Since 2002 Perimeter Institute has been recording seminars, conference talks, and public outreach events using video cameras installed in our lecture theatres. Perimeter now has 7 formal presentation spaces for its many scientific conferences, seminars, workshops and educational outreach activities, all with advanced audio-visual technical capabilities. Recordings of events in these areas are all available On-Demand from this Video Library and on Perimeter Institute Recorded Seminar Archive (PIRSA). PIRSA is a permanent, free, searchable, and citable archive of recorded seminars from relevant bodies in physics. This resource has been partially modelled after Cornell University's arXiv.org.
To date, optical clocks based on singly trapped ions1) and ultracold neutral atoms trapped in the Stark-shift-free optical lattices2) are regarded as promising candidates for future atomic clocks. So far “optical lattice clocks” have been evaluated with uncertainty of 1×10-15 (ref. 3)) limited by that of Cs atomic clocks. Frequency comparison between highly-stable and accurate optical lattice clocks is, therefore, crucial for their further evaluation.
We propose new experiments with high sensitivity to a possible variation of the electron-to-proton mass ratio µ me/mp. We consider a nearly degenerate pair of molecular vibrational levels, each associated with a different electronic potential. With respect to a change in µ, the change in the splitting between such levels can be large both on an absolute scale and relative to the splitting. We demonstrate the existence of such pairs of states in Cs2, where the narrow spectral lines achievable with ultracold molecules make the system promising for future searches for small variations in µ.
We have used molecular hydrogen transitions in high quality spectra of quasars Q0403-443, Q0347-383 and Q0528-250, to search for a change in the proton-to-electron mass ratio, mu. Our improvement on previous works is twofold. Firstly, we use an improved technique to calibrate the wavelength scale of the VLT/UVES data, which reduces systematics. Secondly, we model all the hydrogen Lyman alpha transitions in the vicinity of each molecular hydrogen transition.
High precision measurements in atomic and molecular systems have reached unprecedented accuracy owing to the state-of-the-art quantum control of both light and matter. We have recently completed an evaluation of the uncertainty of our 87Sr optical lattice clock at the 1x10e-16 fractional level, surpassing the best current evaluations of Cs primary standards. By analyzing worldwide measurements of the absolute frequency of the clock transitions in Sr, we constrain temporal variations of fundamental physical constants as well as their possible couplings to the gravitational potential.
We present recent and ongoing work that uses precision frequency generation and phase measurement to test the constancy of the speed of light Local Position Invariance (LPI) and the Lorentz Invariance (LI) of the photon with respect to the Standard Model of Particle Physics under the frame work of the Standard Model Extension (SME). The first experiment consists of a pair of orthogonally orientated single crystal sapphire resonators cooled to cryogenic temperatures and configured as stable oscillators operating in Whispering Gallery Mode (Cryogenic Sapphire Oscillator).
Optical frequency standards based on forbidden transitions of trapped and laser-cooled ions have now achieved significantly higher stability and greater accuracy than primary cesium clocks. At PTB we investigate an optical clock based on the electric quadrupole transition S1/2 – D3/2 at 688 THz in the 171Yb+ ion and have shown that the frequencies realized in two independent ion traps agree to within a few parts in 1016. Results from a sequence of precise measurements of the transition frequency are now available that cover a period of seven years.
At present a number of current or proposed experiments are directed towards a search for a `new physics\' by detecting variations of fundamental physical constants or violations of certain basic symmetries. Various problems related to the phenomenology of such experiments will be considered.
I will present a brief introduction to Big Bang Nucleosynthesis theory and observation. I will then discuss BBN as a probe of hadronic mass variation in the very early universe, including comparison with the observed Li7 discrepancy. Finally I want to explore the possibility of overproducing Li6 by three orders of magnitude in order to match reported observations.