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Yoonbok Lee

Publications and source records attributed to Yoonbok Lee.

15 recordsLinked to original sources
arXiv2025

The $n^{th}$ centered moments of a large orthogonal family of automorphic $L$-functions

We obtain the $n$th centered moments of one level densities of a large orthogonal family of $L$-functions associated with holomorphic Hecke newforms of level $q$, averaged over $q\sim Q$. We verify the Katz-Sarnak conjecture for these statistics, in the range where the sum of the supports of the Fourier transforms of test functions lies in $(-4, 4)$. In so doing, we need to understand certain phantom oversized terms, which allow us to extract the right off-diagonal contributions. We further need to resolve the combinatorial problem that arises when matching our main terms with random matrix predictions.

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arXiv2025

Universality of the zeta function in short intervals

We improve the universality theorem of the Riemann zeta-function in short intervals by establishing universality for significantly shorter intervals $[T,T+H]$. Assuming the Riemann Hypothesis, we prove that universality in such short intervals holds for $H=(\log T)^B$ with an explicitly given $B>0$. Unconditionally, we show that for the same $H$ the set of real numbers $\tau\in[T,T+H]$ such that $\zeta(s+i\tau)$ approximates an arbitrary given analytic function has a positive upper density.

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arXiv2023

The number of zeros of linear combinations of $L$-functions near the critical line

In this paper, we investigate the zeros near the critical line of linear combinations of $L$-functions belonging to a large class, which conjecturally contains all $L$-functions arising from automorphic representations on $\text{GL}(n)$. More precisely, if $L_1, \dots, L_J$ are distinct primitive $L$-functions with $J\ge 2$, and $b_j$ are any nonzero real numbers, we prove that the number of zeros of $F(s)=\sum_{j\leq J} b_j L_j(s)$ in the region $\text{Re}(s)\geq 1/2+1/G(T)$ and $\text{Im}(s)\in [T, 2T]$ is asymptotic to $K_0 T G(T)/\sqrt{\log G(T)}$ uniformly in the range $ \log \log T \leq G(T)\leq (\log T)^ν$, where $K_0$ is a certain positive constant that depends on $J$ and the $L_j$'s. This establishes a generalization of a conjecture of Hejhal in this range. Moreover, the exponent $ν$ verifies $ν\asymp 1/J$ as $J$ grows.

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arXiv2023

Discrepancy bounds for the distribution of $L$-functions near the critical line

We investigate the joint distribution of $L$-functions on the line $ σ= \frac12 + \frac1{G(T)}$ and $ t \in [ T, 2T]$, where $ \log \log T \leq G(T) \leq \frac{ \log T}{ ( \log \log T)^2 } $. We obtain an upper bound on the discrepancy between the joint distribution of $L$-functions and that of their random models. As an application we prove an asymptotic expansion of a multi-dimensional version of Selberg's central limit theorem for $L$-functions on $ σ= \frac12 + \frac1{G(T)}$ and $ t \in [ T, 2T]$, where $ ( \log T)^ε\leq G(T) \leq \frac{ \log T}{ ( \log \log T)^{2+ε} } $ for $ ε> 0$.

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arXiv2022

Omega results for cubic field counts via lower-order terms in the one-level density

In this paper we obtain a precise formula for the $1$-level density of $L$-functions attached to non-Galois cubic Dedekind zeta functions. We find a secondary term which is unique to this context, in the sense that no lower-order term of this shape has appeared in previously studied families. The presence of this new term allows us to deduce an omega result for cubic field counting functions, under the assumption of the Generalized Riemann Hypothesis. We also investigate the associated $L$-functions Ratios Conjecture, and find that it does not predict this new lower-order term. Taking into account the secondary term in Roberts' Conjecture, we refine the Ratios Conjecture to one which captures this new term. Finally, we show that any improvement in the exponent of the error term of the recent Bhargava--Taniguchi--Thorne cubic field counting estimate would imply that the best possible error term in the refined Ratios Conjecture is $O_\varepsilon(X^{-\frac 13+\varepsilon})$. This is in opposition with all previously studied families, in which the expected error in the Ratios Conjecture prediction for the $1$-level density is $O_\varepsilon(X^{-\frac 12+\varepsilon})$.

