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.
Motivated by recent numerical and experimental studies of the spin-1/2 Heisenberg antiferromagnet on kagome, we formulate a many-body model for fermionic spinons, which are just uncoupled spins. The spinons interact with an emergent U(1) gauge field and experience strong short-range attraction in the S=0 channel. The ground state of the model is generically a Z(2) liquid. We calculate the edge of the two-spinon continuum and compare the theory to the slave-fermion approach to the Heisenberg model.
Realizing experimentally continuous phase transitions in the electronic ground state of materials near zero temperature as a function of tuning some external parameter (magnetic field, pressure etc.) offers a unique opportunity to probe the extreme regime (near the transition point) where strong quantum correlations encompass the macroscopic sample as a whole, so called “quantum criticality” . In this regime of strong correlations small perturbations/interactions can stabilize novel forms order or collective fluctuations that otherwise do not exist.
In one extreme, where the interactions
are sufficiently weak compared to the interactions, electrons form a “Fermi
liquid” – the state that accounts for the properties of simple metals. In the other extreme, where the interactions
are dominant, the electrons form various “Mott” insulating or “Wigner
crystalline” phases, often characterized by broken spatial and/or magnetic symmetries. Corresponding charge and/or magnetically
ordered insulating phases are common in nature.
I will present recent work,
done in collaboration with Daniel Roberts, on the global memory of initial
conditions that is sometimes, but not always, retained by fluctuating fields on
de Sitter space, Euclidean anti de Sitter space, and regular infinite trees. I
will discuss applications to the structure of configuration space in de Sitter
space and eternal inflation.