Integration by Parts: Formula & Real/Non-Integer n

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SUMMARY

The formula for integration by parts, represented as \(\int_{-\infty}^{\infty}dxf(x)D^{n}g(x) = (-1)^{n} \int_{-\infty}^{\infty}dxg(x)D^{n}f(x)\), is valid only for integer values of \(n\). The term \((-1)^{n}\) becomes problematic when \(n\) is non-integer, leading to ambiguity in its definition. Integration by parts inherently operates in integer steps, necessitating the use of \(h(x)=Dng(x)\) for non-integer \(n\) to ensure proper execution of the integration process.

PREREQUISITES
  • Understanding of integration techniques, specifically integration by parts.
  • Familiarity with the notation and concepts of derivatives, particularly \(D^{n}\) notation.
  • Knowledge of real and non-integer numbers in mathematical contexts.
  • Basic grasp of limits and improper integrals, especially over infinite intervals.
NEXT STEPS
  • Study the properties of derivatives for non-integer orders, focusing on fractional calculus.
  • Explore the implications of the term \((-1)^{n}\) in mathematical expressions involving non-integer values.
  • Research advanced integration techniques that accommodate non-integer derivatives.
  • Learn about the application of integration by parts in various mathematical fields, including physics and engineering.
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Mathematicians, physics students, and anyone interested in advanced calculus, particularly those dealing with integration techniques and fractional derivatives.

zetafunction
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is the following formula of integration by parts

[tex]\int_{-\infty}^{\infty}dxf(x)D^{n}g(x) = (-1)^{n} \int_{-\infty}^{\infty}dxg(x)D^{n}f (x)[/tex]

valid for real or non-integer n? the problem i see here is the term [tex](-1)^{n}[/tex] , which may be not so well defined for non-integer 'n'
 
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Integration by parts takes place in integer steps, so the formula you presented requires n to be an integer. If n is not an integer, you need to use h(x)=Dng(x) and carry out the parts integration in integer steps. You will never get the right hand side.
 

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