Pub Date : 2025-07-07DOI: 10.1016/j.ffa.2025.102687
Nuno Arala , Sam Chow
We establish expansion properties for suitably generic polynomials of degree d in variables over finite fields. In particular, we show that if is a polynomial of degree d, whose coefficients avoid the zero locus of some explicit polynomial of degree , and are suitably large, then . Our methods rely on a higher-degree extension of a result of Vinh on point–line incidences over a finite field.
{"title":"Expansion properties of polynomials over finite fields","authors":"Nuno Arala , Sam Chow","doi":"10.1016/j.ffa.2025.102687","DOIUrl":"10.1016/j.ffa.2025.102687","url":null,"abstract":"<div><div>We establish expansion properties for suitably generic polynomials of degree <em>d</em> in <span><math><mi>d</mi><mo>+</mo><mn>1</mn></math></span> variables over finite fields. In particular, we show that if <span><math><mi>P</mi><mo>∈</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub><mo>[</mo><msub><mrow><mi>x</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>x</mi></mrow><mrow><mi>d</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>]</mo></math></span> is a polynomial of degree <em>d</em>, whose coefficients avoid the zero locus of some explicit polynomial of degree <span><math><msub><mrow><mi>O</mi></mrow><mrow><mi>d</mi></mrow></msub><mo>(</mo><mn>1</mn><mo>)</mo></math></span>, and <span><math><msub><mrow><mi>X</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>X</mi></mrow><mrow><mi>d</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>⊆</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub></math></span> are suitably large, then <span><math><mo>|</mo><mi>P</mi><mo>(</mo><msub><mrow><mi>X</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>X</mi></mrow><mrow><mi>d</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>)</mo><mo>|</mo><mo>=</mo><mi>q</mi><mo>−</mo><mi>O</mi><mo>(</mo><mn>1</mn><mo>)</mo></math></span>. Our methods rely on a higher-degree extension of a result of Vinh on point–line incidences over a finite field.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"108 ","pages":"Article 102687"},"PeriodicalIF":1.2,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144570241","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 : 2025-07-07DOI: 10.1016/j.ffa.2025.102689
Rezhna M. Hussein, Haval M. Mohammed Salih
In this article, we provide a comprehensive classification of all primitive genus one and genus two systems of the finite group G with , where q is a prime power. Also, we use computational tools to show that G possesses no genus g group if where , and 2.
{"title":"Projective symplectic groups of genus one and two","authors":"Rezhna M. Hussein, Haval M. Mohammed Salih","doi":"10.1016/j.ffa.2025.102689","DOIUrl":"10.1016/j.ffa.2025.102689","url":null,"abstract":"<div><div>In this article, we provide a comprehensive classification of all primitive genus one and genus two systems of the finite group <em>G</em> with <span><math><mi>P</mi><mi>S</mi><mi>p</mi><mo>(</mo><mn>4</mn><mo>,</mo><mi>q</mi><mo>)</mo><mo>≤</mo><mi>G</mi><mo>≤</mo><mi>A</mi><mi>u</mi><mi>t</mi><mo>(</mo><mi>P</mi><mi>S</mi><mi>p</mi><mo>(</mo><mn>4</mn><mo>,</mo><mi>q</mi><mo>)</mo><mo>)</mo></math></span>, where <em>q</em> is a prime power. Also, we use computational tools to show that <em>G</em> possesses no genus <em>g</em> group if <span><math><mi>q</mi><mo>></mo><mn>5</mn></math></span> where <span><math><mi>g</mi><mo>=</mo><mn>1</mn></math></span>, and 2.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"108 ","pages":"Article 102689"},"PeriodicalIF":1.2,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144569057","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 : 2025-07-07DOI: 10.1016/j.ffa.2025.102686
Rajendra Prasad Rajpurohit, Maheshanand Bhaintwal
In this paper, we present a novel construction of maximally recoverable codes with two-level hierarchical locality using a parity-check matrix approach. The construction given in this paper utilizes Gabidulin codes for mid-level heavy parities and linearized Reed-Solomon codes for global heavy parities. When the number of local sets is small, this construction performs better than the previously known constructions as the field size required in our construction is smaller for such cases, making it useful for practical scenarios in distributed data storage systems. We also consider a special case of our construction when the number of global parities is fixed and is equal to 1. In this case, our construction performs better when the number of local sets is small and the number of mid-level parities is even.
