Pub Date : 2025-11-03DOI: 10.1016/j.ffa.2025.102755
Bogdan Nica
We obtain transformation formulas for quadratic character sums with quartic and cubic polynomial arguments.
得到了具有四次和三次多项式参数的二次特征和的变换公式。
{"title":"On quadratic character sums over quartics","authors":"Bogdan Nica","doi":"10.1016/j.ffa.2025.102755","DOIUrl":"10.1016/j.ffa.2025.102755","url":null,"abstract":"<div><div>We obtain transformation formulas for quadratic character sums with quartic and cubic polynomial arguments.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102755"},"PeriodicalIF":1.2,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145466208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-31DOI: 10.1016/j.ffa.2025.102747
Jorge Morales
The relation between cycles of indefinite binary quadratic forms over and continued fractions is classical and well-known. We describe a similar relation for binary quadratic forms over the polynomial ring , where q is a power of an odd prime. In this context, the cycles of the classical theory are replaced by orbits of the metacyclic group acting on the set of reduced forms of a given discriminant, where each orbit corresponds to a proper equivalence class.
{"title":"Continued fractions and indefinite binary quadratic forms over Fq[t]","authors":"Jorge Morales","doi":"10.1016/j.ffa.2025.102747","DOIUrl":"10.1016/j.ffa.2025.102747","url":null,"abstract":"<div><div>The relation between cycles of indefinite binary quadratic forms over <span><math><mi>Z</mi></math></span> and continued fractions is classical and well-known. We describe a similar relation for binary quadratic forms over the polynomial ring <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub><mo>[</mo><mi>t</mi><mo>]</mo></math></span>, where <em>q</em> is a power of an odd prime. In this context, the cycles of the classical theory are replaced by orbits of the metacyclic group <span><math><msubsup><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow><mrow><mo>⁎</mo></mrow></msubsup><mo>⋊</mo><mi>Z</mi></math></span> acting on the set of reduced forms of a given discriminant, where each orbit corresponds to a proper equivalence class.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102747"},"PeriodicalIF":1.2,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-30DOI: 10.1016/j.ffa.2025.102746
Ferdinand Ihringer , Andrey Kupavskii
The famous Erdős-Rado sunflower conjecture suggests that an s-sunflower-free family of k-element sets has size at most for some absolute constant C. In this note, we investigate the analog problem for k-spaces over the field with q elements. For , we show that the largest s-sunflower-free family satisfies For , we show that Our lower bounds rely on an iterative construction that uses lifted maximum rank-distance (MRD) codes.
{"title":"The Erdős-Rado sunflower problem for vector spaces","authors":"Ferdinand Ihringer , Andrey Kupavskii","doi":"10.1016/j.ffa.2025.102746","DOIUrl":"10.1016/j.ffa.2025.102746","url":null,"abstract":"<div><div>The famous Erdős-Rado sunflower conjecture suggests that an <em>s</em>-sunflower-free family of <em>k</em>-element sets has size at most <span><math><msup><mrow><mo>(</mo><mi>C</mi><mi>s</mi><mo>)</mo></mrow><mrow><mi>k</mi></mrow></msup></math></span> for some absolute constant <em>C</em>. In this note, we investigate the analog problem for <em>k</em>-spaces over the field with <em>q</em> elements. For <span><math><mi>s</mi><mo>≥</mo><mi>k</mi><mo>+</mo><mn>1</mn></math></span>, we show that the largest <em>s</em>-sunflower-free family <span><math><mi>F</mi></math></span> satisfies<span><span><span><math><mn>1</mn><mo>≤</mo><mo>|</mo><mi>F</mi><mo>|</mo><mo>/</mo><msup><mrow><mi>q</mi></mrow><mrow><mo>(</mo><mi>s</mi><mo>−</mo><mn>1</mn><mo>)</mo><mrow><mo>(</mo><mtable><mtr><mtd><mrow><mi>k</mi><mo>+</mo><mn>1</mn></mrow></mtd></mtr><mtr><mtd><mn>2</mn></mtd></mtr></mtable><mo>)</mo></mrow><mo>−</mo><mi>k</mi></mrow></msup><mo>≤</mo><msup><mrow><mo>(</mo><mi>q</mi><mo>/</mo><mo>(</mo><mi>q</mi><mo>−</mo><mn>1</mn><mo>)</mo><mo>)</mo></mrow><mrow><mi>k</mi></mrow></msup><mo>.