Cold dark matter in brane cosmology scenario

We analyze the dark matter problem in the context of brane cosmology. We investigate the impact of the non-conventional brane cosmology on the relic abundance of non-relativistic stable particles in high and low reheating scenarios. We show that in case of high reheating temperature, the brane cosmology may enhance the dark matter relic density by many order of magnitudes and a stringent lower bound on the five dimensional scale is obtained. We also consider low reheating temperature scenarios with chemical equilibrium and non-equilibrium. We emphasize that in non-equilibrium case, the resulting relic density is very small. While with equilibrium, it is increased by a factor of O(10^2) with respect to the standard thermal production. Therefore, dark matter particles with large cross section, which is favored by detection expirements, can be consistent with the recent relic density observational limits.Comment: 14 pages, 1 figur

Effect of heat and mass transfer and rotation on peristaltic flow through a porous medium with compliant walls

Purpose: The purpose of this paper is to investigate the peristaltic flow of an incompressible Newtonian fluid in a channel with compliant walls. The effects of rotation and heat and mass transfer are also taken into account. The governing equations of two dimensional fluid have been simplified under long wavelength and low Reynolds number approximation. An exact solutions is presented for the stream function, temperature, concentration field, velocity and heat transfer coefficient. Design/methodology/approach: The effect of the concentration distribution, heat and mass transfer and rotation on the wave frame are analyzed theoretically and computed numerically. Numerical results are given and illustrated graphically in each case considered. Comparison was made with the results obtained in the presence and absence of rotation and heat and mass transfer. Findings: The results indicate that the effect of the permeability and rotation are very pronounced in the phenomena. Originality/value: The objective of the present analysis is to analyze the effects of rotation, heat and mass transfer and compliant walls on the peristaltic flow of a viscous fluid

Inflation and late time acceleration in braneworld cosmological models with varying brane tension

Braneworld models with variable brane tension $\lambda$ introduce a new degree of freedom that allows for evolving gravitational and cosmological constants, the latter being a natural candidate for dark energy. We consider a thermodynamic interpretation of the varying brane tension models, by showing that the field equations with variable $\lambda$ can be interpreted as describing matter creation in a cosmological framework. The particle creation rate is determined by the variation rate of the brane tension, as well as by the brane-bulk energy-matter transfer rate. We investigate the effect of a variable brane tension on the cosmological evolution of the Universe, in the framework of a particular model in which the brane tension is an exponentially dependent function of the scale factor. The resulting cosmology shows the presence of an initial inflationary expansion, followed by a decelerating phase, and by a smooth transition towards a late accelerated de Sitter type expansion. The varying brane tension is also responsible for the generation of the matter in the Universe (reheating period). The physical constraints on the model parameters, resulted from the observational cosmological data, are also investigated.Comment: 25 pages, 8 figures, accepted for publication in European Physical Journal

Rewriting Histories: The Experiences of Pioneering Egyptian Women Architects in the Socio-Political Context of the Nasser Era

The history of modern architecture has particularly emphasized the roles of male architects with little mention of women architects. Since women’s contributions have often been overlooked, feminist scholars worldwide have aimed to showcase women’s history in the architectural profession over the past several years. However, there is still a lack of scholarship on the historical experiences and contributions of women architects in the Middle East, particularly Egypt. This research aims to address this gap in historiography by focusing on the first women architects in Egypt during the Nasser era. As such, the study utilizes archival sources and examines various architecture and engineering magazines and state reports published during the mid-20th century. Our analysis reveals how early architectural pioneers such as Anjil Tawfik, Amina Maher, Zakeya Shafʿi, and Sawsan el-Qusbi faced considerable barriers related to societal norms and educational limitations. We argue that the idealized image of womanhood was a strategy employed by men to maintain the discipline as androcentric. In contrast, Nasser’s regime, which was concerned with Egypt’s modernization and development, enacted progressive policies to promote gender equality. The policies facilitated the entry of women into different fields including engineering and architecture. We examine the complex interplay between state feminism and persistent societal norms, noting how Abdel Nasser redefined the ideal image of women to one that balanced professional work with familial responsibilities. We explore the career trajectories of early pioneering women architects, arguing that al-taklif, the employment order mandated by Abdel Nasser in 1955, was not merely a work policy but also shaped the ideal image of professional life for women architects. We discuss women architects’ strategies to carve out a space for themselves in architectural practice. Finally, we address the lack of recognition for women architects’ work with a focus on Zakeya Shafʿi and Amina Maher, two pioneering Egyptian women architects

