Both an experimental investigation of the interaction effects within commercial particulate recording media and a numerical investigation of the reversal mechanism of particles within the media have been made. The particle systems investigated comprised three audio y-Fe203 tapes, three audio Cr02 tapes and a video metal particle tape. An absolute measure of the interaction effects within particulate tapes has been investigated by comparing the measured properties of isolated particles taken from the medium with the measured bulk properties of the medium. The results indicated negative interactions for all the samples investigated except the video metal particle tape, which indicated positive interactions. However, Al plots for all the samples however, indicated negative interactions. This is contrary to the absolute interactions measured in the video metal particle tape. A possible explanation for this inconsistency was the presence of highly localised alignment of particles, "a chaining effect", within the metal particle system. This effect allows for increased system coercivity without removing the general negative interactions characteristic of all acicular particulate media. A micromagnetic model was developed to study typical y-Fe203 and Cr02 particles measured experimentally in this study. Simulations were performed as a function of the applied field angle and the results compared to the experimental study. The simulations representing typical 'y-Fe203 particles indicated reasonable agreement at the lower applied field angles, while poorer agreement was observed at larger applied field angles. The simulations representing a typical Cr02 particle indicated reasonable agreement at the higher applied field angles, while poorer agreement was observed at low applied field angles. These inconsistencies for both types of particles investigated were accounted for by assumptions and simplifications within the model, particularly the absence of bulk crystalline imperfections, the degree of surface irregularities and the effect of an oversimplified particle shape. The micromagnetic model developed was also used to investigate the effect of model parameters on the reversal mechanism of the 'y-Fe203 particle simulation. It was found that the reversal mechanism was very sensitive to the size and shape of the model particle.

A new era of gravitational wave astronomy has begun with the first direct detections of gravitational waves from the collision of binary black holes and a binary neutron star system. The scientific outcomes from these detections have been magnificent, however in order to increase the event rates for known sources, to be sensitive to new sources, to detect sources at greater distances, and to increase the signal to noise ratio for better extraction of source parameters, further research is required to increase the detectors sensitivity. The Advanced LIGO and Advanced Virgo detectors that enabled these first detections will ultimately be limited in their sensitivity by reaching the standard quantum limit (SQL). One novel technique to reduce the influence of quantum radiation pressure noise in a measurement of strain between two test masses is the speed meter topology. As a proof of concept experiment the Glasgow Sagnac Speed Meter experiment aims to show a reduction in quantum radiation pressure noise compared to an equivalent Michelson interferometer at audio-band frequencies. Two triangular cavities are the core of the experiment and consist of two 100g end test masses and one 1g input test masses per cavity, all suspended from multistage pendulums. In this combination the whole Sagnac Speed Meter experiment should be limited by quantum radiation pressure noise from about 100Hz to 1kHz and it is expected to achieve a reduction of quantum radiation pressure noise by a factor of 3-5 compared to an equivalent Michelson interferometer. This thesis presents the development, design, commissioning and testing of the three main types of suspensions in the Sagnac Speed Meter experiment. The longitudinal displacement noise requirement for both cavity suspension types is < 1.5 x 10-18m/√Hz over the measurement band between 100Hz and about 1kHz. In order to isolate the mirrors from seismic ground motion in the Sagnac Speed Meter experiment, they are suspended from multistage pendulums, resulting ideally in a 1/f^2n response for n pendulum stages above the pendulums rigid body modes. Reduction of thermal noise in the suspension elements (suspension thermal noise) is achieved by the introduction of high quality-factor materials in the lowest pendulum stage, making it fully monolithic. The 100g end test mass suspension is based on an existing design, originally developed for the AEI 10m prototype, as a triple suspension with two stages of vertical blade springs and a fully monolithic lowest pendulum stage. The 1g input test mass suspension, designed as a quadruple pendulum with a fully monolithic lowest pendulum stage, utilises the same vertical blade springs and top mass as the 100g end test mass suspension. The quadruple pendulum design enables passive damping of test mass motion at the penultimate stage. As passive damping introduces force noise due to thermal noise, a switchable passive damping system was developed and tested to mitigate limitation by this force noise. The auxiliary suspension, a double pendulum, serves to suspend the mirrors in the experiment that guide the beam towards the Sagnac Speed Meter, in between the cavities, and towards the balanced homodyne detector. As these are not part of the cavities, the longitudinal displacement noise requirement can be relaxed to < 8 x 10-15m/√Hz at 100Hz. The pendulum dynamics of the auxiliary and 100g end test mass suspension were measured in an optical lever set up and, in case of the auxiliary suspension, additionally with a vibrometer. With these measurements, the models were adjusted and could be used to estimate the longitudinal displacement noise due to coupling from seismic ground motion and thus verify the required performance of the suspensions. The research conducted in this thesis is an important step towards establishing the speed meter topology for consideration in future gravitational wave detectors. The developments in the scope of the monolithic assembly for the 100g end test masses will be applied to the AEI 10m prototype in order to enable sub-SQL measurements.

