Bulletin of the
Korean Mathematical Society
BKMS

ISSN(Print) 1015-8634 ISSN(Online) 2234-3016

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  • 2023-05-31

    On the hybrid mean value of generalized Dedekind sums, generalized Hardy sums and Kloosterman sums

    Qing Tian, Yan Wang

    Abstract : The main purpose of this paper is to study the hybrid mean value problem involving generalized Dedekind sums, generalized Hardy sums and Kloosterman sums. Some exact computational formulas are given by using the properties of Gauss sums and the mean value theorem of the Dirichlet L-function. A result of W. Peng and T. P. Zhang [12] is extended. The new results avoid the restriction that $q$ is a prime.

  • 2023-11-30

    Operators $A$, $B$ for which the Aluthge transform $\widetilde{AB}$ is a generalised $n$-projection

    Bhagwati Duggal, In Hyoun Kim

    Abstract : A Hilbert space operator $A\in{\mathcal B(H)}$ is a generalised \linebreak $n$-projection, denoted $A\in (G-n-P)$, if ${A^*}^n=A$. $(G-n-P)$-operators $A$ are normal operators with finitely countable spectra $\sigma(A)$, subsets of the set $\{0\}\cup\{\sqrt[n+1]{1}\}$. The Aluthge transform $\tilde{A}$ of $A\in{\mathcal B(H)}$ may be $(G-n-P)$ without $A$ being $(G-n-P)$. For doubly commuting operators $A, B\in{\mathcal B(H)}$ such that $\sigma(AB)=\sigma(A)\sigma(B)$ and $\|A\|\|B\|\leq \left\|\widetilde{AB}\right\|$, $\widetilde{AB}\in (G-n-P)$ if and only if $A=\left\|\tilde{A}\right\|(A_{00}\oplus(A_{0}\oplus A_u))$ and $B=\left\|\tilde{B}\right\|(B_0\oplus B_u)$, where $A_{00}$ and $B_0$, and $A_0\oplus A_u$ and $B_u$, doubly commute, $A_{00}B_0$ and $A_0$ are 2 nilpotent, $A_u$ and $B_u$ are unitaries, $A^{*n}_u=A_u$ and $B^{*n}_u=B_u$. Furthermore, a necessary and sufficient condition for the operators $\alpha A$, $\beta B$, $\alpha \tilde{A}$ and $\beta \tilde{B}$, $\alpha=\frac{1}{\left\|\tilde{A}\right\|}$ and $\beta=\frac{1}{\left\|\tilde{B}\right\|}$, to be $(G-n-P)$ is that $A$ and $B$ are spectrally normaloid at $0$.

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  • 2023-09-30

    Relationship between the structure of a factor ring $R/P$ and derivations of $R$

    Karim Bouchannafa, Moulay Abdallah Idrissi, Lahcen Oukhtite

    Abstract : The purpose of this paper is to study the relationship between the structure of a factor ring $R/P$ and the behavior of some derivations of $R$. More precisely, we establish a connection between the commutativity of $R/P$ and derivations of $R$ satisfying specific identities involving the prime ideal $P$. Moreover, we provide an example to show that our results cannot be extended to semi-prime ideals.

  • 2023-11-30

    Two-weight norm estimates for square functions associated to fractional Schr{\"o}dinger operators with Hardy potential

    Tongxin Kang, Yang Zou

    Abstract : Let $d\in\mathbb{N}$ and ${\alpha}\in(0,\min\{2,d\})$. For any $a\in[a^\ast,\infty)$, the fractional Schr\"odinger operator $\mathcal{L}_a$ is defined by \begin{equation*} \mathcal{L}_a:=(-\Delta)^{{\alpha}/2}+a{|x|}^{-{\alpha}}, \end{equation*} where $a^*:=-{\frac{2^{\alpha}{\Gamma}((d+{\alpha})/4)^2}{{\Gamma}((d-{\alpha})/4)^2}}$. In this paper, we study two-weight Sobolev inequalities associated with $\mathcal{L}_a$ and two-weight norm estimates for several square functions associated with $\mathcal{L}_a$.

  • 2023-03-31

    On nuclearity of semigroup crossed products

    Qing Meng

    Abstract : In this paper, we study nuclearity of semigroup crossed products for quasi-lattice ordered groups. We show the relationships among nuclearity of the semigroup crossed product, amenability of the quasi-lattice ordered group and nuclearity of the underlying $C^*$-algebra.

  • 2024-05-31

    On weakly $(m,n)$-prime ideals of commutative rings

    Hani A. Khashan, Ece Yetkin Celikel

    Abstract : Let $R$ be a commutative ring with identity and $m$, $n$ be positive integers. In this paper, we introduce the class of weakly $(m,n)$-prime ideals generalizing $(m,n)$-prime and weakly $(m,n)$-closed ideals. A proper ideal $I$ of $R$ is called weakly $(m,n)$-prime if for $a,b\in R$, $0\neq a^{m}b\in I$ implies either $a^{n}\in I$ or $b\in I$. We justify several properties and characterizations of weakly $(m,n)$-prime ideals with many supporting examples. Furthermore, we investigate weakly $(m,n)$-prime ideals under various contexts of constructions such as direct products, localizations and homomorphic images. Finally, we discuss the behaviour of this class of ideals in idealization and amalgamated rings.

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  • 2024-01-31

    An Abelian category of weakly cofinite modules

    Gholamreza Pirmohammadi

    Abstract : Let $I$ be an ideal of a commutative Noetherian semi-local ring $R$ and $M$ be an $R$-module. It is shown that if $\dim M\leq 2$ and $\Supp_R M\subseteq V(I)$, then $M$ is $I$-weakly cofinite if (and only if) the $R$-modules $\Hom_R(R/I,M)$ and $\Ext^1_R(R/I,M)$ are weakly Laskerian. As a consequence of this result, it is shown that the category of all $I$-weakly cofinite modules $X$ with $\dim X\leq 2$, forms an Abelian subcategory of the category of all $R$-modules. Finally, it is shown that if $\dim R/I\leq 2$, then for each pair of finitely generated $R$-modules $M$ and $N$ and each pair of the integers $i,j\geq 0$, the $R$-modules $\Tor_i^R(N,H^j_I(M))$ and $\Ext^i_R(N,H^j_I(M))$ are $I$-weakly cofinite.

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  • 2023-05-31

    Vanishing theorems for weighted harmonic $1$-forms on smooth metric measure spaces

    Xiaoli Chao, Weili Wang

    Abstract : In this paper, we prove some vanishing theorems under the assumptions of weighted BiRic curvature or $m$-Bakry-\'{E}mery-Ricci curvature bounded from below.

  • 2023-09-30

    Conditional Fourier--Feynman transform and conditional convolution product associated with infinite dimensional conditioning function

    Jae Gil Choi, Sang Kil Shim

    Abstract : In this paper, we use an infinite dimensional conditioning function to define a conditional Fourier--Feynman transform (CFFT) and a conditional convolution product (CCP) on the Wiener space. We establish the existences of the CFFT and the CCP for bounded functions which form a Banach algebra. We then provide fundamental relationships between the CFFTs and the CCPs.

  • 2023-11-30

    Bredon homology of wallpaper groups

    Ramon Flores

    Abstract : In this paper we compute the Bredon homology of wallpaper groups with respect to the family of finite groups and with coefficients in the complex representation ring. We provide explicit bases of the homology groups in terms of irreducible characters of the stabilizers.

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November, 2024
Vol.61 No.6

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