Search Talks

Over the coming decade, tiny fluctuations in temperature and polarization of the Cosmic Microwave Background (CMB) will be mapped with unprecedented resolution. The Planck Surveyor, the Atacama Cosmology Telescope (ACT), and the South Pole Telescope (SPT) are already making great advances. In a few years, high resolution polarization experiments, such as PolarBear, ACTPol, and SPTPol will be in full swing. While these new arc-minute resolution observations will continue to help constrain the physics of the early universe, they will also be unique in a new way - they will allow us to measure the gravitational lensing of the CMB, i.e., the deflection of CMB photons by intervening large scale structure. CMB lensing will probe the growth of structure over cosmic time, helping constrain the total mass of neutrinos and the behavior of dark energy. In the first part of the talk, I will review the recent progress made with ACT, a powerful tool with new capabilities. In the second part, I will discuss the scientific potential of the CMB lensing signal, and its various applications in cross-correlation with other datasets. Finally, I will discuss the upcoming polarized counterpart of ACT --- the ACTPol project, which will have sixteen times better mapping speed than ACT, and will be a premier CMB lensing experiment. I will describe our plans to extract different flavors of science from the ACTPol data, including the cross-correlations with optical lensing and galaxy surveys, such as SDSS, BOSS, DES and LSST.

Although the fact that a large fraction of the matter in the universe is non-baryonic is beyond doubt, the exact composition of the dark matter is still shrouded in mystery. Using ultra-sensitive detectors in the deep underground laboratories, physicists are attempting to directly detect dark matter particles streaming from space. At colliders, physicists hope to manufacture large numbers of dark matter particles and study their properties. I will first use an effective field theory approach to demonstrate the power of colliders by comparing these two approaches. I will then describe the recent efforts on measuring dark matter properties at colliders and how imminent discoveries may change our fundamental understanding of physics and the universe.

We consider one dimensional devices supporting a pair of Majorana bound states at their ends We firstly show [1] that edge Majorana bound modes allow for processes with an actual transfer of electronic material between well-separated points and provide an explicit computation of the tunnelling amplitude for this process. We then show [2] that these devices can produce remarkable Hanbury-Brown Twiss like interference effects between well separated Dirac fermions of pertinent energies: we find indeed that, at these energies, the simultaneous scattering of two incoming electrons or two incoming holes from the Majorana bound states leads exclusively to an electron-hole final state. This "anti-bunching" in electron-hole internal pseudospin space can be detected through a measure of current-current correlations. Finally, we show [2] that, by scattering appropriate spin polarized electrons from the Majorana bound states, one can engineer a non-local entangler of electronic spins useful for quantum information applications. [1] G. W. Semenoff and P. Sodano: J. Phys. B: At. Mol. Opt. Phys. 40, 1479 (2007); [2] S. Bose and P. Sodano: “Non-local Handbury- Brown Twiss Interferometry & Entanglement Generation from Majorana

More than any thing else technology creates our world. It creates our wealth, our economy, our very way of being," says W. Brian Arthur. Yet, until now major questions related to the evolution of technology have gone unanswered. Where do new technologies come from -- how exactly does invention work? What constitutes innovation, and how is it achieved? Why are certain regions -- Cambridge, England, in the 1920s and Silicon Valley today -- hotbeds of innovation, while others languish? Does technology, like biological life, evolve? How do new industries, and the economy itself, emerge from technologies? In this talk, leading thinkers Lee Smolin, Frances Westley, and Thomas Homer-Dixon discuss economist W. Brian Arthur's work on a boldly original way of thinking about technology that gives answers to these questions.