In 2015, a gravitational wave (GW) signal from a binary black hole merger passed through the arms of the US-based Advanced LIGO (aLIGO) interferometers, resulting in the first direct detection of gravitational waves. This long-awaited observation made worldwide news one hundred years after Einstein first predicted the existence of GWs in 1916. Since the first detection, four more binary black hole inspiral events have been detected, as well as the ground-breaking GW observation of a binary neutron star inspiral. To detect these signals, ground-based GW detectors like aLIGO and the French-Italian detector, Advanced Virgo, need to be sensitive to changes in separation of close to 10^-19m between freely suspended test masses spaced up to 4km apart. This has always been a challenge to achieve, thus 50 years of technological developments were needed to make these first detections possible. Following the first observations of coalescing black holes and neutron stars, it is essential to pursue technological advancements that improve the sensitivities of ground-based detectors. Doing so will increase the signal-to-noise ratio of future detectors, which will allow for the better extraction of astrophysical source parameters. Observing more types of astrophysical sources, and at greater distances from the Earth will further the field of GW astronomy. One such area of advancement is to pair the operation of detectors at cryogenic temperatures with improvements in mirror and suspension design, with the aim of improving sensitivities by lessening the effects of thermal noise. Fused silica, currently used for the mirror substrates and suspension fibre elements in all detectors that operate at room temperature, cannot be used in detectors that operate at cryogenic temperatures due to its unfavourable thermo-mechanical properties. Thus a change of mirror substrate and suspension material is necessary for the construction of cryogenic detectors. There are two promising candidates for cryogenic mirrors and suspension elements, sapphire and silicon. Currently one cryogenic detector, the Japan-based KAGRA observatory, is under construction using sapphire as a material for its mirrors and some suspension elements. Other future detectors currently in the design phase, such as the Einstein Telescope (ET) in Europe and Voyager, in the USA may use silicon or sapphire material in their mirror suspensions. In all ground-based detectors the test masses are supported in multi-stage pendulum suspensions, where the last stages are quasi-monolithic. In the quasi-monolithic stage, the test masses are suspended from penultimate masses via fibres, welded to an interface piece, or "ear". Currently these ears are connected to the test masses using a method called hydroxide catalysis bonding, which creates a strong, low noise joint. This bonding technique has been used successfully in room temperature detectors for 17 years. This thesis details research into hydroxide catalysis bonding, with a focus on its use to create cryogenic crystalline suspensions for future ground-based detectors. The use of indium as an alternative bonding technology for joints in low temperature crystalline suspensions is also investigated. The aim of this study is to research possible ways to implement indium bonding into suspension design along with hydroxide catalysis bonds to create a more versatile and easily repairable system. This work was completed with the aim of investigating novel ways of implementing bond techniques into GW detectors, and studying their material properties. The breaking stress and stability of different bond technologies were investigated, as well as their thermal noise levels and impact on overall detector sensitivity. The majority of substrate materials used in this thesis were sapphire and silicon, as these are the two materials of choice for use in future cryogenic detectors. Measurements of the Young's modulus of hydroxide catalysis bonds between fused silica were also completed and used to model the thermal noise contribution of bonds in a prototype test mass for the possible room temperature upgrade to aLIGO, A+. In Chapter 1 an overview of the field of gravitational wave research is given. An explanation of GW sources and a history of the different types of ground-based GW detectors are summarised here, with a focus on Michelson-type interferometric detectors, used to make the first direct GW detections. The noise sources that affect the sensitivity of interferometric detectors are also reviewed. In Chapter 2 there is a summary of several different bonding techniques that could be considered for making joints between the test masses and suspension elements of GW detectors. The mechanisms of bond formation as well as the advantages and disadvantages to each approach are covered, especially in the context of the requirements for use in a GW detector. Finally hydroxide catalysis and indium bonding are introduced