Scientific Series

Displaying 3589 - 3600 of 5113

Twisted quantum double model of topological phases

Yidun Wan Fudan University
November 21, 2012

PIRSA:12110079
Condensed Matter
Quantum Signatures of Chaos

Shohini Ghose Wilfrid Laurier University

November 21, 2012

PIRSA:12110072
Principle of relativity for quantum theory

Marco Zaopo University of Pavia
November 20, 2012

PIRSA:12110073
Quantum Foundations
3 point functions in the AdS4/CFT3 correspondence

Agnese Bissi The Abdus Salam International Centre for Theoretical Physics (ICTP)
November 20, 2012

PIRSA:12110053
Quantum Fields and Strings
An exact solution of the Dirac equation with CP violation.

Tomislav Prokopec Utrecht University
November 20, 2012

PIRSA:12110076
Cosmology
Superradiant Superconductivity

Baskaran Ganapathy Institute of Mathematical Sciences
November 16, 2012

PIRSA:12110071
Condensed Matter
Canonical tensor models with local time

Naoki Sasakura Yukawa Institute for Theoretical Physics
November 15, 2012

PIRSA:12110065
Quantum Gravity
Detecting Gravitational Waves with Millisecond Pulsars

Paul Demorest National Radio Astronomy Observatory (NRAO)
November 15, 2012

PIRSA:12110044
Strong Gravity
Solid of Inflation: An alternative symmetry breaking pattern for an EFT of inflation

Solomon Endlich Stanford University
November 15, 2012

PIRSA:13010005
Cosmology
Massive gravitons, the cosmological constant and new directions in gravity
November 14, 2012

PIRSA:12110061
Cosmology
Quasiprobability representations of qubits

November 13, 2012

PIRSA:12110070
Anomaly-induced transport and thermodynamics

Kristan Jensen University of Victoria
November 13, 2012

PIRSA:12110047
Quantum Fields and Strings

Twisted quantum double model of topological phases

Yidun Wan Fudan University
November 21, 2012

PIRSA:12110079
Condensed Matter
Quantum Signatures of Chaos

Shohini Ghose Wilfrid Laurier University

November 21, 2012

PIRSA:12110072
Principle of relativity for quantum theory

Marco Zaopo University of Pavia
November 20, 2012

PIRSA:12110073
Quantum Foundations
In a generic quantum experiment we have a given set of devices analyzing some physical property of a system. To each device involved in the experiment we associate a set of random outcomes corresponding to the possible values of the variable analyzed by the device. Devices have apertures that permit physical systems to pass through them. Each aperture is labelled as "input" or "output" depending on whether it is assumed that the aperture lets the system go inside or outside the device. Assuming a particular input/output structure for the devices involved in a generic experiment is equivalent to assume a particular causal structure for the space-time events constituted by the outcomes happening on devices. The joint probability distribution of these outcomes is usually predicted assuming an absolutely defined input/output structure of devices. This means that all observers of the experiment agree on whether an aperture is labelled as "input" or "output". In this talk we show that the mathematical formalism of quantum theory permits to predict the joint probability distribution of outcomes in a generic experiment in such a way that the input/output structure is indeed relative to an observer. This means that two observers of the same experiment can predict the joint probability distribution of outcomes assuming different input/output labels for the apertures. Since input/output structure is the causal structure of the space-time events constituting the outcomes involved in the experiment we conclude that in quantum theory, the causal structure of events may not be regarded as absolute but rather as relative to the observer. We finally point out that properly extending this concept to the cosmological domain could shed light on the problem of dark energy.
3 point functions in the AdS4/CFT3 correspondence

Agnese Bissi The Abdus Salam International Centre for Theoretical Physics (ICTP)
November 20, 2012

PIRSA:12110053
Quantum Fields and Strings
I will present recent developments in the computation of three point functions in the AdS4/CFT3 correspondence. More specifically I will consider two different computations for three point functions of operators belonging to the SU(2)XSU(2) sector of ABJM. I will discuss first the generalization of the determinant representation, found by Foda for the three-point functions of the SU(2) sector of N = 4 SYM, to the ABJM theory and secondly semiclassical computations in the case where two operators are heavy and one is light and BPS, comparing the results obtained in the gauge theory side using a coherent state description of the heavy operators with its string theory counterpart calculated holographically.
An exact solution of the Dirac equation with CP violation.

