No solution to general Volterra integral equation of the second type? I encountered a (likely si

Jazmine Sweeney

Jazmine Sweeney

Answered question

2022-04-23

No solution to general Volterra integral equation of the second type?
I encountered a (likely simple) Volterra-style integral equation as part of my work. For an arbitrary function p(s) which is square integrable, I have the following equation relating p(s) and its integral with respect to the real-to-real function Q:
p(x)C0xp(s)dQ(s)=0
where C is a known real constant.
I would hopefully like to show, without further assumptions, that this system has only the solution p(s)=0. I have very little training in differential equations, so I'm a bit lost as where to begin.

Answer & Explanation

icebox2686zsd

icebox2686zsd

Beginner2022-04-24Added 13 answers

Step 1
Write the equation as
p(x)=0xp(s)q(s)ds
where q(s)=CQ(s). The equation shows that p(x) is differentiable, since it is equal to an antiderivative. Therefore by differentiating
p(x)=p(x)q(x).
and also p(0)=00p(s)q(s)ds=0.
Step 2
To prove from this that p(x)=0 for all x, one can use the following trick: Set r(x)=p(x)eCQ(x). Then
r(x)=p(x)eCQ(x)+p(x)eCQ(x)(CQ(x))=eCQ(x)(p(x)p(x)q(x))=0
So r(x)=constant=r(0)=0 and therefore also q(x)=0 for all x.

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