ojm/1475601827<strong>Jeongho Park</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 983--1002.</p><p><strong>Abstract:</strong><br/>
It is shown that when a real quadratic integer $\xi$ of fixed
norm $\mu$ is considered, the fundamental unit $\varepsilon_{d}$
of the field $\mathbb{Q}(\xi) = \mathbb{Q}(\sqrt{d})$ satisfies
$\log \varepsilon_{d} \gg (\log d)^{2}$ almost always. An
easy construction of a more general set containing all the
radicands $d$ of such fields is given via quadratic sequences,
and the efficiency of this substitution is estimated explicitly.
When $\mu = -1$, the construction gives all $d$'s for which
the negative Pell's equation $X^{2} - d Y^{2} = -1$ (or more
generally $X^{2} - D Y^{2} = -4$) is soluble. When $\mu$ is
a prime, it gives all of the real quadratic fields in which
the prime ideals lying over $\mu$ are principal.
</p>projecteuclid.org/euclid.ojm/1475601827_20161004132358Tue, 04 Oct 2016 13:23 EDTOne-fixed-point actions on spheres and Smith setshttp://projecteuclid.org/euclid.ojm/1475601828<strong>Masaharu Morimoto</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 1003--1013.</p><p><strong>Abstract:</strong><br/>
Let $G$ be a finite group. The Smith equivalence for real
$G$-modules of finite dimension gives a subset of real representation
ring, called the primary Smith set. Since the primary Smith
set is not additively closed in general, it is an interesting
problem to find a subset which is additively closed in the
real representation ring and occupies a large portion of the
primary Smith set. In this paper we introduce an additively
closed subset of the primary Smith set by means of smooth
one-fixed-point $G$-actions on spheres, and we give evidences
that the subset occupies a large portion of the primary Smith
set if $G$ is an Oliver group.
</p>projecteuclid.org/euclid.ojm/1475601828_20161004132358Tue, 04 Oct 2016 13:23 EDTLie ideal enhancements of counting invariantshttp://projecteuclid.org/euclid.ojm/1475601829<strong>Gillian Roxanne Grindstaff</strong>, <strong>Sam Nelson</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 1015--1027.</p><p><strong>Abstract:</strong><br/>
We define enhancements of the quandle counting invariant for
knots and links with a finite labeling quandle $Q$ embedded
in the quandle of units of a Lie algebra $\mathfrak{a}$ using
Lie ideals. We provide examples demonstrating that the enhancement
is stronger than the associated unenhanced counting invariant
and image enhancement invariant.
</p>projecteuclid.org/euclid.ojm/1475601829_20161004132358Tue, 04 Oct 2016 13:23 EDTSome families of minimal elements for a partial ordering on prime knotshttp://projecteuclid.org/euclid.ojm/1475601830<strong>Fumikazu Nagasato</strong>, <strong>Anh T. Tran</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 1029--1045.</p><p><strong>Abstract:</strong><br/>
We show that all twist knots and certain double twist knots
are minimal elements for a partial ordering on the set of
prime knots. The keys to these results are presentations of
their character varieties using Chebyshev polynomials and
a criterion for irreducibility of a polynomial of two variables.
These give us an elementary method to discuss the number of
irreducible components of the character varieties, which concludes
the result essentially.
</p>projecteuclid.org/euclid.ojm/1475601830_20161004132358Tue, 04 Oct 2016 13:23 EDTConjugacy class and discreteness in $\mathit{SL}(2, \mathbb{C})$http://projecteuclid.org/euclid.ojm/1475601831<strong>Shihai Yang</strong>, <strong>Tiehong Zhao</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 1047--1053.</p><p><strong>Abstract:</strong><br/>
In this note we establish a new discreteness criterion for
a non-elementary group $G$ in $\mathit{SL}(2, \mathbb{C})$. Namely,
$G$ is discrete if all the two-generator subgroups are discrete,
where one generator is a non-trivial element $f$ in $G$, and
the other is in the conjugacy class of $f$.