Tomislav Prokopec Utrecht University
November 20, 2012

PIRSA:12110076
Cosmology
After a brief overview of electroweak baryogenesis, I will show how to construct a solution of the Dirac equation for a CP violating kink wall. This solution nicely reduces to the known solution for a CP violating thin (step) wall. The novel solution can be helpful for studies of baryogenesis sources at strong first order phase transitions, which is relevant for electroweak scale baryogenesis studies.
Superradiant Superconductivity

Baskaran Ganapathy Institute of Mathematical Sciences
November 16, 2012

PIRSA:12110071
Condensed Matter
In Dicke Superradiance, a collection of 2-level atoms interacting with a single boson mode acquires, through quantum coherence, an enhanced emission property and a rich dynamics. We suggest possibility of Dicke superradiance in a BCS superconductor. The necessary 2-level atoms are identified with Anderson pseudo spins seeing a self consistent mean field in k-space. A way to couple these 2-level bose atoms to an external boson mode and create a novel non equilibrium superradiant superconductivity (SRSC) is suggested. Our mechanism offers a hope to realize transient superconductivity, even at room temperatures, in the pseudo gap phase of certain underdoped cuprates. Recent experiments are briefly discussed in this light. Further SRSC exhibits interesting quantum entanglement and superfluorescence properties.
Canonical tensor models with local time

Naoki Sasakura Yukawa Institute for Theoretical Physics
November 15, 2012

PIRSA:12110065
Quantum Gravity
Tensor models are generalization of matrix models, and are studied as discrete models for quantum gravity for more than two-dimensions. Among them, the rank-three tensor models can be interpreted as theories of dynamical fuzzy spaces, and they generally have the feature of
respecting symmetries. In this talk, after briefly reviewing some results on Euclidean models such as spontaneous generation of fuzzy spaces and Euclidean general relativity respecting the diffeomorphism symmetry on them, I will present a way to introduce “local” time to the rank-three tensor models by constructing “local” Hamiltonians. The consistency among the multiple ways of local time evolutions is guaranteed by the on-shell closure of the constraint algebra among the
local Hamiltonians and the symmetry generators of the tensor models. The constraint algebra is shown to approach the DeWitt algebra in a formal continuum limit. I will also discuss the two-fold uniqueness of the local Hamiltonians, and will briefly show some preliminary results on the quantization.
Detecting Gravitational Waves with Millisecond Pulsars

Paul Demorest National Radio Astronomy Observatory (NRAO)
November 15, 2012

PIRSA:12110044
Strong Gravity
Millisecond spin-period radio pulsars provide us with unique astronomical "laboratories" for exploring fundamental physics in a variety of ways -- from the physics of matter at super-nuclear density, to experimental tests of gravity. They have also provided the only experimental evidence so far for the existence of gravitational waves (GW). A set of millisecond pulsars acting as precise astronomical clocks may also be used as a direct GW detector, sensitive to the nanohertz-frequency GW expected to be emitted by supermassive black hole binary systems or other more exotic sources. In this talk I will present the project status and recent GW upper limits from the NANOGrav project. I will also discuss expected near-future improvements in the measurement, including recent work aimed at better characterizing and mitigating the effect of multi-path propagation effects in the interstellar medium.
Solid of Inflation: An alternative symmetry breaking pattern for an EFT of inflation

