Thursday, October 25, 2018

analysis - Space of continuous functions linear operator eigenvalues



Let V be the vector space of continuous functions from R to R. Let T be the linear operator on V defined as (Tf)(x)=x0f(t)dt



Prove that T doesn't have eigenvalues.



I want to show that it doesn't exist any continuous function f0 with (1) x0f(t)dt=λf(x), for some λ and for all xR



So suppose it does, then λf(0)=00f(t)dt=0, from here it follows f(0)=0. From equation (1) we also arrive to the inequality λ|f(x)||x|max|f(t)|



where max|f(t)| is the maximum the function attains on the [0,x] or [x,0] respectively.



I would like to arrive to an absurd but I couldn't, any hints or suggestions would be greatly appreciated.


Answer




It follows from your equation (1) that f is differentiable and
f(x)=λf(x) for all xR. The general solution of
this differential equation is f(x)=Cexp(x/λ) for some CR.
Since f(0)=0, f is identically zero.


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