In the presence of a cosmological constant, interpreted as a purely geometric entity, absence of matter is represented by a de Sitter spacetime. As a consequence, ordinary Poincaré special relativity is no longer valid and must be replaced by a de Sitter special relativity. By considering the kinematics of a spinless particle in a de Sitter spacetime, we study the geodesics of this spacetime, t...

1 Research report to appear in " New developments in string gravity and physics at the Planck energy scale ". Abstract Recent results on classical and quantum strings in a variety of black hole and cosmological spacetimes, in various dimensions, are presented. The curved backgrounds under consideration include the 2 + 1 black hole anti de Sitter spacetime and its dual, the black string, the ord...

The interaction between the slipstream of propellers and wing an aircraft with distributed electric propulsion (DEP) could benefit aerodynamics. A conceptual design optimization are carried out in order to increase range general aviation without affecting its takeoff landing velocity same fuselage condition. Propellers modelled using actuator disk (AD) theory, is vortex lattice method (VLM) obt...

Background: Structural health monitoring (SHM) addresses an urgent need of our aging infrastructure. The United States spends more than $200 billion each year on the maintenance of plant equipment and facilities. Maintenance and repairs represent about a quarter of commercial aircraft operating costs. Out of approximately 576,600 bridges in our national inventory, 32% are either “structurally d...

I will describe recent evidence that anti-de Sitter spacetime is nonlinearly unstable. Generic small but finite perturbations eventually form small black holes. I will also present evidence that there are special solutions, called geons, which remain close to anti-de Sitter. I will argue that one can put black holes inside the geons to obtain a family of black holes in anti-de Sitter spacetime ...

The energy-momentum tensor for a massless conformally coupled scalar field in de Sitter spacetime in the presence of a couple curved branes is investigated. We assume that the scalar field satisfies the Robin boundary condition on the surfaces. Static de Sitter space is conformally related to the Rindler space, as a result we can obtain vacuum expectation values of energy-momentum tensor for co...

A family of de Sitter vacua introduced in hep-th/0203198 as plausible initial conditions for inflation, are discussed from the point of view of de Sitter holography. The vacua are shown to be physically acceptable and the inflationary picture provides a physical interpretation of a subfamily of de Sitter invariant vacua. Some speculations on the issue of vacuum choice and the connection between...

The Casimir forces on two parallel plates moving by uniform proper acceleration in static de Sitter background due to conformally coupled massless scalar field satisfying Dirichlet boundary conditions on the plates is investigated. Static de Sitter space is conformally related to the Rindler space, as a result we can obtain vacuum expectation values of energy-momentum tensor for conformally inv...

This article proposes a new approach for centralized path planning of multiple aircraft in presence of the obstacle-laden environment under low flying rules. The problem considers as a unified nonlinear constraint optimization problem. The minimum time and control investigate as the cost functions and the maximum velocity and power consider as the constraints. The pseudospectral method applies ...