as possible techniques to join the suspension and mirror elements in GW detectors. In Chapter 3 the breaking stresses of hydroxide catalysis bonds between c-plane sapphire substrates as a function of time is studied. The aim of this experiment is twofold. The breaking stress of bonds that have been allowed to cure for shorter lengths of time is investigated to gain insight into the chemical processes of the bonds as they develop. Additionally, it is crucial to know the breaking stress over longer periods of curing time to be assured that they will not fail in the long term. In fact, this study found that hydroxide catalysis bonded sapphire shows an initial drop in breaking stress, which then levelled off at 15-16MPa. These results agree with similar trends found in shorter curing time tests on sapphire and fused silica completed in the past. In Chapter 4 the effect of crystal orientation on the tensile strength of hydroxide catalysis bonded sapphire is investigated. Specifically, the breaking stress of bonds between a-a and m-m planes of sapphire jointed with hydroxide catalysis bonds is studied, using samples of the same geometry and jointed using the same bonding procedures as those presented in Chapter 3. These samples were allowed to cure at room temperature for 4 weeks, then the samples were strength tested. The breaking stresses were recorded and compared with the breaking stress results of c-c plane sapphire, also cured for 4 weeks at room temperature, reported in the previous chapter. In Chapter 5 a non-destructive technique of measuring the Young's modulus of hydroxide catalysis bonds between silica and between sapphire is developed. This approach uses acoustic pulses from an ultrasonic transducer transmitted through the bonded samples, and the portion of the acoustic wave that is reflected back from the embedded bond layer is recorded and studied. The bond Young's modulus was extracted from the data by analysis of the amplitudes of the acoustic pulses reflected from the bonds. A Young's modulus value of 15.3+/-5.2GPa for \hcbed sapphire and 21.5+/-6.6GPa for bonded fused silica was found with this approach. A Bayesian analysis model of the reflected acoustic signal and the underlying noise background was developed to analyse the low SNR signals of bonds between fused silica. A value of 18.5+/-2GPa, with a 90% confidence range was found with this approach, agreeing well with the results from the pulse amplitude analysis. In Chapter 6 the new Young's modulus value found in Chapter 5 is used to assess the mechanical loss and thermal noise budgets of hydroxide catalysis bonds in different mirror suspension geometries. Two room temperature test masses were modelled; a bonded aLIGO mass and a bonded prototype test mass, of a design suitable for use in A+. Three different cryogenic masses were also modelled; first a sapphire KAGRA mass, followed by a prototype sapphire ET mass, and a prototype silicon ET mass. / The thermal noise budgets of the bonds in all of these cases were found to be below the anticipated technical noise requirement for bonds, which is based on each detector's current design sensitivity curves. This indicates that hydroxide catalysis bonds are suitable for use in current detectors and for the design of future ones. In Chapter 7 different approaches to creating indium bonding procedures for use in cryogenic ground-based detectors are studied. Hybrid suspension designs that utilize both indium and hydroxide catalysis bonding are being considered in cryogenic detector designs such as KAGRA or ET. It is proposed that the \hydroxide catalysis bonds would be used to fix the test masses to the suspension elements. This takes advantage of their high breaking stress under shear and peeling, as has been successfully demonstrated in the past for room temperature detectors such as Virgo, aLIGO, or the Germany-based detector GEO600. Indium's low tensile strength means it cannot be used as a joint under tensile or shear load. However it is being considered for use in compressive joints, such as between the fibres and ears or between the fibres and blade springs. This would be done for contingency reasons, since indium can be de-bonded and re-bonded relatively easily, whereas hydroxide catalysis bonds cannot. In the event of a fibre break or a test mass upgrade, the whole bonded test mass assembly could be removed by de-bonding the indium bond interface. It could then be replaced by re-bonding it, making it a good option for future cryogenic mirror suspensions. Two indium bonding approaches are investigated, diffusion bonding and induction bonding. In both cases the substrates used were polished silicon, and the indium layers between them were made with different combinations of thin thermally deposited films and foils. The tensile strength and a post-break visual inspection of the indium bonds were used as a standard by which to judge bond quality and repeatability.

