Research
Manuscripts and preprints (available upon request):
- Generalization in post-processing type deep learning methods for limited-angle tomography
Abstract: Post-processing type deep learning methods are popular in limited angle tomography. Empirical evaluations have demonstrated generalization ability of these methods in removing artifacts, but the mechanism remains elusive. In this work, we formulate the learning problem as a nonlinear inverse problem, and analyze the generalization using techniques from microlocal analysis. Our result also provides sufficient conditions on training data to achieve generalization ability for reducing artifacts in limited angle tomography.
- A convolutional deep Calderón method for Electrical Impedance Tomography (with T. Hu, B. Jin)
Abstract: Electrical impedance tomography (EIT) is a noninvasive imaging technique utilizing electric properties of the imaging object. Due to its severe ill-posed nature, the problem is challenging to solve numerically. Recent studies using deep learning-based methods have shown promising empirical results but often face instability issues. In this work, we propose a new strategy, namely convolutional deep Calderón method (CDCM) to address the stability-accuracy trade-off in deep learning based approaches for EIT problems. The proposed method is based on a theoretical development that decouples the ill-posedness and nonlinearity of the EIT problem, which consists of a stable but nonlinear step and a linear but unstable deconvolution step. We illustrate the effectiveness of CDCM through numerical experiments, including perturbations with mixed-sign amplitudes, overlapping inclusions, noisy data and an inhomogeneous background. Numerically, we observe that CDCM consistently outperforms the standard deep Calderón method, and yields more stable reconstructions with fewer artifacts.
- The Calderón problem for near Euclidean metrics (with G. Uhlmann)
- The partial data Calderón problem in dimension three (with G. Uhlmann)
- Recovering asymptotics of potentials from the scattering of relativistic
Schrödinger operators (with G. Uhlmann)
- A Lipschitz stability for the Calderón problem with small structure-free anisotropy (with J.-N. Wang)
Abstract: In this paper, we study an anisotropic Calderón problem of recovering potentials by the boundary measurements. We consider the Laplace-Beltrami operator with any Riemannian metric which is a small perturbation of the Euclidean one. We prove that the Dirichlet-to-Neumann map associated with the Schrödinger operator determines the potential with a Lipschitz stability estimate in a negative Sobolev norm under a sign condition. In other words, assuming a priori sign condition, we are able to prove two new results in Calderón problem: small anisotropic media without structure assumption and a Lipchitz stability estimate of reconstructing potentials.
- Rigidity of Lorentzian metrics with the same scattering relations
Abstract: Consider small metric deformations of the Minkowski space. We prove that the scattering relation of null geodesics between two Cauchy surfaces uniquely determines the metric perturbation up to gauge obstructions.
- Microlocal analysis of the light ray transform on globally hyperbolic
Lorentzian manifolds
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Determination of vacuum space-times from the Einstein-Maxwell equations (with M. Lassas, G. Uhlmann)
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Resolvent and radiation fields on non-trapping asymptotically hyperbolic manifolds
Publications:
- Stability of electrical impedance tomography with anisotropies and its application to the deep Calderón method (with T. Hu, B. Jin)
SIAM Journal on Imaging Sciences, accepted.
- Reconstruction of the observable Universe from the integrated Sachs-Wolfe effect (with J. Chung)
SIAM Journal on Applied Mathematics, accepted.
- On finding gravitational waves from anisotropies of the Cosmic Microwave Background
Inverse Problems 42.9 (2026): 95001.
(Focus Collection, Microlocal Insights in Inverse Problems: Theory, Computation, and Applications)
- Generic injectivity of the limited angle Radon transform with weights
The Journal of Geometric Analysis 36.5 (2026): 162.
- Inverse source problem for the Boltzmann equation in cosmology
Annales Henri Poincaré 27.1 (2026): 187-219.
- Iterative reconstruction methods for cosmological X-ray tomography (with J. Chung, L. Onisk)
SIAM Journal on Imaging Sciences 18.3 (2025): 1653-1680.
- The distribution of negative eigenvalues of Schrödinger operators on asymptotically hyperbolic manifolds (with A. Sá Barreto) Journal of Spectral Theory 15.2 (2025): 679-727.
