Fakultät für Physik - Digitale Hochschulschriften der LMU - Teil 03/05

Currently favoured cosmological models for structure formation of the Universe assume that a large fraction of the mass of the Universe is 'dark'. The evidence

for dark matter comes from observations of its gravitational influence. Examples such as the flatness of rotation curves of spiral galaxies or the large velocities of galaxies in galaxy clusters are thought to be manifestations of its presence. Gravitational lensing can now also be used to map the dark matter distribution of the Universe. Despite the fact that the evidence for dark matter has existed for more than 75 years, it is still

not clear what dark matter is made of. Particle physics provides some interesting and well-motivated candidates, but the elusive dark matter particles have not yet been

detected. Therefore, the hunt for dark matter is one of the major joint efforts of cosmology and particle physics. The only way to prove the dark matter hypothesis is the direct detection of dark matter particles in a laboratory. Experiments exploit various techniques to detect dark matter particles. All of these experiments require as input the phase-space distribution of dark matter. This

means they require information on the configuration-space and velocity-space distributions. These insights can only come from cosmology and the theory of structure formation in the Universe. The goal of this thesis is to predict

the expected dark matter phase-space distribution near the solar system and in the dark matter halo of the Milky Way.

A large part of this thesis is dedicated to a detailed analysis of the coarse-grained dark matter distribution near the Sun based on the Aquarius project, the currently largest set of Milky Way-like dark matter halo simulations. Based on these simulations we predict the local dark matter density distribution to be remarkably smooth: the density at the Sun differs from the mean over a best-fit ellipsoidal equidensity contour by less than 15% at the 99.9% confidence level. The local velocity distribution is also very smooth, but it differs systematically from a

(multivariate) Gaussian distribution. This is not due to the presence of individual clumps or streams, but to broad features in the velocity modulus and energy distributions that are stable both in space and time and reflect the detailed assembly history of each halo. These features have a significant impact on the signals predicted for WIMP

(weakly interacting massive particle) and axion searches. For example, WIMP recoil rates can deviate by ~10% from those expected from the best-fit multivariate Gaussian models. The axion spectra in the simulations typically peak

at lower frequencies than in the case of multivariate Gaussian velocity distributions. Also in this case, the spectra show significant imprints of the formation of the halo. This implies that once direct dark matter detection has become routine, features in the detector

signal will allow the study of the dark matter assembly history of the Milky Way. A new field, 'dark matter astronomy', will then emerge.

The main part of this thesis focuses on the fine-grained phase-space structure of the dark matter distribution near the Sun. A new and completely general technique for calculating the fine-grained phase-space structure of dark matter throughout the Galactic halo is presented.

Its goal is to understand dark matter structure on the scales relevant for direct and indirect detection experiments. The method is based on evaluating the geodesic deviation equation along the trajectories of individual dark matter simulation particles. It requires no assumptions about the symmetry or stationarity of the halo formation process. General static potentials that exhibit more complex behaviour than the separable potentials studied previously are discussed. For ellipsoidal logarithmic potentials with a core, phase mixing is

sensitive to the resonance structure, as indicated by the number of independent orbital frequencies. Regions of cha

The subject of this thesis is the investigation and optimization of beam transport elements in the context of the steadily growing field of laser-driven particle acceleration. This cumulative thesis introduces to the theoretical framework of the elements and presents the results via corresponding publications.

The first topic is the examination of the free vacuum expansion of an electron beam at high current density. Unlike in the case of conventional acceleration, laser acceleration yields charge densities which are comparatively high at lower energies. It could be shown that particle tracking codes which are commonly used for the calculation of space charge effects will generate substantial artifacts in the regime considered here. The artifacts occurring hitherto predominantly involve insufficient prerequisites for the Lorentz transformation, the application of inadequate initial conditions and non negligible retardation artifacts. A part of this thesis is dedicated to the development of a calculation approach which uses a more adequate ansatz calculating space charge effects for laser-accelerated electron beams. It can also be used to validate further approaches for the calculation of space charge effects.

The next elements considered are miniature magnetic quadrupole devices for the focusing of charged particle beams. Invented in 1980 by Halbach, miniature permanent magnet quadrupoles yield field gradients at least a factor two higher than superconducting quadrupole devices. General problems involved with their miniaturization concern distorting higher order field components. If these distorting components cannot be controlled, the field of applications is very limited. In this thesis a new method for the characterization and compensation of the distorting components was developed, which might become a standard method when assembling these permanent magnet multipole devices. Consequently, the field where these devices are applicable could be broadened. The newly developed characterization method has been validated at the Mainz Microtron (MAMI) electron accelerator. Now that we can ensure optimum performance, the first application of permanent magnet quadrupole devices in conjunction with laser-accelerated ion beams is presented. The experiment was carried out at the Z-Petawatt laser system at Sandia National Laboratories.

