Four hints and test candidates of the local cosmic expansion

The expansion of the universe on short distance scales is a new frontier to investigate the dark energy. The excess orbital decay in binary pulsars may be related to acceleration by the local cosmic expansion, called the cosmic drag. Modern observations of two independent binaries (PSR B153412 and PSR B1913+16) support this interpretation and result in a scale-independent expansion with viscous uniformity, in which binary systems have a smaller expansion rate than the Hubble constant. This paper shows additional evidential binaries (PSR J1012–5307 and PSR J1906+0746), supporting the cosmic drag picture. The total anomaly of the conventional model is about 3.6 σ including two evidential binaries reported before. In addition, an observable range of the cosmic drag has been calculated for typical models of both NS–NS binary and NS–WD binary. In this region, six test candidates are listed with predictions of the excess orbital decay.