Observational constraints on the Emergent Universe with interacting non-linear fluids and its stability analysis

We investigate a flat Emergent Universe (EU) with a nonlinear equation of state which is equivalent to three different compositions of fluids. In the EU, initially, the evolution of the universe began with no interaction, but as time evolves, an interaction sets in among the three fluids leading to the observed universe. The characteristic of an EU is that it is a singularity-free universe that evolves with all the basic features of the early evolution. A given nonlinear equation of state parameter permits a universe with three different fluids. We get a universe with dark energy, cosmic string, and radiation domination to begin with, which at a later epoch transits into a universe with three different fluids with matter domination, dark matter, and dark energy for a given interaction strength among the cosmic fluids. Later the model parameters are constrained using the observed Hubble data and Type Ia Supernova (SnIa) data from the Pantheon data set. The classical stability analysis of the model is performed using the square speed of sound. It is found that a theoretically stable cosmological model can be obtained in this case, however, the model becomes classically unstable at the present epoch when the observational bounds on the model parameters are taken into account.Comment: 16 pages, 9 figure

Skyrme Fluid in Anisotropic Universes with a Cosmological Constant

Cosmological solutions are obtained in an anisotropic Kantowski-Sachs and Bianchi Type-I universes considering a cosmological constant with Skyrme fluid as a matter source. The solutions in both the KS and Bianchi-I universes obtained here are found to differ significantly, specially with some striking difference like Bianchi-I universe admitting only oscillatory solutions for a particular type of matter configuration. Some new and interesting cosmological solutions are obtained due to the Skyrme fluid in the universe. The anisotropy parameter with the evolution of the universe for both the cases are determined and plotted for comparative study.Comment: The analysis is incomplete and vast change is being done which will reflect major modifications in our obtained result

Barrow Holographic Dark Energy in Brane World Cosmology

Cosmological features of Barrow Holographic Dark Energy (BHDE), a recent generalization of original Holographic dark energy with a richer structure, are studied in the context of DGP brane, RS II brane-world, and the cyclic universe. It is found that a flat FRW scenario with pressure less dust and a dark energy component described as BHDE can produce late time acceleration with Hubble horizon considered as infrared cut off even in absence of any interaction between the dark sectors. BHDE parameter is found to have a significant impact on the evolution of the universe and a classically stable model can not always be obtained.Comment: uses article class, 20 pages, 12 figures, (v2) typo corrected, reference adde

Relativistic Solution for a Class of Static Compact Charged Star in Pseudo Spheroidal Space-Time

Considering Vaidya-Tikekar metric, we obtain a class of solutions of the Einstein-Maxwell equations for a charged static fluid sphere. The physical 3-space (t=constant) here is described by pseudo-spheroidal geometry. The relativistic solution for the theory is used to obtain models for charged compact objects, thereafter a qualitative analysis of the physical aspects of compact objects are studied. The dependence of some of the properties of a superdense star on the parameters of the three geometry is explored. We note that the spheroidicity parameter $a$, plays an important role for determining the properties of a compact object. A non-linear equation of state is required to describe a charged compact object with pseudo-spheroidal geometry which we have shown for known masses of compact objects. We also note that the size of a static compact charged star is more than that of a static compact star without charge.Comment: 24 pages, 18 figures, 8 table

Characterization of an acidophilic α-amylase from Aspergillus niger RBP7 and study of catalytic potential in response to nutritionally important heterogeneous compound

An acidophilic α-amylase from Aspergillus niger RBP7 was purified after solid state fermentation on potato peel substrate. Molecular mass of the purified α-amylase was 37.5 kDa and it exhibited 1.4 mg/ml and 0.992 μ/mol/min Km and Vmax values, respectively. The enzyme was stable in the pH range from 2.0 to 6.0, at high NaCl concentration (3 M) and at temperatures between 40 °C and 70 °C. The enzyme showed an optimal activity at pH 3.0 and at 45 °C. The enzyme was inhibited by Hg2+ and was stable in the presence of different surfactants (Tween 60, Tween 80, and SDS at 1% level) and different inhibitory reagents (β-mercaptoethanol, phenylmethylsulfonyl fluoride, and sodium azide). This acidophilic amylase enzyme can digest heterogeneous food materials, i.e. the mixture of rice, fish, bread and curry with comparable activity to the commercial diastase enzymes available