Talks

10945 - 10956 of 16955 Results

Quantum Field Theory 2 - Lecture 1

Francois David CEA Saclay

November 12, 2012

PIRSA:12110000

Quantum Fields and Strings
Geometric algebra techniques in flux compactifications

Calin Lazaroiu Horia Hulubei National Institute for R and D in Physics and Nuclear Engineering

November 09, 2012

PIRSA:12110058

Mathematical physics
Dynamical evaporation of quantum horizons

November 08, 2012

PIRSA:12110064

Quantum Gravity
Discovery of the Higgs Boson: Sweet Dream or Nightmare

Melissa Franklin Harvard University

November 07, 2012

PIRSA:12110055
Optimal quantum self-tests based on binary nonlocal XOR games

November 07, 2012

PIRSA:12110067
An introduction to quantum channels and their capacities

Graeme Smith Institute for Quantum Computing (IQC)

November 07, 2012

PIRSA:12110066

Quantum Information
What's an unknown POVM, and what does a two qubit state look like?

Matthew Pusey University of York

November 06, 2012

PIRSA:12110068
Holomorphic Blocks in 3d

Tudor Dimofte University of Edinburgh

November 06, 2012

PIRSA:12110056

Quantum Fields and Strings
Primordial Magnetic Fields & Non-Gaussianity

Martin Sloth University of Southern Denmark

November 06, 2012

PIRSA:12110040

Cosmology
Penrose inequalities and the stability of non-uniform black strings

Pau Figueras Queen Mary University of London

November 01, 2012

PIRSA:12110039
What is a Wavefunction?

Wayne Myrvold Western University

November 01, 2012

PIRSA:12110060
An Informal Discussion About Topological Gauge Theory, part 2

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

October 30, 2012

PIRSA:12100132

Quantum Field Theory 2 - Lecture 1

Francois David CEA Saclay

November 12, 2012

PIRSA:12110000

Quantum Fields and Strings
Geometric algebra techniques in flux compactifications

Calin Lazaroiu Horia Hulubei National Institute for R and D in Physics and Nuclear Engineering

November 09, 2012

PIRSA:12110058

Mathematical physics

Using techniques originating in a certain approach to Clifford bundles known as "geometric algebra", I discuss a geometric reformulation of constrained generalized Killing spinor equations which proves to be particularly effective in the study and classification of supersymmetric flux compactifications of string and M-theory. As an application, I discuss the most general N=2 compactifications of M-theory to three dimensions, which were never studied in full generality before. I also touch upon the connection of such techniques with a certain variant of the quantization of spin systems.
Dynamical evaporation of quantum horizons

November 08, 2012

PIRSA:12110064

Quantum Gravity

We describe of the evaporation process as driven by the dynamical evolution of the quantum gravitational degrees of freedom resident at the horizon, as identified by the Loop Quantum Gravity kinematics. Using a parallel with the Brownian motion, we interpret the first law of quantum dynamical horizon in terms of a fluctuation-dissipation relation applied to this fundamental discrete structure. In this way, the horizon evolution is described in terms of relaxation to an equilibrium state balanced by the excitation of Planck scale constituents of the horizon. We show how from this setting the emergence of several conservative scenarios for the final stage of the evaporation process can be microscopically derived. Namely, the leakage of part of the horizon quantum geometry information prior to the Planckian phase and the stabilization of the hole surface shrinkage forming a massive remnant, which can eventually decay, are shown to take place.
Discovery of the Higgs Boson: Sweet Dream or Nightmare

Melissa Franklin Harvard University

November 07, 2012

PIRSA:12110055
Optimal quantum self-tests based on binary nonlocal XOR games

November 07, 2012

PIRSA:12110067

Self-testing a multipartite quantum state means verifying the existence of the state based on the outcomes of unknown or untrusted measurements. This concept is important in device-independent quantum cryptography. There are some previously known results on self-testing which involve nonlocal binary XOR games such as the CHSH test and the GHZ paradox. In our work we expand on these results. We provide a general criterion which, when satisfied, guarantees that a given nonlocal binary XOR game is a robust self-test. The error term in this result is quadratic, which is the best possible. In my talk I will explain the conceptual basis for the criterion and offer some examples. This is joint work with Yaoyun Shi (arXiv:1207.1819).
An introduction to quantum channels and their capacities

Graeme Smith Institute for Quantum Computing (IQC)

November 07, 2012

PIRSA:12110066

Quantum Information

A quantum communication channel can be put to many uses: it can transmit classical information, private classical information, or quantum information. It can be used alone, with shared entanglement, or together with other channels. For each of these settings there is a capacity that quantifies a channel's fundamental potential for communication. In this introductory talk, I will discuss what we known about the various capacities of a quantum channel, including a discussion of synergies between different channels and related additivity questions.
What's an unknown POVM, and what does a two qubit state look like?

Matthew Pusey University of York

November 06, 2012

PIRSA:12110068

If probabilities represent knowledge, what is an "unknown
probability"? De Finetti's theorem licenses the view that it is simply a
convenient metaphor for a certain class of knowledge about a series of
events. There are quantum versions for "unknown states" and "unknown
channels". I will explain how "unknown measurements" can be rehabilitated
too.