This thesis presents results from four different studies on the diffuse interstellar bands and the local interstellar medium. Firstly, a detailed investigation into the profile of the λ6614 diffuse interstellar band (DIB) is presented, which was aimed at ascertaining the origin of the observed fine structure and overall band shape, and why both of these properties change between a number of different lines-of-sight. A new method for normalising DIBs is described, and revealed new information about how the λ6614 band evolves between lines-of-sight. Observations and modelling of the DIB profile towards HD 147889 suggests that this line-of-sight has the highest internal excitation of the carrier, which accounts for its greater width and additional structure. As a continuation of this project, a further fifteen DIB profiles were examined towards HD 179406 and HD 147889, some of which are thought to correlate with the column density of the C2 molecule. It was shown that HD 179406 and HD 147889 demonstrated almost identical band profiles for the ‘C2’ DIBs, which differed considerably to the ‘non-C2’ DIBs investigated in this study. Analysis presented in this chapter strongly supports the idea that the ‘C2’ DIBs form a distinct class, and the normalisation method used provides a new criterion for validating whether a DIB may be classed as a ‘C2’ DIB. A study of small-scale structure in the ultraviolet (UV) region towards three stars within the ρ Ophiuchus system was undertaken using observations from the Hubble Space Telescope, to deduce column densities of atomic and molecular species, and to obtain physical parameters such as density and kinetic temperature through chemical modelling. The biggest absorption differences were found within the C2 molecule profile, and it was found that the medium in which C2 molecules reside is denser towards ρ Oph A and ρ Oph B than ρ Oph D. Modelling additional species, such as Fe I and Fe II which are also thought to be present in the data, may help to further characterise the ISM towards these three stars. Optical and near-infrared (IR) observations of Herschel 36 were undertaken using the Southern African Large Telescope (SALT) and Gemini North. The aim of this project was to investigate the full DIB spectrum along this unusual sight-line, and determine how many DIBs were present and how many demonstrate the behaviour previously observed. A number of issues arose with the optical observations and the data reduction processes, meaning that the overall aim was not fully realised. However, observations from Gemini North showed more promise but did not detect either near-IR DIB, although higher S/N observations are recommended to verify their absence.

This thesis investigates the role of superfluidity in neutron stars and associated phenomena. We model the internal fluid of a neutron star as a two-component system: one of charged particles and one of superfluid neutrons. We derive a set of multi-constituent hydrodynamic equations that allows for a mutual friction between the constituents. We show that when a velocity difference exists between the two constituents the momentum of each constituent is modified by an entrainment parameter. Throughout all of this work we take direction from both theoretical and experimental work on superfluid Helium. This suggests that a force due to vortex lines in the superfluid acts between the two constituents. The hydrodynamic equations are on a scale at which the effect of vortices can be averaged over. The form of the mutual friction between the two constituents depends on the configuration of the vortices. Firstly, we concentrate on an array of vortices. The mutual friction is calculated both for a straight array, and then extended to a ‘moderately’ curved array. We also investigate a turbulent model for the superfluid neutrons in which the vortices are in a tangle. To include rotation in our model we use a phenomenological approach to construct the mutual friction for a polarised tangle. The hydrodynamic equations are used to investigate how entrainment and mutual friction affect plane waves. We show that there are conditions in which the waves are unstable and discuss how this may lead to turbulence. As a first step in considering the neutron star crust we consider how oscillations in the fluid are dissipated on a boundary. As before, we concentrate on the effects of entrainment and mutual friction. Finally, we consider a simple global model of the glitch phenomenon seen in neutron stars in which the important process is a reconfiguration of the vortex array. We use this model to consider how the observational data may constrain parameters.

