One of the basic questions in harmonic analysis is to study the decay properties of the Fourier transform of measures or distributions supported on thin sets in $\mathbb{R}^n$
. When the support is a smooth enough manifold, an almost complete picture is available. One of the early results in this direction is the following: Let $f\in C_c^{\infty}(d\sigma)$
, where $d\sigma$
is the surface measure on the sphere $S^{n-1}\subset\mathbb{R}^n$
. Then
It follows that $\widehat{fd\sigma}\in L^p(\mathbb{R}^n)$
for all
$p>2n/(n-1)$
. This result can be extended to compactly
supported measure on $(n-1)$-dimensional manifolds with
appropriate assumptions on the curvature. Similar results are
known for measures supported in lower dimensional manifolds in
$\mathbb{R}^n$
under appropriate curvature conditions. However, the
picture for fractal measures is far from complete. This thesis is
a contribution to the study of asymptotic properties of the
Fourier transform of measures supported in sets of fractal
dimension $0<\alpha<n$
for $p\leq 2n/\alpha$
.
In 2004, Agranovsky and Narayanan proved that if $\mu$ is a
measure supported in a $C^1$
-manifold of dimension $d<n$
, then
$\widehat{fd\mu}\notin L^p(\mathbb{R}^n)$
for $1\leq p\leq \frac{2n}{d}$
. We
prove that the Fourier transform of a measure $\mu_E$ supported in
a set $E$ of fractal dimension $\alpha$ does not belong to
$L^p(\mathbb{R}^n)$
for $p\leq 2n/\alpha$
. We also study $L^p$
-asymptotics
of the Fourier transform of fractal measures $\mu_E$ under
appropriate conditions on $E$ and give quantitative versions of
the above statement by obtaining lower and upper bounds for the
following:
\(\underset{L\Rightarrow\infty}{\limsup} \frac{1}{L^k} \int_{|\xi|\leq L}|\widehat{fd\mu_E}(\xi)|^pd\xi,\) \(\underset{L\Rightarrow\infty}{\limsup} \frac{1}{L^k} \int_{L\leq |\xi|\leq 2L}|\widehat{fd\mu_E}(\xi)|^pd\xi.\)