I will then move to a totally different topic. The Bloch sphere is handy
for representing qubit states, but the equivalent for two qubits is
15-dimensional! I will advocate instead drawing the set of states that Bob
can steer Alice to, the "steering ellipsoid". I will show how entanglement
and discord look from this perspective, and outline a geometric
classification of separable two qubit states.
Holomorphic Blocks in 3d

Tudor Dimofte University of Edinburgh

November 06, 2012

PIRSA:12110056

Quantum Fields and Strings

Recently techniques have been developed to compute the partition functions of 3d theories with N=2 supersymmetry on curved, compact spaces, in particular S^3 and S^2xS^1 (the latter giving a supersymmetric index). I will discuss how both of these partition functions can be decomposed as products of more fundamental, universal "holomorphic blocks." For 3d gauge theories arising from (auxiliary) 3-manifolds M, these holomorphic blocks are specific Chern-Simons partition functions on M.
Primordial Magnetic Fields & Non-Gaussianity

Martin Sloth University of Southern Denmark

November 06, 2012

PIRSA:12110040

Cosmology

There are indications of a lower bound on magnetic fields in the intergalactic media. Since magnetic fields on such large scales are difficult to generate in the late universe, this might point to inflationary magnetogenesis as the origin of intergalactic magnetic fields. If the magnetic fields are generated during inflation, they are naturally correlated with the inflaton perturbations in a general class of models. This leads to a consistency relation between the power spectrum of primordial magnetic fields and the non-Gaussian three-point cross-correlation of magnetic fields with the inflaton perturbation. The size of non-Gaussianity can be expressed in a new magnetic non-linearity parameter b_NL. In the flattened shape where the non-Gaussianity is maximal, b_NL can be as large as 5000.
Penrose inequalities and the stability of non-uniform black strings

Pau Figueras Queen Mary University of London

November 01, 2012

PIRSA:12110039

In this talk I will first review static black holes in Kaluza-Klein theory. It is well-known that within this theory there exist black strings which are non-uniform along the Kaluza-Klein circle. Using numerical methods, I will explain how to construct (for the first time) non-uniform black strings in D>10, where D is the total number of spacetime dimensions. The stability of such black objects has not been discussed before, and in the last part of the talk I will explain how one can study the stability of non-uniform black strings using Penrose inequalities. This will lead to a new conjecture for the phase diagram of static Kaluza-Klein black holes.
What is a Wavefunction?

Wayne Myrvold Western University

November 01, 2012

PIRSA:12110060

The fact that the quantum wavefunction of a many-particle system is a function on a high-dimensional configuration space, rather than on spacetime, has led some to suggest that any realist understanding of quantum mechanics must regard configuration space as more fundamental than spacetime. Worse, it seems that a wavefunction monist ontology cannot help itself to talk of "configuration space" at all, without particles for the configurations to be configurations of. The wavefunction, it might seem, threatens to become a function defined on a high-dimensional space whose relation to spacetime is obscure. I will argue that such worries are misplaced.
An Informal Discussion About Topological Gauge Theory, part 2

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

October 30, 2012

PIRSA:12100132

Reference:
Topological gauge theories and group cohomology
Robbert Dijkgraaf and Edward Witten
http://projecteuclid.org/DPubS?service=UI&version=1.0&verb=Display&handle=euclid.cmp/1104180750

Braiding statistics approach to symmetry-protected topological phases
Michael Levin, Zheng-Cheng Gu
http://arxiv.org/abs/1202.3120

Title	Date	Collection	Type	Info
Quantum Field Theory 2 - Lecture 1	2012‑11‑12	12/13 PSI - Quantum Field Theory 2	Course	View details
Geometric algebra techniques in flux compactifications	2012‑11‑09	Strings Group Meeting	Scientific Series	View details
Dynamical evaporation of quantum horizons	2012‑11‑08	Quantum Gravity	Scientific Series	View details
Discovery of the Higgs Boson: Sweet Dream or Nightmare	2012‑11‑07	Public Lecture Series	Public Lectures	View details
Optimal quantum self-tests based on binary nonlocal XOR games	2012‑11‑07	Quantum Information	Scientific Series	View details
An introduction to quantum channels and their capacities	2012‑11‑07	Colloquium	Scientific Series	View details
What's an unknown POVM, and what does a two qubit state look like?	2012‑11‑06	Quantum Foundations	Scientific Series	View details
Holomorphic Blocks in 3d	2012‑11‑06	Quantum Fields and Strings	Scientific Series	View details
Primordial Magnetic Fields & Non-Gaussianity	2012‑11‑06	Cosmology and Gravitation	Scientific Series	View details
Penrose inequalities and the stability of non-uniform black strings	2012‑11‑01	Strong Gravity	Scientific Series	View details
What is a Wavefunction?	2012‑11‑01	Quantum Foundations	Scientific Series	View details
An Informal Discussion About Topological Gauge Theory, part 2	2012‑10‑30	Quantum Matter	Other	View details

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