Scientific Series

Displaying 3469 - 3480 of 5085

On memory in exponentially expanding spaces

Douglas Stanford Stanford University
April 23, 2013

PIRSA:13040127
Astrophysics
Quantum transport in one dimension: from integrability to many-body localization and topology

Joel Moore University of California, Berkeley
April 23, 2013

PIRSA:13040125
Condensed Matter
The continuum limit of tensor networks: a path integral representation

David Jennings Imperial College London
April 22, 2013

PIRSA:13040113
Quantum Physics
The imaginary part of the gravitational action and black hole entropy

Yasha Neiman Okinawa Institute of Science and Technology Graduate University
April 18, 2013

PIRSA:13040106
General Relativity & Quantum Cosmology
Energy and the Environment - What Physicists Can Do

John Baez University of California, Riverside
April 17, 2013

PIRSA:13040030
Mathematical Physics
The theory of composition in physics

Lucien Hardy Perimeter Institute for Theoretical Physics
April 16, 2013

PIRSA:13040121
Quantum Physics
Results and highlights from Planck

Kendrick Smith Perimeter Institute for Theoretical Physics
April 16, 2013

PIRSA:13040123
Astrophysics
Continuous-variable entanglement distillation and non-commutative central limit theorems

Earl Campbell University of Sheffield
April 15, 2013

PIRSA:13040122
Quantum Physics
Quantum causal dynamics without absolute space or time
April 11, 2013

PIRSA:13040083
General Relativity & Quantum Cosmology
Spinning black-hole binaries as gravitational and cosmological probes

Enrico Barausse SISSA International School for Advanced Studies
April 11, 2013

PIRSA:13040082
General Relativity & Quantum Cosmology
Large Scale Bayesian Inference in Cosmology

Jens Jasche Institut d'Astrophysique de Paris
April 11, 2013

PIRSA:13040119
Astrophysics
Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.

Max Metlitski Massachusetts Institute of Technology (MIT) - Department of Physics
April 10, 2013

PIRSA:13040117
Condensed Matter

On memory in exponentially expanding spaces

Douglas Stanford Stanford University
April 23, 2013

PIRSA:13040127
Astrophysics
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.
Quantum transport in one dimension: from integrability to many-body localization and topology

Joel Moore University of California, Berkeley
April 23, 2013

PIRSA:13040125
Condensed Matter
Recent advances in analytical theory and numerical methods enable some long-standing questions about transport in one dimension to be answered; these questions are closely related to transport experiments in quasi-1D compounds. The spinless fermion chain with nearest-neighbor interactions at half-filling, or equivalently the XXZ model in zero magnetic field, is an example of an integrable system in which no conventional conserved quantity forces dissipationless transport (Drude weight); we show that there is nevertheless a Drude weight and that at some points its contribution is from a new type of conserved quantity recently constructed by Prosen. Adding an integrability-breaking perturbation leads to a scaling theory of conductivity at low temperature. Adding disorder, we study the question of how Anderson localization is modified by interactions when the system remains fully quantum coherent ("many-body localization"). We find that even weak interactions are a singular perturbation on some quantities: entanglement grows slowly but without limit, suggesting that dynamics in the possible many-body localized phase are glass-like. If time permits, some results on the fractional Luttinger's theorem and the 1D limit of quantum Hall states will be presented.
The continuum limit of tensor networks: a path integral representation

David Jennings Imperial College London
April 22, 2013

PIRSA:13040113
Quantum Physics
I will discuss a path-integral representation of continuum tensor networks that extends the continuous MPS class for 1-D quantum fields to arbitrary spatial dimensions while encoding desirable symmetries. The physical states can be interpreted as arising through a continuous measurement process by a lower dimensional virtual field with Lorentz symmetry. The resultant physical states naturally obey entropy area laws, with the expectation values of observables determined by the dissipative dynamics of the boundary field. The class offers the prospect of powerful new analytical and computational tools to describe the physics of strongly interacting field systems.
The imaginary part of the gravitational action and black hole entropy

Yasha Neiman Okinawa Institute of Science and Technology Graduate University
April 18, 2013

