Talks

10189 - 10200 of 16890 Results

ΛCDM Large Scale Triumphs and Small Scale Challenges

Joel Primack University of California, Santa Cruz

September 17, 2013

PIRSA:13090066

Cosmology
13/14 PSI - Quantum Theory - Lecture 7

Joseph Emerson Institute for Quantum Computing (IQC)

September 17, 2013

PIRSA:13090038
13/14 PSI - Relativity - Lecture 7

Neil Turok University of Edinburgh

September 17, 2013

PIRSA:13090019
13/14 PSI - Quantum Theory - Lecture 6

Joseph Emerson Institute for Quantum Computing (IQC)

September 16, 2013

PIRSA:13090037
13/14 PSI - Relativity - Lecture 6

Neil Turok University of Edinburgh

September 16, 2013

PIRSA:13090018
13/14 PSI - Quantum Theory - Lecture 5

Joseph Emerson Institute for Quantum Computing (IQC)

September 13, 2013

PIRSA:13090034
Edge states at domain wall junctions in supersymmetric gauge theory

Davide Gaiotto Perimeter Institute for Theoretical Physics

September 13, 2013

PIRSA:13090074

Condensed Matter
13/14 PSI - Relativity - Lecture 5

Neil Turok University of Edinburgh

September 13, 2013

PIRSA:13090015
Quantum States are Consistent Probability Distributions

Nadish de Silva University of Oxford

September 12, 2013

PIRSA:13090070

Quantum Foundations
Holography without Strings - Joint Quantum Gravity and String Theory Seminar

Donald Marolf University of California, Santa Barbara

September 12, 2013

PIRSA:13090060

Quantum Gravity
13/14 PSI - Quantum Theory - Lecture 4

Joseph Emerson Institute for Quantum Computing (IQC)

September 12, 2013

PIRSA:13090033
13/14 PSI - Relativity - Lecture 4b

Neil Turok University of Edinburgh

September 12, 2013

PIRSA:13090075

ΛCDM Large Scale Triumphs and Small Scale Challenges

Joel Primack University of California, Santa Cruz

September 17, 2013

PIRSA:13090066

Cosmology

ΛCDM has become the standard cosmological model because its predictions agree so well with observations of the cosmic microwave background and the large-scale structure of the universe. However ΛCDM has faced challenges on smaller scales. Some of these challenges, including the “angular momentum catastrophe" and the absence of density cusps in the centers of small galaxies, may be overcome with improvements in simulation resolution and feedback. Recent simulations appear to form realistic galaxies in agreement with observed scaling relations. Although dark matter halos start small and grow by accretion, the existence of a star-forming band of halo masses naturally explains why the most massive galaxies have the oldest stars, a phenomenon known as galactic “downsizing." The discovery of many faint galaxies in the Local Group is consistent with the large number of subhalos in ΛCDM simulations. There is increasing evidence for such substructure in galaxy dark matter halos from gaps in cold stellar streams in the Milky Way and Andromeda and from gravitational lensing flux anomalies, with the prospect of rapidly increasing data on that from ALMA. The “too big to fail" (TBTF) problem is the latest apparent challenge to ΛCDM. It arose from analysis of the Aquarius and Via Lactea very-high-resolution ΛCDM simulations of Milky-Way-mass dark matter halos. Each simulated halo has ∼10 subhalos so massive and dense that they would appear to be too big to fail to form lots of stars. The TBTF problem is that none of the observed dwarf satellite galaxies of the Milky Way or Andromeda have stars moving as fast as would be expected in these densest subhalos. This may indicate the need for a more complex theory of dark matter – but several recent papers have shown that subhalos in pure dark matter simulations like Aquarius or Via Lactea are significantly modified when baryonic effects are included, so as to solve the TBTF problem. Higher resolution simulations are needed to verify this.
13/14 PSI - Quantum Theory - Lecture 7

Joseph Emerson Institute for Quantum Computing (IQC)

September 17, 2013

PIRSA:13090038
13/14 PSI - Relativity - Lecture 7

Neil Turok University of Edinburgh

September 17, 2013

PIRSA:13090019
13/14 PSI - Quantum Theory - Lecture 6

Joseph Emerson Institute for Quantum Computing (IQC)

