Search Talks

Search results from PIRSA

9541 - 9552 of 16421 Results

Acceleration, Then and Now

Cliff Burgess McMaster University
December 03, 2013

PIRSA:13120059
Astrophysics
Cornering Gluinos at the LHC

Jared Evans Rutgers University
December 02, 2013

PIRSA:13120057
High Energy Physics
13/14 PSI - Condensed Matter - Lecture 15
- Anushya Chandran Perimeter Institute for Theoretical Physics
- Roger Melko University of Waterloo
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
November 29, 2013

PIRSA:13110045
13/14 PSI - Quantum Field Theory II - Lecture 15

Francois David CEA Saclay

November 29, 2013

PIRSA:13110026
General Relativity for Cosmology - Lecture 22

Achim Kempf University of Waterloo

November 28, 2013

PIRSA:13110007
Divergences in Spinfoam Quantum Gravity

Aldo Riello Perimeter Institute for Theoretical Physics
November 28, 2013

PIRSA:13110063
General Relativity & Quantum Cosmology
Collisions in AdS and the thermalisation of heavy-ion collisions

Wilke van der Schee European Organization for Nuclear Research (CERN)
November 28, 2013

PIRSA:13110089
General Relativity & Quantum Cosmology
13/14 PSI - Condensed Matter - Lecture 14
- Anushya Chandran Perimeter Institute for Theoretical Physics
- Roger Melko University of Waterloo
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
November 28, 2013

PIRSA:13110044
13/14 PSI - Quantum Field Theory II - Lecture 14

Francois David CEA Saclay

November 28, 2013

PIRSA:13110025
The Secret to Engagement: Lessons from Video

Derek Muller

November 27, 2013

PIRSA:13110095
Homological Product Codes

Sergey Bravyi IBM (United States)
November 27, 2013

PIRSA:13110091
Quantum Physics
Insightful supersymmetry

Erich Poppitz University of Toronto
November 27, 2013

PIRSA:13110061
High Energy Physics

Acceleration, Then and Now

Cliff Burgess McMaster University
December 03, 2013

PIRSA:13120059
Astrophysics
There is good evidence that the universe underwent an epoch of accelerated expansion sometime in its very early history, and that it is entering a similar phase now. This talk is in two parts. The first part describes what I believe to be the take-home message about inflationary models, coming both from the recent Planck results and from attempts to embed inflation within a UV completion (string theory). I will argue that both point to a particularly interesting class of inflationary models that also evade many of the tuning problems of inflation. These models also turn out to make the tantalizing prediction that the scalar-to-tensor ratio, r, could be just out of reach, being predicted to be proportional to (n_s - 1)^2, where n_s ~ 0.96 is the spectral tilt of the scalar spectrum. The second part provides an update on an approach to solving the "cosmological constant problem", which asks why the vacuum energy seems to gravitate so little. This is the main theoretical obstruction that makes it so difficult to understand the origins of the present epoch of acceleration. In the approach described - Supersymmetric Large Extra Dimensions - observations can be reconciled with a large vacuum energy because the vacuum energy curves the extra dimensions and not the ones measured in cosmology. It leads to a picture of very supersymmetric gravity sector coupled to a completely non-supersymmetric particle-physics sector (which predicts in particular no superpartners to be found at the LHC). The update presented here summarizes the underlying mechanism whereby supersymmetry in the extra dimensions acts to suppress the gravitational effects of quantum fluctuations. Because the large quantum contributions are under control it becomes possible to estimate the size of to be expected of the observed dark energy. For the simplest configuratin the result is of order C (m Mg/4 pi Mp)^4, where m is the heaviest particle on the branes (and so no smaller than the top quark mass), Mg is the extra-dimensional gravity scale (no smaller than 10 TeV due to astrophysical constraints, implying two extra dimensions that are of order a micron in size) and Mp is the 4D Planck mass. C is a constant unsuppressed by symmetry-breaking effects, and C = 6 x 10^6 gives the observed dark energy density, using the smallest values given above for m and Mg. If there is time I will sketch arguments as to why there must be other light degrees of freedom in the theory as well, whose implications might ultimately be used to test the picture.
Cornering Gluinos at the LHC

