For [tex]k_D<<k_F[/tex](adsbygoogle = window.adsbygoogle || []).push({});

[tex]|\frac{\hbar^2k^2_F}{2m}-\frac{\hbar^2k^2}{2m}|\approx \frac{\hbar^2k_F}{m}|k_F-k|[/tex]

Where [tex]k[/tex] goes from [tex]k-k_D[/tex] to [tex]k+k_D[/tex]

[tex]k_F[/tex] - Fermi wave vector

[tex]k_D[/tex] - Debay wave vector

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# Is this approximation OK?

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