Kaluza-Klein Universe with Cosmic Strings and Bulk Viscosity in a Scalar-Tensor Theory of Gravitation

A five dimensional Kaluza-Klein space-time is considered in the frame work of a scalar-tensor theory proposed by Saez and Ballester (Phys. Lett. A 113, 467, 1985) when the source for energy momentum tensor is a bulk viscous fluid containing one dimensional strings. A barotropic equation of state for the pressure and density is assumed to get a determinate solution of the field equations. Also the bulk viscous pressure is assumed to be proportional to the energy density. The physical and kinematical properties of the model are also discussed.     

Bianchi type-III Dark Energy Model in f(R,T) Gravity

A dark energy model with EoS parameter is investigated in f(R,T) gravity in Bianchi type-III space-time in the presence of perfect fluid source. To obtain a determinate solution special law of variation for Hubble’s parameter proposed by Berman (Nuovo Cimento B 74:183, 1983) is used. We have also assumed that the scalar expansion is proportional to shear and the EoS parameter is proportional to skewness parameter. It is observed that the EoS parameter, skewness parameters in the model turn out to be functions of cosmic time. Some physical and kinematical properties of the model are also discussed.     

涉及微差分多项式与分担值的亚纯函数的唯一性

本文研究了亚纯函数与其复微差分多项式的唯一性.在有限级的限制下,文章建立了三个涉及亚纯函数$f$与其微差分多项式$L^{n}_{eta}f=sum_{k=0}^{n}a_{k}f(z+keta)+a_{-1}f''$ 唯一性定理,所获结果进一步刻画了$f(z)equiv L^{n}_{eta}f(z)$的特性,例子说明了结果的精确性.     

Structural and electrical properties of Ca doped BiFeO3 multiferroic nanomaterials prepared by sol-gel auto-combustion method

Sol-gel auto combustion method was adopted for the synthesis of Bi_1-xCa_xFeO₃ (x = 0.00, 0.05, 0.1, 0.15, 0.2 and 0.25) multiferroic nanoparticles and their structural and electric properties were investigated. The two peaks at (012) and (110) planes at diffracting angles (2θ) of 31.9° and 32.1° in the XRD pattern indicates their rhombohedral structure with the R3c space group. The cole-cole plot in the 10 Hz–1 MHz frequency range shows the increasing semicircles shifting towards higher frequency, indicating increasing grain and grain boundaries.     

Two Fluid Scenario for Dark Energy Model in a Scalar-Tensor Theory of Gravitation

In this paper, we investigate the evolution of dark energy parameter in the spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW) model filled with barotropic fluid and dark energy in the framework of scalar-tensor theory of gravitation formulated by Saez and Ballester (Phys. Lett. A 113:467, 1986). To obtain a determinate solution special law of variation for Hubble’s parameter proposed by Bermann (Nuovo Cimento B 74:183, 1983) is used. We consider the two cases of interacting and non-interacting fluid (barotropic and dark energy) scenario and obtained general results. The physical aspects of the results obtained are also discussed.