</p>projecteuclid.org/euclid.ojm/1475601831_20161004132358Tue, 04 Oct 2016 13:23 EDTSome exotic actions of finite groups on smooth 4-manifoldshttp://projecteuclid.org/euclid.ojm/1475601832<strong>Chanyoung Sung</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 1055--1061.</p><p><strong>Abstract:</strong><br/>
Using $G$-monopole invariants, we produce infinitely many
exotic non-free actions of $\mathbb{Z}_{k}\oplus H$ on some
connected sums of finite number of $S^{2}\times S^{2}$, $\mathbb{C}P_{2}$,
$\overline{\mathbb{C}P}_{2}$, and $K3$ surfaces, where $k\geq
2$, and $H$ is any nontrivial finite group acting freely on
$S^{3}$.
</p>projecteuclid.org/euclid.ojm/1475601832_20161004132358Tue, 04 Oct 2016 13:23 EDTOn certain 2-extensions of $\mathbb{Q}$ unramified at 2 and $\infty$http://projecteuclid.org/euclid.ojm/1475601833<strong>Yasushi Mizusawa</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 1063--1088.</p><p><strong>Abstract:</strong><br/>
Based on the method of Boston and Leedham-Green et al. for
computing the Galois groups of tamely ramified $p$-extensions
of number fields, this paper gives a large family of triples
of odd prime numbers such that the maximal totally real $2$-extension
of the rationals unramified outside the three prime numbers
has the Galois group of order $512$ and derived length $3$.
This family is characterized arithmetically, and the explicit
presentation of the Galois group by generators and relations
is also determined completely.
</p>projecteuclid.org/euclid.ojm/1475601833_20161004132358Tue, 04 Oct 2016 13:23 EDTIntegrals on $p$-adic upper half planes and Hida families over totally real fieldshttp://projecteuclid.org/euclid.ojm/1475601834<strong>Isao Ishikawa</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 1089--1124.</p><p><strong>Abstract:</strong><br/>
Bertolini--Darmon and Mok proved a formula of the second derivative
of the two-variable $p$-adic $L$-function of a modular elliptic
curve over a totally real field along the Hida family in terms
of the image of a global point by some $p$-adic logarithm
map. The theory of $p$-adic indefinite integrals and $p$-adic
multiplicative integrals on $p$-adic upper half planes plays
an important role in their work. In this paper, we generalize
these integrals for $p$-adic measures which are not necessarily
$\mathbb{Z}$-valued, and prove a formula of the second derivative
of the two-variable $p$-adic $L$-function of an abelian variety
of $\mathrm{GL}(2)$-type associated to a Hilbert modular form of weight
2.
</p>projecteuclid.org/euclid.ojm/1475601834_20161004132358Tue, 04 Oct 2016 13:23 EDTThe logarithms of Dehn twists on non-orientable surfaceshttp://projecteuclid.org/euclid.ojm/1475601835<strong>Shunsuke Tsuji</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 53, Number 4, 1125--1132.</p><p><strong>Abstract:</strong><br/>
We introduce a Lie algebra associated with a non-orientable
surface, which is an analogue for the Goldman Lie algebra
of an oriented surface. As an application, we deduce an explicit
formula of the Dehn twist along an annulus simple closed curve
on the surface as in Kawazumi--Kuno [4], [5] and Massuyeau--Turaev
[7].
</p>projecteuclid.org/euclid.ojm/1475601835_20161004132358Tue, 04 Oct 2016 13:23 EDTSalem Numbers and Automorphisms of Abelian Surfaceshttp://projecteuclid.org/euclid.ojm/1488531781<strong>Paul Reschke</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 1--15.</p><p><strong>Abstract:</strong><br/>
We classify two-dimensional complex tori admitting automorphisms with positive entropy in terms of the entropies they exhibit. For each possible positive value of entropy, we describe the set of two-dimensional complex tori admitting automorphisms with that entropy.
