The cosmic jerk parameter in f(R) gravity

We derive the expression for the jerk parameter in $f(R)$ gravity. We use the Palatini variational principle and the field equations in the Einstein conformal gauge. For the particular case $f(R)=R-\frac{\alpha^2}{3R}$, the predicted value of the jerk parameter agrees with the SNLS SNIa and X-ray galaxy cluster distance data but does not with the SNIa gold sample data.Comment: 8 pages; published versio