Search results from PIRSA
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Simulating the Capture and Translocation of Rigid fd Viruses though a Nanopore
Hendrick de Hann University of Ontario Institute of Technology
PIRSA:14050036 -
Recent advances in the search for complementary sequences
Ilias Kotsireas Wilfrid Laurier University
PIRSA:14050040 -
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Anomalies of discrete symmetries and Symmetry Protected Topological Phases
Anton Kapustin California Institute of Technology (Caltech) - Division of Physics Mathematics & Astronomy
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Noncommutative geometry and the symmetries of the standard model
Fedele Lizzi University of Naples Federico II
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The Case for an Alternative Cosmology
Jayant Narlikar IUCAA - The Inter-University Centre for Astronomy and Astrophysics
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John Paul Robinson: Art, Science and Myth
PIRSA:14050062 -
Physics, Logic and Mathematics of Time
Louis Kauffman University of Illinois at Chicago
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Frozen Spin Ice Ground States in the Pyrochlore Magnet Tb2 Ti2 O7
Bruce Gaulin Canadian Association of Physicists
PIRSA:14050019 -
Measurements of Noice in Condensed Matter Systems Using Superconducting Qubits and Resonators
Adrian Lupascu Institute for Quantum Computing (IQC)
PIRSA:14050018
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HPC Application in Large Eddy Simulation of Fuel Spray / Air Jet interaction
PIRSA:14050046Along with the development of computational resources computational fluid dynamics (CFD) has evolved in resolving the finest length scales and smallest time scales of the flow. Direct numerical simulation (DNS) resolves the finest flow scales known as Kolmogorov length scales which are responsible for the dissipation of the energy transferred from the large and intermediate length scales. However DNS simulations are computationally costly and demand very powerful resources which are not widely available to this day. Large eddy simulation (LES) is a more feasible tool to resolve the large flow scales and model the sub-grid scales using a Reynolds averaged modeling. High performance computing tools make it possible to perform high fidelity large eddy simulations which reasonably (almost twelve times the Kolmogorov length scale) resolve the flow structures.In the present study large eddy simulation is utilized to simulate interaction of a high speed compressible round air jet with a group of sprays injected from a six-hole nozzle injector into the shear layer of the air jet. Fuel sprays are injected with 10 and 15 MPa injection pressures in the jet cross flows of 125 and 215 m/s. Simulations are performed using 64 processors and 240 GB of memory. The focus of the study is on the spray atomization assisted by air jet cross-flow. Consequent processes of fuel/air mixing are also investigated by focusing on the role of vortical structures resolved using large eddy simulation. -
New insights into polymer-induced drag reduction in turbulent flows
PIRSA:14050041Polymer additives are known to cause significant reduction in turbulent friction drag and reduce the energy dissipation rate of fluid transport. This effect is however bounded by a universal upper limit the maximum drag reduction (MDR) asymptote that does not change with polymer properties. Understanding MDR remains an important unsolved problem in the areas of turbulence and non-Newtonian fluid mechanics. Dynamical trajectories on the boundary in state space between laminar and turbulent plane channel flow - edge states - are computed for Newtonian and viscoelastic fluids. Viscoelasticity has a negligible effect on the properties of these solutions and at least at a low Reynolds number their mean velocity profiles correspond closely to experimental observations for polymer solutions in the MDR regime. These results confirm the existence of weak turbulence states that cannot be suppressed by polymer additives explaining the fact that there is an upper limit for polymer-induced drag reduction. -
Simulating the Capture and Translocation of Rigid fd Viruses though a Nanopore
Hendrick de Hann University of Ontario Institute of Technology
PIRSA:14050036The passage of long biological molecules from one side of a membrane to the other through a nanoscale hole has been the subject of intense research in recent years. Motivated by the possibility of new sequencing technologies the focus of this work has been studying the translocation of DNA across biological and synthetic membranes. In this talk I will present results from a joint experimental-simulation study examining the translocation of rod-like fd viruses through a nanopore. While DNA is relatively flexible the fd virus has a persistence length that is over twice that of its contour length and is thus stiff. In principle translocation in this rod-like limit is much easier to model. However I will show that experimental results for the distribution of translocation times exhibit significant deviations from the expected result. I will present a model for fd translocation that was developed to probe these results. Simulations based on this model yield insight into previously unclear experimental results including i) details of how the polymer is capture by the pore at different external fields ii) a correlation between the translocation time and the conformation at capture and iii) sources for the increased dispersion in the translocation time distributions. -
Recent advances in the search for complementary sequences
Ilias Kotsireas Wilfrid Laurier University
PIRSA:14050040We will present recent developments in the search for complementary sequences namely new theoretical and algorithmic progress. SHARCNET resources are used quite heavily in this project. -
Scattering of emerging excitations in Matrix Product States
Jutho Haegeman Ghent University
