Search Talks

I describe a number of techniques that allow for the generation of (near) scale-invariant fluctuations in the early Universe without inflation or ekpyrosis. The basic ingredient is a decaying maximal speed of propagation, for which a Universal law is found. Connections are made with k-essence, the cuscaton, and the DBI action. However the simplest realizations result from bimetric theories and deformed dispersion relations and DSR. A number of implications to theories of quantum gravity are discussed.

The uncertainty in the equation of state of cold matter above nuclear density is notorious. Despite four decades of neutron-star observations, recent observational estimates of neutron-star radii still range from 8 to 16 km; the pressure above nuclear density is not known to better than a factor of 5; and one cannot yet rule out the possibility that the ground state of cold matter at zero pressure might be strange quark matter -- that the term "neutron star" is a misnomer for strange quark stars. The last few orbits of binary inspiral are sensitive to the stars' distortion, and a major goal of the next generation of gravitational wave detectors is to extract parameters characterizing the high-density equation of state from inspiral waveforms. This talk reports a first study that uses numerical simulations to estimate the accuracy with which the equation of state can be measured.

The Background Imager of Cosmic Extragalactic Polarization (BICEP) experiment is the first polarimeter developed to measure the inflationary B-mode polarization of the CMB. During three seasons of observing at the South Pole, Antarctica beginning in 2006, BICEP mapped 2% of the sky chosen to be clean of polarized foreground emission, with sub-degree resolution. In this colloquium I will present initial results derived from a subset of the data acquired during the first two years of data and discuss the unique design features of BICEP which led to the first meaningful limits on the tensor-to-scalar ratio to come from B-mode polarization. Recently, Xia, Li & Zhang (2009) have claimed a detection of parity-violating "cosmic birefringence" effects using publicly available BICEP data. I will discuss polarimetric fidelity in the light of systematic errors and how such effects are particularly pernicious for probes of cosmic parity violation. I will conclude with a discussion demonstrating how BICEP, and its successor "BICEP2" will inform future measurements of the inflationary gravitational wave background and cosmic birefringence.

I will present recent work [1] on preparation by measurement of Greenberger–Horne–Zeilinger (GHZ) states in circuit quantum electrodynamics. In particular, for the 3-qubit case, when employing a nonlinear filter on the recorded homodyne signal the selected states are found to exhibit values of the Bell–Mermin operator exceeding 2 under realistic conditions. I will discuss the potential of the dispersive readout to demonstrate a violation of the Mermin bound, and present a measurement scheme avoiding the necessity for full detector tomography. [1] Lev S Bishop et al 2009 New J. Phys. 11 073040

In addition to its ability to probe Inflation, CMB polarization offers the intriguing possibility to detect CP-symmetry violation. In some sense these predictions, if true, would be more surprising than confirmation of the inflationary paradigm -- for which ample, albeit circumstantial, evidence already exists. Moreover, recent theoretical predictions imply that, not only are parity violating CMB polarization effects possible, but that they have already been detected at 3\sigma confidence levels in existing polarization data. I will present a worked example showing the impact of experimental systematic effects on such measurements, and present a robust test to help determine the veracity of the theoretical predictions. I will show that the CP-symmetry violating observables are more susceptible to certain systematic effects, and discuss the future prospects for such CMB polarization probes of fundamental physics.