Hi guys! I have a problem with this exercise: 1. The problem statement, all variables and given/known data The stars called white dwarfs may have inside them a density in order of 1011 kg m-3. For semplicity, we assume: these stars are made with non interacting protons and electrons at the same quantity and with uniform density; Inside, the electrons are relatevistic with energy ε=c|p|=cħ|k|; Temperature is nothing. In these hypotheses is evaluated the pressure exerted by this electron gas. 3. The attempt at a solution I'm at T=0, but electrons are relatevistic, so P=-∂U/∂V. Internal energy is: U=∫0εFg(ε)ε dε where: states density g(ε)=(2me3/2V√ε)/(√2π2ħ3) ε=ħck ; k2=p2/ħ2=me2v2/ħ2=2εme/ħ2 ⇒ k=√(2εme/ħ2) Then: U=∫0εF (2me3/2V√ε)/(√2π2ħ3) √(2εme/ħ2) ħc dε = = (me3/2V c εF3/2 √(εFme))/(π2ħ2) So: P=-∂U/∂V=-(me3/2 c εF3/2 √(εFme))/(π2ħ2) Fermi energy is: εF=ħ2/(2me)(3π2N/V)2/3 Then: P=-3/4ħ2c(3π2)1/3(N/V)4/3 This solution is wrong. The correct solution is: P=(ħ c(3π2)1/3(N/V)4/3)/4 Could someone tell me where I'm wrong?