We review the formalism of matrix product states and one of its recent generalisations which allows to variationally determine the dispersion relation of elementary excitations in generic one-dimensional quantum spin chains. These elementary excitations dominate the low energy effective behaviour of the system. We discuss recent work where we show how we can also describe the effective interaction between these excitations – as mediated by the strongly correlated ground state – and how we can extract the corresponding S matrix. With these two ingredients, we can already build a highly non-trivial low-energy description of any microscopic Hamiltonian by assuming that higher order scattering processes are negligible. This allows to extract accurate information about the behaviour of the system under perturbations or at finite temperature, as we illustrate using the spin 1 Heisenberg model. -
Anomalies of discrete symmetries and Symmetry Protected Topological Phases
Anton Kapustin California Institute of Technology (Caltech) - Division of Physics Mathematics & Astronomy
There is a close connection between Symmetry Protected Topological Phases and anomalies: a surface of an SPT phase typically has a global symmetry with a nonvanishing 't Hooft anomaly which is canceled by the anomaly inflow from the bulk. This observation together with the known results about the classification of SPT phases suggest that anomalies are much more ubiquitous than thought previously and do not require chiral fermions We elucidate the physical mechanism of anomalies and give examples of bosonic theories with 't Hooft anomalies in various dimensions. -
Noncommutative geometry and the symmetries of the standard model
Fedele Lizzi University of Naples Federico II
I will describe Connes approach to the standard model based on spectral noncommutative geometry with particular emphasis on the symmetries. The model poses constraints which are satisfied by the standard model group, and does not leave much room for other possibilities. There is however a possibility for a larger symmetry (the ``grand algebra'') which may also be instrumental to obtain the correct mass of the Higgs. -
The Case for an Alternative Cosmology
Jayant Narlikar IUCAA - The Inter-University Centre for Astronomy and Astrophysics
This talk will describe the Quasi-Steady State Cosmology proposed in 1993 by Fred Hoyle, Geoffrey Burbidge and Jayant Narlikar. Starting with the motivation for this exercise, a formal field theoretic framework inspired by Mach’s principle is shown to lead to this model. The model is a generalization of the classical steady state model in the sense that it is driven by a scalar field which causes creation in explosive form. Such ‘minicreation events’ lead to a universe with a long term de Sitter expansion superposed with oscillations of shorter time scales. It is shown that this cosmology explains all the observed cosmological features and that there exist potential tests to distinguish between this cosmology and the standard big bang cosmology. -
John Paul Robinson: Art, Science and Myth
PIRSA:14050062Canadian glass artist and Renaissance man, John Paul Robinson, explores the mythic potential of science. Explaining that, “This is the idea that scientific discovery is changing our mythology by changing our understanding of the world and our place in it.” Backed with a firm understanding of the science he references, his sculptures poetically interpret such theoretical phenomena as wave particles, string mathematics and black holes. Most people, especially scientists see mythology and science as mutually exclusive and many believe that a scientific understanding of the world will eventually eliminate the need for myth. This idea is based on a misunderstanding as to what myth really is and it’s relationship to science. Myth is not superstition, fairy tail or lies nor is it truth, history or fact. Myth is Art. Myth is a picture, a story, a map; we use to navigate the world. Not the external material world but the world we all create and hold in our minds. In every human mind is a mythic picture of the world that provides the stage for all we experience. This picture not only helps us navigate our world but also performs the critical function of informing our sense of place and belonging within that world. Science cannot replace myth but it can inform it for mythology deals not with the mysteries generated by our ignorance of how the world works but by our understanding of how the world works. The mathematics of string theory is a powerful tool to describe the world but even physicists have to close their eyes and picture in their minds the world their equations are describing. The equation is pure logic and reason, but the picture of tiny strings playing the music that creates the universe is pure mythology. Award-winning glass artist and instructor John Paul Robinson was educated at the Georgian College of Arts and Technology in Barrie, Ontario, and the Ontario College of Art, where he subsequently taught for a number of years. His work has been exhibited in solo shows throughout Canada and the United States, in cities such as Montreal, Toronto and Chicago. Robinson’s works are held in the collections of The Museum of Civilization in Ottawa, Ontario, the Museum of American Glass in Millville, New Jersey and the Musée des Beaux-arts de Montréal, Québec. He has also created the Amber Archive, an annual participatory art project to communicate our existence and creative endeavours (by artists, designers and scientists) to beings millions of years in the future. -
Physics, Logic and Mathematics of Time
Louis Kauffman University of Illinois at Chicago
Consider discrete physics with a minimal time step taken to be
tau. A time series of positions q,q',q'', ... has two classical
observables: position (q) and velocity (q'-q)/tau. They do not commute,
for observing position does not force the clock to tick, but observing
velocity does force the clock to tick. Thus if VQ denotes first observe
position, then observe velocity and QV denotes first observe velocity,
then observe position, we have
VQ: (q'-q)q/tau
QV: q'(q'-q)/tau
(since after one tick the position has moved from q to q').
