Solve Harmonic Wave Equation: Manish from Germany

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Discussion Overview

The discussion revolves around whether the function f(x,t)=exp[-i(ax+bt)^2] qualifies as a harmonic wave. Participants explore the implications of the quadratic exponent in the context of harmonic wave equations, examining definitions and properties of harmonic functions.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Manish questions if f(x,t)=exp[-i(ax+bt)^2] qualifies as a harmonic wave.
  • One participant suggests that separating the real and imaginary parts could indicate it qualifies as a harmonic wave.
  • Another participant raises concerns about the quadratic exponent, questioning if it still meets the criteria for a harmonic wave.
  • A different viewpoint argues that cos(x^2) or cos(2x*t) does not represent a harmonic wave, citing the requirement f''=A*f for a constant A.
  • Another participant contends that cos[(kx+wt)^2] could be harmonic, claiming it fulfills the requirement f''=A*f.
  • One participant expresses confusion over the mathematical derivation, indicating that the second derivative does not suggest the existence of a constant A that satisfies the harmonic wave equation for all x and t.

Areas of Agreement / Disagreement

Participants express differing views on whether the given function qualifies as a harmonic wave, with no consensus reached on the implications of the quadratic exponent or the definitions of harmonic functions.

Contextual Notes

There are unresolved mathematical steps regarding the second derivative and the conditions under which the function may or may not qualify as harmonic. The discussion reflects varying interpretations of the harmonic wave criteria.

reedc15
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Dear Guys,

Does f(x,t)=exp[-i(ax+bt)^2] qualify as a harmonic wave? Please help!

Manish
Germany
 
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reedc15 said:
Dear Guys,

Does f(x,t)=exp[-i(ax+bt)^2] qualify as a harmonic wave? Please help!

Manish
Germany

Yes. Separate the real (cosine) and imaginary parts (sine).
 
Ok, but what about the quadratic exponent? Would my wave equation still be harmonic?
 
i actually think not, cos(x^2) or cos(2x*t) is not an harmonic wave.
in general, an harmonic function f is a function that gives f''=A*f when A is a constant. the function you gave do not fulfil this requirement.
 
Yes, cos(x^2) is not a harmonic wave, but cos[(kx+wt)^2] is, I think. "f''=A*f when A is a constant" this requirement is also fulfilled, as f comes from w, and it will take integer multiple (given by constant A)
 
I didn't understand what you mean,
d^2 f/dx^2= -f*(2xk^2+2kwt)-2k^2*sin((kx+wt)^2)
and nothing here suggest that there exist a constant A that for every t and every x
d^2 f/dx^2=Af.
 

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