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 Subjects -> MATHEMATICS (Total: 912 journals)     - APPLIED MATHEMATICS (76 journals)    - GEOMETRY AND TOPOLOGY (20 journals)    - MATHEMATICS (678 journals)    - MATHEMATICS (GENERAL) (41 journals)    - NUMERICAL ANALYSIS (19 journals)    - PROBABILITIES AND MATH STATISTICS (78 journals) MATHEMATICS (678 journals)                  1 2 3 4 | Last

1 2 3 4 | Last

 Czechoslovak Mathematical Journal   [SJR: 0.364]   [H-I: 21]   [1 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1572-9141 - ISSN (Online) 0011-4642    Published by Springer-Verlag  [2355 journals]
• Generalized outerplanar index of a graph
• Authors: Zahra Barati
Pages: 1 - 9
Abstract: We define the generalized outerplanar index of a graph and give a full characterization of graphs with respect to this index.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0365-16

• Non-Wieferich primes in number fields and abc -conjecture
• Authors: Srinivas Kotyada; Subramani Muthukrishnan
Pages: 1 - 9
Abstract: Let K/Q be an algebraic number field of class number one and let O K be its ring of integers. We show that there are infinitely many non-Wieferich primes with respect to certain units in OK under the assumption of the abc-conjecture for number fields.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0485-16

• Recognition of some families of finite simple groups by order and set of
orders of vanishing elements
• Authors: Maryam Khatami; Azam Babai
Pages: 1 - 10
Abstract: Let G be a finite group. An element g ∈ G is called a vanishing element if there exists an irreducible complex character χ of G such that χ(g)= 0. Denote by Vo(G) the set of orders of vanishing elements of G. Ghasemabadi, Iranmanesh, Mavadatpour (2015), in their paper presented the following conjecture: Let G be a finite group and M a finite nonabelian simple group such that Vo(G) = Vo(M) and G = M . Then G ≌ M. We answer in affirmative this conjecture for M = Sz(q), where q = 22n+1 and either q − 1, $$q - \sqrt {2q} + 1$$ or q + $$\sqrt {2q} + 1$$ is a prime number, and M = F4(q), where q = 2 n and either q4 + 1 or q4 − q2 + 1 is a prime number.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0355-16

• When a line graph associated to annihilating-ideal graph of a lattice is
planar or projective
Pages: 1 - 16
Abstract: Let (L,∧, ∨) be a finite lattice with a least element 0. AG(L) is an annihilating-ideal graph of L in which the vertex set is the set of all nontrivial ideals of L, and two distinct vertices I and J are adjacent if and only if I ∧ J = 0. We completely characterize all finite lattices L whose line graph associated to an annihilating-ideal graph, denoted by L(AG(L)), is a planar or projective graph.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0635-15

• Group algebras whose groups of normalized units have exponent 4
• Authors: Victor Bovdi; Mohammed Salim
Pages: 1 - 8
Abstract: We give a full description of locally finite 2-groups G such that the normalized group of units of the group algebra FG over a field F of characteristic 2 has exponent 4.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0386-16

• Graphs with small diameter determined by their D -spectra
• Authors: Ruifang Liu; Jie Xue
Pages: 1 - 18
Abstract: Let G be a connected graph with vertex set V(G) = {v1, v2,..., v n }. The distance matrix D(G) = (d ij )n×n is the matrix indexed by the vertices of G, where d ij denotes the distance between the vertices v i and v j . Suppose that λ1(D) ≥ λ2(D) ≥... ≥ λ n (D) are the distance spectrum of G. The graph G is said to be determined by its D-spectrum if with respect to the distance matrix D(G), any graph having the same spectrum as G is isomorphic to G. We give the distance characteristic polynomial of some graphs with small diameter, and also prove that these graphs are determined by their D-spectra.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0505-15

• Character Connes amenability of dual Banach algebras
Pages: 1 - 13
Abstract: We study the notion of character Connes amenability of dual Banach algebras and show that if A is an Arens regular Banach algebra, then A** is character Connes amenable if and only if A is character amenable, which will resolve positively Runde’s problem for this concept of amenability. We then characterize character Connes amenability of various dual Banach algebras related to locally compact groups. We also investigate character Connes amenability of Lau product and module extension of Banach algebras. These help us to give examples of dual Banach algebras which are not Connes amenable.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0451-16

• A dispersion inequality in the Hankel setting
• Authors: Saifallah Ghobber
Pages: 1 - 15
Abstract: The aim of this paper is to prove a quantitative version of Shapiro’s uncertainty principle for orthonormal sequences in the setting of Gabor-Hankel theory.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0445-16

• L p harmonic 1-form on submanifold with weighted Poincaré inequality
• Authors: Xiaoli Chao; Yusha Lv
Pages: 1 - 23
Abstract: We deal with complete submanifolds with weighted Poincaré inequality. By assuming the submanifold is δ-stable or has sufficiently small total curvature, we establish two vanishing theorems for L p harmonic 1-forms, which are extensions of the results of Dung-Seo and Cavalcante-Mirandola-Vitório.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0415-16

• The exceptional set for Diophantine inequality with unlike powers of prime
variables
• Authors: Wenxu Ge; Feng Zhao
Pages: 1 - 20
Abstract: Suppose that λ1, λ2, λ3, λ4 are nonzero real numbers, not all negative, δ > 0, V is a well-spaced set, and the ratio λ1/λ2 is algebraic and irrational. Denote by E(V,N, δ) the number of v ∈ V with v ≤ N such that the inequality $$\left {{\lambda _1}p_1^2 + {\lambda _2}p_2^3 + {\lambda _3}p_3^4 + {\lambda _4}p_4^5 - \upsilon } \right < {\upsilon ^{ - \delta }}$$ has no solution in primes p1, p2, p3, p4. We show that $$E\left( {\upsilon ,N,\delta } \right) \ll {N^{1 + 2\delta - 1/72 + \varepsilon }}$$ for any ɛ > 0.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0388-16

