Finalized PhD theses

Número de entradas: 79

The formation of large scale structures in the Universe: new hints from the power spectrum and the three-point correlation function

Estado: defended (26/06/2002)
Estudiante: Barriga Carrasco, Jose
Supervisada por: Enrique Gaztañaga

The formation of large scale structures in the Universe: new hints from the power spectrum and the three-point correlation function. We present a new algorithm to compare the 3-point correlation function in theory and in N-body simulations. We also present a comparison of the power spectrum as measure…
Estado: defended (26/06/2002)
Estudiante: Barriga Carrasco, Jose
Supervisada por: Enrique Gaztañaga

The formation of large scale structures in the Universe: new hints from the power spectrum and the three-point correlation function. We present a new algorithm to compare the 3-point correlation function in theory and in N-body simulations. We also present a comparison of the power spectrum as measure by CMB and galaxy observations to test the the ci

Gravitational lensing with relativistic objects

Estado: defended (27/05/2002)
Estudiante: Ernesto Eiroa
Supervisada por: Diego F. Torres ; Romero, G.
Universidad: Universidad Nacional de Buenos Aires, Argentina

See the full record in the link below (from Fermilab library)
Estado: defended (27/05/2002)
Estudiante: Ernesto Eiroa
Supervisada por: Diego F. Torres ; Romero, G.
Universidad: Universidad Nacional de Buenos Aires, Argentina

See the full record in the link below (from Fermilab library)

Sea Surface Determination Using GNSS Reflected Signals

Estado: defended (08/03/2002)
Estudiante: Estel Cardellach Galí
Supervisada por: Antonio Rius Jordán
Universidad: Universitat Politècnica de Catalunya

The Global Navigation Satellite Systems (GNSS) are large, stable and calibrated sets of spaceborne L-band microwave transmitters with very well characterized properties. They provide global and permanent coverage as required by the meteorological, oceanographical and climate scientist. All these features…
Estado: defended (08/03/2002)
Estudiante: Estel Cardellach Galí
Supervisada por: Antonio Rius Jordán
Universidad: Universitat Politècnica de Catalunya

The Global Navigation Satellite Systems (GNSS) are large, stable and calibrated sets of spaceborne L-band microwave transmitters with very well characterized properties. They provide global and permanent coverage as required by the meteorological, oceanographical and climate scientist. All these features make the GNSS signal an appropriate candidate to be an excellent source of opportunity for bistatic monitoring of the Oceans' surface.

The dissertation 'Sea Surface Determination Using GNSS Reflected Signals' tackles the question of how the GNSS signal scattered off the ocean surface can be used to obtain geophysical information about the sea-air interface. The focus is put on the retrieval of the surface roughness and/or the wind.

The thesis defends a scatterometric approach where the distribution of the scattered power crosswise the illuminated area is used to infer the roughness of the surface. The distribution or mapping is achieved by parceling the sea area in cells whose scattered signal has different delay and frequency properties. This information is gathered in anobservable called waveform.

The structure of the thesis has been divided in three main parts: (a) the modeling of the scattered GNSS signal (GNSSr); (b) the feasibility study; and (c) the experimental validation.

The scatterometric GNSSr forward and backward models are presented. The former generates the waveform of the reflected signal as a function of the geometry of the scattering, instrumental parameters, as well as the roughness of the sea surface. The backward approach proposed at this level tries to infer the sea surface roughness characteristics of the illuminated area through the inversion of the waveform.

The expected performance of the scatterometric-GNSSr system is analyzed as a first order examination of its capabilities in terms of resolution and accuracy of the wind measurements. The aim of this part of the study is to determine how precisely can the wind be measured by the GPSr techniques proposed in the backward model, as wellas how can these observations cover the Oceans.

Col·lisions d'objectes compactes amb SPH

Estado: defended (05/12/2001)
Estudiante: Josep Guerrero
Supervisada por: Jordi Isern Vilaboy; García-Berro, E.
Universidad: Universitat Autònoma de Barcelona

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Estado: defended (05/12/2001)
Estudiante: Josep Guerrero
Supervisada por: Jordi Isern Vilaboy; García-Berro, E.
Universidad: Universitat Autònoma de Barcelona

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The use of Global Navigation Satellite Systems (GNSS) signals in Numerical Weather Prediction

Estado: defended (05/06/2001)
Estudiante: Lídia Cucurull
Supervisada por: Antonio Rius Jordán; Redaño, A.
Universidad: Universitat de Barcelona

Not Available
Estado: defended (05/06/2001)
Estudiante: Lídia Cucurull
Supervisada por: Antonio Rius Jordán; Redaño, A.
Universidad: Universitat de Barcelona

Not Available

Atmospheric Tomography Using Satellite Radio Signals

Estado: defended (04/02/2000)
Estudiante: Alejandro Flores
Supervisada por: Antonio Rius Jordán
Universidad: Universitat Politècnica de Catalunya

The Global Navigation Satellite Systems (GPS and GLONASS) have become a basic tool to obtain geodetic measurements of the Earth and a source of data for the atmospheric analysis. Since these systems provide a global, dense and permanent coverage with precise and accurate data, the radio signals they…
Estado: defended (04/02/2000)
Estudiante: Alejandro Flores
Supervisada por: Antonio Rius Jordán
Universidad: Universitat Politècnica de Catalunya

