U(N) and holomorphic methods for LQG and Spin Foams

The U(N) framework and the spinor representation for loop quantum gravity are two new points of view that can help us deal with the most fundamental problems of the theory. Here, we review the detailed construction of the U(N) framework explaining how one can endow the Hilbert space of N-leg intertwiners with a Fock structure. We then give a description of the classical phase space corresponding to this system in terms of the spinors, and we will study its quantization using holomorphic techniques. We take special care in constructing the usual holonomy operators of LQG in terms of spinors, and in the description of the Hilbert space of LQG with the different polarization given by these spinors.Comment: 16 pages. Proceedings for the 3rd Quantum Geometry and Quantum Gravity School in Zakopane (2011

The continuous star formation history of a giant HII region in M101

We present results about the star formation process in the giant HII region NGC 5471 in the outskirts of M101. From resolved HST/WPFC2 photometry we find that star formation has been going for the last 70 Myr. We further compare previous results from integrated infrared-optical photometry with the stellar resolved CMD and we discuss the star formation properties of this region and its individual knots, as well as characterizing the different stellar content. This result has very important consequences in our understanding of the burst versus continuous star formation activity in spiral galaxies.Comment: 2 pages, 2 figures. Proceeding of the conference From Stars to Galaxies: Building the pieces to build up the Universe (Venice, Italy

Litoestratigrafia del Carbonifero del Altiplano de Bolivia

Se presenta aqui una nueva subdivision de las unidades litoestratigraficas formales del Carbonifero del Altiplano de Bolivia, de acuerdo con la informacion reciente disponible sobre la sedimentologia, estratigrafia secuencial, correlacion bioestratigrafica (palinologia y conodontos) y revision de sus limites: El grupo Ambo (Fameniano Superior a Viseano) incluye las siguientes unidades: Formacion Diamicitas de Cumana, Formacion Areniscas y Lutitas de Kasa y Formacion Lutitas y Areniscas con Carbones de Siripaca. Una discontinuidad cartografica de caracter erosivo del Carbonifero Medio separa este grupo de las siguientes unidades del Carbonifero Superior del Grupo Titikaka: Formacion Areniscas de Yaurichambi y Formacion Calizas, Areniscas y Margas de Copacabana (Résumé d'auteur)

Interfacial tension behavior of binary and ternary mixtures of partially miscible Lennard-Jones fluids: a molecular dynamics simulation

By means of extensive equilibrium molecular dynamics simulations we have investigated, the behavior of the interfacial tension $\gamma$ of two immiscible symmetrical Lennard-Jones fluids. This quantity is studied as function of reduced temperature $T^{*}={{k_{_B} T}\over \epsilon}$ in the range $0.6 \leq T^{*} \leq 3.0$. We find that, unlike the monotonic decay obtained for the liquid-vapor interfacial tension, for the liquid-liquid interface, $\gamma (T)$ has a maximum at a specific temperature. We also investigate the effect that surfactant-like particles has on the thermodynamic as well as the structural properties of the liquid-liquid interface. It is found that $\gamma$ decays monotonically as the concentration of the surfactant-like particles increases.Comment: LaTeX-Revtex file with 7 encapsulated postscript figures. Accepted for publication in Journal of Chemical Physic

Inflight magnetic characterization of the test masses onboard LISA Pathfinder

LISA Pathfinder is a science and technology demonstrator of the European Space Agency within the framework of its LISA mission, the latter aiming to be the first space-borne gravitational wave observatory. The payload of LISA Pathfinder is the so-called LISA Technology Package, which is designed to measure relative accelerations between two test masses in nominal free fall. The diagnostics subsystem consists of several modules, one of which is the magnetic diagnostics unit. Its main function is the assessment of the differential acceleration noise between the test masses due to magnetic effects. This subsystem is composed of two onboard coils intended to produce controlled magnetic fields at the location of the test masses. These magnetic fields couple with the remanent magnetic moment and susceptibility and produce forces and torques on the test masses. These, in turn, produce kinematic excursions of the test masses which are sensed by the onboard interferometer. We prove that adequately processing these excursions, the magnetic properties of the test masses can be estimated using classical multi-parameter estimation techniques. Moreover, we show that special processing procedures to minimize the effect of the multi channel cross-talks are needed. Finally, we demonstrate that the quality of our estimates is frequency dependent. We also suggest that using a multiple frequency experiment the global estimate can be obtained in such a way that the results of the magnetic experiment are more reliable. Finally, using our procedure we compute the the contribution of the magnetic noise to the total proof-mass acceleration noise.Comment: 12 pages, 7 figures, Physical Review D, accepted on Feb 6th, 201

Diseño de filtros planares para radiometría

Diseño de tres prototipos de filtros para apliaciones de radiometría (LICEF) -Filtro microstrip de orden 6, con dos ceros de transmisión. Síntesis de filtros sin pérdidas. -Filtro microstrip asíncrono de orden 6, con un cero de transmisión. Síntesis de filtros sin pérdidas -Filtro microstrip de orden 6 , con dos ceros de transmisión. Síntesis por técnicas avanzadas de filtros con pérdidas. Procedimiento: -Anális de resonadores sobre diferentes dieléctricos -Síntesis a partir de matriz de acoplamientos -Simulación con ADS -Simulación con Momentum -Comparación de prototipo