</mo></math></span></span></span> For <span><math><mi>s</mi><mo>≤</mo><mi>k</mi></math></span>, we show that<span><span><span><math><msup><mrow><mi>q</mi></mrow><mrow><mo>−</mo><mrow><mo>(</mo><mtable><mtr><mtd><mrow><mi>k</mi><mo>+</mo><mn>1</mn></mrow></mtd></mtr><mtr><mtd><mn>2</mn></mtd></mtr></mtable><mo>)</mo></mrow></mrow></msup><mo>≤</mo><mo>|</mo><mi>F</mi><mo>|</mo><mo>/</mo><msup><mrow><mi>q</mi></mrow><mrow><mo>(</mo><mi>s</mi><mo>−</mo><mn>1</mn><mo>)</mo><mrow><mo>(</mo><mtable><mtr><mtd><mrow><mi>k</mi><mo>+</mo><mn>1</mn></mrow></mtd></mtr><mtr><mtd><mn>2</mn></mtd></mtr></mtable><mo>)</mo></mrow><mo>−</mo><mi>k</mi></mrow></msup><mo>≤</mo><msup><mrow><mo>(</mo><mi>q</mi><mo>/</mo><mo>(</mo><mi>q</mi><mo>−</mo><mn>1</mn><mo>)</mo><mo>)</mo></mrow><mrow><mi>k</mi></mrow></msup><mo>.</mo></math></span></span></span> Our lower bounds rely on an iterative construction that uses lifted maximum rank-distance (MRD) codes.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102746"},"PeriodicalIF":1.2,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-30DOI: 10.1016/j.ffa.2025.102749
Ferruh Özbudak, İlknur Öztürk
We prove that the third generalized covering radius of binary primitive double-error-correcting BCH codes of length is 7 if is an even integer. We also prove that the third generalized covering radius of binary primitive double-error-correcting BCH codes of length is either 6 or 7 if is an odd integer. We use some methods derived from the theory of algebraic curves over finite fields in our proofs and we obtain some further related results.
{"title":"The third generalized covering radius for binary primitive double-error-correcting BCH codes","authors":"Ferruh Özbudak, İlknur Öztürk","doi":"10.1016/j.ffa.2025.102749","DOIUrl":"10.1016/j.ffa.2025.102749","url":null,"abstract":"<div><div>We prove that the third generalized covering radius of binary primitive double-error-correcting BCH codes of length <span><math><msup><mrow><mn>2</mn></mrow><mrow><mi>m</mi></mrow></msup><mo>−</mo><mn>1</mn></math></span> is 7 if <span><math><mi>m</mi><mo>≥</mo><mn>8</mn></math></span> is an even integer. We also prove that the third generalized covering radius of binary primitive double-error-correcting BCH codes of length <span><math><msup><mrow><mn>2</mn></mrow><mrow><mi>m</mi></mrow></msup><mo>−</mo><mn>1</mn></math></span> is either 6 or 7 if <span><math><mi>m</mi><mo>≥</mo><mn>9</mn></math></span> is an odd integer. We use some methods derived from the theory of algebraic curves over finite fields in our proofs and we obtain some further related results.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102749"},"PeriodicalIF":1.2,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416451","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-29DOI: 10.1016/j.ffa.2025.102750
Junfeng Jia, Yanxun Chang
Flag codes, as a generalization of subspace codes, can transmit more information since the subspace channel is used many times. In this paper, we construct optimum distance flag codes of the (generalized) full admissible type on with cardinality , where with and . Let denote the maximum cardinality of such codes. We provide a lower bound for this quantity. We further present a systematic construction of cardinality-consistent flag codes with larger cardinality for general flag distances. By the composition of subspace polynomials, we construct cardinality-consistent cyclic flag codes on with larger cardinality than those presented in the literature.
