arXiv subjects

Satyabrat Sahoo

Publications and source records attributed to Satyabrat Sahoo.

13 recordsLinked to original sources

arXiv2026

Generalized Fermat equation over number fields

Let $K$ be a number field with ring of integers $\mathcal{O}_K$, and let $A,B,C \in \mathcal{O}_K \setminus\{0\}$. Denote by $S_K'$ the set of prime ideals of $\mathcal{O}_K$ dividing $2ABC$. Assuming two standard conjectures concerning the modularity of mod-$p$ Galois representations and the Eichler-Shimura correspondence over number fields, we study the asymptotic behavior of the generalized Fermat equation $Ax^p+By^p+Cz^p=0$ over $K$. Using the modular method, we establish an asymptotic criterion in terms of the solutions of the associated $S_K'$-unit equation. As an application, we obtain asymptotic results for certain imaginary quadratic fields $K=\mathbb{Q}(\sqrt{-d})$. In particular, for a family of squarefree integers $d$, we determine the relevant $S_K'$-unit solutions explicitly and deduce that the generalized Fermat equation has no asymptotic solutions. Finally, we show that this family of squarefree integers has relative density $5/6$ among all squarefree positive integers.

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arXiv2026

Generalized Fermat equation over cyclotomic $\mathbb{Z}_l$-extensions of totally real fields

Let $K$ be a totally real number field of odd degree in which $2$ is inert. Let $l \geq 5$ be a prime with $l \nmid [K:\mathbb{Q}]$ and $\gcd(\frac{l-1}{2}, [K:\mathbb{Q}])=1$. We prove that if $2$ is inert in $K$, $l$ is non-Wieferich, i.e., $2^{l-1} \not\equiv 1 \pmod{l^2}$, and $l$ is totally ramified in $K$, then the asymptotic Fermat's Last Theorem holds over each $n$-th layer $K_{n,l}$ of the cyclotomic $\mathbb{Z}_l$-extension of $K$. We then prove that the generalized Fermat equation $Ax^p+By^p+Cz^p=0$ has no asymptotic solution over each $n$-th layer $K_{n,l}$ when $A,B,C \in \{u2^r : u\in \mathcal{O}_K^\times,\ r \in \mathbb{Z}_{\geq 0}\}$. For any odd prime $d$, we also prove that if $A,B,C \in \{\pm 2^r d^s : r,s \in \mathbb{Z}_{\geq 0}\}$ and $h_{\mathbb{Q}_{n,l}}^+$ is odd, then the generalized Fermat equation $Ax^p+By^p+Cz^p=0$ has no effective asymptotic solution $(a,b,c) \in \mathcal{O}_{\mathbb{Q}_{n,l}}^3$ with $2 \mid abc$. The effectivity in the case of $\mathbb{Q}_{n,l}$ follows from a result of Thorne proving the modularity of elliptic curves over $\mathbb{Q}_{n,l}$.

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arXiv2026

Generalized Fruit Diophantine equation over number fields

Let $K$ be a number field and $\mathcal{O}_K$ be the ring of integers of $K$. In this article, we study the solutions of the generalized fruit Diophantine equation $ax^d-y^2-z^2 +xyz-c=0$ over $K$, where $d \geq 3$ is an integer and $a,c\in \mathcal{O}_K\setminus \{0\}$. Subsequently, we provide explicit values of square-free integers $t$ such that the equation $ax^d-y^2-z^2 +xyz-c=0$ has no solution $(x_0, y_0, z_0) \in \mathcal{O}_{\mathbb{Q}(\sqrt{t})}^3$ with $2 | x_0$, and demonstrate that the set of all such square-free integers $t$ with $t \geq 2$ has density exactly $\frac{1}{6}$. As an application, we construct infinitely many elliptic curves $E$ defined over number fields $K$ having no integral point $(x_0,y_0) \in \mathcal{O}_K^2$ with $2|x_0$.

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arXiv2025

A survey on the generalized Fermat equation of various signatures over totally real fields

Following the famous proof of Fermat's Last Theorem by Andrew Wiles using the modularity of elliptic curves over $\mathbb{Q}$, significant developments have been made in the study of Diophantine equations using the modularity method. This article presents a survey of numerous results on the solutions of the generalized Fermat equation of signatures $(p,p,p)$, $(p,p,2)$, $(p,p,3)$, and $(r,r,p)$ over totally real number fields using the modularity method.

