In the Starobinsky inflationary model inflation is driven by quantum corrections to the vacuum Einstein equation. We reduce the Wheeler-DeWitt equation corresponding to the Starobinsky model to a Schroedinger form containing time. The Schroedinger equation is solved with a Gaussian ansatz. Using the prescription for the normalization constant of the wavefunction given in our previous work, we s...

Using the coherent-state representation we show that the classical Einstein equation for the FRW cosmological model with a general minimal scalar field can be derived from the semiclassical quantum Einstein equation. E-Mail: [email protected] E-Mail: [email protected] E-Mail: [email protected] 1 Canonical quantum gravity has been initiated by DeWitt in the seminal paper [1]. As ...

In this thesis, we analytically and numerically study quantized vortex states aswell as their dynamics in rotating Bose-Einstein condensate at extremely low tem-perature.We present an efficient method–gradient flow with discrete normalization tofind the stationary solutions of the Gross-Pitaevskii equation and coupled Gross-Pitaevskii equations. We give a mathematical justif...

Causal structure, inertial path structure and compatibility with quantum mechanics demand no full Lorentz metric, but only an integrable Weyl geometry for space time (Ehlers/Pirani/Schild 1972, Audretsch e.a. 1984). A proposal of (Tann 1998, Drechsler/Tann 1999) for a minimal coupling of the Hilbert-Einstein action to a scale covariant scalar vacuum field φ (weight −1) plus (among others) a Kle...

We show how classical spacetime emerges from quantum gravity through the study of a quantum FRW cosmological model coupled to a free massive scalar field using a new asymptotic expansion method of the Wheeler-DeWitt equation. It is shown that the coherent states of the nonadiabatic basis of a particular generalized invariant give rise to the quantum back reaction of matter field proportional to...

The Gross-Pitaevskii equation is discussed at the level of an advanced course on statistical physics. In the standard literature the Gross-Pitaevskii equation is usually obtained in the framework of the second quantisation formalism, which in many cases goes beyond the material covered in many advanced undergraduate courses. In this paper, we motivate the derivation of the Gross-Pitaevskii equa...

In this paper we present analytical breather solutions of the three-dimensional nonlinear generalized Gross-Pitaevskii equation. We use an Ansatz to reduce the three-dimensional equation with space- and time-dependent coefficients into a one-dimensional equation with constant coefficients. The key point is to show that both the space- and time-dependent coefficients of the nonlinear equation ca...

We solve the local Cauchy problem for the nonlinear Schrödinger equation with harmonic potential, an equation appearing in the study of Bose-Einstein condensation. We prove that the mathematical study of this equation is very close to the study of the same equation without potential, thanks to two explicit operators. We prove the analogue of the pseudo-conformal conservation law, and results fo...