arXiv subjects

Nazar Arakelian

Publications and source records attributed to Nazar Arakelian.

15 recordsLinked to original sources

arXiv2026

Frobenius nonclassicality of generalized Fermat curves with respect to conics

The effective application of the Stöhr-Voloch theory for the linear system of plane curves of a fixed degree to bound the number of rational points of a family of plane curves defined over $\mathbb{F}_q$ requires the characterization of the $\mathbb{F}_q$-Frobenius nonclassical curves in the family. In this paper, we provide necessary and sufficient conditions for certain generalized Fermat curves $\mathcal{F}$ defined over $\mathbb{F}_q$ to be $\mathbb{F}_q$-Frobenius nonclassical with respect to the linear system of conics. In the Frobenius classical cases, we obtain nice bounds for the number $N_q(\mathcal{F})$ of rational points of $\mathcal{F}$ via Stöhr-Voloch theory, whereas in the Frobenius nonclassical cases, we derive explicit formulas for $N_q(\mathcal{F})$.

math.AG↗

arXiv2026

Algebraic curves admitting automorphism groups of large prime square order

Let $\mathbb{K}$ denote an algebraically closed field of arbitrary characteristic. In this paper we provide bounds for the size of a prime $\ell$ for which there are curves defined over $\mathbb{K}$ admitting automorphism groups of order $\ell^2$. In addition, we also give a classification of the families of curves attaining the upper bounds for $\ell$ in both tame and wild case. Finally, we present the full automorphism groups of the curves attaining the highest bounds.

math.AG↗

arXiv2026

Curves on Frobenius nonclassical loci of hypersurfaces

Let $\mathcal{S} \subset \mathbb{P}^n$ be an absolutely irreducible projective hypersurface defined over a finite field $\mathbb{F}_q$, equipped with the $\mathbb{F}_q$-Frobenius map $Φ_q$. In this paper, we investigate irreducible curves $\mathcal{X} \subset \mathcal{S}_{Φ_q}$, where $\mathcal{S}_{Φ_q}$ is the $\mathbb{F}_q$-Frobenius nonclassical locus of $\mathcal{S}$. In particular, we show that every curve $\mathcal{X} \subset \mathcal{S}_{Φ_q}$ such that the restriction of the Gauss map of $\mathcal{S}$ to $\mathcal{X}$ is inseparable is $\mathbb{F}_q$-Frobenius nonclassical. This provides a way to construct new Frobenius nonclassical curves, which are curves that tend to have many $\mathbb{F}_q$-rational points. We also prove that a certain type of Frobenius nonclassical hypersurfaces $\mathcal{S}$ defined by separated variables are such that their Gauss maps restricted to any curve contained in $\mathcal{S}$ is inseparable. Finally, in parallel with the plane curve cases, we show that if the strict Gauss map $Γ$ of a $\mathbb{F}_q$-Frobenius nonclassical hypersurface $\mathcal{S}$ is given by $p$ powers, then $Γ$ is purely inseparable.

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arXiv2024

Cyclotomic function fields over finite fields with irreducible quadratic modulus

Let $\mathbb{F}_q$ be the finite field of order $q$ and $F=\mathbb{F}_q(x)$ the rational function field. In this paper, we give a characterization of the cyclotomic function fields $F(Λ_M)$ with modulus $M$, where $M \in \mathbb{F}_q[T]$ is a monic and irreducible polynomial of degree two. We also provide the full automorphism group of $F(Λ_M)$ in odd characteristic, extending results of \cite{MXY2016} where the automorphism group of $F(Λ_M)$ over $\mathbb{F}_q$ was computed.

math.NT↗

arXiv2023

Duality for certain multi-Frobenius nonclassical curves in higher dimensional spaces

We show how a type of multi-Frobenius nonclassicality of a curve defined over a finite field $\mathbb{F}_q$ of characteristic $p$ reflects on the geometry of its strict dual curve. In particular, in such cases we may describe all the possible intersection multiplicities of its strict dual curve with the linear system of hyperplanes. Among other consequence, using a result by Homma, we are able to construct nonreflexive space curves such that their tangent surfaces are nonreflexive as well, and the image of a generic point by a Frobenius map is in its osculating hyperplane. We also obtain generalizations and improvements of some known results of the literature.

math.AG↗

arXiv2020

Algebraic curves with automorphism groups of large prime order

Let $\mathcal{X}$ be an algebraic curve of genus $g$ defined over an algebraically closed field $K$ of characteristic $p \geq 0$, and $q$ a prime dividing $|\mbox{Aut}(\mathcal{X})|$. We say that $\mathcal{X}$ is a $q$-curve. Homma proved that either $q \leq g+1$ or $q = 2g+1$, and classified $(2g+1)$-curves. In this note, we classify $(g+1)$-curves, and fully characterize the automorphism groups of $q$-curves for $q= 2g+1, g+1$. We also give some partial results on $q$-curves for $q = g, g-1$.

math.AG↗

arXiv2019

Separable degree of the Gauss map and strict dual curves over finite fields

Let $\mathcal{X}$ be a projective algebraic curve and denote by $\mathcal{X}^{'}$ its strict dual curve. The map $γ:\mathcal{X} \longrightarrow \mathcal{X}^{'}$ is called (strict) Gauss map of $\mathcal{X}$. In this manuscript, we study the separable degree of the Gauss map of curves defined over finite fields. In particular, we give a generalization of a known result on the separable degree of the Gauss map of plane Frobenius nonclassical curves. We also obtain a characterization of certain plane strange curves.