PIRSA:13040106
General Relativity & Quantum Cosmology
I present a candidate for a new derivation of black hole entropy. The key observation is that the action of General Relativity in bounded regions has an imaginary part, arising from the boundary term. The formula for this imaginary part is closely related to the Bekenstein-Hawking entropy formula, and coincides with it for certain classes of regions. This remains true in the presence of matter, and generalizes appropriately to Lovelock gravity. The imaginary part of the action is a versatile notion, requiring neither stationarity nor any knowledge about asymptotic infinity. Thus, it may provide a handle on quantum gravity in finite and dynamical regions. I derive the above results, make connections with standard approaches to black hole entropy, and speculate on the meaning of it all. Implications for loop quantum gravity are also discussed.
Energy and the Environment - What Physicists Can Do

John Baez University of California, Riverside
April 17, 2013

PIRSA:13040030
Mathematical Physics
The global warming crisis is part of a bigger transformation in which humanity realizes that the Earth is a finite system and that our population, energy usage, and the like cannot continue to grow exponentially. While politics and economics pose the biggest challenges, physicists are in a good position to help make this transition a bit easier. After a quick review of the problems, we discuss a few ways physicists can help.
The theory of composition in physics

Lucien Hardy Perimeter Institute for Theoretical Physics
April 16, 2013

PIRSA:13040121
Quantum Physics
We develop a theory for describing composite objects in physics. These can be static objects, such as tables, or things that happen in spacetime (such as a region of spacetime with fields on it regarded as being composed of smaller such regions joined together). We propose certain fundamental axioms which, it seems, should be satisfied in any theory of composition. A key axiom is the order independence axiom which says we can describe the composition of a composite object in any order. Then we provide a notation for describing composite objects that naturally leads to these axioms being satisfied. In any given physical context we are interested in the value of certain properties for the objects (such as whether the object is possible, what probability it has, how wide it is, and so on). We associate a generalized state with an object. This can be used to calculate the value of those properties we are interested in for for this object. We then propose a certain principle, the composition principle, which says that we can determine the generalized state of a composite object from the generalized states for the components by means of a calculation having the same structure as the description of the generalized state. The composition principle provides a link between description and prediction.
Results and highlights from Planck

Kendrick Smith Perimeter Institute for Theoretical Physics
April 16, 2013

PIRSA:13040123
Astrophysics
Cosmological results from Planck, a third-generation satellite mission to measure the cosmic microwave background, have just been announced. These results improve constraints on essentially all cosmological parameters, and have implications for several preexisting sources of tension with the standard cosmological model, while also raising new puzzles. I will discuss these results and their significance, as well as the next steps forward.
Continuous-variable entanglement distillation and non-commutative central limit theorems

Earl Campbell University of Sheffield
April 15, 2013

PIRSA:13040122
Quantum Physics
Entanglement distillation transforms weakly entangled noisy states into highly entangled states, a primitive to be used in quantum repeater schemes and other protocols designed for quantum communication and key distribution. In this work, we present a comprehensive framework for continuous-variable entanglement distillation schemes that convert noisy non-Gaussian states into Gaussian ones in many iterations of the protocol. Instances of these protocols include the recursive Gaussifier protocol and the pumping Gaussifier protocol. The flexibility of these protocols give rise to several beneficial trade-offs related to success probabilities or memory requirements that can be adjusted to reflect experimental specifics. Despite these protocols involving measurements, we relate the convergence in this protocols to new instances of non-commutative central limit theorems. Implications of the findings for quantum repeater schemes are discussed.
Quantum causal dynamics without absolute space or time
April 11, 2013

PIRSA:13040083
General Relativity & Quantum Cosmology
I will describe a discrete model of spacetime which is quantum-mechanical, causal, and background free. The kinematics is described by networks whose vertices are labelled with arrows. These networks can be evolved forwards (or backwards) in time by using unitary replacement rules. The arrow structure permits one to define dynamics without using an absolute time parameter. Based on arXiv:1201.2489.
Spinning black-hole binaries as gravitational and cosmological probes

Enrico Barausse SISSA International School for Advanced Studies
April 11, 2013

PIRSA:13040082
General Relativity & Quantum Cosmology
Large Scale Bayesian Inference in Cosmology

