LCDM as privileged state of parameter space in generic f(R) gravity

CONTEXT: In this work we propose a generic modified gravity action with two free parameters and derive the dynamics of universe through this action in Palatini formalism. We noted that in special case the action resembles to  ΛCDM as  a special case of this generic action in the parameter space.

AIM: We do cosmological comparison of this model with observed data to find the best parameters of model in flat universe.

METHOD: To constraint the free parameters of model we use the SNIa type Ia two data sets of Gold and Union Sample, CMB-shift parameter, Baryon Acoustic oscillation, gas mass fraction in cluster of galaxies and large scale structure data.

RESULT: The  best  parameters  from  observational  data  shows  that LCDM  as  a special point in the  parameter  space  is privileged by the observation.