September 16, 2013

PIRSA:13090037
13/14 PSI - Relativity - Lecture 6

Neil Turok University of Edinburgh

September 16, 2013

PIRSA:13090018
13/14 PSI - Quantum Theory - Lecture 5

Joseph Emerson Institute for Quantum Computing (IQC)

September 13, 2013

PIRSA:13090034
Edge states at domain wall junctions in supersymmetric gauge theory

Davide Gaiotto Perimeter Institute for Theoretical Physics

September 13, 2013

PIRSA:13090074

Condensed Matter
13/14 PSI - Relativity - Lecture 5

Neil Turok University of Edinburgh

September 13, 2013

PIRSA:13090015
Quantum States are Consistent Probability Distributions

Nadish de Silva University of Oxford

September 12, 2013

PIRSA:13090070

Quantum Foundations

We describe a notion of state for a quantum system which is given in terms of a collection of empirically realizable probability distributions and is formally analogous to the familiar concept of state from classical statistical mechanics. We first demonstrate the mathematical equivalence of this new notion to the standard quantum notion of density matrix. We identify the simple logical consistency condition (a generalization of the familiar no-signalling condition) which a collection of distributions must obey in order to reconstruct the unique quantum state from which they arise. In this way, we achieve a formal expression of the common intuition of a quantum state as being classical distributions on compatible observables.
Holography without Strings - Joint Quantum Gravity and String Theory Seminar

Donald Marolf University of California, Santa Barbara

September 12, 2013

PIRSA:13090060

Quantum Gravity

A defining feature of holographic dualities is that, along with the bulk equations of motion, boundary correlators at any given time t determine those of observables deep in the bulk. We argue that this property emerges from the bulk gravitational Gauss law together with bulk quantum entanglement as embodied in the Reeh-Schlieder theorem. Stringy bulk degrees of freedom are not required and play little role even when they exist. As an example we study a toy model whose matter sector is a free scalar field. The energy density (\rho) sources what we call a pseudo-Newtonian potential (\Phi) through Poisson's equation on each constant time surface, but there is no back-reaction on the matter. We show the Hamiltonian to be essentially self-adjoint on the domain generated from the vacuum by acting with boundary observables localized in an arbitrarily small neighborhood of the chosen time t. Since the Gauss law represents the Hamiltonian as a boundary term, the model is holographic in the sense stated above.
13/14 PSI - Quantum Theory - Lecture 4

Joseph Emerson Institute for Quantum Computing (IQC)

September 12, 2013

PIRSA:13090033
13/14 PSI - Relativity - Lecture 4b

Neil Turok University of Edinburgh

September 12, 2013

PIRSA:13090075

Title	Date	Collection	Type	Info
ΛCDM Large Scale Triumphs and Small Scale Challenges	2013‑09‑17	Cosmology and Gravitation	Scientific Series	View details
13/14 PSI - Quantum Theory - Lecture 7	2013‑09‑17	13/14 PSI - Quantum Theory	Course	View details
13/14 PSI - Relativity - Lecture 7	2013‑09‑17	13/14 PSI - Relativity	Course	View details
13/14 PSI - Quantum Theory - Lecture 6	2013‑09‑16	13/14 PSI - Quantum Theory	Course	View details
13/14 PSI - Relativity - Lecture 6	2013‑09‑16	13/14 PSI - Relativity	Course	View details
13/14 PSI - Quantum Theory - Lecture 5	2013‑09‑13	13/14 PSI - Quantum Theory	Course	View details
Edge states at domain wall junctions in supersymmetric gauge theory	2013‑09‑13	Quantum Matter	Scientific Series	View details
13/14 PSI - Relativity - Lecture 5	2013‑09‑13	13/14 PSI - Relativity	Course	View details
Quantum States are Consistent Probability Distributions	2013‑09‑12	Quantum Foundations	Scientific Series	View details
Holography without Strings - Joint Quantum Gravity and String Theory Seminar	2013‑09‑12	Quantum Gravity	Scientific Series	View details
13/14 PSI - Quantum Theory - Lecture 4	2013‑09‑12	13/14 PSI - Quantum Theory	Course	View details
13/14 PSI - Relativity - Lecture 4b	2013‑09‑12	13/14 PSI - Relativity	Course	View details

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