A characterization of shellable and sequentially Cohen-Macaulay
S.
Moradi
Amirkabir University of Technology
author
D.
Kiani
Amirkabir University of Technology
author
text
article
2011
eng
We consider a class of hypergraphs called
hypercycles and we show that a hypercycle $C_n^{d,alpha}$ is
shellable or sequentially the Cohen--Macaulay if and only if
$nin{3,5}$. Also, we characterize Cohen--Macaulay hypercycles.
These results are hypergraph versions of results proved for cycles
in graphs.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
1
9
http://bims.iranjournals.ir/article_347_7a249698165516accceec04e5a5ba578.pdf
Non-linear ergodic theorems in complete non-positive curvature metric spaces
B.
Ahmadi Kakavandi
Tarbiat Modares University
author
M.
Amini
Tarbiat Modares University
author
text
article
2011
eng
Hadamard (or complete $CAT(0)$) spaces are complete, non-positive curvature, metric spaces. Here,
we prove a nonlinear ergodic theorem for continuous non-expansive semigroup in these spaces as well as a strong convergence theorem for
the commutative case. Our results extend the standard non-linear
ergodic theorems for non-expansive maps on real Hilbert spaces,
to non-expansive maps on Hadamard spaces, which include for example (possibly infinite-dimensional) complete simply
connected Riemannian manifolds with non-positive sectional
curvature.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
11
20
http://bims.iranjournals.ir/article_348_bd937fd396e4bfd643f273cb0f5b9aed.pdf
A characterization of L-dual frames and L-dual Riesz bases
A.
Ahmadi
author
A.
Askari Hemmat
author
text
article
2011
eng
This paper is an investigation of $L$-dual frames with respect
to a function-valued inner product, the so called $L$-bracket
product on $L^{2}(G)$, where G is a locally compact abelian group
with a uniform lattice $L$. We show that several well known theorems
for dual frames and dual Riesz bases in a Hilbert space
remain valid for $L$-dual frames and $L$-dual Riesz bases in $L^{2}(G)$.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
21
32
http://bims.iranjournals.ir/article_349_e505bfd0f796940777bc05b6fd51c8f5.pdf
On rainbow 4-term arithmetic progressions
M. H.
Shirdareh Haghighi
author
P.
Salehi Nowbandegani
author
text
article
2012
eng
{sl Let $[n]={1,dots, n}$ be colored in $k$ colors. A rainbow
AP$(k)$ in $[n]$ is a $k$ term arithmetic progression whose
elements have different colors. Conlon, Jungi'{c} and
Radoiv{c}i'{c} cite{conlon} prove that there exists an
equinumerous 4-coloring of $[4n]$ which is rainbow AP(4) free,
when $n$ is even. Based on their construction, we show that such
a coloring of $[4n]$
also exists for odd $n>1$.
We conclude that for nonnegative integers $kgeq 3$
and $n > 1$, every equinumerous $k$-coloring of $[kn]$ contains a
rainbow AP$(k)$ if and only if $k=3$.}
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2012
33
37
http://bims.iranjournals.ir/article_350_89e63dba5b5df3fefe16dd3a01425b8e.pdf
Second symmetric powers of chain complexes
A.
Frankild
author
S.
Sather-Wagstaff
author
A.
Taylor
author
text
article
2011
eng
We investigate Buchbaum and Eisenbud's construction of the second
symmetric power $s_R(X)$ of a chain complex $X$ of modules over
a commutative ring $R$. We state and prove a number of results
from the folklore of the subject for which we know of no good
direct references. We also provide several explicit computations
and examples. We use this construction to prove the following
version of a result of Avramov, Buchweitz, and c{S}ega: let
$Rto S$ be a module-finite ring homomorphism such that $R$ is
noetherian and local, and such that 2 is a unit in $R$. Let $X$
be a complex of finite rank free $S$-modules such that $X_n=0$
for each $n<0$. If
$cup_nass_R(HH_n(Xotimes_SX))subseteqass(R)$ and if
$X_{p}simeq S_{p}$ for each $pinass(R)$, then $Xsimeq S$.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
39
75
http://bims.iranjournals.ir/article_352_3993b9c37fc0e81314ac0cd20be606cf.pdf
General Hardy-Type Inequalities with Non-conjugate Exponents
A.
Cizmesija
author
M.
Krnic
author
J.
Pecaric
author
text
article
2012
eng
We derive whole series of new integral
inequalities of the Hardy-type, with non-conjugate exponents.
First, we prove and discuss two equivalent general
inequa-li-ties of such type, as well as their corresponding
reverse inequalities. General results are then applied to special
Hardy-type kernel and power weights. Also, some estimates of
weight functions and constant factors are obtained. In
particular, we obtain generalizations and improvements of some
recent results, in the literature.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2012
77
108
http://bims.iranjournals.ir/article_351_52e9e19972fed6970fe01efd0a82b904.pdf
Some Optimal Codes From Designs
M.
