Finalized PhD theses

Número de entradas: 80

Variable stars and eclipsing binaries in M31

Estado: defended (09/03/2009)
Estudiante: Vilardell, F.
Supervisada por: Ignasi Ribas Canudas; Jordi, C.
Universidad: Universitat de Barcelona

The main objective of the PhD thesis is the use of variable stars (Cepheids) and eclipsing binaries for an accurate determination of the distance to M31. The observational data for the project was obtained over the corse of a 4-yr campaign at the 2.5-m INT telescope (La Palma). The survey has provided photometry of some 450 eclipsing binary stars and 410 Cepheid variables. In the case of the eclipsing binaries the photometry is complemented with spectroscopy obtained from the 8-m Gemini North telescope. From the overall analysis, a distance determination to M31 with an uncertainty below 3% is antipated, thus meaning a very significant improvement over the current 10%. The results of this project will help to better establish the Cosmic Distance Scale by accurately calibrating the distance to Local Group galaxies.
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Estado: defended (09/03/2009)
Estudiante: Vilardell, F.
Supervisada por: Ignasi Ribas Canudas; Jordi, C.
Universidad: Universitat de Barcelona

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Large scale structure and dark energy

Estado: defended (30/06/2008)
Estudiante: Anna Cabre Albos
Supervisada por: Enrique Gaztañaga
Universidad: Universitat de Barcelona

Physicists currently believe that the universe is composed basically of dark energy (70%) and dark matter (25%), both unknown components. The rest is made of known (barionic) matter. The first part of the thesis studies the clustering in galaxies through the 2 and 3 point auto-correlation function in Sloan Sky Digital Survey (SDSS). This allows a direct measurement of the dark matter component and the global amplitude of fluctuations modulated by some bias. The second part of the thesis cross-correlates CMB (with WMAP data) with fluctuations in the number of galaxies (with SDSS) in order to obtain extra information about the structure of the universe. Dark energy is responsible for the accelerated expansion of the universe during late times. We can detect it through the redshift or blueshift that experiment photons coming from the Cosmic Microwave Background (CMB) when they pass through dark matter potentials (Integrated Sachs-Wolfe effect). A join analysis of both cross and auto correlations represents a novel approach to understand structure formation in the universe.
The standard cosmological model starts with Big Bang, followed by a rapid period of expansion of the universe called inflation. After that, tiny almost homogeneous fluctuations that conform the primordial universe, start to grow while universe expands now in a relatively slow rhythm. 300,000 years…
Estado: defended (30/06/2008)
Estudiante: Anna Cabre Albos
Supervisada por: Enrique Gaztañaga
Universidad: Universitat de Barcelona

The standard cosmological model starts with Big Bang, followed by a rapid period of expansion of the universe called inflation. After that, tiny almost homogeneous fluctuations that conform the primordial universe, start to grow while universe expands now in a relatively slow rhythm. 300,000 years after the Big Bang, the temperature is low enough to make the universe become neutral after the recombination of atoms with electrons. Photons are almost free of interactions since then and reach us in the form of a Cosmic Microwave Background (CMB). We can measure the spatial anisotropy spectrum of CMB temperatures and compare it to the expected spectrum of acoustic oscillations. This comparison provides a direct geometrical test from which we can deduce that universe is flat or nearly flat. This can be explained if we introduce a new constituent in the universe apart from matter, the dark energy. Dark energy acts as anti-gravity that accelerates the expansion and is also observed through standard candles Supernovae Ia. Although there is a well motivated model that can explain observations, neither dark matter nor dark energy are known elements, so it is important to use the large amount of newly available data to obtain tighter constraints on the constituents of the universe, the evolution of growth perturbations, the expansion history, and also other alternatives, such as modification of gravity at large scales. In the first part of the thesis, we study the Integrated Sachs-Wolfe effect (ISW), through the cross-correlation between large scale clustering, traced by galaxies (in our case from the catalog SDSS) and primordial temperature fluctuations from CMB (using the catalog WMAP). Photons that come from the last scattering surface can be red or blue shifted by the time evolution of fluctuations in the gravitational potentials created by large scale structures, which are traced by the large scale galaxy distribution. The ISW effect gives us information about dark energy (DE), because DE modifies the evolution of dark matter gravitational potential. There is no ISW effect in a flat universe without DE (ie in the Einstein-de-Sitter universe) because in this case the gravitational potential remains constant (in the linear regime, which corresponds to large angular scales). In principle, the ISW effect can probe dark energy independently from other observations, such as Supernovae Ia. The correlation between galaxies in redshift space can also be used to study the evolution of the dark matter gravitational potential in a way that is complementary to the cross-correlation of galaxies with CMB photons. In the second part of the thesis, we will study this effect in the luminous red galaxies of the SDSS. These galaxies trace very large volumes which is important to have more signal, and they have a known evolution which make easy to work with them.