Thus [Q,V]= QV - VQ = (q'-q)^2/tau. If we consider the equation
[Q,V] = k (a constant), then k = (q'-q))^2/tau and this is recognizably
the diffusion constant that arises in a process of Brownian motion.
Thus, starting with the simplest assumptions for discrete physics, we are
lead to recognizable physics. We take this point of view and follow it
in both physical and mathematical directions. A first mathematical
direction is to see how i, the square root of negative unity, is related
to the simplest time series: ..., -1,+1,-1,+1,... and making the
above analysis of time series more algebraic leads to the following
interpetation for i. Let e=[-1,+1] and e'=[+1,-1] denote, as ordered
pairs, two phase-shifted versions of the alternating series above.
Define an operator b such that eb = be' and b^2 = 1. Regard b as a time
shifting operator. The operator b shifts the alternating series by one
half its period. Regard e' = -e and ee' = [-1.-1] = -1 (combining term by
term). Then let i = eb. We have ii = (eb)(eb) = ebeb = ee'bb = -1. Thus ii = -1
through the definition of i as eb, a temporally sensitive entity that
shifts it phase in the course of interacting with (a copy of) itself.
By going to i as a discrete dynamical system, we can come back to the
general features of discrete dynamical systems and look in a new way at
the role of i in quantum mechanics. Note that the i we have constructed is
already part of a simple Clifford algebra generated by e and b with
ee = bb = 1 and eb + be = 0. We will discuss other mathematical physical
structures such as the Schrodinger equation, the Dirac equation and the
relationship of a simple logical operator (generalizing negation) with
Majorana Fermions. -
Frozen Spin Ice Ground States in the Pyrochlore Magnet Tb2 Ti2 O7
Bruce Gaulin Canadian Association of Physicists
PIRSA:14050019Tb2Ti2O7 was one of the first pyrochlore magnets to be studied as a candidate for a spin liquid or cooperative paramagnet, and its ground state has remained enigmatic for fifteen years. Recent time-of-flight neutron scattering studies have shown that it enters a glassy Spin Ice ground state, characterized by frozen short range order over about 8 conventional unit cells, and the formation of a ~ 0.08 meV gap in its spin excitation spectrum at the appropriate quasi-Bragg wave vectors. I will introduce the relevant Spin Ice physics background, and describe how the experiments are performed. The new H-T phase diagram for Tb2Ti2O7 in a [110] magnetic field will be presented. This shows that its frozen (i.e. glassy) Spin Ice ground state (at low temperature and zero field) and its conventional field-induced ordered phase (at low temperature and high fields) bracket the cooperative paramagnetic phase which generated the original interest in this fascinating magnet. -
Measurements of Noice in Condensed Matter Systems Using Superconducting Qubits and Resonators
Adrian Lupascu Institute for Quantum Computing (IQC)
PIRSA:14050018Superconducting qubits based on Josephson junctions and resonators are presently leading candidates for the implementation of quantum computing. These systems couple strongly to their environment, which often makes preservation of coherence challenging. This strong coupling can be turned into an advantage: it enables the investigation of noise and loss at low temperatures. I will discuss two topics. The first topic is the use of superconducting flux qubits to measure magnetic flux noise. The second topic is the measurement of microwave loss in amorphous dielectric materials. Experiments with superconducting coherent systems can be used to extract new information on flux noise and dielectric loss, not accessible using other methods used in the past, providing useful input to theoretical developments.