A Free Electron Laser (FEL) delivers coherent photon beams at higher energies than what can be reached by conventional laser systems. A promising application for laser-accelerated electron beams is the FEL in a university-scale size. The first discussion of all relevant aspects concerning a laser driven FEL is presented.

The operation of an FEL depends on many factors, among which is the average electron beam size while propagating through the undulator. The undulator length could be reduced significantly if the average beam size can be reduced. This goal motivates the development of a new undulator concept, based on miniature magnetic quadrupoles, which is presented here. This quadrupole undulator yields strong intrinsic focusing properties which allow to keep the electron beam at a comparatively small and constant size over a long propagation range.

The experimental realization of a compact FEL involves the first step of building a test undulator with a short undulator period length. This undulator device was assembled and experiments aiming at undulator radiation have been carried out at the MAMI electron accelerator facility in the course of this thesis.

The investigations presented in this thesis mark important development steps on the route towards many applications of laser-accelerated particle beams. Especially laser-driven compact Free-Electron-Lasers are an attractive alternative to costly large-scale conventional facilities.

The cosmic large scale structure is of special relevance for testing current cosmological theories about the origin and evolution of the Universe. Throughout cosmic history, it evolved from tiny quantum fluctuations, generated during the early epoch of inflation, to the filamentary cosmic web presently observed by our telescopes. Observations and analyses of this large scale structure will hence test this picture, and will provide valuable information on the processes of cosmic structure formation as well as they will reveal the cosmological parameters governing the dynamics of the Universe.

Beside measurements of the cosmic microwave backround, galaxy observations are of particular interest to modern precision cosmology. They are complementary to many other sources of information, such as cosmic microwave background experiments, since they probe a different epoch. Galaxies report the cosmic evolution over an enormous period ranging from the end of the epoch of reionization, when luminous objects first appeared, till today. For this reason, galaxy surveys are excellent probes of the dynamics and evolution of the Universe.

Especially the Sloan Digital Sky Survey is one of the most ambitious

surveys in the history of astronomy. It provides measurements of 930,000 galaxy spectra as well as the according angular and redshift positions of galaxies over an area which covers more than a quarter of the sky. This enormous amount of precise data allows for an unprecedented access to the three dimensional cosmic matter distribution and its evolution. However, observables, such as positions and properties of galaxies, provide only an inaccurate picture of the cosmic large scale structure due to a variety of statistical and systematic observational uncertainties. In particular, the continuous cosmic density field is only traced by a set of discrete galaxies introducing statistical uncertainties in the form of Poisson distributed noise. Further, galaxy surveys are subject to a variety of complications such as instrumental limitations or the nature of the observation itself.

The solution to the underlying problem of characterizing the large scale structure in the Universe therefore requires a statistical approach.

The main theme of this PhD-thesis is the development of new Bayesian data analysis methods which provide a complete statistical characterization and a detailed cosmographic description of the large scale structure in our Universe. The required epistemological concepts, the mathematical framework of Bayesian statistics as well as numerical considerations are thoroughly discussed. On this basis two Bayesian data analysis computer algorithms are developed. The first of which is called ARES (Algorithm for REconstruction and Sampling). It aims at the joint inference of the three dimensional density field and its power-spectrum from galaxy observations. The ARES algorithm accurately treats many observational systematics and statistical uncertainties, such as the survey geometry, galaxy selection effects, blurring effects and noise. Further, ARES provides a full statistical characterization of the three dimensional density field, the power-spectrum and their joint uncertainties by exploring the high dimensional space of their joint posterior via a very efficient Gibbs sampling scheme. The posterior is the probability of the model given the observations and all other available informations. As a result, ARES provides a sampled representation of the joint posterior, which conclusively characterizes many of the statistical properties of the large scale structure. This probability distribution allows for a variety of scientific applications, such as reporting any desired statistical summary or testing of cosmological models via Bayesian model comparison or Bayesian odds factors.

The second computer algorithm, HADES (Hamiltonian Density Estimation and Sampling), is specifically designed to infer the fully evolved cosmic density field deep i

This dissertation presents the analysis of a large and deep XMM-Newton survey of the second large Local Group spiral galaxy M 31. The survey observations, taken between June 2006 and February 2008, together with re-analysed archival observations from June 2000 to July 2004 cover, for the first time, the whole D25 ellipse of M 31 with XMM-Newton down to a limiting luminosity of ~10^35 erg/s in the 0.2-4.5 keV band.

