Primordial nucleosynthesis in higher dimensional cosmology

We investigate nucleosynthesis and element formation in the early universe in the framework of higher dimensional cosmology. For this purpose we utilize a previous solution of the present author, which may be termed as the generalized Friedmann-Robertson-Walker model. We find that temperature decays less rapidly in higher dimensional cosmology, which we believe may have nontrivial consequences \emph{vis-a-vis} primordial physics

Utility and productivity enhancing public capital in a growing economy

We examine the impact of fiscal policy on macroeconomic performance and welfare when public capital provides both productive and utility services to the private sector. When these services are subject to congestion, a consumption tax is distortionary, generating a dynamic adjustment that contrasts with that of an income tax. In correcting for congestion, an income tax-consumption sub-sidy combination is the preferred policy when factor-substitutability in production is limited. On the other hand, an increase in the elasticity of substitution in production raises the e¢ cacy of a consumption tax as an alternative to the income tax. Not recognizing the relative importance of public capital in utility services might lead the fiscal authority to incorrectly estimate the impact of public policies on welfare. The design of optimal scal policy demonstrates the possibilities for using both income and consumption-based fiscal instruments as opposed to relying on only the income tax rate

Spherical collapse of a heat conducting fluid in higher dimensions without horizon

We consider a scenario where the interior spacetime,described by a heat conducting fluid sphere is matched to a Vaidya metric in higher dimensions.Interestingly we get a class of solutions, where following heat radiation the boundary surface collapses without the appearance of an event horizon at any stage and this happens with reasonable properties of matter field.The non-occurrence of a horizon is due to the fact that the rate of mass loss exactly counterbalanced by the fall of boundary radius.Evidently this poses a counter example to the so-called cosmic censorship hypothesis.Two explicit examples of this class of solutions are also given and it is observed that the rate of collapse is delayed with the introduction of extra dimensions.The work extends to higher dimensions our previous investigation in 4D.Comment: 6 page

Thermodynamics of the Variable Modified Chaplygin gas

A cosmological model with a new variant of Chaplygin gas obeying an equation of state(EoS), $P = A\rho - \frac{B}{\rho^{\alpha}}$ where $B= B_{0}a^{n}$ is investigated in the context of its thermodynamical behaviour. Here $B_{0}$ and $n$ are constants and $a$ is the scale factor. We show that the equation of state of this `Variable Modified Chaplygin gas' (VMCG) can describe the current accelerated expansion of the universe. Following standard thermodynamical criteria we mainly discuss the classical thermodynamical stability of the model and find that the new parameter, $n$ introduced in VMCG plays a crucial role in determining the stability considerations and should always be \emph{negative.} We further observe that although the earlier model of Lu explains many of the current observational findings of different probes it fails the desirable tests of thermodynamical stability. We also note that for $n < 0$ our model points to a phantom type of expansion which, however, is found to be compatible with current SNe Ia observations and CMB anisotropy measurements. Further the third law of thermodynamics is obeyed in our case. Our model is very general in the sense that many of earlier works in this field may be obtained as a special case of our solution. An interesting point to note is that the model also apparently suggests a smooth transition from the big bang to the big rip in its whole evaluation process.Comment: 19 pages, 8 figure