Random matrix models in Chern-Simons theory

Estado: defended (02/06/2008)
Estudiante: Tierz, M.
Supervisada por: Emilio Elizalde
Universidad: Universitat de Barcelona

Chern-Simmons and zeta functions
Random matrix models in Chern-Simons theory
Estado: defended (02/06/2008)
Estudiante: Tierz, M.
Supervisada por: Emilio Elizalde
Universidad: Universitat de Barcelona

Random matrix models in Chern-Simons theory

Testing the initial-final mass relationship of white dwarfs

Estado: defended (13/03/2008)
Estudiante: Silvia Catalán Ruiz
Supervisada por: Jordi Isern Vilaboy; García-Berro, E.
Universidad: Universitat Politècnica de Catalunya

To be added shortly
Estado: defended (13/03/2008)
Estudiante: Silvia Catalán Ruiz
Supervisada por: Jordi Isern Vilaboy; García-Berro, E.
Universidad: Universitat Politècnica de Catalunya

To be added shortly

Thermal Diagnostics in the LISA Technology Package Experiment

Estado: defended (13/12/2007)
Estudiante: Miquel Nofrarias Serra
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

The LISA Pathfinder mission (LPF) is an ESA mission, with NASA contributions, planned to fly in 2010. The LPF is a technology readiness mission devoted to pave the way to the future spaceborne gravitational wave observatory LISA. The LISA Technology Package (LTP) experiment in the LPF mission will measure…
Estado: defended (13/12/2007)
Estudiante: Miquel Nofrarias Serra
Supervisada por: José Alberto Lobo Gutiérrez
Universidad: Universitat de Barcelona

The LISA Pathfinder mission (LPF) is an ESA mission, with NASA contributions, planned to fly in 2010. The LPF is a technology readiness mission devoted to pave the way to the future spaceborne gravitational wave observatory LISA. The LISA Technology Package (LTP) experiment in the LPF mission will measure the relative distance between two free falling test masses to the picometer resolution by using both masses as end mirrors of an interferometer together with an active control loop, known as drag-free, that will act to keep the spacecraft centered around the geodetic motion of the masses. The work in this thesis deals with the thermal diagnostics subsystem, intended to measure and characterise the thermal noise contribution to the instrument performance: from the qualification of the high stability electronics designed to measure temperature fluctuations onboard the satellite to the characterisation of heaters aimed to generate controlled perturbation during mission operations. Analytic solutions together with simulations and experimental results have been used to this end. The results obtained have allowed the characterisation of the temperature subsystem and, also, to define a methodology to deal with the thermal data that will be obtained from the satellite during flight operations.

Dark energy problem in Friedmann cosmology with ideal fluid and in modified gravity

Estado: defended (30/10/2007)
Estudiante: O.G. Gorbunova
Supervisada por: Sergei D Odintsov
Universidad: Tomsk State Pedagogical University

DE problem is investigated
Estado: defended (30/10/2007)
Estudiante: O.G. Gorbunova
Supervisada por: Sergei D Odintsov
Universidad: Tomsk State Pedagogical University

DE problem is investigated

Cosmology and structure formation

Estado: defended (26/06/2007)
Estudiante: Marc Manera Miret
Supervisada por: Enrique Gaztañaga

