Paper 4, Section II, J

Probability and Measure
Part II, 2016

Give the definitions of the convolution fgf * g and of the Fourier transform f^\widehat{f} of ff, and show that fg^=f^g^\widehat{f * g}=\widehat{f} \widehat{g}. State what it means for Fourier inversion to hold for a function ff.

State the Plancherel identity and compute the L2L^{2} norm of the Fourier transform of the function f(x)=ex1[0,1]f(x)=e^{-x} \mathbf{1}_{[0,1]}.

Suppose that (fn),f\left(f_{n}\right), f are functions in L1L^{1} such that fnff_{n} \rightarrow f in L1L^{1} as nn \rightarrow \infty. Show that f^nf^\widehat{f}_{n} \rightarrow \widehat{f} uniformly.

Give the definition of weak convergence, and state and prove the Central Limit Theorem.