We investigate equilibrium configurations and oscillation spectra of neutron stars, modelled as rotating magnetised fluid bodies in Newtonian gravity. We also explore the idea that these model neutron stars could have dynamics analogous to rigid-body free precession. In axisymmetry, the equations of magnetohydrodynamics reduce to a purely toroidal-field case and a mixed-field case (with a purely poloidal-field limit). We solve these equations using a nonlinear code which finds stationary rotating magnetised stars by an iterative procedure. We find that despite the general nature of our approach, the mixed-field configurations we produce are all dominated by their poloidal component. We calculate distortions induced both by magnetic fields and by rotation; our results suggest that the relationship between the magnetic energy and the induced ellipticity should be close to linear for all known neutron stars. We then investigate the oscillation spectra of neutron stars, using these stationary configurations as a background on which to study perturbations. This is done by evolving the perturbations numerically, making the Cowling approximation and specialising to purely toroidal fields for simplicity. The results of the evolutions show a number of magnetically-restored Alfv´en modes. We find that in a rotating star pure inertial and pure Alfv´en modes are replaced by hybrid magneto-inertial modes. We also show that magnetic fields appear to reduce the effect of the r-mode instability. Finally, we look at precession-like dynamics in magnetised fluid stars, using both analytic and numerical methods. Whilst these studies are only preliminary, they indicate deficiencies in previous research on this topic. We suggest ways in which the problem of magnetised-fluid precession could be better understood.

Gravitational waves are considered as ripples in the curvature of space-time and were predicted by Einstein in his general theory of relativity. Gravitational waves interact very weakly with matter which makes them very difficult to detect. However, research groups around the world are engaged in building a network of ultra sensitive ground and space based interferometers for the first detection of these signals. Their detection will open a new window in the field of astronomy and astrophysics. The nature of gravitational waves is such that when incident on a particle, they stretch and squeeze the particle orthogonally thus producing a tidal strain. The strain amplitude expected for gravitational waves which may be detected on earth are of the order of hrms ~10-22 to 10-23 (over a frequency range from few Hz to a few kHz). A network of instruments based on the Michelson interferometer design currently exists around the world. These detectors are undergoing a major upgrade and once online by 2015-16 the improved sensitivity and increased sky coverage may lead to the first detection of the gravitational waves signals. The Institute for Gravitational Research in the University of Glasgow in collaboration with the Albert Einstein Institute in Hannover, Golm and the University of Cardiff has been actively involved in the research for the development of instruments and data analysis techniques to detect gravitational waves. This includes construction of a long ground based interferometer in Germany called GEO 600 (upgraded to GEO-HF) having an arm length 600 m and strong involvement in the larger detectors of the LIGO (Laser interferometer gravitational wave observatory) project in USA having arm lengths of 4 km (Operated by MIT, Boston and CALTECH, Pasadena). An upgrade to LIGO called Advanced LIGO (aLIGO) is currently under construction with significant input from the University of Glasgow. Thermal noise is one of the most significant noise sources affecting the sensitivity of the detector at a range of frequencies. Thermal noise arises due to the random fluctuations of atoms and molecules in the materials of the test mass mirrors and suspension elements, and is related to mechanical loss in these materials. The work presented in chapter 3 of this