{"title":"Cardinality-consistent flag codes with larger cardinality","authors":"Junfeng Jia, Yanxun Chang","doi":"10.1016/j.ffa.2025.102750","DOIUrl":"10.1016/j.ffa.2025.102750","url":null,"abstract":"<div><div>Flag codes, as a generalization of subspace codes, can transmit more information since the subspace channel is used many times. In this paper, we construct optimum distance flag codes of the (generalized) full admissible type <span><math><mi>t</mi><mo>=</mo><mo>(</mo><mn>1</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>k</mi><mo>,</mo><mi>n</mi><mo>−</mo><mi>k</mi><mo>,</mo><mo>…</mo><mo>,</mo><mi>n</mi><mo>−</mo><mn>1</mn><mo>)</mo></math></span> on <span><math><msubsup><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msubsup></math></span> with cardinality <span><math><msubsup><mrow><mo>∑</mo></mrow><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>s</mi><mo>−</mo><mn>1</mn></mrow></msubsup><msup><mrow><mi>q</mi></mrow><mrow><mi>i</mi><mi>k</mi><mo>+</mo><mi>h</mi></mrow></msup><mo>+</mo><mn>1</mn></math></span>, where <span><math><mi>n</mi><mo>=</mo><mi>s</mi><mi>k</mi><mo>+</mo><mi>h</mi></math></span> with <span><math><mi>s</mi><mo>≥</mo><mn>2</mn></math></span> and <span><math><mn>0</mn><mo>≤</mo><mi>h</mi><mo><</mo><mi>k</mi></math></span>. Let <span><math><msubsup><mrow><mi>A</mi></mrow><mrow><mi>q</mi></mrow><mrow><mi>f</mi></mrow></msubsup><mo>(</mo><mi>n</mi><mo>,</mo><msup><mrow><mi>D</mi></mrow><mrow><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></mrow></msup><mo>,</mo><mi>t</mi><mo>)</mo></math></span> denote the maximum cardinality of such codes. We provide a lower bound for this quantity. We further present a systematic construction of cardinality-consistent flag codes with larger cardinality for general flag distances. By the composition of subspace polynomials, we construct cardinality-consistent cyclic flag codes on <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub></math></span> with larger cardinality than those presented in the literature.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102750"},"PeriodicalIF":1.2,"publicationDate":"2025-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this article, we study the existence and distribution of elements in finite field extensions with prescribed traces in several intermediate extensions that are also either normal or primitive normal. In the former case, we fully characterize the conditions under which such elements exist and provide an explicit enumeration of these elements. In the latter case we provide asymptotic results.
{"title":"Normal and primitive normal elements with prescribed traces in intermediate extensions of finite fields","authors":"Arpan Chandra Mazumder , Giorgos Kapetanakis , Dhiren Kumar Basnet","doi":"10.1016/j.ffa.2025.102745","DOIUrl":"10.1016/j.ffa.2025.102745","url":null,"abstract":"<div><div>In this article, we study the existence and distribution of elements in finite field extensions with prescribed traces in several intermediate extensions that are also either normal or primitive normal. In the former case, we fully characterize the conditions under which such elements exist and provide an explicit enumeration of these elements. In the latter case we provide asymptotic results.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102745"},"PeriodicalIF":1.2,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-23DOI: 10.1016/j.ffa.2025.102742
Farhana Kousar , Maosheng Xiong
In a recent paper [30] Zhang et al. constructed 17 families of permutation pentanomials of the form over where . In this paper for 14 of these 17 families we provide a simple explanation as to why they are permutations. We also extend these 14 families into three general classes of permutation pentanomials over .
{"title":"Some permutation pentanomials over finite fields of even characteristic","authors":"Farhana Kousar , Maosheng Xiong","doi":"10.1016/j.ffa.2025.102742","DOIUrl":"10.1016/j.ffa.2025.102742","url":null,"abstract":"<div><div>In a recent paper <span><span>[30]</span></span> Zhang et al. constructed 17 families of permutation pentanomials of the form <span><math><msup><mrow><mi>x</mi></mrow><mrow><mi>t</mi></mrow></msup><mo>+</mo><msup><mrow><mi>x</mi></mrow><mrow><msub><mrow><mi>r</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mi>q</mi><mo>−</mo><mn>1</mn><mo>)</mo><mo>+</mo><mi>t</mi></mrow></msup><mo>+</mo><msup><mrow><mi>x</mi></mrow><mrow><msub><mrow><mi>r</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mi>q</mi><mo>−</mo><mn>1</mn><mo>)</mo><mo>+</mo><mi>t</mi></mrow></msup><mo>+</mo><msup><mrow><mi>x</mi></mrow><mrow><msub><mrow><mi>r</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>(</mo><mi>q</mi><mo>−</mo><mn>1</mn><mo>)</mo><mo>+</mo><mi>t</mi></mrow></msup><mo>+</mo><msup><mrow><mi>x</mi></mrow><mrow><msub><mrow><mi>r</mi></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>q</mi><mo>−</mo><mn>1</mn><mo>)</mo><mo>+</mo><mi>t</mi></mrow></msup></math></span> over <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></msub></math></span> where <span><math><mi>q</mi><mo>=</mo><msup><mrow><mn>2</mn></mrow><mrow><mi>m</mi></mrow></msup></math></span>. In this paper for 14 of these 17 families we provide a simple explanation as to why they are permutations. We also extend these 14 families into three general classes of permutation pentanomials over <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></msub></math></span>.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102742"},"PeriodicalIF":1.2,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-22DOI: 10.1016/j.ffa.2025.102739
Stephen D. Cohen , Peter V. Danchev , Tomás Oliveira e Silva
We classify those finite fields whose members are the sum of an n-potent element with and a 4-potent element. It is shown that there are precisely ten non-trivial pairs for which this is the case. This continues a recent publication by Abyzov et al. (2024) [1] in which the tripotent version was examined in-depth, inasmuch as it extends recent results in this seam of research established by Abyzov and Tapkin (2024) [4].