Rotational Effects on Magneto-Thermoelastic Stoneley, Love and Rayleigh Waves in Fibre-Reinforced Anisotropic General Viscoelastic Media of Higher Order

In this paper, we investigated the propagation of the rmo elastic surface waves in fibre-reinforced anisotropic general viscoelastic media of higher order ofnth order, including time rate of strain under the influence of rotation.The general surface wave speed is derived to study the effects of rotation and thermal on surface waves. Particular cases for Stoneley, Love and Rayleigh waves are discussed. The results obtained in this investigation are more general in the sense that some earlier published results are obtained from our result as special cases. Our results for viscoelastic of order zero are well agreed to fibre-reinforced materials. Comparison was made with the results obtained in the presence and absence of rotation and parameters for fibre-reinforced of the material medium. It is also observed that, surface waves cannot propagate in a fast rotating medium. Numerical results for particular materials are given and illustrated graphically. The results indicate that the effect of rotation on fibre-reinforced anisotropic general viscoelastic media are very pronounced

A One Step Optimal Homotopy Analysis Method for Propagation of Harmonic Waves in Nonlinear Generalized Magnetothermoelasticity with Two Relaxation Times under Influence of Rotation

The aim of this paper is to apply OHAM to solve numerically the problem of harmonic wave propagation in a nonlinear thermoelasticity under influence of rotation, thermal relaxation times, and magnetic field. The problem is solved in one-dimensional elastic half-space model subjected initially to a prescribed harmonic displacement and the temperature of the medium. The HAM contains a certain auxiliary parameter which provides us with a simple way to adjust and control the convergence region and rate of convergence of the series solution. This optimal approach has a general meaning and can be used to get fast convergent series solutions of the different type of nonlinear fractional differential equation. The displacement and temperature are calculated for the models with the variations of the magnetic field, relaxation times, and rotation. The results obtained are displayed graphically to show the influences of the new parameters.</jats:p

Reflection of PlaneWaves from Electro-magneto-thermoelastic Half-space with a Dual-Phase-Lag Model

The aim of this paper is to study the reflection of plane harmonic waves from a semi-infinite elastic solid under the effect of magnetic field in a vacuum. The expressions for the reflection coefficients, which are the relations of the amplitudes of the reflected waves to the amplitude of the incident waves, are obtained. Similarly, the reflection coefficient ratio variations with the angle of incident under different conditions are shown graphically. Comparisons are made with the results predicted by the dual-phase-lag model and Lord-Shulman theory in the presence and absence of magnetic field

Mathematical modelling of Stoneley wave in a transversely isotropic thermoelastic media

This paper is concerned with the study of propagation of Stoneley waves at the interface of two dissimilar transversely isotropic thermoelastic solids without energy dissipation and with two temperatures. The secular equation of Stoneley waves is derived in the form of the determinant by using appropriate boundary conditions i.e. the stresses components, the displacement components, and temperature at the boundary surface between the two media are considered to be continuous at all times and positions . The dispersion curves giving the Stoneley wave velocity and Attenuation coefficients with wave number are computed numerically. Numerical simulated results are depicted graphically to show the effect of two temperature and anisotropy on resulting quantities. Copper material has been chosen for the medium and magnesium for the medium Some special cases are also deduced from the present investigation

Structural Continuous Dependence in Micropolar Porous Bodies

Our study is dedicated to mixed initial boundary value problem for porous micropolar bodies. We prove that the solution of this problem depends continuously on coefficients which couple the micropolar deformation equations with the equations that model the evolution of voids. The evaluation of this dependence is made by using an appropriate measure