The Einstein-Hilbert worldspace action is used to investigate the dynamics of extended object. In the Robertson-Walker worldspace, this is seen to introduce a pressureless density which could contribute to dark matter. Such pressureless energy density, present from the very beginning, should have enormous consequences on large scale structure formation in the early Universe. Generalizing the id...

The silver toughened alumina ceramics, which were fabricated via a conventional ceramic processing route using commercially available alumina and silver oxide powders as the starting materials, exhibit a higher fracture toughness (6 to 9 MPamo.5) than the monolithic alumina ceramic ( 2.5 to 3.0 MPamo.5). The weak interfacial bonding between the silver inclusions and the alumina matrix is charac...

Abstract. The equations of isothermal gas dynamics are studied in the limit when the sound speed vanishes, giving the so-called pressureless gas equations. The collision of two clouds of dust is modeled with these equations in the case where the clouds have finite extent and are surrounded by vacuum. The delta shock that arises in the initial stage of the collision evolves into a delta rarefact...