Solomon Endlich Stanford University
November 15, 2012

PIRSA:13010005
Cosmology
In this talk I will discuss a cosmological model where primordial inflation is driven by a `solid', defined as a system of three derivatively coupled scalar fields obeying certain symmetries and spontaneously breaking a certain subgroup of these. The symmetry breaking pattern differs drastically from that of standard inflationary models: time translations are unbroken. This prevents our model from fitting into the standard effective field theory description of adiabatic perturbations. Consequently, it exhibits a novel non-Gaussian `shape'.
Massive gravitons, the cosmological constant and new directions in gravity
November 14, 2012

PIRSA:12110061
Cosmology
The solutions to the cosmological constant problems may involve modifying the very long-range dynamics of gravity by adding new degrees of freedom. As an example of a conservative and minimal such modification, we consider the possibility that the graviton has a very small mass. Massive gravity has received renewed interest due to recent advances which have resolved its traditional problems. This kind of modification has some peculiar and unexpected features, and it points us towards a universe which looks quite unfamiliar.
Support for this colloquium is provided by The Templeton Frontiers Program.
Quasiprobability representations of qubits

November 13, 2012

PIRSA:12110070

Negativity in a quasi-probability representation is typically interpreted as an indication of nonclassical behavior. However, this does not preclude bases that are non-negative from having interesting applications---the single-qubit stabilizer states have non-negative Wigner functions and yet play a fundamental role in many quantum information tasks. We determine what other sets of quantum states and measurements of a qubit can be non-negative in a quasiprobability representation, and identify nontrivial groups of unitary transformations that permute such states. These sets of states and measurements are analogous to the single-qubit stabilizer states. We show that no quasiprobability representation of a qubit can be non-negative for more than two bases in any plane of the Bloch sphere. Furthermore, there is a single family of sets of four bases that can be non-negative in an arbitrary quasiprobability representation of a qubit. We provide an exhaustive list of the sets of single-qubit bases that are nonnegative in some quasiprobability representation and are also closed under a group of unitary transformations, revealing two families of such sets of three bases. We also show that not all two-qubit Clifford transformations can preserve non-negativity in any quasiprobability representation that is non-negative for the computational basis. This is in stark contrast to the qutrit case, in which the discrete Wigner function is non-negative for all n-qutrit stabilizer states and Clifford transformations. We also provide some evidence that extending the other sets of non-negative single-qubit states to multiple qubits does not give entangled states.
Anomaly-induced transport and thermodynamics

Kristan Jensen University of Victoria
November 13, 2012

PIRSA:12110047
Quantum Fields and Strings
I will discuss recent progress in the study of anomaly-induced transport, focusing on the chiral vortical effect in 3+1 dimensions. Most of my discussion will be framed in light of a larger story, namely progress in making exact statements about finite-temperature quantum field theory, for which the chiral magnetic and vortical effects are instructive prototypes.

Title	Speaker(s)	Date	Talk Type	Info link
Twisted quantum double model of topological phases	Yidun Wan	2012-11-21	Scientific Series	View details
Quantum Signatures of Chaos	Shohini Ghose	2012-11-21	Scientific Series	View details
Principle of relativity for quantum theory	Marco Zaopo	2012-11-20	Scientific Series	View details
3 point functions in the AdS4/CFT3 correspondence	Agnese Bissi	2012-11-20	Scientific Series	View details
An exact solution of the Dirac equation with CP violation.	Tomislav Prokopec	2012-11-20	Scientific Series	View details
Superradiant Superconductivity	Baskaran Ganapathy	2012-11-16	Scientific Series	View details
Canonical tensor models with local time	Naoki Sasakura	2012-11-15	Scientific Series	View details
Detecting Gravitational Waves with Millisecond Pulsars	Paul Demorest	2012-11-15	Scientific Series	View details
Solid of Inflation: An alternative symmetry breaking pattern for an EFT of inflation	Solomon Endlich	2012-11-15	Scientific Series	View details
Massive gravitons, the cosmological constant and new directions in gravity		2012-11-14	Scientific Series	View details
Quasiprobability representations of qubits		2012-11-13	Scientific Series	View details
Anomaly-induced transport and thermodynamics	Kristan Jensen	2012-11-13	Scientific Series	View details

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