Predicting the peculiar velocities of nearby PSCz galaxies using the LeastAction Principle

We use the Least Action Principle to predict the peculiar velocities of PSC z galaxies inside cz=2000 km s(-1). Linear theory is used to account for ti dal effects to cz=15 000 km s(-1), and we iterate galaxy positions to accou nt for redshift distortions. As the Least Action Principle is valid beyond linear theory, we can predict reliable peculiar velocities even for very ne arby galaxies (i.e., cz less than or equal to 500 km s(-1)). These predicte d peculiar velocities are then compared with the observed velocities of 12 galaxies with Cepheid distances. The combination of the PSCz galaxy survey (with its large sky coverage and uniform selection) with the accurate Cephe id distances makes this comparison relatively free from systematic effects. We find that galaxies are good tracers of the mass, even at small (less th an or equal to 10 h(-1) Mpc) scales; under the assumption of no biasing, 0. 25 less than or equal to beta less than or equal to0.75 (at 90 per cent con fidence). We use the reliable predicted peculiar velocities to estimate the Hubble constant H-0 from the local volume without 'stepping up' the distan ce ladder, finding a confidence range of 65-75 km s(-1) Mpc(-1) (at 90 per cent confidence).