thesis is devoted to the analysis of aspects of mechanical loss and thermal noise in the final stages of the GEO suspension. GEO-600 is currently undergoing an upgrade to GEO-HF targeting sensitivity improvements in the kiloHertz region. However, the planned upgrade requires access to the vacuum tanks enclosing the fused silica suspension system. There is a risk of damaging the suspension, which has led to a repair scenario being developed in Glasgow, to reduce the downtime of the detector. An optimised design of the fused silica fibre has been proposed. A study of mechanical loss has been undertaken through Finite Element Analysis (FEA) modeling techniques. The mechanical loss of the optimised fibre is estimated to be lower than the original GEO fibre by a factor of ~4. In terms of thermal noise performance the optimised fibre gives an improvement of ~1.8. The repair scenario of the monolithic suspension has led to the development of tools and welding procedures. Three prototype suspensions involving metal masses were successfully built, before fabricating the monolithic fused silica suspension in Glasgow. The work in chapter 4 focuses on the theory of photoelasticty and birefringence techniques. The production and use of various forms of polarised light has been discussed. A setup of plane and a circular polariscope using two polarisers and two-quarter wave plates has been shown. The retardation of light due to the birefringence in the sample can be measured using the Tardy method of compensation and a Babinet-Soleil compensator. Finally a discussion on the stress-optic law has shown that the relative stress in a sample can be measured once the retardance is known. The silica fibres in the aLIGO detector would be laser welded using a 100 W CO2 laser. The laser welding would lead to high temperature and development of thermal gradients. This could result in residual thermal stress in fused silica, which could lead to an additional mechanical loss. A study of mechanical and thermal stress induced in fused silica has been discussed in chapter 5 of this thesis. To understand the working of photoelastic techniques learned in chapter 4, a study of mechanical stress was undertaken by applying a load on the sample to induce temporary birefringence. The estimated values of stress showed a good agreement when compared with the theoretical predictions and FEA modelling. Thermal stress was induced in fused silica by applying a 25 W CO2 laser beam for 10 seconds and the relative stress was measured using photoelastic birefringence techniques. Thermal modelling of the stressed sample was performed using the techniques developed in FEA. The experimental values show a good agreement with the estimated 1st principal stress (FEA model) and equivalent stress. A study of thermal stress in fused silica welds has also been presented in chapter 5. Two fused silica samples were welded using CO2 laser welding and the relative stress at different points were measured. The stress in the weld region was measured to be relatively lower than other areas. At a distance of 3 mm away from the weld line the maximum stress was measured which was greater than the stress in the weld region by a factor of ~5. The work discussed in chapter 6 focuses on the study of the suspension thermal noise in aLIGO detector for applying incremental upgrades. To further enhance the sensitivity of the aLIGO detector, incremental upgrades could be applied to the suspension system to improve the thermal noise. The incremental upgrades focused on two aspects: improving the dissipation dilution factor, and obtaining a lower mechanical loss than the aLIGO baseline. Based on the results from FEA, two designs were compared, each having a suspension of length 100 cm but different stock diameter - 3mm and 5 mm. A comparison with the aLIGO baseline showed that these two models obtained a lower mechanical loss by a factor of 3.4 to 6.8. In terms of suspension thermal noise there was an improvement by factor of 2.5 to 3.7, which could lead to rise in the sensitivity of the detector by a factor of 2.5.