{"title":"A new construction of maximally recoverable codes with hierarchical locality","authors":"Rajendra Prasad Rajpurohit, Maheshanand Bhaintwal","doi":"10.1016/j.ffa.2025.102686","DOIUrl":"10.1016/j.ffa.2025.102686","url":null,"abstract":"<div><div>In this paper, we present a novel construction of maximally recoverable codes with two-level hierarchical locality using a parity-check matrix approach. The construction given in this paper utilizes Gabidulin codes for mid-level heavy parities and linearized Reed-Solomon codes for global heavy parities. When the number of local sets is small, this construction performs better than the previously known constructions as the field size required in our construction is smaller for such cases, making it useful for practical scenarios in distributed data storage systems. We also consider a special case of our construction when the number of global parities is fixed and is equal to 1. In this case, our construction performs better when the number of local sets is small and the number of mid-level parities is even.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"109 ","pages":"Article 102686"},"PeriodicalIF":1.2,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144570348","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 : 2025-07-07DOI: 10.1016/j.ffa.2025.102693
Joachim König
Many interesting questions in arithmetic dynamics revolve, in one way or another, around the (local and/or global) reducibility behavior of iterates of a polynomial. We show that for very general families of integer polynomials f (and, more generally, rational functions over number fields), the set of stable primes, i.e., primes modulo which all iterates of f are irreducible, is a density zero set. Compared to previous results, our families cover a much wider ground, and in particular apply to 100% of polynomials of any given odd degree, thus adding evidence to the conjecture that polynomials with a “large” set of stable primes are necessarily of a very specific shape, and in particular are necessarily postcritically finite.
{"title":"On the set of stable primes for postcritically infinite maps over number fields","authors":"Joachim König","doi":"10.1016/j.ffa.2025.102693","DOIUrl":"10.1016/j.ffa.2025.102693","url":null,"abstract":"<div><div>Many interesting questions in arithmetic dynamics revolve, in one way or another, around the (local and/or global) reducibility behavior of iterates of a polynomial. We show that for very general families of integer polynomials <em>f</em> (and, more generally, rational functions over number fields), the set of stable primes, i.e., primes modulo which all iterates of <em>f</em> are irreducible, is a density zero set. Compared to previous results, our families cover a much wider ground, and in particular apply to 100% of polynomials of any given odd degree, thus adding evidence to the conjecture that polynomials with a “large” set of stable primes are necessarily of a very specific shape, and in particular are necessarily postcritically finite.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"108 ","pages":"Article 102693"},"PeriodicalIF":1.2,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144570240","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 : 2025-07-07DOI: 10.1016/j.ffa.2025.102688
Marilena Crupi , Antonino Ficarra
Blocking semiovals and the determination of their (minimum) sizes constitute one of the central research topics in finite projective geometry. In this article we introduce the concept of blocking set with the -property in a finite projective plane , with a line of and q a prime power. This notion greatly generalizes that of blocking semioval. We address the question of determining those integers k for which there exists a blocking set of size k with the -property. To solve this problem, we build new theory which deeply analyzes the interplay between blocking sets in finite projective and affine planes.