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arXiv2020

$n$-level density of the low-lying zeros of primitive Dirichlet $L$-functions

Katz and Sarnak conjectured that the statistics of low-lying zeros of various family of $L$-functions matched with the scaling limit of eigenvalues from the random matrix theory. In this paper we confirm this statistic for a family of primitive Dirichlet $L$-functions matches up with corresponding statistic in the random unitary ensemble, in a range that includes the off-diagonal contribution. To estimate the $n$-level density of zeros of the $L$-functions, we use the asymptotic large sieve method developed by Conrey, Iwaniec and Soundararajan. For the random matrix side, a formula from Conrey and Snaith allows us to solve the matchup problem.

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arXiv2018

On the zeros of Epstein zeta functions near the critical line

Let $Q$ be a positive definite quadratic form with integral coefficients and let $E(s,Q)$ be the Epstein zeta function associated with $Q$. Assume that the class number of $Q$ is bigger than $1$. Then we estimate the number of zeros of $E(s,Q)$ in the region $ \Re s > σ_T ( θ) := 1/2 + ( \log T)^{- θ}$ and $ T < \Im s < 2T$, to provide its asymptotic formula for fixed $ 0 < θ< 1$ conditionally. Moreover, it is unconditional if the class number of $Q$ is $2$ or $3$ and $ 0 < θ< 1/13$.

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arXiv2017

The $a$-values of the Riemann zeta function near the critical line

We study the value distribution of the Riemann zeta function near the line $\Re s = 1/2$. We find an asymptotic formula for the number of $a$-values in the rectangle $ 1/2 + h_1 / (\log T)^θ\leq \Re s \leq 1/2+ h_2 /(\log T)^θ$, $T \leq \Im s \leq 2T$ for fixed $h_1, h_2>0$ and $ 0 < θ<1/13$. To prove it, we need an extension of the valid range of Lamzouri, Lester and Radziwiłł's recent results on the discrepancy between the distribution of $ζ(s)$ and its random model. We also propose the secondary main term for the Selberg's central limit theorem by providing sharper estimates on the line $\Re s = 1/2 + 1/(\log T)^θ$.

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arXiv2015

Zero-density estimates for Epstein zeta functions

We investigate the zeros of Epstein zeta functions associated with a positive definite quadratic form with rational coefficients in the vertical strip $ σ_1 < \Re s < σ_2 $, where $ 1/2 < σ_1 < σ_2 < 1 $. When the class number of the quadratic form is bigger than 1, Voronin gives a lower bound and Lee gives an asymptotic formula for the number of zeros. In this paper, we improve their results by providing a new upper bound for the error term.

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arXiv2015

Joint universality for Lerch zeta-functions

For $0<α, λ\leq 1$, the Lerch zeta-function is defined by $L(s;α, λ)$$:= \sum_{n=0}^\infty e^{2πiλn} (n+α)^{-s}$, where $σ>1$. In this paper, we prove joint universality for Lerch zeta-functions with distinct $λ_1,\ldots,λ_m$ and transcendental $α$.

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arXiv2013

Simple zeros of primitive Dirichlet $L$-functions and the asymptotic large sieve

Assuming the Generalized Riemann Hypothesis (GRH), we show using the asymptotic large sieve that 91% of the zeros of primitive Dirichlet $L$-functions are simple. This improves on earlier work of Özlük which gives a proportion of at most 86%. We further compute an $q$-analogue of the Pair Correlation Function $F(α)$ averaged over all primitive Dirichlet $L$-functions in the range $|α| < 2$ . Previously such a result was available only when the average included all the characters $χ$.

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arXiv2012

On the zeros of Epstein zeta functions

We investigate the zeros of Epstein zeta functions associated with a positive definite quadratic form with rational coefficients. Davenport and Heilbronn, and also Voronin, proved the existence of zeros of Epstein zeta functions off the critical line when the class number of the quadratic form is bigger than 1. These authors give lower bounds for the number of zeros in strips that are of the same order as the more easily proved upper bounds. In this paper, we improve their results by providing asymptotic formulas for the number of zeros.

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