oh, the integral is definitely scale invariant, sorry ...but then isn't scale invariance exactly what your differentiation under the integral sign proves? /me is confused
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Replying to @Corey_Yanofsky @InertialObservr
I am not sure if it answers your question but if you differentiate a function, say f(alpha), with respect to alpha and the result is zero, than f is constant with respect to alpha, so f(alpha) = c and f(0) = f(1) = c. They use this result to prove that I(alpha) = I(0) = I(1).
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Replying to @InertialObservr @Corey_Yanofsky
yes, that is exactly what you did.
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I think you can write exp() and cosine in Taylor series and try to solve the resulting integrals. Does it help?
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Replying to @agpatriota @Corey_Yanofsky
Tried that.. and I got close, but didn’t care to carry it out.. since there will only be even terms in the exp series surviving you have to show by induction the systematic cancellation
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Replying to @InertialObservr @Corey_Yanofsky
yes, I know... Your derivation is very interesting. It reminds me some tricks I learnt with my professor João Mauricio at undergrad at UFC (Federal University of Ceará)
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Replying to @agpatriota @Corey_Yanofsky
Agreed.. some people like sudoku, I like integrals :D
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Replying to @InertialObservr @Corey_Yanofsky
Not sure if it helps, also I am about to sleep: exp(i t) = cos(t) + i sin(t) cos(t) = [exp(i t) + exp(-i t)]/2 exp(a cos(x)) [exp(i a sin(x) ) + exp(-i a sin(x))]/2= =[exp(a cos(x) + i a sin(x) ) + exp(a cos(x) -i a sin(x)) ]/2= =[exp(a exp(i x) ) + exp( a exp(- i x )) ]/2
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Notice that exp(a exp(i x) ) = 1 + a exp(i x) + a^2 exp(2 i x)/2 + ... exp(a exp(-i x) ) = 1 + a exp(-i x) + a^2 exp(-2 i x)/2 + ... Then in_0^{2pi} [exp(a exp(i x) ) + exp( a exp(- i x )) ]/2 dx= 2(2pi)/2 = 2pi because int_0^{2pi} exp(-i k x) dx = 0 correct me if I am wrong
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I’ll have to get back to you, I’m about to head out.. but indeed looks promising
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