Hyerim Ko

activity

20152025

most citedCircular average relative to fractal measures

4 citations · 11 across the 14 of their papers we have counts for

collaborators

14 papers

math.CA2025

Weighted wave envelope estimates for the parabola

Jongchon Kim, Hyerim Ko

In this paper, we extend the Córdoba-Fefferman square function estimate for the parabola to a weighted setting. Our weighted square function estimate is derived from a weighted wav…

math.AP2025

Maximal estimates for orthonormal systems of wave equations with sharp regularity

Hyerim Ko, Sanghyuk Lee, Shobu Shiraki

We study maximal estimates for the wave equation with orthonormal initial data. In dimension $d = 3$ , we establish optimal results with the sharp regularity exponent up to the endpoi…

math.AP2025

Maximal estimates for orthonormal systems of wave equations

Shinya Kinoshita, Hyerim Ko, Shobu Shiraki

This paper investigates maximal estimates of the wave operators for orthonormal families of initial data. We extend the classical maximal estimates for the wave operator by making…

math.CA2025

Local smoothing and maximal estimates for average over surfaces of codimension 2 in $R^{4}$

Seheon Ham, Hyerim Ko

In this paper, we obtain local smoothing estimates for the averages over nondegenerate surfaces of codimension $2$ in $R^{4}$ . We make use of multilinear restriction estimate…

math.CA2022

Remarks on dimension of unions of curves

Seheon Ham, Hyerim Ko, Sanghyuk Lee +1

We study an analogue of Marstrand's circle packing problem for curves in higher dimensions. We consider collections of curves which are generated by translation and dilation of a c…

math.CA2022

Pointwise convergence of sequential Schrödinger means

Chu-Hee Cho, Hyerim Ko, Youngwoo Koh +1

We study pointwise convergence of the fractional Schrödinger means along sequences $t_{n}$ which converge to zero. Our main result is that bounds on the maximal function $\sup_{n} |e…

math.CA2021★ 1 cited

Sharp Sobolev regularity of restricted X-ray transforms

Hyerim Ko, Sanghyuk Lee, Sewook Oh

We study $L^{p}$ -Sobolev regularity estimate for the restricted X-ray transforms generated by nondegenerate curves. Making use of the inductive strategy in the recent work by the aut…

math.CA2021★ 4 cited

Circular average relative to fractal measures

Seheon Ham, Hyerim Ko, Sanghyuk Lee

We prove new $L^{p}$ - $L^{q}$ estimates for averages over dilates of the circle with respect to $α$ -dimensional fractal measure, which unify different types of maximal estimates for th…

math.CA2021★ 1 cited

Sharp smoothing properties of averages over curves

Hyerim Ko, Sanghyuk Lee, Sewook Oh

We prove sharp smoothing properties of the averaging operator defined by convolution with a measure on a smooth nondegenerate curve $γ$ in $R^{d}$ , $d \geq 3$ . Despite the simp…

math.AP2021★ 1 cited

Dimension of divergence set of the wave equation

Seheon Ham, Hyerim Ko, Sanghyuk Lee

We consider the Hausdorff dimension of the divergence set on which the pointwise convergence $lim_{t \to 0} e^{i t - Δ} f (x) = f (x)$ fails when $f \in H^{s} (R^{d})$ …

math.CA2021

Maximal estimates for averages over space curves

Hyerim Ko, Sanghyuk Lee, Sewook Oh

Let $M$ be the maximal operator associated to a smooth curve in $R^{3}$ which has nonvanishing curvature and torsion. We prove that $M$ is bounded on $L^{p}$ if and only if $p>…

math.CA2018

Remarks on estimates for the adjoint restriction operator to curves over the sphere

Seheon Ham, Hyerim Ko, Sanghyuk Lee

Recently, two of the authors obtained estimates for the adjoint restriction operator to finite type curves with respect to general measures. Strikingly, it turns out that some of s…

math.AP2018★ 3 cited

Pointwise convergence of the fractional Schrödinger equation in $R^{2}$

Chu-hee Cho, Hyerim Ko

We investigate the pointwise convergence of the solution to the fractional Schrödinger equation in $R^{2}$ . By establishing $H^{s} (R^{2}) - L^{3} (R^{2})$ estimates for…

math.AP2015★ 1 cited

Fourier transform and regularity of characteristic functions

Hyerim Ko, Sanghyuk Lee

Let $E$ be a bounded domain in $R^{d}$ . We study regularity property of $χ_{E}$ and integrability of $χ_{E}$ when its boundary $\partial E$ satisfies some conditions.…

Weighted wave envelope estimates for the parabola

Maximal estimates for orthonormal systems of wave equations with sharp regularity

Maximal estimates for orthonormal systems of wave equations

Local smoothing and maximal estimates for average over surfaces of codimension 2 in R4

Remarks on dimension of unions of curves

Pointwise convergence of sequential Schrödinger means

Sharp Sobolev regularity of restricted X-ray transforms

Circular average relative to fractal measures

Sharp smoothing properties of averages over curves

Dimension of divergence set of the wave equation

Maximal estimates for averages over space curves

Remarks on estimates for the adjoint restriction operator to curves over the sphere

Pointwise convergence of the fractional Schrödinger equation in R2

Fourier transform and regularity of characteristic functions

Local smoothing and maximal estimates for average over surfaces of codimension 2 in $R^{4}$

Pointwise convergence of the fractional Schrödinger equation in $R^{2}$