math.AG↗

arXiv2018

The Hurwitz curve over a finite field and its Weierstrass points for the morphism of lines

For any smooth Hurwitz curve $\mathcal{H}_n: \, XY^n+YZ^n+X^nZ=0$ over the finite field $\mathbb{F}_{p}$, an explict description of its Weierstrass points for the morphism of lines is presented. As a consequence, the full automorphism group ${\rm Aut}(\mathcal{H}_n)$, as well as the genera of all Galois subcovers of $\mathcal{H}_n$, with $n\neq 3, p^r$, are computed. Finally, a question by F. Torres on plane non nonsingular maximal curves is answered.

math.AG↗

arXiv2017

Number of rational branches of a plane singular curve over a finite field

Let $\mathcal{F}$ be a plane singular curve defined over a finite field $\mathbb{F}_q$. The linear system of plane curves of a given degree passing through the singularities of $\cF$ provides potentially good bounds for the number of points on a non-singular model of $\mathcal{F}$. In this note, the case of a curve with two singularities such that the sum of their multiplicities is precisely the degree of the curve is investigated in more depth. In particular, such plane models are completely characterized, and for $p > 3$, a curve of this type attaining one of the obtained bounds is presented.

math.NT↗

arXiv2016

On the spectrum for the genera of maximal curves over small fields

Motivated by previous computations in Garcia, Stichtenoth and Xing (2000) paper ,we discuss the spectrum $\mathbf{M}(q^2)$ for the genera of maximal curves over finite fields of order $q^2$ with $7\leq q\leq 16$. In particular, by using a result in Kudo and Harashita(2016) paper, the set $\mathbf{M}(7^2)$ is completely determined.

math.AG↗

arXiv2016

Bounds for the number of points on curves over finite fields

Let $\mathcal{X}$ be a projective irreducible nonsingular algebraic curve defined over a finite field $\mathbb{F}_q$. This paper presents a variation of the Störh-Voloch theory and sets new bounds to the number of $\mathbb{F}_{q^r}$-rational points on $\mathcal{X}$. In certain cases, where comparison is possible, the results are shown to improve other bounds such as Weil's, Störh-Voloch's and Ihara's.

math.AG↗

arXiv2016

On generalizations of Fermat curves over finite fields and their automorphisms

Let $\mathcal{X}$ be an irreducible algebraic curve defined over a finite field $\mathbb{F}_q$ of characteristic $p>2$. Assume that the $\mathbb{F}_q$-automorphism group of $\mathcal{X}$ admits as an automorphism group the direct product of two cyclic groups $C_m$ and $C_n$ of orders $m$ and $n$ prime to $p$ such that both quotient curves $\mathcal{X}/C_n$ and $\mathcal{X}/C_m$ are rational. In this paper, we provide a complete classification of such curves, as well as a characterization of their full automorphism groups.

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arXiv2015

Frobenius nonclassicality of Fermat curves with respect to cubics

For Fermat curves $\mathcal{F}:aX^n+bY^n=Z^n$ defined over $\mathbb{F}_q$, we establish necessary and sufficient conditions for $\mathcal{F}$ to be $\mathbb{F}_q$-Frobenius nonclassical with respect to the linear system of plane cubics. In the $\mathbb{F}_q$-Frobenius nonclassical cases, we determine explicit formulas for the number $N_q(\mathcal{F})$ of $\mathbb{F}_q$-rational points on $\mathcal{F}$. For the remaining Fermat curves, nice upper bounds for $N_q(\mathcal{F})$ are immediately given by the Stöhr-Voloch Theory.

math.AG↗

arXiv2015

A characterization of the Artin-Mumford curve

Let $\mathcal{M}$ be the Artin-Mumford curve over the finite prime field $\mathbb{F}_p$ with $p>2$. By a result of Valentini and Madan, $\mbox{Aut}_{\mathbb{F}_p}(\mathcal{M})\cong H$ with $H=(C_p\times C_p)\rtimes D_{p-1}$. We prove that if $\mathcal{X}$ is an algebraic curve of genus $g=(p-1)^2$ such that $\mbox{Aut}_{\mathbb{F}_p}(\mathcal{X})$ contains a subgroup isomorphic to $H$ then $\mathcal{X}$ is birationally equivalent over $\mathbb{F}_p$ to the Artin-Mumford curve $\mathcal{M}$.

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arXiv2014

Frobenius nonclassicality with respect to linear systems of curves of arbitrary degree

For each integer $s\geq 1$, we present a family of curves that are $\mathbb{F}_q$-Frobenius nonclassical with respect to the linear system of plane curves of degree s. In the case $s = 2$, we give necessary and sufficient conditions for such curves to be $\mathbb{F}_q$-Frobenius nonclassical with respect to the linear system of conics. In the $\mathbb{F}_q$-Frobenius nonclassical cases, we determine the exact number of $\mathbb{F}_q$-rational points. In the remaining cases, an upper bound for the number of $\mathbb{F}_q$-rational points will follow from Stöhr-Voloch theory.

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