{"title":"Generalizing blocking semiovals in finite projective planes","authors":"Marilena Crupi , Antonino Ficarra","doi":"10.1016/j.ffa.2025.102688","DOIUrl":"10.1016/j.ffa.2025.102688","url":null,"abstract":"<div><div>Blocking semiovals and the determination of their (minimum) sizes constitute one of the central research topics in finite projective geometry. In this article we introduce the concept of blocking set with the <span><math><msub><mrow><mi>r</mi></mrow><mrow><mo>∞</mo></mrow></msub></math></span>-property in a finite projective plane <span><math><mtext>PG</mtext><mo>(</mo><mn>2</mn><mo>,</mo><mi>q</mi><mo>)</mo></math></span>, with <span><math><msub><mrow><mi>r</mi></mrow><mrow><mo>∞</mo></mrow></msub></math></span> a line of <span><math><mtext>PG</mtext><mo>(</mo><mn>2</mn><mo>,</mo><mi>q</mi><mo>)</mo></math></span> and <em>q</em> a prime power. This notion greatly generalizes that of blocking semioval. We address the question of determining those integers <em>k</em> for which there exists a blocking set of size <em>k</em> with the <span><math><msub><mrow><mi>r</mi></mrow><mrow><mo>∞</mo></mrow></msub></math></span>-property. To solve this problem, we build new theory which deeply analyzes the interplay between blocking sets in finite projective and affine planes.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"108 ","pages":"Article 102688"},"PeriodicalIF":1.2,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144570245","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 : 2025-07-07DOI: 10.1016/j.ffa.2025.102692
C. Martínez, F. Molina, A. Piñera-Nicolás
Group codes are linear codes that can be identified with (two-sided) ideals of a group algebra . Assuming that is semisimple, we use its decomposition as the direct sum of two ideals, one of them the group code, to design two decoding algorithms. The first one generalizes Meggitt's algorithm designed for cyclic codes, while the other one is inspired in the decoding algorithm studied in [10] and aims to improve it.
{"title":"Decoding algorithms in group codes","authors":"C. Martínez, F. Molina, A. Piñera-Nicolás","doi":"10.1016/j.ffa.2025.102692","DOIUrl":"10.1016/j.ffa.2025.102692","url":null,"abstract":"<div><div>Group codes are linear codes that can be identified with (two-sided) ideals of a group algebra <span><math><mi>K</mi><mi>G</mi></math></span>. Assuming that <span><math><mi>K</mi><mi>G</mi></math></span> is semisimple, we use its decomposition as the direct sum of two ideals, one of them the group code, to design two decoding algorithms. The first one generalizes Meggitt's algorithm designed for cyclic codes, while the other one is inspired in the decoding algorithm studied in <span><span>[10]</span></span> and aims to improve it.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"108 ","pages":"Article 102692"},"PeriodicalIF":1.2,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144570386","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 : 2025-07-03DOI: 10.1016/j.ffa.2025.102690
Hiroshi Nozaki
<div><div>Let <em>X</em> be a finite set in the Euclidean space <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span>. If the squared distance between any two distinct points in <em>X</em> is an odd integer, then the cardinality of <em>X</em> is bounded above by <span><math><mi>d</mi><mo>+</mo><mn>2</mn></math></span>, as shown by Rosenfeld (1997) or Smith (1995). They proved that there exists a <span><math><mo>(</mo><mi>d</mi><mo>+</mo><mn>2</mn><mo>)</mo></math></span>-point set <em>X</em> in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span> having only odd integral squared distances if and only if <span><math><mi>d</mi><mo>+</mo><mn>2</mn></math></span> is congruent to 0 modulo 4. The distances can be interpreted as an element of the finite field <span><math><mi>Z</mi><mo>/</mo><mn>2</mn><mi>Z</mi></math></span>. We generalize this result for a local ring <span><math><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>,</mo><mi>p</mi><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>)</mo></math></span> as follows. Let <em>K</em> be an algebraic number field that can be embedded into <span><math><mi>R</mi></math></span>. Fix an embedding of <em>K</em> into <span><math><mi>R</mi></math></span>, and <em>K</em> is interpreted as a subfield of <span><math><mi>R</mi></math></span>. Let <span><math><mi>A</mi><mo>=</mo><msub><mrow><mi>O</mi></mrow><mrow><mi>K</mi></mrow></msub></math></span> be the ring of integers of <em>K</em>, and <span><math><mi>p</mi></math></span> a prime ideal of <span><math><msub><mrow><mi>O</mi></mrow><mrow><mi>K</mi></mrow></msub></math></span>. Let <span><math><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>,</mo><mi>p</mi><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>)</mo></math></span> be the local ring obtained from the localization <span><math><msup><mrow><mo>(</mo><mi>A</mi><mo>∖</mo><mi>p</mi><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mi>A</mi></math></span>, which is interpreted as a subring of <span><math><mi>R</mi></math></span>. If the squared distances of <span><math><mi>X</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span> are in <span><math><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span> and each squared distance is congruent to some constant <span><math><mi>k</mi><mo>≢</mo><mn>0</mn></math></span> modulo <span><math><mi>p</mi><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span>, then <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≤</mo><mi>d</mi><mo>+</mo><mn>2</mn></math></span>, as shown by Nozaki (2023). In this paper, we prove that there exists a set <span><math><mi>X</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span> attaining the upper bound <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≤</mo><mi>d</mi><mo>+</mo><mn>2</mn></math>
{"title":"Euclidean sets with only one distance modulo a prime ideal","authors":"Hiroshi Nozaki","doi":"10.1016/j.ffa.2025.102690","DOIUrl":"10.1016/j.ffa.2025.102690","url":null,"abstract":"<div><div>Let <em>X</em> be a finite set in the Euclidean space <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span>. If the squared distance between any two distinct points in <em>X</em> is an odd integer, then the cardinality of <em>X</em> is bounded above by <span><math><mi>d</mi><mo>+</mo><mn>2</mn></math></span>, as shown by Rosenfeld (1997) or Smith (1995). They proved that there exists a <span><math><mo>(</mo><mi>d</mi><mo>+</mo><mn>2</mn><mo>)</mo></math></span>-point set <em>X</em> in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span> having only odd integral squared distances if and only if <span><math><mi>d</mi><mo>+</mo><mn>2</mn></math></span> is congruent to 0 modulo 4. The distances can be interpreted as an element of the finite field <span><math><mi>Z</mi><mo>/</mo><mn>2</mn><mi>Z</mi></math></span>. We generalize this result for a local ring <span><math><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>,</mo><mi>p</mi><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>)</mo></math></span> as follows. Let <em>K</em> be an algebraic number field that can be embedded into <span><math><mi>R</mi></math></span>. Fix an embedding of <em>K</em> into <span><math><mi>R</mi></math></span>, and <em>K</em> is interpreted as a subfield of <span><math><mi>R</mi></math></span>. Let <span><math><mi>A</mi><mo>=</mo><msub><mrow><mi>O</mi></mrow><mrow><mi>K</mi></mrow></msub></math></span> be the ring of integers of <em>K</em>, and <span><math><mi>p</mi></math></span> a prime ideal of <span><math><msub><mrow><mi>O</mi></mrow><mrow><mi>K</mi></mrow></msub></math></span>. Let <span><math><mo>(</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>,</mo><mi>p</mi><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>)</mo></math></span> be the local ring obtained from the localization <span><math><msup><mrow><mo>(</mo><mi>A</mi><mo>∖</mo><mi>p</mi><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mi>A</mi></math></span>, which is interpreted as a subring of <span><math><mi>R</mi></math></span>. If the squared distances of <span><math><mi>X</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span> are in <span><math><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span> and each squared distance is congruent to some constant <span><math><mi>k</mi><mo>≢</mo><mn>0</mn></math></span> modulo <span><math><mi>p</mi><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span>, then <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≤</mo><mi>d</mi><mo>+</mo><mn>2</mn></math></span>, as shown by Nozaki (2023). In this paper, we prove that there exists a set <span><math><mi>X</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span> attaining the upper bound <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≤</mo><mi>d</mi><mo>+</mo><mn>2</mn></math>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"108 ","pages":"Article 102690"},"PeriodicalIF":1.2,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534171","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 : 2025-06-30DOI: 10.1016/j.ffa.2025.102684
Ruikai Chen , Sihem Mesnager
In this paper, we investigate permutation polynomials over the finite field with , focusing on those in the form , where and L is a 2-linear polynomial over . By calculating certain character sums, we characterize these permutation polynomials and provide additional constructions.
