The geometry of the universe from high resolution VLBI data of AGN shocks

We propose to use the linear diameters of the shocks in AGN jets as standard rods for estimating the geometry of the Universe. The unique feature of shocks is that we can directly estimate their linear diameters from total flux density monitoring data and light travel time arguments. We demonstrate this method by using a small sample of 14 22 GHz VLBI observations. The accuracy of the derived values (qo similar or equal to 0,Ohm (m) similar or equal to 0) compares favorably with traditional methods using much larger samples.