Friday. Told Mayumi about Aaron. I thought I gave a nice talk yesterday, but today, I am not so sure. Being tired in the middle of a talk is not a good thing to do--must keep energy up during the talk.
1110.5514
Three QSOs acting as strong gravitational lenses
Courbin, Faure, Djorgovski, Rerat, Tewes, Meylan, Stern, Mahabal, Boroson, Dheeraj, Sluse
Found in SDSS, host galaxy masses comparable to the SLACS sample of early-type strong lenses.
1110.5528
Probing dark energy with Alpha shapes and Betti numbers
van de Weygaert, Pranav, Jones, Bos, Vegter, Edelsbrunner, Teillaud, Hellwing, Park, Hidding, Wintrraecken
Weblike patter in the distribution of galaxies and matter: scale dependent Betti numbers (formalize the topological information content of the cosmic mass distribution. Does not fully quantify topology, but extends the information beyond genus and Euler characteristic. Richer information, availability of fast algorithms to calculate them). When measured as a function of scale, they provide a "Betti signature" for a point distribution that is a sensitive yet robust discriminator of structure. Highly effective in revealing differences in structure arising in different cosmological models, and is exploited towards distinguishing between different dark energy models and may likewise be used to trace primordial non-Gaussianities.
MPIfR Lunch Colloquium (Nov. 2, 13:00)
Geodetic VLBI and the 100m telescope
Axel Nothnagel
* Geodesy: branch of mathematic dealing with the shape and area of the earth, or large portions of it.
Primary results of geodetic and astrometric VLBI observations: radio telescope coordinates, earth rotation variations, and quasar positions. Networks of radio telescope simultaneously observe quasars and other extra-galactic radio sources recording the noise patterns emitted by the radio sources. Geodesists observe many quasars repeatedly for only 40-200 seconds each. Recordings employed to determine group delay observables in a correlation and fringe fitting process. Data analysis provides variety of highly precise and unique geodetic, geophysical and astrometric results. Radio source positions define a quasi-inertial reference frame, the only one which is available today. Radio telescope coordinates and velocities are used to establish and maintain a terrestrial reference from for geodetic and geophysical studies. Studies of tectonic stability in central Europe studied with Effelsburg 100m telescope. The enormous size of the telescope requires a detailed analysis of its deformation characteristics.
1110.5738
Self-similar dynamical relaxation of dark matter haloes in an expanding universe
Lapi, Cavaliere
Advanced model of spherical collapse and accretion in an expanding Universe--investigate structure of CDM haloes. Based on solving time-dependent equations for the moments of the phase-space distribution function in the fluid approximation; approach includes non-radial random motions, and an advanced treatment of both dynamical relaxation effects that takes place in the infalling matter: (1) phase-mixing associated to shell crossing, and (2) collective collisions related to physical clumpiness. Find self-similar solutions for the spherically-averaged profiles of mass density rho(r), pseudo phase-space density Q(r) and anisotropy parameter beta(r). Profiles agree with the outcomes of state-of-the-art N-body simulations in the radial range currently probed by the latter; provide specific predictions at smaller radii. With the self-similar solutions, link the halo structure to its two-stage growth history, and propose the following picture: During the early fast collapse of the inner region dominated by a few merging clumps, efficient dynamical relaxation plays a key role in producing a closely universal mass density and pseudo phase-space density profiles; these are found to depend only weakly on the detailed shape of the initial perturbation and the related collapse times. The subsequent inside-out growth of the outer regions feeds on the slow accretion of many small clumps and diffuse matter; thus the outsckirts are only mildly affected by dynamical relaxation but are more sensitive to asymmetries and cosmological variance.
* Sounds like it agrees with Neal Delal's halo picture (I want to compare them!).
1110.5634
Conceptual problems in cosmology
Vieira
How could philosophy help cosmologists? Knowledge-building in cosmology should begin with visions of the reality, then taking technical form whenever concepts and relations in between are translated into a mathematical structure. Mandatory that the meaning of such concepts be the same for all cosmologists, and any relationship among all of them be tested both logically as well as mathematically. In other words, improbability of our universe assures to cosmologists a privileged degree of freedom for formulating interpretations and theories. At the same time, demands for their formulations and conclusions to be considered in the light of data taken from astrophysical observations [i.e., actual, real-life data].
* Are they stating the obvious? (given that I didn't transcribe the first-half of this abstract...)
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