arXiv subjects

Neha Prabhu

Publications and source records attributed to Neha Prabhu.

7 recordsLinked to original sources

arXiv2023

A central limit theorem for Hilbert modular forms

For a prime ideal $\mathfrak{p}$ in a totally real number field $L$ with the adele ring $\mathbb{A}$, we study the distribution of angles $θ_π(\mathfrak{p})$ coming from Satake parameters corresponding to unramified $π_\mathfrak{p}$ where $π_\mathfrak{p}$ comes from a global $π$ ranging over a certain finite set $Π_{\underline{k}}(\mathfrak{n})$ of cuspidal automorphic representations of GL$_2(\mathbb{A})$ with trivial central character. For such a representation $π$, it is known that the angles $θ_π(\mathfrak{p})$ follow the Sato-Tate distribution. Fixing an interval $I\subseteq [0,π]$, we prove a central limit theorem for the number of angles $θ_π(\mathfrak{p})$ that lie in $I$, as $\mathrm{N}(\mathfrak{p})\to\infty$. The result assumes $\mathfrak{n}$ to be a squarefree integral ideal, and that the components in the weight vector $\underline{k}$ grow suitably fast as a function of $x$.

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arXiv2021

Equidistribution of $αp^θ$ with a Chebotarev condition and applications to extremal primes

We establish a joint distribution result concerning the fractional part of $αp^θ$ for $θ\in (0,1), \ α>0$, where $p$ is a prime satisfying a Chebotarev condition in a fixed finite Galois extension over $\mathbb{Q}$. As an application, for a fixed non-CM elliptic curve $E/\mathbb{Q}$, an asymptotic formula is given for the number of primes at the extremes of the Sato-Tate measure modulo a large prime $\ell$. These are precisely the primes $p$ for which the Frobenius trace $a_p(E)$ satisfies the congruence $a_p(E)\equiv [2\sqrt{p}] \bmod \ell$. We assume a zero-free region hypothesis for Dedekind zeta functions of number fields.

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arXiv2019

Central limit theorems for elliptic curves and modular forms with smooth weight functions

The second and third-named authors (arXiv:1705.04115) established a Central Limit Theorem for the error term in the Sato-Tate law for families of modular forms. This method was adapted to families of elliptic curves in by the first and second-named authors (arXiv:1705.09229). In this context, a Central Limit Theorem was established only under a strong hypothesis going beyond the Riemann Hypothesis. In the present paper, we consider a smoothed version of the Sato-Tate conjecture, which allows us to overcome several limitations. In particular, for the smoothed version, we are able to establish a Central Limit Theorem for much smaller families of modular forms, and we succeed in proving a theorem of this type for families of elliptic curves under the Riemann Hypothesis for $L$-functions associated to Hecke eigenforms for the full modular group.

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arXiv2019

The error term in the Sato-Tate theorem of Birch

We establish an error term in the Sato-Tate theorem of Birch. That is, for $p$ prime, $q=p^r$ we show that $\#\{ (a,b) \in \mathbb{F}_q^2 : θ_{a,b}\in I\} =μ_{ST}(I)q^2 + O_r(q^{7/4})$ for any interval $I\subseteq[0,π]$ where for an elliptic curve $E: y^2= x^3 +ax +b$, the quantity $θ_{a,b}$ is defined by $2\sqrt{q}\cosθ_{a,b} = q+1-E(\mathbb{F}_q)$ and $μ_{ST}(I)$ denotes the Sato-Tate measure of the interval $I$.

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arXiv2018

Moments of the error term in the Sato-Tate law for elliptic curves

We derive new bounds for moments of the error in the Sato-Tate law over families of elliptic curves. Our estimates are stronger than those obtained by W.D. Banks and I.E. Shparlinski (arXiv:math/0609144) and L. Zhao and the fist-named author in (arXiv:math/0608318) for the first and second moments, but this comes at the cost of larger ranges of averaging. As applications, we deduce new almost-all results for the said errors and a conditional Central Limit Theorem on the distribution of these errors. Our method is different from those used in the above-mentioned papers and builds on recent work by the second-named author and K. Sinha (arXiv:1705.04115) who derived a Central Limit Theorem on the distribution of the errors in the Sato-Tate law for families of cusp forms for the full modular group. In addition, identities by Birch and Melzak play a crucial rule in this paper. Birch's identities connect moments of coefficients of Hasse-Weil $L$-functions for elliptic curves with the Kronecker class number and further with traces of Hecke operators. Melzak's identity is combinatorial in nature.

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arXiv2017

Fluctuations in the distribution of Hecke eigenvalues about the Sato-Tate measure

We study fluctuations in the distribution of families of $p$-th Fourier coefficients $a_f(p)$ of normalised holomorphic Hecke eigenforms $f$ of weight $k$ with respect to $SL_2(\mathbb{Z})$ as $k \to \infty$ and primes $p \to \infty.$ These families are known to be equidistributed with respect to the Sato-Tate measure. We consider a fixed interval $I \subset [-2,2]$ and derive the variance of the number of $a_f(p)$'s lying in $I$ as $p \to \infty$ and $k \to \infty$ (at a suitably fast rate). The number of $a_f(p)$'s lying in $I$ is shown to asymptotically follow a Gaussian distribution when appropriately normalised. A similar theorem is obtained for primitive Maass cusp forms.

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arXiv2016

Density of solutions to quadratic congruences

A classical result in number theory is Dirichlet's theorem on the density of primes in an arithmetic progression. We prove a similar result for numbers with exactly k prime factors for k>1. Building upon a proof by E.M. Wright in 1954, we compute the natural density of such numbers where each prime satisfies a congruence condition. As an application, we obtain the density of squarefree n not greater than x with k prime factors such that a fixed quadratic equation has exactly 2^k solutions modulo n.

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