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We consider the wave equation $(\p_t^2-\Delta_g)u(t,x)=f(t,x)$, in $\R^n$, $u|_{\R_-\times \R^n}=0$, where the metric $g=(g_{jk}(x))_{j,k=1}^n$ is known outside an open and bounded set $M\subset \R^n$ with smooth boundary $\p M$. We define…

Analysis of PDEs · Mathematics 2010-11-12 Tapio Helin , Matti Lassas , Lauri Oksanen

We analyze the inverse problem, originally formulated by Dix in geophysics, of reconstructing the wave speed inside a domain from boundary measurements associated with the single scattering of seismic waves. We consider a domain $\tilde M$…

Analysis of PDEs · Mathematics 2012-12-04 Maarten V. de Hoop , Sean F. Holman , Einar Iversen , Matti Lassas , Bjørn Ursin

Passive imaging refers to problems where waves generated by unknown sources are recorded and used to image the medium through which they travel. The sources are typically modelled as a random variable and it is assumed that some statistical…

Analysis of PDEs · Mathematics 2016-11-07 Tapio Helin , Matti Lassas , Lauri Oksanen , Teemu Saksala

Consider the geometric inverse problem: There is a set of delta-sources in spacetime that emit waves travelling at unit speed. If we know all the arrival times at the boundary cylinder of the spacetime, can we reconstruct the space, a…

Differential Geometry · Mathematics 2023-08-09 Maarten V. de Hoop , Joonas Ilmavirta , Matti Lassas , Teemu Saksala

We consider a strongly damped wave equation on compact manifolds, both with and without boundaries, and formulate the corresponding inverse problems. For closed manifolds, we prove that the metric can be uniquely determined, up to an…

Analysis of PDEs · Mathematics 2023-09-29 Li Li , Yang Zhang

We consider inverse problems in space-time $(M, g)$, a $4$-dimensional Lorentzian manifold. For semilinear wave equations $\square_g u + H(x, u) = f$, where $\square_g$ denotes the usual Laplace-Beltrami operator, we prove that the…

Analysis of PDEs · Mathematics 2016-06-21 Matti Lassas , Gunther Uhlmann , Yiran Wang

We consider the inverse problem to determine a smooth compact Riemannian manifold with boundary $(M, g)$ from a restriction $\Lambda_{\Src, \Rec}$ of the Dirichlet-to-Neumann operator for the wave equation on the manifold. Here $\Src$ and…

Analysis of PDEs · Mathematics 2015-01-14 Matti Lassas , Lauri Oksanen

This paper is concerned with the direct and inverse random source scattering problems for elastic waves where the source is assumed to be driven by an additive white noise. Given the source, the direct problem is to determine the…

Analysis of PDEs · Mathematics 2016-08-10 Gang Bao , Chuchu Chen , Peijun Li

We consider the inverse problem to determine a smooth compact Riemannian manifold $(M,g)$ from a restriction of the source-to-solution operator, $\Lambda_{\mathcal{S,R}}$, for the wave equation on the manifold. Here, $\mathcal{S}$ and…

Analysis of PDEs · Mathematics 2023-03-24 Matti Lassas , Medet Nursultanov , Lauri Oksanen , Lauri Ylinen

This paper is concerned with an inverse source problem for the stochastic biharmonic operator wave equation. The driven source is assumed to be a microlocally isotropic Gaussian random field with its covariance operator being a classical…

Analysis of PDEs · Mathematics 2021-06-25 Peijun Li , Xu Wang

We consider boundary measurements for the wave equation on a bounded domain $M \subset \R^2$ or on a compact Riemannian surface, and introduce a method to locate a discontinuity in the wave speed. Assuming that the wave speed consist of an…

Analysis of PDEs · Mathematics 2011-06-17 Lauri Oksanen

This paper is concerned with an inverse random source problem for the one-dimensional stochastic Helmholtz equation with attenuation. The source is assumed to be a microlocally isotropic Gaussian random field with its covariance operator…

Numerical Analysis · Mathematics 2020-09-30 Peijun Li , Xu Wang

Given a connected compact Riemannian manifold $(M,g)$ without boundary, $\dim M\ge 2$, we consider a space--time fractional diffusion equation with an interior source that is supported on an open subset $V$ of the manifold. The…

Analysis of PDEs · Mathematics 2019-03-12 Tapio Helin , Matti Lassas , Lauri Ylinen , Zhidong Zhang

Consider the one-dimensional stochastic Helmholtz equation where the source is assumed to be driven by the white noise. This paper concerns the stability analysis of the inverse random source problem which is to reconstruct the statistical…

Analysis of PDEs · Mathematics 2016-07-25 Peijun Li , Ganghua Yuan

We prove that the metric tensor $g$ of a complete Riemannian manifold is uniquely determined, up to isometry, from the knowledge of a local source-to-solution operator. This later is associated to a fractional power of the Laplace-Belrami…

Analysis of PDEs · Mathematics 2023-11-13 Mourad Choulli , El Maati Ouhabaz

We consider how a closed Riemannian manifold $M$ and its metric tensor $g$ can be approximately reconstructed from local distance measurements. Moreover, we consider an inverse problem of determining $(M,g)$ from limited knowledge on the…

Differential Geometry · Mathematics 2025-05-30 Charles Fefferman , Sergei Ivanov , Matti Lassas , Jinpeng Lu , Hariharan Narayanan

Given a fixed $\alpha \in (0,1)$, we study the inverse problem of recovering the isometry class of a smooth closed and connected Riemannian manifold $(M,g)$, given the knowledge of a source-to-solution map for the fractional Laplace…

Analysis of PDEs · Mathematics 2024-02-29 Ali Feizmohammadi

In this paper we consider two inverse problems on a closed connected Riemannian manifold $(M,g)$. The first one is a direct analog of the Gel'fand inverse boundary spectral problem. To formulate it, assume that $M$ is divided by a…

Analysis of PDEs · Mathematics 2007-09-17 Katsiaryna Krupchyk , Yaroslav Kurylev , Matti Lassas

We consider a fixed angle inverse scattering problem in the presence of a known Riemannian metric. First, assuming a no caustics condition, we study the direct problem by utilizing the progressing wave expansion. Under a symmetry assumption…

Analysis of PDEs · Mathematics 2021-07-21 Shiqi Ma , Mikko Salo

We consider inverse problems consisting of the reconstruction of an unknown signal $f$ from noisy measurements $y=Ff+\text{noise}$, where $Ff$ is a function on a Riemannian manifold without boundary $\mathcal M$. We consider the case when…

Functional Analysis · Mathematics 2026-04-24 Giovanni S. Alberti , Ernesto De Vito , Bianca Gariboldi , Giacomo Gigante
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