# Mark Agranovsky - Bar Ilan University

## Contact Details

NameMark Agranovsky |
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AffiliationBar Ilan University |
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CityRamat Gan |
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CountryIsrael |
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## Pubs By Year |
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## Pub CategoriesMathematics - Complex Variables (6) Mathematics - Analysis of PDEs (6) Mathematics - Mathematical Physics (4) Mathematical Physics (4) Mathematics - Differential Geometry (2) Mathematics - Numerical Analysis (1) Mathematics - Functional Analysis (1) Mathematics - Classical Analysis and ODEs (1) Mathematics - Metric Geometry (1) |

## Publications Authored By Mark Agranovsky

Let $D$ be a bounded domain $D$ in $\mathbb R^n $ with infinitely smooth boundary and $n$ is odd. We prove that if the volume cut off from the domain by a hyperplane is an algebraic function of the hyperplane, free of real singular points, then the domain is an ellipsoid. This partially answers a question of V. Read More

Let $D$ be a bounded domain in $\mathbb R^n,$ with smooth boundary. Denote $V_D(\omega,t), \ \omega \in S^{n-1}, t \in \mathbb R,$ the Radon transform of the characteristic function $\chi_{D}$ of the domain $D,$ i.e. Read More

It is proved that if a Paley-Wiener family of eigenfunctions of the Laplace operator in $\mathbb R^3$ vanishes on a real analytically ruled two-dimensional surface $S \subset \mathbb R^3$ then $S$ is a union of cones, each of which is contained in a translate of the zero set of a nonzero harmonic homogeneous polynomial. If $S$ is an immersed $C^1-$ manifold then $S$ is a Coxeter system of planes. Full description of common nodal sets of the Laplace spectra of convexly supported distributions is given. Read More

A version of the argument principle is established for varieties of holomorphic mappings from the unit disc to $\mathbb C^n,$ parametrized by points of real manifolds. Applications to characterization of CR functions and estimating CR dimensions of real submanifolds in $\mathbb C^n$ are given. Read More

Let $B^n$ be the unit ball in $\mathbb C^n$ and let the points $a_1,... Read More

Let $B^n$ be the $n$-dimensional unit complex ball and let $a$ and $b$ be two distinct points in its closure. Let $f$ be a real-analytic function on the complex unit sphere $\partial B^n.$ Suppose that for any complex line $L,$ meeting the two points set $\{a,b\},$ the function $f$ admits one-dimensional holomorphic extension in the cross-section $L \cap B^n. Read More

One-parameter smooth families of circles in the complex plane with the following property are described: a function is polyanalytic if and only if it has meromorphic extension inside any circle from the family, with the only singularity-a pole at the center. Read More

Let f(x) belong to L^p(R^n) and R>0. The transform is considered that integrates the function f over (almost) all spheres of radius R in R^n. This operator is known to be non-injective (as one can see by taking Fourier transform). Read More

The transform under study is defined by integration of functions over spheres centered on a sphere. Such transform is of interest due to its applications in analysis and (thermoacoustic) tomography. The range of this transform has been described recently. Read More

The paper is devoted to the range description of the Radon type transform that averages a function over all spheres centered on a given sphere. Such transforms arise naturally in thermoacoustic tomography, a novel method of medical imaging. Range descriptions have recently been obtained for such transforms, and consisted of smoothness and support conditions, moment conditions, and some additional orthogonality conditions of spectral nature. Read More

The paper contains a simple approach to reconstruction in Thermoacoustic and Photoacoustic Tomography. The technique works for any geometry of point detectors placement and for variable sound speed satisfying a non-trapping condition. A uniqueness of reconstruction result is also obtained. Read More

Let $\Omega$ be a smooth real analytic submanifold of a complex manifold $X$. We establish and study the link between the following 3 subjects: 1) topological properties of smooth families of attached analytic discs, the manifold $\Omega$ admits, 2) lower bounds for dimensions of complex tangent spaces of $\Omega$, 3) a generalization of the argument principle for smooth families of holomorphic mappings from the standard complex disc to $X$. In particular, we obtain characterization of complex manifolds and their boundaries in terms of attached analytic discs. Read More

We prove that generic homologically nontrivial $(2n-1)$-parameter family of analytic discs attached by their boundaries to a CR manifold $\Omega$ in $\mathbb C^n, n \le 2$ tests CR functions: if a smooth function on $\Omega$ extends analytically inside each analytic disc then it satisfies the tangential CR equations. In particular, we answer, in real analytic category, two open questions: on characterization of analytic functions in planar domains (the strip-problem), and on characterization of boundary values of holomorphic functions in domains in $\mathbb C^n$ (a conjecture of Globevnik and Stout). We also characterize complex curves in $\mathbb C^2$ as real 2-manifolds admitiing homologically nontrivial 1-parameter families of attached analytic discs. Read More

**Affiliations:**

^{1}Bar Ilan University,

^{2}Tufts University

**Category:**Mathematics - Analysis of PDEs

We consider the Cauchy problem for the wave equation in the whole space, R^n, with initial data which are distributions supported on finite sets. The main result is a precise description of the geometry of the sets of stationary points of the solutions to the wave equation. Read More