Let $q(x)$ be real-valued compactly supported sufficiently smooth function.
It is proved that the scattering data $A(-\beta,\beta,k)$ $\forall \beta\in
S^2$, $\forall k>0,$ determine $q$ uniquely.
Let $G(k)=\int_0^1g(x)e^{kx}dx$, $g\in L^1(0,1)$. The main result of this
paper is the following theorem.
{\bf Theorem}. {\it If $\limsup_{k\to +\infty}|G(k)|<\infty$, then $g=0$.
There exists $g\not\equiv 0$, $g\in L^1(0,1)$, such that $G(k_j)=0$,
$k_j<k_{j+1}$, $\lim_{j\to \infty}k_j=\infty$, $\lim_{k\to \infty}|G(k)|$ does
not exist, $\limsup_{k\to +\infty}|G(k)|=\infty$. This $g$ oscillates
infinitely often in any interval $[1-\delta, 1]$, however small $\delta>0$ is.}
A new understanding of the notion of the stable solution to ill-posed
problems is proposed. The new notion is more realistic than the old one and
better fits the practical computational needs. A method for constructing stable
solutions in the new sense is proposed and justified.
In this paper a new method for inverting the Laplace transform from the real
axis is formulated. This method is based on a quadrature formula. We assume
that the unknown function $f(t)$ is continuous with (known) compact support. An
adaptive iterative method and an adaptive stopping rule, which yield the
convergence of the approximate solution to $f(t)$, are proposed in this paper.
Let $\ell_j:=-\frac{d^2}{dx^2}+k^2q_j(x),$ $k=const>0, j=1,2,$ $0<c_0\leq
q_j(x)\leq c_1,$ %$q\in BV([0,1])$, $q$ has finitely many discontinuity points
$x_m\in [0,1],$ and is real-analytic on the intervals $[x_m,x_{m+1}]$ between
these points. The set of such functions $q$ is denoted by $M.$ Only the
following property of $M$ is used: if $q_j\in M$, $j=1,2,$ then the function
$p(x):=q_2(x)-q_1(x)$ changes sign on the interval $[0, 1]$ at most finitely
many times.
A method is given for creating material with a desired refraction
coefficient. The method consists of embedding into a material with known
refraction coefficient many small particles of size $a$. The number of
particles per unit volume around any point is prescribed, the distance between
neighboring particles is $O(a^{\frac{2-\kappa}{3}})$ as $a\to 0$, $0<\kappa<1$
is a fixed parameter. The total number of the embedded particle is
$O(a^{\kappa-2})$.
A method is given for creating material with a desired refraction
coefficient. The method consists of embedding into a material with known
refraction coefficient many small particles of size $a$. The number of
particles per unit volume around any point is prescribed, the distance between
neighboring particles is $O(a^{\frac{2-\kappa}{3}})$ as $a\to 0$, $0<\kappa<1$
is a fixed parameter. The total number of the embedded particle is
$O(a^{\kappa-2})$.
An evolution equation, arising in the study of the Dynamical Systems Method
(DSM) for solving equations with monotone operators, is studied in this paper.
The evolution equation is a continuous analog of the regularized Newton method
for solving ill-posed problems with monotone nonlinear operators $F$. Local and
global existence of the unique solution to this evolution equation are proved,
apparently for the firs time, under the only assumption that $F'(u)$ exists and
is continuous with respect to $u$. The earlier published results required more
smoothness of $F$.
It is proposed to create materials with a desired refraction coefficient in a
bounded domain $D\subset \R^3$ by embedding many small balls with constant
refraction coefficients into a given material. The number of small balls per
unit volume around every point $x\in D$, i.e., their density distribution, is
calculated, as well as the constant refraction coefficients in these balls.
Embedding into $D$ small balls with these refraction coefficients according to
the calculated density distribution creates in $D$ a material with a desired
refraction coefficient.
Boundary integral equation is derived for the problem of scattering of
electromagnetic waves by 3D homogeneous body of arbitrary shape.
A 3D singular integral equation is derived for electromagnetic wave
scattering by bodies of arbitrary shape. Its numerical solution by a projection
method is outlined.
Sufficient conditions are given for a hard implicit function theorem to hold.
The result is established by an application of the Dynamical Systems Method
(DSM). It allows one to solve a class of nonlinear operator equations in the
case when the Fr\'echet derivative of the nonlinear operator is a smoothing
operator, so that its inverse is an unbounded operator.