The Fourier transform in variable exponent Lebesgue spaces

In this work we define a Fourier transform for each $f\in L^{p(\cdot )}(\mathbb{R})$, for a large class of exponent functions $p(\cdot )$, as the distributional derivative of a Hölder continuous function. A norm is defined in the space of such Fourier transforms so that it is isometrically isomorphic to $L^{p(\cdot )}(\mathbb{R})$. We also prove several properties of this Fourier transform, such as inversion in norm and an exchange theorem.