latex fix

src/4_sommerfeld_model.md

@@ -238,7 +238,7 @@ N &\overset{\mathrm{3D}}{=}2_s \left(\frac{L}{2\pi}\right)^3\int_{\varepislon(\m
 &=\frac{V}{\pi^2}\int k^2\mathrm{d}k,
 \end{align}
 $$
-We rewrite the expression above by substituting $k=\hbar^{-1}\sqrt{2m\varepsilon}}$ and $\mathrm{d}k=\hbar^{-1}\sqrt{2m/\varepsilon}}\.d\varepsilon$:
+We rewrite the expression above by substituting $k=\hbar^{-1}\sqrt{2m\varepsilon}$ and $\mathrm{d}k=\hbar^{-1}\sqrt{2m/\varepsilon}\.d\varepsilon$:
 $$
 \begin{align}
 N &=\frac{V}{\pi^2}\int\frac{2m \varepsilon}{\hbar^3}\sqrt{\frac{m}{2\varepsilon}}\mathrm{d}\varepsilon\\