• Two-weighted estimates for generalized fractional maximal operators on
non-homogeneous spaces
Pages: 1 - 18
Abstract: Let μ be a nonnegative Borel measure on R d satisfying that μ(Q) ⩽ l(Q)n for every cube Q ⊂ R n , where l(Q) is the side length of the cube Q and 0 < n ⩽ d. We study the class of pairs of weights related to the boundedness of radial maximal operators of fractional type associated to a Young function B in the context of non-homogeneous spaces related to the measure μ. Our results include two-weighted norm and weak type inequalities and pointwise estimates. Particularly, we give an improvement of a two-weighted result for certain fractional maximal operator proved in W.Wang, C. Tan, Z. Lou (2012).
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0337-16

• On the maximal run-length function in the Lüroth expansion
• Authors: Yu Sun; Jian Xu
Pages: 1 - 15
Abstract: We obtain a metrical property on the asymptotic behaviour of the maximal run-length function in the Lüroth expansion. We also determine the Hausdorff dimension of a class of exceptional sets of points whose maximal run-length function has sub-linear growth rate.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0474-16

• Fundamental groupoids of digraphs and graphs
• Authors: Alexander Grigor'yan; Rolando Jimenez; Yuri Muranov
Pages: 1 - 31
Abstract: We introduce the notion of fundamental groupoid of a digraph and prove its basic properties. In particular, we obtain a product theorem and an analogue of the Van Kampen theorem. Considering the category of (undirected) graphs as the full subcategory of digraphs, we transfer the results to the category of graphs. As a corollary we obtain the corresponding results for the fundamental groups of digraphs and graphs. We give an application to graph coloring.
PubDate: 2018-01-26
DOI: 10.21136/cmj.2018.0683-15

• Groups with only two nonlinear non-faithful irreducible characters
• Authors: Xiaoyou Chen; Mark L. Lewis
Pages: 1 - 3
Abstract: We determine the groups with exactly two nonlinear non-faithful irreducible characters whose kernels intersect trivially.
PubDate: 2017-12-14
DOI: 10.21136/cmj.2017.0348-17

• A remark concerning Putinar’S model of hyponormal weighted shifts
• Authors: Vasile Lauric
Pages: 1 - 6
Abstract: The question whether a hyponormal weighted shift with trace class self-commutator is the compression modulo the Hilbert-Schmidt class of a normal operator, remains open. It is natural to ask whether Putinar’s construction through which he proved that hyponormal operators are subscalar operators provides the answer to the above question. We show that the normal extension provided by Putinar’s theory does not lead to the extension that would provide a positive answer to the question.
PubDate: 2017-12-13
DOI: 10.21136/cmj.2017.0129-17

• A higher rank Selberg sieve and applications
• Authors: Akshaa Vatwani
Pages: 1 - 25
Abstract: We develop an axiomatic formulation of the higher rank version of the classical Selberg sieve. This allows us to derive a simplified proof of the Zhang and Maynard-Tao result on bounded gaps between primes. We also apply the sieve to other subsequences of the primes and obtain bounded gaps in various settings.
PubDate: 2017-12-12
DOI: 10.21136/cmj.2017.0410-16

• Arithmetic genus of integral space curves
• Authors: Hao Sun
Pages: 1 - 11
Abstract: We give an estimation for the arithmetic genus of an integral space curve which is not contained in a surface of degree k−1. Our main technique is the Bogomolov-Gieseker type inequality for P3 proved by Macrì.
PubDate: 2017-12-08
DOI: 10.21136/cmj.2017.0093-17

• A note on weakly-supplemented subgroups of finite groups
• Authors: Hong Pan
Pages: 1 - 4
Abstract: A subgroup H of a finite group G is weakly-supplemented in G if there exists a proper subgroup K of G such that G = HK. In the paper, we extend one main result of Kong and Liu (2014).
PubDate: 2017-12-08
DOI: 10.21136/cmj.2017.0067-17

• Automorphisms of metacyclic groups
• Authors: Haimiao Chen; Yueshan Xiong; Zhongjian Zhu
Pages: 1 - 13
Abstract: A metacyclic group H can be presented as 〈α, β: α n = 1, β m = α t , βαβ-1 = αr〉 for some n, m, t, r. Each endomorphism σ of H is determined by σ(α) = $${\alpha ^{{x_1}}}{\beta ^{{y_1}}}$$ , σ(β) = $${\alpha ^{{x_2}}}{\beta ^{{y_2}}}$$ for some integers x1, x2, y1, y2. We give sufficient and necessary conditions on x1, x2, y1, y2 for σ to be an automorphism.
PubDate: 2017-12-07
DOI: 10.21136/cmj.2017.0656-16

• Remarks on local Lie algebras of pairs of functions
• Authors: Josef Janyška
Pages: 1 - 23
Abstract: Starting by the famous paper by Kirillov, local Lie algebras of functions over smooth manifolds were studied very intensively by mathematicians and physicists. In the present paper we study local Lie algebras of pairs of functions which generate infinitesimal symmetries of almost-cosymplectic-contact structures of odd dimensional manifolds.
PubDate: 2017-12-06
DOI: 10.21136/cmj.2017.0626-16

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