Medium Modification of the Proton Form Factor

I argue that the double ratio of proton-recoil polarization-transfer coefficients, P'_x and P'_z, of the quasielastic 4He(e,e'p)3H reaction with respect to the elastic 1H(e,e'p) reaction is sensitive to possible medium modifications of the proton form factor in 4He. Recent measurements at both Mainz and Jefferson Lab of this double ratio at four-momentum transfers squared between between 0.4 GeV2 and 2.6 GeV2 are discussed. I show that the data challenge state-of-the-art conventional meson-nucleon calculations, as these are unable to describe the results. The data hint at the need to include medium modifications of the proton form factor, as predicted by a quark-meson-coupling model, in the calculations. A recently approved follow-up experiment at a Q2 of 0.8 GeV2 and 1.3 GeV2 with unprecedented precision will provide one of the most stringent tests of the applicability of various calculations.Comment: presented at ``Fourth International Conference on Perspectives in Hadronic Physics'', ICTP, Trieste, 12 -- 16 May 200

Low elements in dominant Shi regions

This note is a complement of a recent paper about low elements in affine Coxeter groups. We explain in terms of ad-nilpotent ideals of a Borel subalgebra why the minimal elements of dominant Shi regions are low. We also give a survey of the bijections involved in the study of dominant Shi regions in affine Weyl groups.Comment: 8 page

Voxelbasert 3D visualisering i OpenGL

This thesis deals with volume rendering in OpenGL and looks at the different areas at which 3D modeling and visualization is used. The thesis focuses on voxel rendering, its advantages and drawbacks, and also the implementation of such a renderer. The aim of the thesis was to develop a voxel renderer in OpenGL from scratch, to a fully functional application that could visualize different 3D data sets generated from for example Diffpack. The data sets are scalar fields which are visualized by associating transparency and color to voxels from the values in the data sets. There are multiple ways to visualize voxels, I have mainly used a method that uses textures mapped to a 2D plane, which are assembled into a 3D voxel set. This is a method that is supported by common 3D hardware. To get maximum performance from the different 3D graphics cards that are available, you can use different graphics libraries. For PC’s there are two low-level graphics libraries to choose from, OpenGL and DirectX. OpenGL is developed by Silicon Graphics and are compatible with a number of different operating systems. DirectX is developed by Microsoft and is only supported in Microsoft Windows. For this thesis I chose OpenGL as the tool to use. OpenGL is a powerful software library which utilizes modern graphics hardware. Through OpenGL you get access to most of the graphic cards functions. OpenGL is however a low-level library and demands a lot of knowledge on a fundamental level to be able to visualize complex objects and scenes. I therefore take a closer look at how OpenGL works and at the theory at which it is built. I also look at the opportunities, advantages and drawbacks with voxel rendering, and looks at the requirements which is demanded by the hardware to be able to solve the tasks efficiently. I conclude this thesis by comparing my OpenGL voxel renderer with other available voxel renderers, such as The Visualization Toolkit (VTK)

Storing and representing smart nudges in a user profile

Oppgaven handler om hvordan informasjon og struktur en bruker profil trenger for og og kunne lagre smart nudges, og bruke dette til og finne brukerens preferanser. Et design på brukerprofil er laget og dette designet er brukt for og implementere en brukerprofil som inneholder smart nudger