  We study the expansion history of the universe up to a redshift of z=1.75
using the 194 recently published SnIa data by Tonry et. al. and Barris et. al.
In particular we find the best fit forms of several cosmological models and
$H(z)$ ansatze, determine the best fit values of their parameters and rank them
according to increasing value of $\chi_{min}^2$ (the minimum value of $\chi^2$
for each $H(z)$ ansatz). We use a prior of $\Omega_{0m} = 0.3$ and assume flat
geometry of the universe. No prior assumptions are made about validity of
energy conditions. The fitted models are fourteen and include SCDM, LCDM, dark
energy with constant equation of state parameter $w$ (quiessence), third order
polynomial for $H(1+z)$, Chaplygin gas, Cardassian model, $w(z)=w_0 + w_1 z$,
$w(z)=w_0 + z w_1/(1+z)$, an oscillating ansatz for $H(z)$ etc. All these
models with the exception of SCDM are consistent with the present data.
However, the quality of the fit differs significantly among them and so do the
predicted forms of $w(z)$ and $H(z)$ at best fit. The worst fit among the
data-consistent models considered corresponds to the simplest model LCDM
($\chi_{min}^2 = 198.7$ for $\Omega_{0m} = 0.34$) while the best fit is
achieved by the three parameter oscillating ansatz ($\chi_{min}^2 = 194.1$).
Most of the best fit ansatze have an equation of state parameter $w(z)$ that
varies between $w(z) \simeq -1$ for $z<0.5$ to $w(z) > 0$ for $z>1$. This
implies that the sign of the pressure of the dark energy may be alternating as
the redshift increases. The goodness of fit of the oscillating $H(z)$ ansatz
lends further support to this possibility.