{"title":"Permutation polynomials of finite fields of even characteristic from character sums","authors":"Ruikai Chen , Sihem Mesnager","doi":"10.1016/j.ffa.2025.102684","DOIUrl":"10.1016/j.ffa.2025.102684","url":null,"abstract":"<div><div>In this paper, we investigate permutation polynomials over the finite field <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 <span><math><mi>q</mi><mo>=</mo><msup><mrow><mn>2</mn></mrow><mrow><mi>m</mi></mrow></msup></math></span>, focusing on those in the form <span><math><mi>Tr</mi><mo>(</mo><mi>A</mi><msup><mrow><mi>x</mi></mrow><mrow><mi>q</mi><mo>+</mo><mn>1</mn></mrow></msup><mo>)</mo><mo>+</mo><mi>L</mi><mo>(</mo><mi>x</mi><mo>)</mo></math></span>, where <span><math><mi>A</mi><mo>∈</mo><msubsup><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow><mrow><mo>⁎</mo></mrow></msubsup></math></span> and <em>L</em> is a 2-linear polynomial over <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>. By calculating certain character sums, we characterize these permutation polynomials and provide additional constructions.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"108 ","pages":"Article 102684"},"PeriodicalIF":1.2,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144513839","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 : 2025-06-27DOI: 10.1016/j.ffa.2025.102683
Bence Csajbók
Let D denote the set of directions determined by the graph of a polynomial f of , where q is a power of the prime p. If D is contained in a multiplicative subgroup M of , then by a result of Carlitz and McConnel it follows that for some . Of course, if , then and hence f is a permutation. If we assume the weaker condition , then f is not necessarily a permutation, but Sziklai conjectured that follows also in this case. When q is odd, and the index of M is even, then a result of Ball, Blokhuis, Brouwer, Storme and Szőnyi combined with a result of Göloğlu and McGuire proves the conjecture. Assume . We prove that if the size of is less than , then f is a permutation of . We use this result to prove the conjecture of Sziklai.
{"title":"Extending a result of Carlitz and McConnel to polynomials which are not permutations","authors":"Bence Csajbók","doi":"10.1016/j.ffa.2025.102683","DOIUrl":"10.1016/j.ffa.2025.102683","url":null,"abstract":"<div><div>Let <em>D</em> denote the set of directions determined by the graph of a polynomial <em>f</em> of <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub><mo>[</mo><mi>x</mi><mo>]</mo></math></span>, where <em>q</em> is a power of the prime <em>p</em>. If <em>D</em> is contained in a multiplicative subgroup <em>M</em> of <span><math><msubsup><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow><mrow><mo>×</mo></mrow></msubsup></math></span>, then by a result of Carlitz and McConnel it follows that <span><math><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mo>=</mo><mi>a</mi><msup><mrow><mi>x</mi></mrow><mrow><msup><mrow><mi>p</mi></mrow><mrow><mi>k</mi></mrow></msup></mrow></msup><mo>+</mo><mi>b</mi></math></span> for some <span><math><mi>k</mi><mo>∈</mo><mi>N</mi></math></span>. Of course, if <span><math><mi>D</mi><mo>⊆</mo><mi>M</mi></math></span>, then <span><math><mn>0</mn><mo>∉</mo><mi>D</mi></math></span> and hence <em>f</em> is a permutation. If we assume the weaker condition <span><math><mi>D</mi><mo>⊆</mo><mi>M</mi><mo>∪</mo><mo>{</mo><mn>0</mn><mo>}</mo></math></span>, then <em>f</em> is not necessarily a permutation, but Sziklai conjectured that <span><math><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mo>=</mo><mi>a</mi><msup><mrow><mi>x</mi></mrow><mrow><msup><mrow><mi>p</mi></mrow><mrow><mi>k</mi></mrow></msup></mrow></msup><mo>+</mo><mi>b</mi></math></span> follows also in this case. When <em>q</em> is odd, and the index of <em>M</em> is even, then a result of Ball, Blokhuis, Brouwer, Storme and Szőnyi combined with a result of Göloğlu and McGuire proves the conjecture. Assume <span><math><mi>deg</mi><mo></mo><mi>f</mi><mo>≥</mo><mn>1</mn></math></span>. We prove that if the size of <span><math><msup><mrow><mi>D</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mi>D</mi><mo>=</mo><mo>{</mo><msup><mrow><mi>d</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>d</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>:</mo><mi>d</mi><mo>∈</mo><mi>D</mi><mo>∖</mo><mo>{</mo><mn>0</mn><mo>}</mo><mo>,</mo><mspace></mspace><msup><mrow><mi>d</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>∈</mo><mi>D</mi><mo>}</mo></math></span> is less than <span><math><mi>q</mi><mo>−</mo><mi>deg</mi><mo></mo><mi>f</mi><mo>+</mo><mn>2</mn></math></span>, then <em>f</em> is a permutation of <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub></math></span>. We use this result to prove the conjecture of Sziklai.