• Title, Summary, Keyword: multiplicative character

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GAUSS SUMS FOR U(2n + 1,$q^2$)

  • Kim, Dae-San
    • Journal of the Korean Mathematical Society
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    • v.34 no.4
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    • pp.871-894
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    • 1997
  • For a lifted nontrivial additive character $\lambda'$ and a multiplicative character $\chi$ of the finite field with $q^2$ elements, the 'Gauss' sums $\Sigma\lambda'$(tr $\omega$) over $\omega$ $\in$ SU(2n + 1, $q^2$) and $\Sigma\chi$(det $\omega$)$\lambda'$(tr $\omega$) over $\omega$ $\in$ U(2n + 1, $q^2$) are considered. We show that the first sum is a polynomial in q with coefficients involving certain new exponential sums and that the second one is a polynomial in q with coefficients involving powers of the usual twisted Kloosterman sums and the average (over all multiplicative characters of order dividing q-1) of the usual Gauss sums. As a consequence we can determine certain 'generalized Kloosterman sum over nonsingular Hermitian matrices' which were previously determined by J. H. Hodges only in the case that one of the two arguments is zero.

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ON THE DENOMINATOR OF DEDEKIND SUMS

  • Louboutin, Stephane R.
    • Bulletin of the Korean Mathematical Society
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    • v.56 no.4
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    • pp.815-827
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    • 2019
  • It is well known that the denominator of the Dedekind sum s(c, d) divides 2 gcd(d, 3)d and that no smaller denominator independent of c can be expected. In contrast, here we prove that we usually get a smaller denominator in S(H, d), the sum of the s(c, d)'s over all the c's in a subgroup H of order n > 1 in the multiplicative group $(\mathbb{Z}/d\mathbb{Z})^*$. First, we prove that for p > 3 a prime, the sum 2S(H, p) is a rational integer of the same parity as (p-1)/2. We give an application of this result to upper bounds on relative class numbers of imaginary abelian number fields of prime conductor. Finally, we give a general result on the denominator of S(H, d) for non necessarily prime d's. We show that its denominator is a divisor of some explicit divisor of 2d gcd(d, 3).

SPECTRAL LOCALIZING SYSTEMS THAT ARE t-SPLITTING MULTIPLICATIVE SETS OF IDEALS

  • Chang, Gyu-Whan
    • Journal of the Korean Mathematical Society
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    • v.44 no.4
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    • pp.863-872
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    • 2007
  • Let D be an integral domain with quotient field K, A a nonempty set of height-one maximal t-ideals of D, F$({\Lambda})={I{\subseteq}D|I$ is an ideal of D such that $I{\subseteq}P$ for all $P{\in}A}$, and $D_F({\Lambda})={x{\in}K|xA{\subseteq}D$ for some $A{\in}F({\Lambda})}$. In this paper, we prove that if each $P{\in}A$ is the radical of a finite type v-ideal (resp., a principal ideal), then $D_{F({\Lambda})}$ is a weakly Krull domain (resp., generalized weakly factorial domain) if and only if the intersection $D_{F({\Lambda})}={\cap}_{P{\in}A}D_P$ has finite character, if and only if $F({\Lambda})$ is a t-splitting set of ideals, if and only if $F({\Lambda})$ is v-finite.

A Note on S-Noetherian Domains

  • LIM, JUNG WOOK
    • Kyungpook Mathematical Journal
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    • v.55 no.3
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    • pp.507-514
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    • 2015
  • Let D be an integral domain, t be the so-called t-operation on D, and S be a (not necessarily saturated) multiplicative subset of D. In this paper, we study the Nagata ring of S-Noetherian domains and locally S-Noetherian domains. We also investigate the t-Nagata ring of t-locally S-Noetherian domains. In fact, we show that if S is an anti-archimedean subset of D, then D is an S-Noetherian domain (respectively, locally S-Noetherian domain) if and only if the Nagata ring $D[X]_N$ is an S-Noetherian domain (respectively, locally S-Noetherian domain). We also prove that if S is an anti-archimedean subset of D, then D is a t-locally S-Noetherian domain if and only if the polynomial ring D[X] is a t-locally S-Noetherian domain, if and only if the t-Nagata ring $D[X]_{N_v}$ is a t-locally S-Noetherian domain.

Private Wildcard Query over FHE-Encrypted Databases (동형암호기반의 안전한 와일드카드 쿼리)

  • Kim, Myungsun
    • Journal of Security Engineering
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    • v.14 no.2
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    • pp.115-130
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    • 2017
  • In this paper, we deal with a method to securely process a query to a database outsourced to a remote server. In particular we are interested in a wildcard query in which a database query statement contains a wildcard character. Moreover, we consider a setting where users' data are very sensitive (e.g., medical information) so that they should be handled very carefully in the light of security. To this end, we use a fully homomorphic encryption scheme as a baseline encryption. Together with this encryption scheme, our basic idea to the wildcard query problem is to segment an input string as ${\tau}$-gram and to represent the ${\tau}$-gram into the correspnong polynomial $Q_{\tau}(x)$. Later a user sends a wildcard pattern including p, then the server evaluate the polynomial as $Q_{\tau}(p)$, and so if the evaluation result is equal to 0, then it implies that the string involves the pattern p as a substring. All computations are performed on encryptions so that we can guarantee that it is as secure as the baseline encryption scheme applied to the protocol. Finally our construction only requires multiplicative depth $O(log_2k)$ where k is the maximum length of strings.

An Analysis of Teachers' Pedagogical Content Knowledge about Teaching Ratio and Rate (비와 비율 지도에 대한 교사의 PCK 분석)

  • Park, Seulah;Oh, Youngyoul
    • Journal of Elementary Mathematics Education in Korea
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    • v.21 no.1
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    • pp.215-241
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    • 2017
  • This study analyzed teachers' Pedagogical Content Knowledge (PCK) regarding the pedagogical aspect of the instruction of ratio and rate in order to look into teachers' problems during the process of teaching ratio and rate. This study aims to clarify problems in teachers' PCK and promote the consideration of the materialization of an effective and practical class in teaching ratio and rate by identifying the improvements based on problems indicated in PCK. We subdivided teachers' PCK into four areas: mathematical content knowledge, teaching method and evaluation knowledge, understanding knowledge about students' learning, and class situation knowledge. The conclusion of this study based on analysis of the results is as follows. First, in the 'mathematical content knowledge' aspect of PCK, teachers need to understand the concept of ratio from the perspective of multiplicative comparison of two quantities, and the concept of rate based on understanding of two quantities that are related proportionally. Also, teachers need to introduce ratio and rate by providing students with real-life context, differentiate ratios from fractions, and teach the usefulness of percentage in real life. Second, in the 'teaching method and evaluation knowledge' aspect of PCK, teachers need to establish teaching goals about the students' comprehension of the concept of ratio and rate and need to operate performance evaluation of the students' understanding of ratio and rate. Also, teachers need to improve their teaching methods such as discovery learning, research study and activity oriented methods. Third, in the 'understanding knowledge about students' learning' aspect of PCK, teachers need to diversify their teaching methods for correcting errors by suggesting activities to explore students' own errors rather than using explanation oriented correction. Also, teachers need to reflect students' affective aspects in mathematics class. Fourth, in the 'class situation knowledge' aspect of PCK, teachers need to supplement textbook activities with independent consciousness and need to diversify the form of class groups according to the character of the activities.

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