We obtain restrictions on the universal baryon fraction, f B ≡ Ω B /Ω 0 , by assuming that the observed microlensing events towards the Large Magellanic Cloud are due to baryonic MACHOs in the halo of the Galaxy and by extracting a bound to the total mass of the Milky Way from the motion of tracer galaxies in the Local Group. We find a lower bound f B > 0.31 +0.19 −0.15. Consistency with the pr...

We show that a class of Affleck–Dine baryogenesis directly relates the observed mass density of baryons, ΩB, to that of dark matter, ΩDM . In this scenario, the ratio of baryon to dark matter mass density is solely determined by the low energy parameters, except for an O(0.1) effective CP-violating phase. We find that ΩB/ΩDM = O(0.1) with reasonable parameters, which lies surprisingly just in t...

Some Bianchi type I viscous fluid cosmological models with a variable cosmological constant are investigated in which the expansion is considered only in two direction i.e. one of the Hubble parameter (H1 = A4 A ) is zero. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient of shear viscosity is considered as constant in firs...

We obtain restrictions on the universal baryon fraction, f B ≡ Ω B /Ω 0 , by assuming that the observed microlensing events towards the Large Magellanic Cloud are due to baryonic MACHOs in the halo of the Galaxy and by extracting a bound to the total mass of the Milky Way from the motion of tracer galaxies in the Local Group. We find a lower bound f B > 0.29 +0.18 −0.15. Consistency with the pr...

We have investigated past measurements of the local supermassive black hole mass density, correcting for hitherto unknown dependencies on the Hubble constant, which, in some cases, had led to an underestimation of the mass density by factors of ∼2. Correcting for this, we note that the majority of (but not all) past studies yield a local supermassive black hole mass density that is consistent w...

Acoustic metamaterials utilizing periodic deep subwavelength resonators can attain negative acoustic properties unavailable in nature. We have developed a negative acoustic index metamaterial for water that combines Helmholtz and rod-spring resonators to control effective bulk modulus and mass density, respectively. Effective properties extracted from full-wave simulations of our metamaterial s...

We discuss two cosmological issues in a generic gauge-mediated supersymmetry~SUSY-!breaking model, namely, the Universe’s baryon asymmetry and the gravitino dark-matter density. We show that both problems can be simultaneously solved if there exist extra matter multiplets of a SUSY-invariant mass of the order of the ‘‘m term,’’ as suggested in several realistic SUSY grand-unified theories. We p...

The general relativistic model of Cooperstock & Tieu, which attempts to fit rotation curves of spiral galaxies without invoking dark matter, is tested empirically using observations of the Milky Way. In particular, predictions for the mass density in the solar neighbourhood and the vertical density distribution at the position of the Sun are compared with observations. It is shown that the mode...

Hoyle and Narlikar’s C-field cosmology is extended in the framework of higher dimensional spacetime and a class of exact solutions is obtained. Adjusting the arbitrary constants of integration one can show that our model is amenable to the desirable property of dimensional reduction so that the universe ends up in an effective 4D one.Further with matter creation from the C-field the mass densit...

We study eigenvibrations for inhomogeneous string consisting of two parts with strongly contrasting stiffness and mass density. In this work we treat a critical case for the high frequency approximations, namely the case when the order of mass density inhomogeneity is the same as the order of stiffness inhomogeneity, with heavier part being softer. The limit problem for high frequency approxima...