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.
I will present recent and ongoing work in collaboration with Tsutomu Yanagida and Simeon Hellerman (arXiv:1309.0692 and 1312.xxxx) on a new way to obtain charge quantization, without a GUT or monopole solution. In the CP^1 model, SU(2)_G/U(1)_H, consistency conditions for a charged field and its transformation properties over the entire group manifold lead to a charge quantization condition. By gauging the U(1)_H and identifying it with hypercharge, we find charge quantization in the SM without a monopole or GUT, purely from the structure and dynamics of the nonlinear sigma model.
Quantum spin liquid (QSL) is an exotic phase of matter and provides an interesting example of emergent non-locality. Even though many materials have been proposed as candidates for QSLs, there is no direct confirmation of QSLs in any of these systems. Quantum spin ice (QSI) is a physical realization of U(1) QSLs on the pyrochlore lattice. We consider a class of electron systems in which dipolar-octupolar Kramers doublets arise on the pyrochlore lattice. In the localized limit, the Kramers doublets are described by the effective spin 1/2 pseudospins.
The increasing demand for antibiotics has contributed to the investigation of possible novel antibiotics by many researchers. For this purpose experimental and theoretical studies have been carried out to draw scientists' attention to antimicrobial peptides and their interaction with the surface of bacterial membranes. Their ability to disrupt the functioning of bacterial membranes has been probed from different perspectives. The most desirable antimicrobial peptides are those which do not harm plant or animals' membranes but which disrupt bacterial membranes.
As an extension to previous ab initio studies on water  we present 400 psBorn-Oppenheimer ab initio Molecular dynamics study on water at deep supercooled temperatures (down to 220 K) and confirm a crossover from a fragile to strongliquid around the Widom line. This crossover is accompanied by the passage from relatively weaker hydrogen bonds in the dominantly high density liquid (HDL) at high temperatures to strong hydrogen bond in dominantly low density liquid (LDL).
Monte Carlo simulation is used to study the structural properties of the system consisting of a self-avoiding polymer chain confined between a fluid membrane and a flat hard surface. As the adhesion between the soft membrane and the hard-wall surface increases the polymer is subject to a strong confinement; a pancake-shaped polymer conformation state eventually yields to a bud state through an abrupt first-order phase transition.
By including composition fluctuations in our dynamical simulation of the time-dependent Landau-Brazovskii model for a diblock copolymer melt we find that disordered micelles form above the order-disorder transition to a BCC phase. At high-temperatures the micelle number density and volume fraction are effectively zero and the melt is disordered at the molecular level. As we lower the temperature the micelle number density increases gradually and approaches the number density in the BCC phase.
Recent experimental work  suggests that the increased motility of cancer cells observed in a confluent monolayer of normal cells is due to the mechanical mismatch between the two cell types. The soft cancer cell undergoes large deformations and can squeeze between small channels defined by the space between the normal cells. We developed a phase-field model description of cellular monolayers to study such a process. The system is setup as a free-boundary problem where each cell is a highly deformable soft body .
Although a few of very promising methods now exist for extracting free energy profiles of a many-body system from non-equilibrium work performed on it the implementation of these methods have proven to be non-trivial. These methods (most notable of all the Jarzynski equality the FR method and the Brownian dynamic FDT) typically require a proper sampling of the work performed on the system along many trajectories in the available phase space that connect the desired initial and final macrostates.
Tissue topology such as proliferating epithelium topology shows striking similarities for various species. Thissuggests unified mechanism for tissue formation which can be explored with the help of physical or mathematicalmodels. Indeed it has been shown that cell divisions along with local cell rearrangements can reproduce commonlyobserved epithelium topology by using topological models.Tightly packed cells in epithelium resemble polygons. This observation gave rise to models where cells aretreated as polygons in junctional network.