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arXiv2025

Effective Generalized Fermat equation of signature $(2p, 2q, r)$ with odd narrow class number

Fix a rational prime $r \geq 5$. In this article, we study the integer solutions of the generalized Fermat equation of signature $(2p,2q,r)$, namely $x^{2p}+y^{2q}=z^r$, where the primes $p,q \geq 5$ are varying. For each rational prime $r \geq 5$, we first establish a condition on the solutions of the $S$-unit equation over $\mathbb{Q}(ζ_r+ ζ_r^{-1})$ such that there exists a constant $V_{r}>0$ (depending on $r$) for which the equation $x^{2p}+y^{2q}=z^r$ with $p,q \geq V_r$ has no non-trivial primitive integer solutions. Then for each rational prime $r \geq 2$, we prove that every elliptic curve over $\mathbb{Q}(ζ_r+ ζ_r^{-1})$ is modular. As an application of this, we prove that the above constant $V_r$ is effectively computable. Finally, we provide a criterion for $r$ such that the equation $x^{2p}+y^{2q}=z^r$ with $p,q \geq V_r$ has no non-trivial primitive integer solutions when the narrow class number of $\mathbb{Q}(ζ_r+ ζ_r^{-1})$ is odd.

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arXiv2025

Asymptotic Fermat equation of signature $(r, r, p)$ over totally real fields

Let $K$ be a totally real number field and $ \mathcal{O}_K$ be the ring of integers of $K$. This manuscript examines the asymptotic solutions of the Fermat equation of signature $(r, r, p)$, specifically $x^r+y^r=dz^p$ over $K$, where $r,p \geq5$ are rational primes and odd $d\in \mathcal{O}_K \setminus \{0\}$. For a certain class of fields $K$, we first prove that the equation $x^r+y^r=dz^p$ has no asymptotic solution $(a,b,c) \in \mathcal{O}_K^3$ with $2 |c$. Then, we study the asymptotic solutions $(a,b,c) \in \mathcal{O}_K^3$ to the equation $x^5+y^5=dz^p$ with $2 \nmid c$. We use the modular method to prove these results.

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arXiv2025

Lower bounds for heights on some algebraic dynamical systems

Let $v$ be a finite place of a number field $K$ and write $K^{nr,v}$ for the maximal field extension of $K$ in which $v$ is unramified. The purpose of this paper is split up into two parts. The first one generalizes a theorem of Pottmeyer: If $E$ is an elliptic curve defined over $K$ with split multiplicative reduction at $v$, then the Néron-Tate height of a non-torsion point $P\in E(\bar{K})$ is bounded from below by $C / e_v(P)^{2 e_v(P)+1}$, where $C>0$ is an absolute constant and $e_v(P)$ is the maximum of all ramification indices $e_w(K(P) \vert K)$ with $w\vert v$. Among other things, we refine this result by showing that given a simple abelian variety $A$ defined over $K$ that is degenerate at $v$, the Néron-Tate height of a non-torsion point $P\in A(\bar{K})$ is at least $C / \mathrm{lcm}_{w\vert v} \{e_w(K(P)\vert K)\}^2$, where $C>0$ is an absolute constant. We then give applications towards Lehmer's conjecture. Next, we provide the first examples of polynomials $ϕ\in K[X]$ of degree at least $2$ so that the canonical height $\hat{h}_ϕ$ of any point in $\bbP^1(K^{nr,v})$ is either $0$ or bounded from below by an absolute positive constant.

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arXiv2025

Asymptotic solutions of the generalized Fermat-type equation of signature $(p,p,3)$ over totally real number fields

In this article, we study the asymptotic solutions of the generalized Fermat-type equation of signature $(p,p,3)$ over totally real number fields $K$, i.e., $Ax^p+By^p=Cz^3$ with prime exponent $p$ and $A,B,C \in \mathcal{O}_K \setminus \{0\}$. For certain class of fields $K$, we prove that $Ax^p+By^p=Cz^3$ has no asymptotic solutions over $K$ (resp., solutions of certain type over $K$) with restrictions on $A,B,C$ (resp., for all $A,B,C \in \mathcal{O}_K \setminus \{0\}$). Finally, we present several local criteria over $K$.