</p>projecteuclid.org/euclid.ojm/1488531781_20170303040403Fri, 03 Mar 2017 04:04 ESTThe normal holonomy of $CR$-submanifoldshttp://projecteuclid.org/euclid.ojm/1488531782<strong>Antonio J. Di Scala</strong>, <strong>Francisco Vittone</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 17--35.</p><p><strong>Abstract:</strong><br/>
We study the normal holonomy group, i.e. the holonomy group of the normal connection, of a $CR$-submanifold of a complex space form. We show that the normal holonomy group of a coisotropic submanifold acts as the holonomy representation of a Riemannian symmetric space. In case of a totally real submanifold we give two results about reduction of codimension. We describe explicitly the action of the normal holonomy in the case in which the totally real submanifold is contained in a totally real totally geodesic submanifold. In such a case we prove the compactness of the normal holonomy group.
</p>projecteuclid.org/euclid.ojm/1488531782_20170303040403Fri, 03 Mar 2017 04:04 ESTEffects of Randomization on asymptotic periodicity of nonsingular transformationshttp://projecteuclid.org/euclid.ojm/1488531783<strong>Hiroshi Ishitani</strong>, <strong>Kensuke Ishitani</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 37--53.</p><p><strong>Abstract:</strong><br/>
It is known that the Perron--Frobenius operators of piecewise expanding $\mathcal{C}^2$ transformations possess an asymptotic periodicity of densities. On the other hand, external noise or measurement errors are unavoidable in practical systems; therefore, all realistic mathematical models should be regarded as random iterations of transformations. This paper aims to discuss the effects of randomization on the asymptotic periodicity of densities.
</p>projecteuclid.org/euclid.ojm/1488531783_20170303040403Fri, 03 Mar 2017 04:04 ESTPolylogarithmic analogue of the Coleman-Ihara formula, Ihttp://projecteuclid.org/euclid.ojm/1488531784<strong>Hiroaki Nakamura</strong>, <strong>Kenji Sakugawa</strong>, <strong>Zdzisław Wojtkowiak</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 55--74.</p><p><strong>Abstract:</strong><br/>
The Coleman-Ihara formula expresses Soule's $p$-adic characters restricted to $p$-local Galois group as the Coates-Wiles homomorphism multiplied by $p$-adic $L$-values at positive integers. In this paper, we show an analogous formula that $\ell$-adic polylogarithmic characters for $\ell=p$ restrict to the Coates-Wiles homomorphism multiplied by Coleman's $p$-adic polylogarithms at any roots of unity of order prime to $p$.
</p>projecteuclid.org/euclid.ojm/1488531784_20170303040403Fri, 03 Mar 2017 04:04 ESTWillmore-like functionals for surfaces in 3-dimensional Thurston geometrieshttp://projecteuclid.org/euclid.ojm/1488531785<strong>Dmitry Berdinsky</strong>, <strong>Yuri Vyatkin</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 75--83.</p><p><strong>Abstract:</strong><br/>
We find analogues of the Willmore functional for each of the Thurston geometries with $4$--dimensional isometry group such that the CMC--spheres in these geometries are critical points of these functionals.
</p>projecteuclid.org/euclid.ojm/1488531785_20170303040403Fri, 03 Mar 2017 04:04 ESTRigidity of manifolds with boundary under a lower Ricci curvature boundhttp://projecteuclid.org/euclid.ojm/1488531786<strong>Yohei Sakurai</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 85--119.</p><p><strong>Abstract:</strong><br/>
We study Riemannian manifolds with boundary under a lower Ricci curvature bound, and a lower mean curvature bound for the boundary. We prove a volume comparison theorem of Bishop-Gromov type concerning the volumes of the metric neighborhoods of the boundaries. We conclude several rigidity theorems. As one of them, we obtain a volume growth rigidity theorem. We also show a splitting theorem of Cheeger-Gromoll type under the assumption of the existence of a single ray.