Emami
author
Ch.
Maysoori
author
text
article
2011
eng
The binary and ternary codes spanned by the rows of the point by
block incidence matrices of some 2-designs and their
complementary
and orthogonal designs are studied. A new method is also introduced to study optimal codes.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
109
115
http://bims.iranjournals.ir/article_353_1c31d56b10fe384966174ee83e0eb049.pdf
Extension functors of local cohomology modules
M.
Aghapournahr
author
A.
Taherizadeh
author
A.
Vahidi
author
text
article
2011
eng
Let $R$ be a commutative Noetherian ring with non-zero identity,
$fa$ an ideal of $R$, and $X$ an $R$--module. Here, for fixed
integers $s, t$ and a finite $fa$--torsion $R$--module $N$, we
first study the membership of $Ext^{s+t}_{R}(N, X)$ and
$Ext^{s}_{R}(N, H^{t}_{fa}(X))$ in the Serre subcategories of
the category of $R$--modules. Then, we present some conditions
which ensure the existence of an isomorphism between them.
Finally, we introduce the concept of the Serre cofiniteness as a
generalization of cofiniteness and study this property for
certain local cohomology modules.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
117
134
http://bims.iranjournals.ir/article_354_a36964c381b38b75e5e066579630220a.pdf
Convergence of product integration method applied for numerical
solution of linear weakly singular Volterra
systems
B.
Babayar-Razlighi
author
K.
Ivaz
author
M.
Mokhtarzadeh
author
text
article
2011
eng
We develop and apply the product integration method to a large class of linear weakly singular Volterra
systems. We show that under certain sufficient conditions this
method converges. Numerical implementation of the method is
illustrated by a benchmark problem originated from heat
conduction.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
135
148
http://bims.iranjournals.ir/article_355_4c05419e0679e03a7d612b134a6c9404.pdf
On Semi-artinian Weakly Co-semisimple Modules
E.
Momtahan
author
text
article
2011
eng
We show that every semi-artinian module which is contained in a
direct sum of
finitely presented modules in $si[M]$, is weakly co-semisimple if and only if it is regular in $si[M]$.
As a consequence, we observe that every
semi-artinian ring is regular in the sense of von Neumann if
and only if its simple modules are $FP$-injective.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
149
157
http://bims.iranjournals.ir/article_356_cf010bff12b9e95965d9ffb69052de01.pdf
Various topological forms of Von Neumann regularity in Banach algebras
G.
Esslamzadeh
author
M.
Shadab
author
text
article
2011
eng
We study topological von Neumann regularity
and principal von Neumann regularity of Banach algebras. Our
main objective is comparing these two types of Banach algebras and
some other known Banach algebras with one another. In particular,
we show that the class of topologically von Neumann regular Banach
algebras contains all $C^*$-algebras, group algebras of compact
abelian groups and certain weakly amenable Banach algebras while
it excludes measure algebras, of certain locally compact Abelian
groups. Moreover, we show that in a unital amenable Banach
algebra, principal regularity implies topological regularity.
Finally, we use topological regularity to obtain some information
about hereditary $C^*$-subalgebras of a given $C^*$-algebra.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
159
170
http://bims.iranjournals.ir/article_357_bceaa5c7dfeb6e2303668f1f6eee51b4.pdf
Insertion of a gamma-continuous function
M.
Mirmiran
author
text
article
2011
eng
A necessary and sufficient condition in terms of lower cut sets
are given for the insertion of a $gamma-$continuous function
between two comparable real-valued functions.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
171
181
http://bims.iranjournals.ir/article_358_585a7ccdab5fde974ec45e285e1cc82f.pdf
Monomial Irreducible sln-Modules
M.
Shahryari
author
text
article
2011
eng
In this article, we introduce monomial irreducible representations of the special linear Lie
algebra $sln$. We will show that this kind of representations have bases for
which the action of the Chevalley generators of the Lie algebra on the basis elements
can be given by a simple formula.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
183
195
http://bims.iranjournals.ir/article_359_c314a69d352fa6f7d05794e57d93f5e2.pdf
Permanence and global asymptotic stability of a delayed
predator-prey model with Hassell-Varley type functional response
K.
Wang
author
Y.
Zhu
author
text
article
2011
eng
Here, a predator-prey model with Hassell-Varley type functional
responses is studied. Some sufficient conditions are obtained
for the permanence and global asymptotic stability of the
system by using comparison theorem and constructing a suitable
Lyapunov functional. Moreover, an example is illustrated to
verify the results by simulation.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
197
215
http://bims.iranjournals.ir/article_360_e5991d60269c657b39ab2541a80032d9.pdf
Semistar dimension of polynomial rings and Prufer-like
domains
P.
