Jan 26

"Optimising the next generation of Dark Energy Surveys"
David Parkinson, University of Sussex, England

"The next generation of large scale surveys will provide us with far greater constraints on the nature of the dark energy. Given the large investment such experiments require, it is important to design such experiments to give the best possible scientific return. In this talk I will outline the techniques of optimising such surveys, with particular regard to WFMOS (the Wide-field Multi-object Spectrograph), a next generation experiment designed to probe the dark energy through measurements of the Baryon Acoustic Oscillations."

Feb 02

"Weak Lensing and Large Scale Structure"
Jun Zhang, University of California, Berkeley

"In the first part of my talk, I will introduce a simple and efficient way of measuring the cosmic shear from galaxy shapes in weak lensing. The method is mathematically simple, well defined regardless of the morphologies of the galaxy and the point spread function. It allows us to probe weak lensing effects on galaxy substructures, thereby improving the signal-to-noise ratio significantly. It also enable us to remove the systematic errors due to the photon noise and the pixelation effect in the shear measurement. In the second part of my talk, I will briefly talk about the most recent progresses we have achieved in understanding how to generate dark matter halo merger histories consistently based on the Extended Press-Schechter theory."

Feb 23

"Primordial Non-Gaussianity from Preheating"
Andrei Frolov, Simon Fraser University, Canada

"The idea of inflation (a period of rapid quasi-exponential expansion of the Universe) neatly solves several issues in cosmology. While the Universe is inflating, its contents is cold. Eventually, inflation ends and the field driving the inflation must decay, depositing energy into high-energy particles. This process, known as reheating, starts the hot big bang history as we know it. I will discuss a few scalar field models of reheating, which for all their simplicity have rich physics involving parametric resonance, non-linear evolution, and turbulence, and illustrate their dynamical behavior with simulations using a new numerical solver I developed. Most interestingly, preheating can create primordial non-Gaussian fluctuations at potentially observable levels, which could give a glimpse of physics at energies we know very little about."

Mar 09

"Testing Gravity with Gravitational Lensing and Dynamics"
Bhuvnesh Jain, University of Pennsylvania

"Modifications of general relativity provide an alternative explanation to dark energy for the observed acceleration of the universe. Modified gravity theories have richer observational consequences for large-scale structure than conventional dark energy models - for example, how perturbations affect light rays and galaxy dynamics differs from general relativity. In this talk, I will introduce gravitational lensing and its recent applications such as lensing tomography. I will then discuss tests of gravity from kpc-Gpc scales using dynamics, lensing and redshift space probes of large-scale structure."

Apr 21

"Do Halo Mergers Trigger Quasars?"
Jorge Moreno, Haverford College, Haverford, Pennsylvania

"Understanding the growth of supermassive black holes at the center of most galaxies is a quite interesting challenge today. It is believed that their growth is enhanced by galaxy mergers, in which cold gas is driven to the center of the remnant. We present an analytic model where quasars are triggered by major mergers of dark matter haloes. Theoretical merger rates beyond the standard EPS prescription, and compatible with the Millennium Simulation, are used. The impact of mergers on the luminosity function is discussed, along with the impact of varying the accretion parameters involved. Shutdown at low redshifts is addressed as well."