Jared Evans Rutgers University
December 02, 2013

PIRSA:13120057
High Energy Physics
Gluinos are expected to be light for a natural electroweak scale, but the LHC has not seen them yet. Many possibilities have been proposed to hide natural gluinos in the LHC data, but are these methods really effective? In this talk, I will discuss the current status of kinematically accessible gluinos. By noting the most common features - MET, tops, and high multiplicity - which pervade natural gluino decays, I will argue that there are few places left to hide. I will briefly discuss the remaining weaknesses in LHC coverage and how to bolster them.
13/14 PSI - Condensed Matter - Lecture 15
- Anushya Chandran Perimeter Institute for Theoretical Physics
- Roger Melko University of Waterloo
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
November 29, 2013

PIRSA:13110045
13/14 PSI - Quantum Field Theory II - Lecture 15

Francois David CEA Saclay

November 29, 2013

PIRSA:13110026
General Relativity for Cosmology - Lecture 22

Achim Kempf University of Waterloo

November 28, 2013

PIRSA:13110007
Divergences in Spinfoam Quantum Gravity

Aldo Riello Perimeter Institute for Theoretical Physics
November 28, 2013

PIRSA:13110063
General Relativity & Quantum Cosmology
The most relevant evidences in favour of the Lorentzian EPRL-FK spinfoam model come from its capibility of reproducing the expected semiclassical limit in the large spin regime. The main examples of this are the large spin limit of the vertex amplitude, later extended to arbitrary triangulations, and that of the spinfoam graviton propagator, which was calculated on the simplest possible two complex. These results are very promising. Nonetheless, their relevance may be endangered by the effects associated to radiative corrections. In this seminar, I will focus on the role played by the simplest diverging graph, the so called 'melon graph', which is known to play a fundamental role in tensorial group field theories. In particular, I will discuss its most divergent part and its geometrical interpretation. I will finally comment on the result, with particular attention to its physical consequences, especially in relation with the semiclassical limit of the spinfoam graviton propagator.
Collisions in AdS and the thermalisation of heavy-ion collisions

Wilke van der Schee European Organization for Nuclear Research (CERN)
November 28, 2013

PIRSA:13110089
General Relativity & Quantum Cosmology
The motivation of this seminar is to understand the thermalisation of heavy ion collisions using AdS/CFT. These collisions can be modelled as colliding planar gravitational shock waves. This gives rise to rich and interesting dynamics; wide shocks come to a full stop and expand hydrodynamically, as was previously found by Chesler and Yaffe. High energy collisions (corresponding to thin shocks) pass through each other, after which a plasma forms in the middle, within a proper time 1/T, with T the local temperature at that time. After this I will discuss recent results where we studied the influence of microscopic structure in the longitudinal direction of the shock waves, and thereby found a coherent regime. This has implications for both fluctuations in nucleus-nucleus collisions, and for recent proton-lead collisions at at LHC. The final part will cover a radially expanding calculation, where some simplifications allowed us to solve the model all the way till the final particle spectra, with an interesting comparison with experimental data.
13/14 PSI - Condensed Matter - Lecture 14
- Anushya Chandran Perimeter Institute for Theoretical Physics
- Roger Melko University of Waterloo
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
November 28, 2013

PIRSA:13110044
13/14 PSI - Quantum Field Theory II - Lecture 14

Francois David CEA Saclay

November 28, 2013

PIRSA:13110025
The Secret to Engagement: Lessons from Video

Derek Muller

November 27, 2013

PIRSA:13110095

Derek Muller from YouTube's Veritasium will present a webcast on Wednesday November 27, 2013 at 7pm EST from the Mike Lazaridis Theatre of Ideas at Perimeter Institute.Derek will discuss the question: Do videos really improve student learning? Derek’s PhD in physics education research suggests the answer may be no! In this one hour talk, he will share insights from his research as well as the incredible physics phenomena he has captured for his YouTube channel.Derek Muller created the popular YouTube channel Veritasium in January 2011. With almost 1 million subscribers, Derek’s 140 videos have received over 45 million views.
Homological Product Codes