</p>projecteuclid.org/euclid.ojm/1488531786_20170303040403Fri, 03 Mar 2017 04:04 ESTComplex structures and non-degenerate closed 2-forms of compact real parallelizable nilmanifoldshttp://projecteuclid.org/euclid.ojm/1488531787<strong>Takumi Yamada</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 121--128.</p><p><strong>Abstract:</strong><br/>
In this paper, we consider a relation of non-degenerate closed $2$-forms and complex structures on compact real parallelizable nilmanifolds.
</p>projecteuclid.org/euclid.ojm/1488531787_20170303040403Fri, 03 Mar 2017 04:04 ESTQuadratic approximation in $\mathbb{F}_q(\!(T^{-1})\!)$http://projecteuclid.org/euclid.ojm/1488531788<strong>Tomohiro Ooto</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 129--156.</p><p><strong>Abstract:</strong><br/>
In this paper, we study Diophantine exponents $w_n$ and $w_n ^{*}$ for Laurent series over a finite field. Especially, we deal with the case $n=2$, that is, quadratic approximation. We first show that the range of the function $w_2-w_2 ^{*}$ is exactly the closed interval $[0,1]$. Next, we estimate an upper bound of the exponent $w_2$ of continued fractions with low complexity partial quotients.
</p>projecteuclid.org/euclid.ojm/1488531788_20170303040403Fri, 03 Mar 2017 04:04 ESTL'anneau de cohomologie des variétés de Seifert non-orientableshttp://projecteuclid.org/euclid.ojm/1488531789<strong>Anne Bauval</strong>, <strong>Claude Hayat</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 157--195.</p><p><strong>Abstract:</strong><br/>
If $p$ is a prime number, the cohomology ring with coefficients in $\mathbb{Z}/p\mathbb{Z}$ of an orientable or non-orientable Seifert manifold $M$ is obtained using a $\Delta$-simplicial decomposition of $M$. Several choices must be made before applying the Alexander-Whitney formula. The answers are given in terms of the classical cellular generators.
</p>projecteuclid.org/euclid.ojm/1488531789_20170303040403Fri, 03 Mar 2017 04:04 ESTMidpoints for Thompson's metric on symmetric coneshttp://projecteuclid.org/euclid.ojm/1488531790<strong>Bas Lemmens</strong>, <strong>Mark Roelands</strong>. <p><strong>Source: </strong>Osaka Journal of Mathematics, Volume 57, Number 1, 197--208.</p><p><strong>Abstract:</strong><br/>
We characterise the affine span of the midpoints sets, $\mathcal{M}(x,y)$, for Thompson's metric on symmetric cones in terms of a translation of the zero-component of the Peirce decomposition of an idempotent. As a consequence we derive an explicit formula for the dimension of the affine span of $\mathcal{M}(x,y)$ in case the associated Euclidean Jordan algebra is simple. In particular, we find for $A$ and $B$ in the cone positive definite Hermitian matrices that \[ \dim({\rm aff}\, \mathcal{M}(A,B))=q^2, \] where $q$ is the number of eigenvalues $\mu$ of $A^{-1}B$, counting multiplicities, such that \[ \mu\neq \max\{\lambda_+(A^{-1}B),\lambda_-(A^{-1}B)^{-1}\}, \] where $\lambda_+(A^{-1}B):=\max \{\lambda\colon \lambda\in\sigma(A^{-1}B)\}$ and $\lambda_-(A^{-1}B):=\min\{\lambda\colon \lambda\in\sigma(A^{-1}B)\}$. These results extend work by Y. Lim [18].
</p>projecteuclid.org/euclid.ojm/1488531790_20170303040403Fri, 03 Mar 2017 04:04 EST