  We investigate the viability of the phaseless finite temperature auxiliary
field quantum Monte Carlo (ph-FT-AFQMC) method for ab initio systems using the
uniform electron gas as a model. Through comparisons with exact results and
finite temperature coupled cluster theory, we find that ph-FT-AFQMC is
sufficiently accurate at high to intermediate electronic densities. We show
both analytically and numerically that the phaseless constraint at finite
temperature is fundamentally different from its zero temperature counterpart
(i.e., ph-ZT-AFQMC) and generally one should not expect ph-FT-AFQMC to agree
with ph-ZT-AFQMC in the low temperature limit. With an efficient
implementation, we are able to compare exchange-correlation energies to
existing results in the thermodynamic limit and find that existing
parameterizations are highly accurate. In particular, we found that ph-FT-AFQMC
exchange-correlation energies are in a better agreement with a known
parametrization than is restricted path-integral Monte Carlo in the regime of
$\Theta\le0.5$ and $r_s \le 2$, which highlights the strength of ph-FT-AFQMC.