This is an ongoing theses on large scale structure and its relation to dark energy. Both a theoretical and a more data focused aproach is taken. We study the growth of structure in non-standard cosmological models like Dvali Gabadadze and Porrati, Cardassian, or Chapligyn gas. We show the diference in the linear growth of density fluctuations and higer order statistics like the skewness between these models and the LCDM concordance cosmology. Cluster number counts are also considered as a tool discriminating between dark energy models in the future. On a more observational aproach we study the dark energy by analising the crosscorrelation between CMB temperature maps and galaxy surveys, which are dark matter tracers.
In the rst part of this thesis we look at several non-standard cosmological models. These models have been introduced in the literature mainly to explain the accelerated expansion that we see the universe is currently undertaken. We want to study if they can also reproduce the observations of the…
Estado: defended (26/06/2007)
Estudiante: Marc Manera Miret
Supervisada por: Enrique Gaztañaga

In the rst part of this thesis we look at several non-standard cosmological models. These models have been introduced in the literature mainly to explain the accelerated expansion that we see the universe is currently undertaken. We want to study if they can also reproduce the observations of the large scale structure and its evolution. For doing so we t introduce a formalism to compute the growth of structure in non-standard cosmologies. Then, for each of these non-standard models, we will focus in computing observables like the linear growth, the skewness, or the cluster number counts. In the second part of this thesis we will look at the cross-correlation between CMB-temperature maps and galaxy (or other dark matter tracers ) surveys maps. This cross-correlation is a way to measure the Integrated Sachs Wolfe (ISW) e ect, which can be directly related to the growth of structure. We will use the ISW signal dependence in redshift and in angular scale to constrain and the equation of state parameter w. In this part of the thesis we will also focus on studying di erent error estimators for the sky maps cross-correlation measurements. We will actually present a new method, which estimate the errors in the con guration space. This method will be compared with other error estimators widely used in the literature: the Jack-knife, the Monte Carlo errors and the theoretical harmonic space errors. The problem of bias. In order to compare models to observations we need to address a crucial point: does light trace mass? In other words: how well the structure we see traces the dark matter we can't see?. Are the observations biased tracers of the mass?. This is a key point to be abble to compare models of growth of structure with observations in the real world. Unfortunately in detail, this requires understanding how star's and galaxies form and shine. As the the universe expands, the dark matter clumps into halos and lamentary structure. This can be very clearly seen in dark matter cosmological simulations, which allow us to study the gravitational clustering separately from other (but also interesting) physical e ects. Like galaxies, halos are not perfect traces of the underlying dark matter uctuations, but biased ones. In fact, we believe that galaxies form inside dark matter halos, so that understanding halo bias is the rst step towards understanding galaxy bias. In part three of this thesis we will use a cosmological dark matter simulation to study the halo clustering and bias. More speci cally, we wonder to what extend the the local bias model could be applied to the predictions and analyses of the two and three point halo correlation functions.

Gamma-ray emission from regions of star formation: theory and first observations with the MAGIC telescope

Estado: defended (03/03/2006)
Estudiante: Eva Domingo-Santamaria
Supervisada por: Cortina, J.; Diego F. Torres
Universidad: Universitat Autònoma de Barcelona

See the link below for a full copy (there go to Fermilab Library Server).
Estado: defended (03/03/2006)
Estudiante: Eva Domingo-Santamaria
Supervisada por: Cortina, J.; Diego F. Torres
Universidad: Universitat Autònoma de Barcelona

See the link below for a full copy (there go to Fermilab Library Server).

The Friedmann cosmological models in dilatation and modified gravity and account of quantum effects.

Estado: defended (26/02/2006)
Estudiante: Yu.Shaido
Supervisada por: Sergei D Odintsov
Universidad: Tomsk State Pedagogical University

The study of Friedmann universe in modified gravity with account of quantum effects is presented. The conformal anomaly effects are taken into account. The new model of dark energy as modified gravity with ideal fluid described by equation of state with bulk viscosity is suggested. The scalar-tensor…
Estado: defended (26/02/2006)
Estudiante: Yu.Shaido
Supervisada por: Sergei D Odintsov
Universidad: Tomsk State Pedagogical University

The study of Friedmann universe in modified gravity with account of quantum effects is presented. The conformal anomaly effects are taken into account. The new model of dark energy as modified gravity with ideal fluid described by equation of state with bulk viscosity is suggested. The scalar-tensor friedmann cosmology is investigated.

