Fixed-charge Reissner-Nordstrom temperature maximum
= Fixed-charge Reissner-Nordstrom temperature maximum
{title2=$M_{\max}=2|Q|/\sqrt3,\quad T_{\max}=1/(6\sqrt3\,\pi|Q|)$}
Set $y=r_+/|Q|\geq1$. Then $M/|Q|=(y+y^{-1})/2$ and $|Q|T=(y^{-1}-y^{-3})/(4\pi)$. Differentiation gives a unique maximum at $y=\sqrt3$, proving the displayed <mass> and <temperature>. The curve is zero at extremality and asymptotic to $1/(8\pi M)$ at large <mass>.