- Robustness of data-driven approaches in limited angle tomography (with Y. Zhong)
SIAM Journal on Imaging Sciences 18.1 (2025): 345-358.
- Identification of nonlinear beam-hardening effects in X-ray tomography
SIAM Journal on Mathematical Analysis 56.6 (2024): 7290-7305.
- Inverse problems in cosmological X-ray tomography
Microlocal Analysis and Inverse Problems in Tomography and Geometry
Radon Series on Computational and Applied Mathematics, Volume 30, 2024.
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The anisotropic Calderón problem for high fixed frequency (with G. Uhlmann)
SIAM Journal on Mathematical Analysis 56.3 (2024): 4084-4103.
- Existence of resonances for Schrödinger operators on hyperbolic space (with D. Borthwick)
Analysis&PDE 17.6 (2024): 2077-2108.
- Recovery of black hole mass from a single quasinormal mode (with G. Uhlmann)
Communications in Mathematical Physics 401.1 (2023): 925-936.
- Some integral geometry problems for wave equations
Inverse Problems 38.8 (2022): 084001.
(Special issue of Emerging Talents)
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Inverse scattering for critical semilinear wave equations (with A. Sá Barreto, G. Uhlmann)
Pure and Applied Analysis 4.2 (2022): 191-223.
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Sharp resolvent estimates on non-positively curved asymptotically hyperbolic manifolds
International Mathematics Research Notices 2022.8 (2022): 6107-6134.
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Streak artifacts from non-convex metal objects in X-ray tomography (with Y. Zou)
Pure and Applied Analysis 3.2 (2021): 295-318.
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On the light ray transform of wave equation solutions (with A. Vasy)
Communications in Mathematical Physics 384.1 (2021): 503-532.
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Singularities generated by the triple interaction of semilinear conormal waves (with A. Sá Barreto)
Analysis&PDE 14.1 (2021): 135-170.
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Convolutional neural networks in phase space and inverse problems (with G. Uhlmann)
SIAM Journal on Applied Mathematics 80.6 (2020): 2560-2585.
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Determination of space-time structures from gravitational perturbations (with G. Uhlmann)
Communications on Pure and Applied Mathematics 73.6 (2020): 1315-1367.
(Top cited article 2020-2021)
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Nonlinear interaction of waves in elastodynamics and an inverse problem (with M. de Hoop, G. Uhlmann)
Mathematische Annalen 376.1-2 (2020): 765-795.
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Nonlinear responses from the interaction of two progressing waves at an interface (with M. de Hoop, G. Uhlmann)
Annales de l'Institut Henri Poincaré, Analyse Non Linéaire 36.2 (2019): 347-363.
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Distribution of resonances for analytic asymptotically hyperbolic spaces
Journal of Spectral Theory 9.2 (2019): 651-675.
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Inverse problems for quadratic derivative nonlinear wave equations (with T. Zhou)
Communications in Partial Differential Equations 44.11 (2019): 1140-1158.
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The scattering operator on asymptotically hyperbolic manifolds (with A. Sá Barreto)
Journal of Spectral Theory 9.1 (2019): 269-314.
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Quantitative analysis of metal artifacts in X-ray tomography (with B. Palacios, G. Uhlmann)
SIAM Journal on Mathematical Analysis 50.5 (2018): 4914-4936.
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Parametrices for the light ray transform on Minkowski spacetime
Inverse Problems and Imaging 12.1 (2018): 229-237.
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Inverse problems for semilinear wave equations on Lorentzian manifolds (with M. Lassas, G. Uhlmann)
Communications in Mathematical Physics 360.2 (2018): 555-609.
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Reducing streaking artifacts in quantitative susceptibility mapping (with B. Palacios, G. Uhlmann)
SIAM Journal on Imaging Sciences 10.4 (2017): 1921-1934.
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The semiclassical resolvent on conformally compact manifolds with variable curvature at infinity (with A. Sá Barreto)
Communications in Partial Differential Equations 41.8 (2016): 1230-1302.
Last updated: 10-2026.
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