The Global Navigation Satellite Systems (GPS and GLONASS) have become a basic tool to obtain geodetic measurements of the Earth and a source of data for the atmospheric analysis. Since these systems provide a global, dense and permanent coverage with precise and accurate data, the radio signals they transmit can be used for the spatio-temporal representation of the atmosphere. GPS receivers technology has evolved at a surprising pace: nowadays they have sufficient measurement quality as to be used in geodetic studies, together with other techniques such as the Very Long Base Interferometry (VLBI), and in atmospheric studies whose results can be input into meteorological analysis. In the thesis "Atmospheric Tomography Using Satellite Radio Signals" we have focused on the use of GPS system due to the better quality and quantity of references and tools for the data processing. This notwithstanding, we have proven the possibility to broaden the concept to include any other radio signal transmitting satellite system as an atmospheric sounder. The thesis has been divided into two main areas: GPS data processing to extract the information related to the atmospheric parameters under study, and the implementation of tomographic techniques to the solution of the inverse problem. In particular, tomography has been applied to the ionosphere and to the neutral atmosphere. In both cases, results have a socio-economic impact: a) monitoring the ionosphere is essential for radio transmissions across it because of the perturbations it may produce on the signal, and b) estimating water vapour content in the troposphere is highly useful for meteorological and climate forecast For the ionospheric tomography we initally only used the data from the global IGS network. Vertical resolution was afterwards improved using the occultation data of the GPS/MET experiment. The improvement, however, was limited to the region where these data existed. Finally, we used altimeter data from the TOPEX/POSEIDON satellite to improve the maps and to prove the radar altimeter calibration capability of the tomographic technique. The application to the troposphere was possible after the improvement and refinement of both the GPS data processing and the tomographic inversion. The first results were obtained using the experimental data from the permanent network in Kilauea, Hawaii. The particular geometry of the receivers in this local network made it highly suited for these initial results, which proved the possibility of obtaining spatio-temporal representations of the troposphere using GPS data. The data analysis of the REGINA campaign, which took place at the Onsala Space Observatory, provided the description of a complex meteorological phenomenon using only GPS data tropospheric tomography. We verified the results with a direct comparison with radiosonde data. Concluding, we have demonstrated the capabilities of atmospheric tomography using satellite radio signals, with particular emphasis on the GPS signals.

The motion sensing problem in spherical Gravitational Wave detectors

Estado: defended (08/04/1999)
Estudiante: Maria Angeles Serrano Moral
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

Not available
Estado: defended (08/04/1999)
Estudiante: Maria Angeles Serrano Moral
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

Not available

Cosmological perturbation theory and the spherical collapse model

Estado: defended (30/06/1998)
Estudiante: Pablo Fosalba Vela
Supervisada por: Enrique Gaztañaga ; Emilio Elizalde
Universidad: Universitat de Barcelona

We present a simple and intuitive approximation for solving perturbation theory (PT) of small cosmic fluctuations. We consider only the spherically symmetric or monopole contribution to the PT integrals, which yields the exact result for tree-graphs (i.e. at leading order). We find that the non-linear…
Estado: defended (30/06/1998)
Estudiante: Pablo Fosalba Vela
Supervisada por: Enrique Gaztañaga ; Emilio Elizalde
Universidad: Universitat de Barcelona

We present a simple and intuitive approximation for solving perturbation theory (PT) of small cosmic fluctuations. We consider only the spherically symmetric or monopole contribution to the PT integrals, which yields the exact result for tree-graphs (i.e. at leading order). We find that the non-linear evolution in Lagrangian space is then given by a simple local transformation over the initial conditions, although it is not local in Euler space. This transformation is found to be described the spherical collapse (SC) dynamics, as it is the exact solution in the shearless (and therefore local) approximation in Lagrangian space. Taking advantage of this property, it is straightforward to derive the one-point cumulants, for both the unsmoothed and smoothed density fields to arbitrary order in the perturbative regime. To leading order this reproduces, and provides with a simple explanation for, the exact results obtained by Bernardeau (1992, 1994). We then show that the SC model leads to accurate estimates for the next corrective terms when compared to the results derived in the exact perturbation theory making use of the loop calculations (Scoccimarro & Frieman 1996). The agreement is within a few per cent for the hierarchical ratios $S_J$. We compare our analytic results to N-body simulations, which turn out to be in very good agreement up to scales where $\sigma \approx 1$. A similar treatment is presented to estimate higher order corrections in the Zel'dovich approximation. These results represent a powerful and readily usable tool to produce analytical predictions to describe the gravitational clustering of large scale structure in the weakly non-linear regime.

Search for monochromatic GW signals in data from the antenna EXPLORER

Estado: defended (17/04/1998)
Estudiante: Miquel Montero Torralbo
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

This Thesis is about the design and development of various filtering strategies for the analysis of data generated by a resonant bar gravitational wave (GW) antenna, with the goal to assess the presence (or absence) therein of long-duration monochromatic GW signals, as well as the eventual amplitude…
Estado: defended (17/04/1998)
Estudiante: Miquel Montero Torralbo
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

This Thesis is about the design and development of various filtering strategies for the analysis of data generated by a resonant bar gravitational wave (GW) antenna, with the goal to assess the presence (or absence) therein of long-duration monochromatic GW signals, as well as the eventual amplitude and frequency of the signals, within the sensitivity band of the detector. Such signals are most likely generated in the fast rotation of slightly asymmetric spinning stars. We develop practical procedures, together with a study of their statistical properties, which provide us with useful information on the performance of each technique. The selection of candidate events is then established according to threshold-crossing probabilities, based on the Neyman­-Pearson criterion. In particular, it is shown that this approach, based on phase estimation, presents a better signal-to-noise ratio than does pure spectral analysis, the most common approach. The methodology is applied and validated with data from the real GW detector EXPLORER, kindly provided by the Frascati (near Rome) Group, who designed, built and run the detector.

Spherical GW detectors

Estado: defended (17/03/1997)
Estudiante: Jose Antonio Ortega Ruiz
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

Shortly available
Estado: defended (17/03/1997)
Estudiante: Jose Antonio Ortega Ruiz
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

Shortly available
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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
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