ABSTRACT
Titanium-rich subluminous supernovae are rare and challenge current SN nucleosynthesis models. We present a model in which ejecta from a standard supernova is impacted by a second explosion of the neutron star (a quark nova), resulting in spallation reactions that lead to (56)Ni destruction and (44)Ti creation under the right conditions. Basic calculations of the spallation products shows that a delay between the two explosions of â¼5 days reproduces the observed abundance of (44)Ti in Cas A and explains its low luminosity as a result of the destruction of (56)Ni. Our results could have important implications for light curves of subluminous as well as superluminous supernovae.
ABSTRACT
We reexamine the surface composition of strange stars. Strange quark stars are hypothetical compact stars which could exist if strange quark matter was absolutely stable. It is widely accepted that they are characterized by an enormous density gradient (10(26) g/cm4) and large electric fields at the surface. By investigating the possibility of realizing a heterogeneous crust, comprised of nuggets of strange quark matter embedded in an uniform electron background, we find that the strange star surface has a much reduced density gradient and negligible electric field. We comment on how our findings will impact various proposed observable signatures for strange stars.
ABSTRACT
We propose that the origin of ultrahigh energy cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff and the origin of small cosmological constant can both be explained by vacuum tunneling effects in a theory with degenerate vacua and fermionic doublets. By considering the possibility of tunneling from a particular winding number state, accompanied by violation of some global quantum number of fermions, the small value of the vacuum dark energy and the production of high energy cosmic rays are shown to be related. We predict that the energy of such cosmic rays should be at least 5x10(14) GeV.
