Paper 1, Section II, G

Analysis II | Part IB, 2015

Define what it means for a sequence of functions fn:[0,1]Rf_{n}:[0,1] \rightarrow \mathbb{R} to converge uniformly on [0,1][0,1] to a function ff.

Let fn(x)=npxenqxf_{n}(x)=n^{p} x e^{-n^{q} x}, where p,qp, q are positive constants. Determine all the values of (p,q)(p, q) for which fn(x)f_{n}(x) converges pointwise on [0,1][0,1]. Determine all the values of (p,q)(p, q) for which fn(x)f_{n}(x) converges uniformly on [0,1][0,1].

Let now fn(x)=enx2f_{n}(x)=e^{-n x^{2}}. Determine whether or not fnf_{n} converges uniformly on [0,1][0,1].

Let f:[0,1]Rf:[0,1] \rightarrow \mathbb{R} be a continuous function. Show that the sequence xnf(x)x^{n} f(x) is uniformly convergent on [0,1][0,1] if and only if f(1)=0f(1)=0.

[If you use any theorems about uniform convergence, you should prove these.]

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