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arXiv2024

On the solutions of the generalized Fermat equation over totally real number fields

Let $K$ be a totally real number field and $\mathcal{O}_K$ be the ring of integers of $K$. In this article, we study the asymptotic solutions of the generalized Fermat equation $Ax^p+By^p+Cz^p=0$ over $K$ with prime exponent $p$, where $A,B,C \in \mathcal{O}_K \setminus \{0\}$. For certain class of fields $K$, we prove that the equation $Ax^p+By^p+Cz^p=0$ has no asymptotic solution $(a,b,c) \in \mathcal{O}_K^3$ with $2|abc$. Then, under some assumptions on $A,B,C$, we also prove that $Ax^p+By^p+Cz^p=0$ has no asymptotic solution in $K^3$. Finally, we give several purely local criteria of $K$ such that $Ax^p+By^p+Cz^p=0$ has no asymptotic solutions in $K^3$, and calculate the density of such fields $K$ when $K$ is a real quadratic field.

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arXiv2024

On the solutions of $x^2= By^p+Cz^p$ and $2x^2= By^p+Cz^p$ over totally real fields

In this article, we study the solutions of certain type over $K$ of the Diophantine equation $x^2= By^p+Cz^p$ with prime exponent $p$, where $B$ is an odd integer and $C$ is either an odd integer or $C=2^r$ for $r \in \mathbb{N}$. Further, we study the non-trivial primitive solutions of the Diophantine equation $x^2= By^p+2^rz^p$ ($r\in {1,2,4,5}$) (resp., $2x^2= By^p+2^rz^p$ with $r \in \mathbb{N}$) with prime exponent $p$, over $K$. We also present several purely local criteria of $K$.

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arXiv2024

Lehmer-Type bounds and counting rational points of bounded heights on Abelian varieties

In this article, we study Lehmer-type bounds for the Néron-Tate height of $\bar{K}$-points on abelian varieties $A$ over number fields $K$. Then, we estimate the number of $K$-rational points on $A$ with Néron-Tate height $\leq \log B$ for $B\gg 0$. This estimate involves a constant $C$, which is not explicit. However, for elliptic curves and the product of elliptic curves over $K$, we make the constant explicitly computable.

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arXiv2023

On the solutions of $x^p+y^p=2^r z^p$, $x^p+y^p=z^2$ over totally real fields

In this article, we study the non-trivial primitive solutions of a certain type for the Diophantine equations $x^p+y^p=2^rz^p$ and $x^p+y^p=z^2$ of prime exponent $p$, $r \in \mathbb{N}$, over a totally real field $K$. Then for $r=2,3$, we study the non-trivial primitive solutions over $\mathcal{O}_K$ for the equation $x^p+y^p=2^rz^p$ of prime exponent $p$. Finally, we give several purely local criteria for $K$ such that the equation $x^p+y^p=2^rz^p$ has no non-trivial primitive solutions over $\mathcal{O}_K$.

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arXiv2022

On generation of the coefficient field of a primitive Hilbert modular form by a single Fourier coefficient

For a primitive Hilbert modular form $f$ over $F$ of weight $k$, under certain assumptions on image of $\barρ_{f,λ}$, we calculate the Dirichlet density of primes $\mathfrak{p}$ for which the $\mathfrak{p}$-th Fourier coefficient $C(\mathfrak{p}, f)$ generates the coefficient field $E_f$. If $k=2$, then we show that the assumption on the image of $\barρ_{f,λ}$ is satisfied when the degrees of $E_f, F$ are equal and odd prime. We also compute the density of primes $\mathfrak{p}$ for which $C^*(\mathfrak{p}, f)$ generates $F_f$. Then, we provide some examples of $f$ to support our results. Finally, we calculate the density of primes $\mathfrak{p}$ for which $C(\mathfrak{p}, f) \in K$ for any field $K$ with $F_f \subseteq K \subseteq E_f$. This density is completely determined by the inner twists of $f$ associated with $K$. This work can be thought of as a generalization of~\cite{KSW08} to primitive Hilbert modular forms.

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