The main goal of the thesis was a study of the different source populations of M 31 that can be observed in X-rays. Therefore a catalogue was created, which contains all 1948 sources detected in the 0.2-12.0 keV range. 961 of these sources were detected in X-rays for the first time. Source classification and identification was based on X-ray hardness ratios, spatial extent of the sources, and by cross correlating with catalogues in the X-ray, optical, infrared and radio wavelengths. An additional classification criterion was the long-term temporal variability of the sources in X-rays. This variability allows us to distinguish between X-ray binaries and active galactic nuclei. Furthermore, supernova remnant classifications of previous studies that did not use long-term variability as a classification criterion, could be validated. Including previous Chandra and ROSAT observations in the long-term variability study allowed me to detect additional transient or at least highly variable sources, which are good candidates for being X-ray binaries.

Fourteen of the 40 supersoft source (SSS) candidates correlated with optical novae and therefore can be considered the supersoft emission of the optical novae. Among them is the first nova/SSS detected in a globular cluster of M 31. Correlations with previous ROSAT and Chandra studies revealed that only three SSSs are visible for at least one decade. This result underlines the strong long-term variability found for the class of SSSs. In addition the correlations demonstrated that strict selection criteria have to be applied to securely select SSSs.

An investigation of the spatial distribution of the 25 supernova remnants (SNRs) and 37 SNR candidates showed that many of these sources are consistent with the location of the 10 kpc dust ring and other star forming regions in M 31. This connection between SNRs and star forming regions implies that most of the remnants are from type II supernovae.

The brightest sources of M 31 belong to the class of X-ray binaries (XRBs). Ten low mass XRBs (LMXBs) and 26 LMXB candidates were identified based on their temporal variability. In addition 36 LMXBs and 17 LMXB candidates were identified due to correlations with globular clusters and globular cluster candidates. From the LMXBs located in globular clusters one is a black hole candidate and another a neutron star candidate. From optical and X-ray colour-colour diagrams, possible high mass XRB (HMXB) candidates were selected. Two of these candidates have an X-ray spectrum as is expected for an HMXB containing a neutron star primary.

To investigate the logN-logS relations of sources in the field of M 31, a catalogue of sources detected in the 2.0-10.0 keV energy range was created. The slope of the logN-logS relation for the whole galaxy is consistent with the expectation for spiral galaxies (Colbert et al. 2004). Subtracting the background logN-logS relation, the region beyond the D25 ellipse still contains about 13 sources/deg^2 of M 31 with fluxes above the completeness limit of ~3.2x10^{-14} erg/cm^2/s (~2.3x10^36 erg/s at the distance of M 31). The radial dependence of the source distribution in M 31's disc can be well fitted with an exponential profile, for limiting fluxes of ~3.2x10^{-14} erg/cm^2/s and 10^{-13} erg/cm^2/s (~7.3x10^36 erg/s).

About 60% of all sources with fluxes above 3.2x10^{-14} erg/cm^2/s are background sources. While the contribution of background sources lies at ~20% in the inner disc region, the fraction increases to >~80% in the outer areas of M 31.

For the

Based on a straightforward physical model, a new lightning parameterization has been developed:

A two-plate capacitor represents the basic dipole charge structure of a thunderstorm, which

is charged by the generator current and discharged by lightning. In this approach, the

generator current as well as the discharge strength are parameterized using the graupel-mass field.

If these two quantities

are known, and if the charging and discharging are in equilibrium, then the flash rate is uniquely

determined. This approach remedies shortcomings of earlier theoretical approaches that relate the flash

rate e.g., to generator power. No distinction is made between intracloud and

cloud-to-ground discharges.

In order to test this approach, polarimetric radar

data were used, from which the graupel distribution in observed thunderstorms could be inferred. The lightning

activity was detected using the LINET network. The comparison between

theoretically-predicted and measured flash rates is encouraging: Over a wide range of flash rates,

the theoretical approach yields accurate results for isolated thunderstorms. Two existing

parameterizations, which only use the depth of the clouds as predictor, produce

substantially less accurate forecasts.

These two existing approaches, the one developed in this study, as well as a fourth one based on updraft velocity,

were implemented in the convection-resolving COSMO-DE numerical weather prediction model. With this model,

real-world convective scenarios were simulated. The output of the lightning scheme includes the location and time

of every simulated discharge.

Testing the performance of the

parameterizations with modeled convection is difficult as there is no one-to-one correspondence between

observed and modeled convective clouds. Where a comparison between modeled and observed flash rates of individual clouds

was possible, the results for individual cells were promising.

The comparison of the bulk lightning activity over an area comprising southern Germany and adjacent countries

suggests that none of the four parameterizations captures the overall lightning activity well. This is mainly

because COSMO-DE does not simulate the observed number of cells at the correct times.