Sahandi
author
text
article
2011
eng
Let $D$ be an integral domain and $star$ a semistar operation stable and of finite type on
it. We define the semistar dimension (inequality) formula and
discover their relations with $star$-universally catenarian
domains and $star$-stably strong S-domains. As an application, we
give new characterizations of $star$-quasi-Pr"{u}fer domains
and UM$t$ domains in terms of dimension inequality formula (and
the notions of universally catenarian domain, stably strong
S-domain, strong S-domain, and Jaffard domain). We also extend
Arnold's formula to the setting of semistar operations.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
217
233
http://bims.iranjournals.ir/article_361_6dbe9e5fa7817562fab715a62353d061.pdf
A Sharp Maximal Function Estimate for Vector-Valued Multilinear
Singular Integral Operator
Zhou
Xiaosha
author
Liu
Lanzhe
author
text
article
2011
eng
We establish a sharp maximal function estimate for some vector-valued multilinear singular integral operators.
As an application, we obtain the $(L^p, L^q)$-norm inequality for vector-valued multilinear operators.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
235
248
http://bims.iranjournals.ir/article_362_3e71d982083b4f407804702f349a53e1.pdf
Symmetric curvature tensor
A.
Heydari
author
N.
Boroojerdian
author
E.
Peyghan
author
text
article
2011
eng
Recently, we have used the symmetric bracket of vector fields,
and developed the notion of the symmetric derivation. Using this
machinery, we have defined the concept of symmetric curvature.
This concept is natural and is related to the notions divergence
and Laplacian of vector fields. This concept is also related to
the derivations on the algebra of symmetric forms which has been
discussed by the authors. We introduce a new class of geometric
vector fields and prove some basic facts about them. We call
these vector fields affinewise. By contraction of the symmetric
curvature, we define two new curvatures which have direct
relations to the notions of divergence, Laplacian, and the Ricci
tensor.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
249
267
http://bims.iranjournals.ir/article_363_e4d5cfe09b33d8f0691b0f0663d7edef.pdf
The (R,S)-symmetric and (R,S)-skew symmetric solutions of the pair of matrix equations A1XB1 = C1 and A2XB2 = C2
M.
Dehghan
author
M.
Hajarian
author
text
article
2011
eng
Let $Rin textbf{C}^{mtimes m}$ and $Sin textbf{C}^{ntimes n}$ be nontrivial involution matrices; i.e., $R=R^{-1}neq pm~I$ and $S=S^{-1}neq pm~I$.
An $mtimes n$ complex matrix $A$ is said to be an $(R, S)$-symmetric ($(R, S)$-skew symmetric) matrix if $RAS =A$ ($ RAS =-A$).
The $(R, S)$-symmetric and $(R, S)$-skew symmetric matrices have
a number of special properties and widely used in engineering and
scientific computating. Here, we introduce the necessary and
sufficient conditions for the solvability of the pair of matrix
equations $A_{1}XB_{1}=C_{1}$ and $A_{2}XB_{2}=C_{2}$, over $(R,
S)$-symmetric and $(R, S)$-skew symmetric matrices, and give the
general expressions of the solutions for the solvable cases.
Finally, we give necessary and sufficient conditions for the
existence of $(R, S)$-symmetric and $(R, S)$-skew symmetric
solutions and representations of these solutions to the pair of
matrix equations in some special cases.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
269
279
http://bims.iranjournals.ir/article_364_7532efcddc42e213d1eae59596ad5a4a.pdf
On the nilpotency class of the automorphism group of some finite
p-groups
S.
Fouladi
author
R.
Orfi
author
text
article
2011
eng
Let $G$ be a $p$-group of order $p^n$ and $Phi$=$Phi(G)$ be the
Frattini subgroup of $G$. It is shown that the nilpotency class of
$Autf(G)$, the group of all automorphisms of $G$ centralizing $G/
Fr(G)$, takes the maximum value $n-2$ if and only if $G$ is of
maximal class. We also determine the nilpotency class of
$Autf(G)$ when $G$ is a finite abelian $p$-group.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
281
289
http://bims.iranjournals.ir/article_365_cf69e5755ef787ecc4678fb8887eef0b.pdf
Linear Sphericity Testing of 3-Connected Single Source Digraphs
A.
Dolati
author
text
article
2011
eng
It has been proved that sphericity testing for digraphs is an
NP-complete problem. Here, we
investigate sphericity of 3-connected single source digraphs. We
provide a new combinatorial characterization of sphericity and give
a linear time algorithm for sphericity testing. Our algorithm tests
whether a 3-connected single source digraph with $n$ vertices is
spherical in $O(n)$ time.
Bulletin of the Iranian Mathematical Society
Iranian Mathematical Society (IMS)
1017-060X
37
v.
No. 3
no.
2011
291
304
http://bims.iranjournals.ir/article_366_32f7b095391488c7c2d848a209f52492.pdf