Current analysis techniques for space physics 2D numerical data are based on scruti-nising the data with the eyes. Space physics data sets acquired from the natural lab of the interstellar medium may contain events that may be masked by noise making it difficult to identify. This thesis presents research on the use of sound as an adjunct to current data visualisation techniques to explore, analyse and augment signatures in space physics data. This research presents a new sonification technique to decom-pose a space physics data set into different components (frequency, oscillatory modes, etc…) of interest, and its use as an adjunct to data visualisation to explore and analyse space science data sets which are characterised by non-linearity (a system which does not satisfy the superposition principle, or whose output is not propor-tional to its input). Integrating aspects of multisensory perceptualization, human at tention mechanisms, the question addressed by this dissertation is: Does sound used as an adjunct to current data visualisation, augment the perception of signatures in space physics data masked by noise? To answer this question, the following additional questions had to be answered: a) Is sound used as an adjunct to visualisation effective in increasing sensi-tivity to signals occurring at attended, unattended, unexpected locations, extended in space, when the occurrence of the signal is in presence of a dynamically changing competing cognitive load (noise), that makes the signal visually ambiguous? b) How can multimodal perceptualization (sound as an adjunct to visualisa-tion) and attention control mechanisms, be combined to help allocate at-tention to identify visually ambiguous signals? One aim of these questions is to investigate the effectiveness of the use of sound to-gether with visual display to increase sensitivity to signal detection in presence of visual noise in the data as compared to visual display only. Radio, particle, wave and high energy data is explored using a sonification technique developed as part of this research. The sonification technique developed as part of this research, its application and re-sults are numerically validated and presented. This thesis presents the results of three experiments and results of a training experiment. In all the 4 experiments, the volun-teers were using sound as an adjunct to data visualisation to identify changes in graphical visual and audio representations and these results are compared with those of using audio rendering only and visual rendering only. In the first experiment audio rendering did not result in significant benefits when used alone or with a visual display. With the second and third experiments, the audio as an adjunct to visual rendering became significant when a fourth cue was added to the spectra. The fourth cue con-sisted of a red line sweeping across the visual display at the rate the sound was played, to synchronise the audio and visual present. The results prove that a third congruent multimodal stimulus in synchrony with the sound helps space scientists identify events masked by noise in 2D data. Results of training experiments are reported.

Central massive objects like supermassive black holes and stellar nuclear clusters are common in all type of galaxies. I use N-body simulations to study the formation and evolution of nuclear clusters and to investigate the influence of the dynamical evolution of disc galaxies on the structural and kinematical properties of the host galaxy. I show that the second moment of velocities determine a lower limit on the dissipative formation process, which is about 50% in the case of the nuclear cluster in the late-type spiral galaxy NGC 4244. The vertical anisotropy of nuclear clusters can be used to determine an upper limit on the formation process due to merger or accretion of star clusters, which is about 10% for the nuclear cluster in NGC 4244. This is the first time that we have strong evidence of a hybrid formation scenario for nuclear clusters. In a set of 25 galaxy simulations I study bar formation in disc galaxies. I show that bar formation lead to the increase in mass in the central region of galaxies. This mass increase raises the velocity dispersion of stars in the disc and bulge component, which explains the offset of barred galaxies in the relation between the mass of the supermassive black hole, Ml, and the velocity dispersion of stars in the bulge, se , the Ml - se relation (Gueltekin et al. 2009). While Graham et al. (2011) argued that the orbital structure of stars within the bar could be responsible for the observed offset of barred galaxies from the Ml - se relation of unbarred galaxies, I show that the effect of stellar orbits in bars on se is less than 15% compared to the increase in mass which raises se by 40%. The offset I find in the simulation is comparable to the offset using the recent sample of Ml measurements of elliptical, unbarred and barred disc galaxies from Gueltekin et al. (2009).

We investigate phenomenologies arising from two distinct sets of modifications introduced in Loop Quantum Cosmology (LQC), namely, the inverse volume and the holonomy corrections. We find scaling solutions in each setting and show they give rise to a period of super-inflation soon after the universe starts expanding. This type of inflation is explicitly shown to resolve the horizon problem with far fewer number of e-foldings compared to the standard inflationary model. Scalar field perturbations are obtained and we demonstrate their near scale invariance in agreement with the latest observations of the Cosmic Microwave Background (CMB). Consideration of tensor perturbations of the metric results in a large blue tilt for these fluctuations, which implies their amplitude will be suppressed by many orders of magnitude on the CMB compared to the predictions of the standard inflation. This LQC result is shared by the ekpyrotic model and the model of a universe sourced by a phantom field. Exploring a correspondence map at the cosmological background level between braneworld cosmologies and the inverse volume corrected LQC, we discover this map not to hold at the level of linear perturbations. This is found to be due to the different behaviour of the rate of the Hubble parameter in the two classes of models. A complete dynamical analysis of Friedmann-Robertson-Walker spacetimes we carry out results in the most general forms of late time attractor scaling solutions. Our examination includes expanding and contracting universes when a scalar field evolves along a positive or a negative potential. Known results in the literature are demonstrated to correspond to certain limits of our solutions.