{"title":"Finite fields whose members are the sum of a potent and a 4-potent","authors":"Stephen D. Cohen , Peter V. Danchev , Tomás Oliveira e Silva","doi":"10.1016/j.ffa.2025.102739","DOIUrl":"10.1016/j.ffa.2025.102739","url":null,"abstract":"<div><div>We classify those finite fields <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub></math></span> whose members are the sum of an <em>n</em>-potent element with <span><math><mi>n</mi><mo>></mo><mn>1</mn></math></span> and a 4-potent element. It is shown that there are precisely ten non-trivial pairs <span><math><mo>(</mo><mi>q</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> for which this is the case. This continues a recent publication by Abyzov et al. (2024) <span><span>[1]</span></span> in which the tripotent version was examined in-depth, inasmuch as it extends recent results in this seam of research established by Abyzov and Tapkin (2024) <span><span>[4]</span></span>.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102739"},"PeriodicalIF":1.2,"publicationDate":"2025-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A function from to is said to be kth order sum-free if the sum of its values over each k-dimensional -affine subspace of is nonzero. This notion was recently introduced by C. Carlet as, among other things, a generalization of APN functions. At the center of this new topic is a conjecture about the sum-freedom of the multiplicative inverse function (with defined to be 0). It is known that is 2nd order (equivalently, th order) sum-free if and only if n is odd, and it is conjectured that for , is never kth order sum-free. The conjecture has been confirmed for even n but remains open for odd n. In the present paper, we show that the conjecture holds under each of the following conditions: (1) ; (2) ; (3) ; (4) the smallest prime divisor l of n satisfies . We also determine the “right” q-ary generalization of the binary multiplicative inverse function in the context of sum-freedom. This q-ary generalization not only maintains most results for its binary version, but also exhibits some extraordinary phenomena that are not observed in the binary case.
{"title":"On sum-free functions","authors":"Alyssa Ebeling , Xiang-dong Hou , Ashley Rydell , Shujun Zhao","doi":"10.1016/j.ffa.2025.102744","DOIUrl":"10.1016/j.ffa.2025.102744","url":null,"abstract":"<div><div>A function from <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub></math></span> to <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub></math></span> is said to be <em>kth order sum-free</em> if the sum of its values over each <em>k</em>-dimensional <span><math><msub><mrow><mi>F</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>-affine subspace of <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub></math></span> is nonzero. This notion was recently introduced by C. Carlet as, among other things, a generalization of APN functions. At the center of this new topic is a conjecture about the sum-freedom of the multiplicative inverse function <span><math><msub><mrow><mi>f</mi></mrow><mrow><mtext>inv</mtext></mrow></msub><mo>(</mo><mi>x</mi><mo>)</mo><mo>=</mo><msup><mrow><mi>x</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> (with <span><math><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> defined to be 0). It is known that <span><math><msub><mrow><mi>f</mi></mrow><mrow><mtext>inv</mtext></mrow></msub></math></span> is 2nd order (equivalently, <span><math><mo>(</mo><mi>n</mi><mo>−</mo><mn>2</mn><mo>)</mo></math></span>th order) sum-free if and only if <em>n</em> is odd, and it is conjectured that for <span><math><mn>3</mn><mo>≤</mo><mi>k</mi><mo>≤</mo><mi>n</mi><mo>−</mo><mn>3</mn></math></span>, <span><math><msub><mrow><mi>f</mi></mrow><mrow><mtext>inv</mtext></mrow></msub></math></span> is never <em>k</em>th order sum-free. The conjecture has been confirmed for even <em>n</em> but remains open for odd <em>n</em>. In the present paper, we show that the conjecture holds under each of the following conditions: (1) <span><math><mi>n</mi><mo>=</mo><mn>13</mn></math></span>; (2) <span><math><mn>3</mn><mo>|</mo><mi>n</mi></math></span>; (3) <span><math><mn>5</mn><mo>|</mo><mi>n</mi></math></span>; (4) the smallest prime divisor <em>l</em> of <em>n</em> satisfies <span><math><mo>(</mo><mi>l</mi><mo>−</mo><mn>1</mn><mo>)</mo><mo>(</mo><mi>l</mi><mo>+</mo><mn>2</mn><mo>)</mo><mo>≤</mo><mo>(</mo><mi>n</mi><mo>+</mo><mn>1</mn><mo>)</mo><mo>/</mo><mn>2</mn></math></span>. We also determine the “right” <em>q</em>-ary generalization of the binary multiplicative inverse function <span><math><msub><mrow><mi>f</mi></mrow><mrow><mtext>inv</mtext></mrow></msub></math></span> in the context of sum-freedom. This <em>q</em>-ary generalization not only maintains most results for its binary version, but also exhibits some extraordinary phenomena that are not observed in the binary case.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102744"},"PeriodicalIF":1.2,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-20DOI: 10.1016/j.ffa.2025.102743
Tongliang Zhang , Lijing Zheng , Hengtai Wang , Jie Peng , Yanjun Li
Let . In a recent paper [34], Zhang and Zheng investigated several classes of permutation pentanomials of the form over with a certain linearized polynomial . They applied the multivariate method and specific techniques to analyze the number of solutions of certain equations, and proposed an open problem: the permutation property of some pentanomials of this form remains unproven. In this paper, inspired by the idea of [12], we further characterize the permutation property of such pentanomials over . The techniques presented in this paper will be useful for investigating more new classes of permutation polynomials.
{"title":"Further results on permutation pentanomials over Fq3 in characteristic two","authors":"Tongliang Zhang , Lijing Zheng , Hengtai Wang , Jie Peng , Yanjun Li","doi":"10.1016/j.ffa.2025.102743","DOIUrl":"10.1016/j.ffa.2025.102743","url":null,"abstract":"<div><div>Let <span><math><mi>q</mi><mo>=</mo><msup><mrow><mn>2</mn></mrow><mrow><mi>m</mi></mrow></msup></math></span>. In a recent paper <span><span>[34]</span></span>, Zhang and Zheng investigated several classes of permutation pentanomials of the form <span><math><msub><mrow><mi>ϵ</mi></mrow><mrow><mn>0</mn></mrow></msub><msup><mrow><mi>x</mi></mrow><mrow><msub><mrow><mi>d</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup><mo>+</mo><mi>L</mi><mo>(</mo><msub><mrow><mi>ϵ</mi></mrow><mrow><mn>1</mn></mrow></msub><msup><mrow><mi>x</mi></mrow><mrow><msub><mrow><mi>d</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msup><mo>+</mo><msub><mrow><mi>ϵ</mi></mrow><mrow><mn>2</mn></mrow></msub><msup><mrow><mi>x</mi></mrow><mrow><msub><mrow><mi>d</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msup><mo>)</mo></math></span> over <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mn>3</mn></mrow></msup></mrow></msub><mspace></mspace><mo>(</mo><msub><mrow><mi>d</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>=</mo><mn>1</mn><mo>,</mo><mn>2</mn><mo>,</mo><mn>4</mn><mo>)</mo></math></span> with a certain linearized polynomial <span><math><mi>L</mi><mo>(</mo><mi>x</mi><mo>)</mo></math></span>. They applied the multivariate method and specific techniques to analyze the number of solutions of certain equations, and proposed an open problem: the permutation property of some pentanomials of this form remains unproven. In this paper, inspired by the idea of <span><span>[12]</span></span>, we further characterize the permutation property of such pentanomials over <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mn>3</mn></mrow></msup></mrow></msub><mspace></mspace><mo>(</mo><msub><mrow><mi>d</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>=</mo><mn>1</mn><mo>,</mo><mn>2</mn><mo>,</mo><mn>4</mn><mo>)</mo></math></span>. The techniques presented in this paper will be useful for investigating more new classes of permutation polynomials.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"110 ","pages":"Article 102743"},"PeriodicalIF":1.2,"publicationDate":"2025-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}