Calibration, Validation and Polarimetry in 2D Aperture Synthesis: Application to MIRAS

Estado: defended (30/06/2005)
Estudiante: Serni Ribó
Supervisada por: Martín-Neira, M.; Torres, F.
Universidad: Universitat Politècnica de Catalunya

The SMOS mission of the European Space Agency (scheduled 2007) is devoted to measure Soil Moisture and Ocean Salinity, which are key parameters on the understanding of global climate change. The single instrument of this mission is the MIRAS (Microwave Imaging Radiometer using Aperture Synthesis), a…
Estado: defended (30/06/2005)
Estudiante: Serni Ribó
Supervisada por: Martín-Neira, M.; Torres, F.
Universidad: Universitat Politècnica de Catalunya

The SMOS mission of the European Space Agency (scheduled 2007) is devoted to measure Soil Moisture and Ocean Salinity, which are key parameters on the understanding of global climate change. The single instrument of this mission is the MIRAS (Microwave Imaging Radiometer using Aperture Synthesis), a new kind of instrument devoted to Earth observation. It is a thinned Y-shaped array with 21 elements per arm. With this technique a large synthetic aperture antenna with relative low weight can be obtained. This novel technique has been selected for the SMOS mission in order to fulfil both criteria ground resolution (35-50km) and revisit time (3 days). Similar instruments to MIRAS have already been used for radio astronomy but in that case only sources with a narrow angular size (stars and galaxies) were observed. In the case of MIRAS, the Earth is an extended source of thermal radiation, which almost fills up the complete field of view of MIRAS. The consequence of it is that the calibration techniques developed for radio astronomy may not be used in the SMOS mission. This thesis is mainly focused to experimentally test several calibration techniques and to prove the imaging properties of MIRAS. A second part is devoted to the polarimetric mode of MIRAS and its capability to improve its performance. This thesis was started thanks to a two year grant (from summer 2000 to summer 2002) at the ESTEC centre of the European Space Agency in the Netherlands. During this time the first experimental campaigns aimed to test calibration methods and imaging capabilities of MIRAS were done. In these so called image validation tests a first MIRAS prototype was used. The planning, preparation, execution and data processing for different tests was done. The capability of the calibration methods was demonstrated, showing also in which direction further research should be undertaken in order to refine them. The imaging properties of MIRAS were also demonstrated with the measurement of its impulsional response. The most important results are presented here. At the ESTEC centre theoretical work and simulations on polarimetric interferometry have also been done. This research contributed to the formulation of the polarimetric visibility function and the definition of the polarimetric operation mode of MIRAS. After the two years stage at ESTEC, the thesis was continued at the Laboratory of Space Technology (LST) of the Helsinki University of Technology (HUT) for three months (August 2002 to October 2002), as an invited researcher. There the HUT-2D interferometric radiometer, an airborne demonstrator instrument for MIRAS, was being constructed. The experience gained in the previous campaigns was shared with the HUT-2D team and the calibration methods were tested in a different instrument, confirming the previous results. In February 2003 this thesis was continued at the Institut d'Estudis Espacials de Catalunya (IEEC) under a research contract of the Spanish ministry of research. There the effect of Faraday rotation on MIRAS was studied. A solution for compensating it was proposed, making use of the polarimteric operation mode of MIRAS. The thesis was continued at IEEC, designing and manufacturing the Electrical Ground Support Equipment (EGSE) of an airborne demonstrator of MIRAS, known as SAM (Small Airborne MIRAS). This work was done for ESA. This instrument implements the complete calibration scheme with two-level noise injection, which is arefinement of the calibration schemes used in previous MIRAS prototypes. Preliminary experimental results of this novel calibration technique are also presented in this thesis.
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An institute of the Consejo Superior de Investigaciones Científicas
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