We present an approach to describe the phase matching of high harmonics emitted by laser driven atoms in a nonperturbative regime, for which the atomic response displays an intrinsic intensity-dependent phase. We show that the traditional phase-matching conditions involving conservation of wave vectors should be modified by taking into account the gradient of this atomic phase. We investigate vari

Normative reasons are of constant importance to us as agents trying to navigate through life. For this reason it is natural and vital to ask philosophical questions about reasons and the normative realm. This thesis explores various issues concerning reasons and normativity. The thesis consists of five free-standingpapers and an extended introduction. The aim of the extended introduction is not me

In this article we will discuss the basic calculational concepts to simulate particle physics events at high energy colliders. We will mainly focus on the physics in hadron colliders and particularly on the simulation of the perturbative parts, where we will in turn focus on the next-to-leading order QCD corrections.

A new scheme for calculating the electronic structure of crystals, based on the CNDO (complete neglect of differential overlap) approximation, is used to calculate the potential energy surfaces of diamond. Elastic properties such as the stiffness constants, the angular dependences of the anisotropy factor of Young's modulus, the Poisson ratios, and the Debye temperature are investigated on the bas

The chemical bonding in a series of nickel mixed oxides, namely Li2NiO2, Na2NiO2, tetragonal and orthorhombic La2NiO4 for Ni(II), LiNiO2, NaNiO2, LaNiO3 for Ni(III), BaNiO3 for Ni(IV) and LaNiO2, 'LaSrNiO3' for Ni(I), is investigated from the results of electronic structure calculations, including both band structure and local properties, i.e. atomic charges, covalent bond orders and atomic valenc

We propose a model where neutrino masses are generated at three loop order but neutrinoless double beta decay occurs at one loop. Thus we can have large neutrinoless double beta decay observable in the future experiments even when the neutrino masses are very small. The model receives strong constraints from the neutrino data and lepton flavor violating decays, which substantially reduces the numb

The recent advances concerning high-order harmonic generation processes in strong laser fields are discussed. We show how the width of the plateau inherent to the production of high harmonics varies with the pulse width, the laser wavelength and the atomic medium. Phase matching effects are discussed in terms of coherence length owing to the laser focusing. Finally, we show that the idea of genera

Singly, doubly, triply, and quadruply charged krypton ions are formed by multiphoton absorption processes in krypton atoms. They are induced by a 50-psec laser pulse at 1.064 m in the 1013-1014-W-cm-2 intensity range. The percentage ratio between the numbers of doubly and singly ionized Kr atoms is 10% at 8×1013 W cm-2. It is shown that Kr2+ ions result from a direct 33-photon absorption process.

We present a theoretical interpretation of the experimental results on three-photon-resonant four-photon ionization of Kr reported by Landen, Perry, and Campbell [Phys. Rev. Lett. 59, 2558 (1987)] and Perry and Landen [Phys. Rev. A 38, 2815 (1988)]. Our calculations are based on multichannel quantum-defect theory combined with a density-matrix formalism describing the spatiotemporal development of

We present results of experiments testing the influence of elliptical polarization on the production of high-order harmonics. Experiments were conducted both with a 600-nm, 1-psec dye laser and with an 825-nm, 140-fsec Cr:LiSAF6 (Cr:LiSAF) laser system, over a wide range of intensities and target gases (xenon, argon, and neon), using a detection system with a dynamical range of more than three ord