Jens Jasche Institut d'Astrophysique de Paris
April 11, 2013

PIRSA:13040119
Astrophysics
Already the last decade has witnessed unprecedented progress in the collection of cosmological data. Presently proposed and designed future cosmological probes and surveys permit us to anticipate the upcoming avalanche of cosmological information during the next decades.
The increase of valuable observations needs to be accompanied with the development of efficient and accurate information processing technology in order to analyse and interpret this data. In particular, cosmography projects, aiming at studying the origin and inhomogeneous evolution of
the Universe, involve high dimensional inference methods. For example, 3d cosmological density and velocity field inference requires to explore on the order of 10^7 or more parameters. Consequently, such projects critically rely on state-of-the-art information processing techniques
and, nevertheless, are often on the verge of numerical feasibility with present day computational resources. For this reason, in this talk I will address the problem of high dimensional Bayesian inference from cosmological data sets, subject to a variety of statistical and systematic uncertainties. In particular, I will focus on the discussion of selected Markov Chain Monte Carlo techniques, permitting to efficiently solve inference problems with on the order of 10^7 parameters. Furthermore, these methods will be exemplified in various cosmological applications, raging from 3d non-linear density and photometric redshift inference to 4d physical state inference. These techniques permit us to exploit cosmologically relevant information from
observations to unprecedented detail and hence will significantly contribute to the era of precision cosmology.
Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.

Max Metlitski Massachusetts Institute of Technology (MIT) - Department of Physics
April 10, 2013

PIRSA:13040117
Condensed Matter
In this talk, I will construct a symmetry protected topological phase of bosons in 3d with particle number conservation and time reversal symmetries, which is the direct bosonic analogue of the familiar electron topological insulator. The construction employs a parton decomposition of bosons, followed by condensation of parton-monopole composites. The surface of the resulting state supports a gapped symmetry respecting phase with intrinsic toric code topological order where both e and m anyons carry charge 1=2. It is well-known that one signature of the 3d electron topological insulator is the Witten eect: if the system is coupled to a compact electromagnetic gauge eld, a monopole in the bulk acquires a half-odd-integer polarization charge. I will discuss the corresponding phenomenon for the constructed topological insulator of bosons: a monopole can remain electrically neutral, but its statistics are transmuted from bosonic to fermionic. This \sta- tistical Witten eect" guarantees that the surface is either gapless, symmetry broken or carries an intrinsic topological order.

Title	Speaker(s)	Date	Talk Type	Info link
On memory in exponentially expanding spaces	Douglas Stanford	2013-04-23	Scientific Series	View details
Quantum transport in one dimension: from integrability to many-body localization and topology	Joel Moore	2013-04-23	Scientific Series	View details
The continuum limit of tensor networks: a path integral representation	David Jennings	2013-04-22	Scientific Series	View details
The imaginary part of the gravitational action and black hole entropy	Yasha Neiman	2013-04-18	Scientific Series	View details
Energy and the Environment - What Physicists Can Do	John Baez	2013-04-17	Scientific Series	View details
The theory of composition in physics	Lucien Hardy	2013-04-16	Scientific Series	View details
Results and highlights from Planck	Kendrick Smith	2013-04-16	Scientific Series	View details
Continuous-variable entanglement distillation and non-commutative central limit theorems	Earl Campbell	2013-04-15	Scientific Series	View details
Quantum causal dynamics without absolute space or time		2013-04-11	Scientific Series	View details
Spinning black-hole binaries as gravitational and cosmological probes	Enrico Barausse	2013-04-11	Scientific Series	View details
Large Scale Bayesian Inference in Cosmology	Jens Jasche	2013-04-11	Scientific Series	View details
Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.	Max Metlitski	2013-04-10	Scientific Series	View details

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Format results

On memory in exponentially expanding spaces

Quantum transport in one dimension: from integrability to many-body localization and topology

The continuum limit of tensor networks: a path integral representation

The imaginary part of the gravitational action and black hole entropy

Energy and the Environment - What Physicists Can Do

The theory of composition in physics

Results and highlights from Planck

Continuous-variable entanglement distillation and non-commutative central limit theorems

Quantum causal dynamics without absolute space or time

Spinning black-hole binaries as gravitational and cosmological probes

Large Scale Bayesian Inference in Cosmology

Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.

On memory in exponentially expanding spaces

Quantum transport in one dimension: from integrability to many-body localization and topology

The continuum limit of tensor networks: a path integral representation

The imaginary part of the gravitational action and black hole entropy

Energy and the Environment - What Physicists Can Do

The theory of composition in physics

Results and highlights from Planck

Continuous-variable entanglement distillation and non-commutative central limit theorems

Quantum causal dynamics without absolute space or time

Spinning black-hole binaries as gravitational and cosmological probes

Large Scale Bayesian Inference in Cosmology

Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.