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"108 ","pages":"Article 102683"},"PeriodicalIF":1.2,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144489462","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 : 2025-06-27DOI: 10.1016/j.ffa.2025.102685
Sartaj Ul Hasan, Ramandeep Kaur
We focus on permutation polynomials of the form over , where is the finite field with elements, p is a prime number, m is a positive integer, is the relative trace function from to , is a linearized polynomial over , and is a positive integer. More precisely, we present six new classes of permutation polynomials over of the aforementioned form: one class over finite fields of even characteristic, three classes over finite fields of odd characteristic, and the remaining two over finite fields of arbitrary characteristic. Furthermore, we show that these classes of permutation polynomials are inequivalent to the known ones of the same form. We also provide explicit expressions for the compositional inverses of each of these classes of permutation polynomials.
{"title":"Some new classes of permutation polynomials and their compositional inverses","authors":"Sartaj Ul Hasan, Ramandeep Kaur","doi":"10.1016/j.ffa.2025.102685","DOIUrl":"10.1016/j.ffa.2025.102685","url":null,"abstract":"<div><div>We focus on permutation polynomials of the form <span><math><mi>L</mi><mo>(</mo><mi>X</mi><mo>)</mo><mo>+</mo><msubsup><mrow><mi>Tr</mi></mrow><mrow><mi>m</mi></mrow><mrow><mn>3</mn><mi>m</mi></mrow></msubsup><msup><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow><mrow><mi>s</mi></mrow></msup></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></math></span>, where <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub></math></span> is the finite field with <span><math><mi>q</mi><mo>=</mo><msup><mrow><mi>p</mi></mrow><mrow><mi>m</mi></mrow></msup></math></span> elements, <em>p</em> is a prime number, <em>m</em> is a positive integer, <span><math><msubsup><mrow><mi>Tr</mi></mrow><mrow><mi>m</mi></mrow><mrow><mn>3</mn><mi>m</mi></mrow></msubsup><mo>(</mo><mo>⋅</mo><mo>)</mo></math></span> is the relative trace function from <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>p</mi></mrow><mrow><mn>3</mn><mi>m</mi></mrow></msup></mrow></msub></math></span> to <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>p</mi></mrow><mrow><mi>m</mi></mrow></msup></mrow></msub></math></span>, <span><math><mi>L</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> is a linearized polynomial over <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mn>3</mn></mrow></msup></mrow></msub></math></span>, and <span><math><mi>s</mi><mo>></mo><mn>1</mn></math></span> is a positive integer. More precisely, we present six new classes of permutation polynomials over <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>q</mi></mrow><mrow><mn>3</mn></mrow></msup></mrow></msub></math></span> of the aforementioned form: one class over finite fields of even characteristic, three classes over finite fields of odd characteristic, and the remaining two over finite fields of arbitrary characteristic. Furthermore, we show that these classes of permutation polynomials are inequivalent to the known ones of the same form. We also provide explicit expressions for the compositional inverses of each of these classes of permutation polynomials.</div></div>","PeriodicalId":50446,"journal":{"name":"Finite Fields and Their Applications","volume":"108 ","pages":"Article 102685"},"PeriodicalIF":1.2,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144489390","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}