We consider Kerr-de Sitter spacetimes and evaluate their mass, angular momentum and entropy according to the boundary counterterm prescription. We provide a physicall interpretation for angular velocity and angular momentum at future/past infinity. We show that the entropy of the four-dimensional Kerr-de Sitter spacetimes is less than of pure de Sitter spacetime in agreement to the entropic N-b...

The creation of 4d de Sitter (inflationary) boundary gluing two d5 de Sitter bulks on the classical as well as on quantum level (with account of brane QFT via corresponding trace anomaly induced effective action) is discussed. Quantum effects decrease the classical de Sitter brane radius or create new de Sitter brane with even smaller radius. It is important that brane CFT may be chosen to be d...

We study the propagation of a massless scalar wave in de Sitter spacetime perturbed by an arbitrary central mass. By focusing on late time limit, this probes portion signal traveling inside null cone. Unlike asymptotically flat spacetimes, amplitude field detected observer at timelike infinity does not decay back to zero but develops constant shift---both zeroth and first order mass $M$. This i...

Stochastic inflation can resolve strong inflationary perturbations, which seed primordial black holes. I present a fast and accurate way to compute these perturbations in typical hole producing single-field models, treating the short-wavelength Fourier modes beyond de Sitter approximation. The squeezing freezing of reduces problem one dimension, resulting new form stochastic equations, dubbed `...

A special relativity based on the de Sitter group is introduced. Like ordinary special relativity, it retains the quotient character of spacetime, and consequently a notion of homogeneity. This means that the underlying spacetime will be a de Sitter spacetime, the quotient space between de Sitter and the Lorentz groups. Since the local symmetry will also be given by the de Sitter group, each ta...

The creation of 4d de Sitter (inflationary) boundary gluing two d5 de Sitter bulks on the classical as well as on quantum level (with account of brane QFT via corresponding trace anomaly induced effective action) is discussed. Quantum effects decrease the classical de Sitter brane radius or create new de Sitter brane with even smaller radius. It is important that brane CFT may be chosen to be d...

We consider two nonlinear sigma models on de Sitter background which involve the same derivative interactions as quantum gravity but without gauge issue. The first model contains only a single field, can be reduced to free theory by local field redefinition; second fields and cannot so reduced. Loop corrections in both produce large temporal spatial logarithms cause perturbation break down at l...

Freeplay is one of the most important nonlinearities that affect the control surfaces of the aircraft; it can induce flutter phenomena and limit the performances of the same airplane. To investigate the effect of control surface freeplay, an aeroelastic wind tunnel model of a T-tail has been developed. A variable amplitude freeplay has been introduced in the control chain by a specifically desi...

Birds appear to use their tails during flight, but until recently the aerodynamic role that tails fulfil was largely unknown. In recent years delta-wing theory, devised to predict the aerodynamics of high-performance aircraft, has been applied to the tails of birds and has been successful in providing a model for the aerodynamics of a bird's tail. This theory now provides the conventional expla...

In this paper, we present the development of a reconfigurable hybrid unmanned aerial vehicle (UAV): U-Lion [Ang et al., 11th IEEE Int. Conf. Control Automation (ICCA), pp. 750–755]. U-Lion is a small-scale UAV that is capable of vertical takeoff and landing (VTOL) and fixedwing Cruise modes through its unique mechanical design. Mainly built with carbon fiber and expanded polyolefin (EPO) foam, ...