Sergey Bravyi IBM (United States)
November 27, 2013

PIRSA:13110091
Quantum Physics
Quantum codes with low-weight stabilizers known as LDPC codes have been actively studied recently due to their potential applications in fault-tolerant quantum computing. However, all families of quantum LDPC codes known to this date suffer from a poor distance scaling limited by the square-root of the code length. This is in a sharp contrast with the classical case where good families of LDPC codes are known that combine constant encoding rate and linear distance. Here we propose the first family of good quantum codes with low-weight stabilizers. The new codes have a constant encoding rate, linear distance, and stabilizers acting on at most square root of n qubits, where n is the code length. For comparison, all previously known families of good quantum codes have stabilizers of linear weight. Our proof combines two techniques: randomized constructions of good quantum codes and the homological product operation from algebraic topology. We conjecture that similar methods can produce good stabilizer codes with stabilizer weight n^a for any a>0. Finally, we apply the homological product to construct new small codes with low-weight stabilizers. This is a joint work with Matthew Hastings.
Insightful supersymmetry

Erich Poppitz University of Toronto
November 27, 2013

PIRSA:13110061
High Energy Physics
It has recently been realized that some studies of supersymmetric gauge theories, when properly interpreted, lead to insights whose importance transcends supersymmetry. I will illustrate the insightful nature of supersymmetry by two examples having to do with the microscopic description of the thermal deconfinement transition, in non-supersymmetric pure Yang-Mills theory and in QCD with adjoint fermions. A host of strange ``topological" molecules will be seen to be the major players in the confinement-deconfinement dynamics. Interesting connections between topology, ``condensed-matter" gases of electric and magnetic charges, and attempts to interpret the divergent perturbation series will emerge. Much of the presentation will be aimed at non-experts.

Title	Date	Collection	Type	Info
Acceleration, Then and Now	2013‑12‑03	Cosmology and Gravitation	Scientific Series	View details
Cornering Gluinos at the LHC	2013‑12‑02	Particle Physics	Scientific Series	View details
13/14 PSI - Condensed Matter - Lecture 15	2013‑11‑29	13/14 PSI - Condensed Matter	Course	View details
13/14 PSI - Quantum Field Theory II - Lecture 15	2013‑11‑29	13/14 PSI - Quantum Field Theory II	Course	View details
General Relativity for Cosmology - Lecture 22	2013‑11‑28	General Relativity for Cosmology - 2013	Course	View details
Divergences in Spinfoam Quantum Gravity	2013‑11‑28	Quantum Gravity	Scientific Series	View details
Collisions in AdS and the thermalisation of heavy-ion collisions	2013‑11‑28	Strong Gravity	Scientific Series	View details
13/14 PSI - Condensed Matter - Lecture 14	2013‑11‑28	13/14 PSI - Condensed Matter	Course	View details
13/14 PSI - Quantum Field Theory II - Lecture 14	2013‑11‑28	13/14 PSI - Quantum Field Theory II	Course	View details
The Secret to Engagement: Lessons from Video	2013‑11‑27	Public Lecture Series	Other	View details
Homological Product Codes	2013‑11‑27	Perimeter Institute Quantum Discussions	Scientific Series	View details
Insightful supersymmetry	2013‑11‑27	Colloquium	Scientific Series	View details

Supported by

Format results

Acceleration, Then and Now

Cornering Gluinos at the LHC

13/14 PSI - Condensed Matter - Lecture 15

13/14 PSI - Quantum Field Theory II - Lecture 15

General Relativity for Cosmology - Lecture 22

Divergences in Spinfoam Quantum Gravity

Collisions in AdS and the thermalisation of heavy-ion collisions

13/14 PSI - Condensed Matter - Lecture 14

13/14 PSI - Quantum Field Theory II - Lecture 14

The Secret to Engagement: Lessons from Video

Homological Product Codes

Insightful supersymmetry

Acceleration, Then and Now

Cornering Gluinos at the LHC

13/14 PSI - Condensed Matter - Lecture 15

13/14 PSI - Quantum Field Theory II - Lecture 15

General Relativity for Cosmology - Lecture 22

Divergences in Spinfoam Quantum Gravity

Collisions in AdS and the thermalisation of heavy-ion collisions

13/14 PSI - Condensed Matter - Lecture 14

13/14 PSI - Quantum Field Theory II - Lecture 14

The Secret to Engagement: Lessons from Video

Homological Product Codes

Insightful supersymmetry