Strong Lensing Probabilities in a Cosmological Model with a Running Primordial Power Spectrum

The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data with other finer scale cosmic microwave background (CMB) experiments (CBI and ACBAR) and two structure formation measurements (2dFGRS and Lyman $\alpha$ forest) suggest a $\Lambda$CDM cosmological model with a running spectral power index of primordial density fluctuations. Motivated by this new result on the index of primordial power spectrum, we present the first study on the predicted lensing probabilities of image separation in a spatially flat $\Lambda$CDM model with a running spectral index (RSI-$\Lambda$CDM model). It is shown that the RSI-$\Lambda$CDM model suppress the predicted lensing probabilities on small splitting angles of less than about 4$^{''}$ compared with that of standard power-law $\Lambda$CDM (PL-$\Lambda$CDM) model.