This thesis proposes two complementary scenarios to observe Bell correlations in the motion of two macroscopically separated material particles. Both are based on the gradual dissociation of ultracold Feshbach molecules and result in macroscopic delocalizations of the single-atom states. By giving a full account of these scenarios, including the coupled-channel description of the Feshbach dissociation, the optically guided dispersive propagation, interferometric processing and the final position measurements, I demonstrate for both cases their potential to violate a Bell inequality under experimentally viable conditions that correspond to delocalizations and interatomic separations on the order of centimeters.

The Standard model of particle physics is a very successful theory of strong weak and electromagnetic interactions.This theory is perturbative at sufficiently high energies and renormalizable thus it describes these interactions at quantum level. However it has a number of limitations, one being the fact that it has 28 free parameters assuming massive neutrinos. Within the Standard model these parameters can not be explained, however they can be accommodated in the standard theory. Particularly the masses of the fermions are not predicted by the theory. The existence of the neutrino masses can be regarded as the first glimpse of the physics beyond the standard model.

In this thesis we have described the quark and lepton masses and mixings in context of non-SUSY SO(10) and four zero texture (FZT). In the four zero texture case the fermion masses and mixing can be related. We have made some predictions using tribimaximal mixing, the near tribimaximal (TBM) mixing and the triminimal parameterization. Our results show that under the TBM the

neutrinos have normal, but weak hierarchy. Under near tribimaximal mixing and the triminimal parameterization we find that the neutrino masses in general increase, if the value of solar angle increases from its TBM value and vice versa.

It appears that the neutrinos become more and more degenerate for solar angle values higher than TBM value and hierarchical for lower values of solar angle. We also briefly discuss neutrino parameters in the SUSY SO(10) theories. An overview of SUSY SO(10) theories and proton decay is also presented.

Fluorescence Correlation Spectroscopy (FCS) allows one to measure protein-membrane binding, self-assembly and other molecular reactions and parameters quantitatively in

buffer as well as in complex media. Subject of this thesis was to investigate protein-membrane interactions within blood coagulation in buffer as well as in their biological

environment with FCS.

Binding of Factor VIII (FVIII) to phosphatidylserine (PS)-expressing platelets is a key process in the intravascular pathway of the blood coagulation cascade. Representing a complex component of the highly regulated network of the coagulation cascade, this protein-membrane interaction is influrenced by many cofactors, such as annexin, which binds to PS-containing membranes as well. Since defects in coagulation, particularly in FVIII binding to membranes lead to severe bleeding disorders, a better understanding

of the underlying biophysical and biochemical mechanisms and regulatory influences of this interaction could boost diagnosis and therapy of such diseases, especially when used

in combination with an improved systems biology description of the cascade.

This thesis investigates the mechanism of FVIII binding to PS-containing model membranes and its regulation by annexin using FCS. Activated FVIII, in contrast to inactivated FVIII, was found to exhibit a striking binding anomaly, consisting in a sharply peaked dependence of the binding constant K(PS) as a function of the PS content. It exceeds the binding of inactivated FVIII in a regime around 12% PS, including physiological concentrations. Furthermore, the regulatory influence of annexin, which can both, increase as well as decrease the binding of activated FVIII, was explained based on this binding anomaly. A quantitative model of this regulatory mechanism assuming efficient shielding of charges by annexin was developed, which allows for the reconstruction of the full three-dimensional phase diagram of FVIII binding to membranes as a function of their PS-content and the concentration of annexin. In order to prove the relevance of these results for coagulation, the experiments were repeated in plasma.

Since plasma is a scattering medium, which is crowded by macromolecules and hence strongly affects FCS experiments, a procedure to analyze measurements performed in such complex media was developed. To this end, the influences of scattering and crowding on FCS were investigated using a model system of GFP in highly concentrated vesicle solutions. Scattering was found to enhance and distort the focal volume, whereas crowding slows down diffusion. Taking both effects into account, corrections could be applied, which were demonstrated to allow for artifact-free analysis of binding measurements in complex soft matter systems. To further improve the performance of FCS in complex

media and, particularly, in cells, a two-photon FCS microscope was set up.

Based on the results of the investigations on scattering and crowding, FCS experiments on living cells were performed. The effective viscosity in dictyostelium discoideum cells was probed and compared to values obtained in lysate. The enhancement of viscosity in the cytoplasm was found to be due to crowding by polydisperse macromolecules, whereas the viscosity of the actin cortex was determined by actin polymerization. Drug treatment allowed for regulation of the polymerization level in the cytoplasm and for detection and determination of the viscosity of actin waves.

A project in close colaboration with the groups of Prof. Bein and Prof. Bräuchle succeded in the design, characterization and testing of a drug delivery system employing colloidal mesoporous silica nanoparticles efficiently coated by lipids with a solvent exchange method. Using cross-correlation spectroscopy the lipids were shown to form a close and dense bilayer around the nanoparticles. In-vitro drug delivery experiments gave evidence of the capping-mechanism of the lipids and in-vivo studies proved the effc