How to Approach Solving a Complex Trigonometric Integral?

In summary, the conversation discusses an integral for the function S_T(ω) and its solution according to a paper. The solution involves the variables k_B, T, g, c, D, l, ω, and ω_0, and can be verified by differentiating or using computational tools. Transforming ω to θ simplifies the integral.
  • #1
Excom
61
0
Hello everyone

Can someone help me out solving this integral:
\begin{equation}
S_T(\omega)=\frac{2k_BT^2g}{4\pi^2c^2}\int_0^{\infty}\frac{sin^2(kl)}{k^2l^2}\frac{k^2}{D^2k^4+\omega^2}dk
\end{equation}

Where $$D=g/c$$

According to this paper https://doi.org/10.1103/PhysRevB.13.556. The solution to the integral is:

\begin{equation}
S_T(\omega)=\frac{k_BT^2D^{1/2}}{4\sqrt{2}l^2c\pi\omega^{3/2}}(1-e^{-\theta}(sin(\theta)+cos(\theta)))
\end{equation}

Where $$\theta=(\omega/\omega_0)^{1/2}$$ and $$\omega_0=D/2l^2$$

I am not able to reach the result they present in the paper. Hence any help will be very much appreciated.
 
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  • #2
If you only want to verify it, why don't you just differentiate?
 
  • #3
fresh_42 said:
If you only want to verify it, why don't you just differentiate?
It is a specific integral, not an antiderivative.

WolframAlpha and similar tools should be able to verify it, at least numerically.

Going from w to θ should simplify the integral significantly.
 

Related to How to Approach Solving a Complex Trigonometric Integral?

1. How do I identify which trigonometric identity to use when solving an integral?

When solving a trigonometric integral, it is important to first identify the type of function present in the integrand. This can be done by factoring out any common factors and simplifying the expression as much as possible. Then, refer to a list of common trigonometric identities to determine which one can be used to simplify the integral.

2. What is the process for solving a trigonometric integral?

The process for solving a trigonometric integral involves using trigonometric identities and substitution techniques to simplify the expression into a form that can be easily integrated. This may involve using double angle, half angle, or power reducing identities, as well as substitution methods such as u-substitution or trigonometric substitution.

3. How can I check my answer when solving a trigonometric integral?

To check your answer when solving a trigonometric integral, you can differentiate the resulting function and see if it matches the original integrand. Additionally, you can use online tools or graphing calculators to graph both functions and see if they match.

4. Are there any tips for solving tricky trigonometric integrals?

Some tips for solving tricky trigonometric integrals include: factoring out common factors, simplifying the expression as much as possible, using trigonometric identities to simplify the integral, and trying different substitution techniques. It is also important to practice and familiarize yourself with common trigonometric identities to make the process easier.

5. What are some common mistakes to avoid when solving trigonometric integrals?

Some common mistakes to avoid when solving trigonometric integrals include: forgetting to use the appropriate substitution or identity, making errors when manipulating the expression, and forgetting to add the constant of integration at the end. It is important to be careful and double check each step when solving a trigonometric integral to avoid making mistakes.

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