Scientific Series

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Possible Astrophysical Observables of Quantum Gravity Effects near Black Holes

Ue-Li Pen
Canadian Institute for Theoretical Astrophysics (CITA)
March 27, 2014

PIRSA:14030115
Quantum Gravity
Bungee jumping of black holes in AdS universe
March 27, 2014

PIRSA:14030108
Strong Gravity
The invasion of physics by information theory

Robert Spekkens
Perimeter Institute for Theoretical Physics
March 26, 2014

PIRSA:14030085
Quantum Foundations
GeV Gamma-Rays from the Central Milky Way and the Case for Annihilating Dark Matter

Tracy Slatyer
Massachusetts Institute of Technology (MIT) - Department of Physics
March 26, 2014

PIRSA:14030120
Particle Physics
Far from equilibrium energy flow in quantum critical systems
March 25, 2014

PIRSA:14030089
Quantum Fields and Strings
Naturalness and the Weak Gravity Conjecture

Clifford Cheung
California Institute of Technology (Caltech) - Physics Office
March 25, 2014

PIRSA:14030119
Particle Physics
Cosmic initial conditions and the CMB

Daniel Grin
California Institute of Technology
March 25, 2014

PIRSA:14030112
Cosmology
Ambiguities in order-theoretic formulations of thermodynamics

Harvey Brown
University of Oxford
March 21, 2014

PIRSA:14030093
Quantum Foundations
Universal topological quantum computation from a superconductor/Abelian quantum Hall heterostructure

Roger Mong
University of Pittsburgh
March 19, 2014

PIRSA:14030118
Quantum Information
Exact results in supersymmetric gauge theories in various dimensions

Sara Pasquetti
University of Milan
March 19, 2014

PIRSA:14030084
Particle Physics
A histories perpective on bounding quantum correlations

Joe Henson
BNP Paribas Asset Management London
March 18, 2014

PIRSA:14030111
Quantum Foundations
Before the Bang

Raman Sundrum
University of Maryland, College Park
March 18, 2014

PIRSA:14030113
Particle Physics

Possible Astrophysical Observables of Quantum Gravity Effects near Black Holes

Ue-Li Pen
Canadian Institute for Theoretical Astrophysics (CITA)
March 27, 2014

PIRSA:14030115
Quantum Gravity
Recent implications of results from quantum information theory applied to black holes has led to the confusing conclusions that requires either abandoning the equivalence principle (e.g. the firewall picture), or the no-hair theorem (e.g. the fuzzball picture), or even more unpalatable options. The recent discovery of a pulsar orbiting a black hole opens up new possibilities for tests of theories of gravity. We examine possible observational effects of semiclassical quantum gravity in the vicinity of black holes, as probed by pulsars and event horizon telescope imaging of flares. Pulsar radiation is observable at wavelengths only two orders of magnitude shorter than the Hawking radiation, so precision interferometry of lensed pulsar images may shed light on the quantum gravitational processes and interaction of Hawking radiation with the spacetime near the black hole. This paper discusses the impact on the pulsar radiation interference pattern, which is observable through the modulation index in the foreseeable future, and discusses a possible classical limit of BHC.
Bungee jumping of black holes in AdS universe
March 27, 2014

PIRSA:14030108
Strong Gravity
C-metric describes uniformly accelerated black holes. We will review a global structure of these solutions especially in Lambda<0 context. It turns out that for an acceleration larger than the cosmological one the metric describes pairs of black holes "bungee jumping" into spacetime from AdS infinity.
The invasion of physics by information theory

Robert Spekkens
Perimeter Institute for Theoretical Physics
March 26, 2014

PIRSA:14030085
Quantum Foundations
When we think of a revolution in physics, we usually think of a physical theory that manages to overthrow its predecessor. There is another kind of revolution, however, that typically happens more slowly but that is often the key to achieving the first sort: it is the discovery of a novel perspective on an existing physical theory. The use of least-action principles, symmetry principles, and thermodynamic principles are good historical examples. It turns out that we can refine our understanding of many of these principles by characterizing certain properties of physical states as resources. I will discuss some of the highlights of two resource theories: the resource theory of asymmetry, which characterizes the relations among quantum states that break a symmetry; and the resource theory of athermality, which characterizes the relations among quantum states that deviate from thermal equilibrium. In particular, I will discuss how Noether's theorem does not capture all of the consequences of symmetries of the dynamics, and how the second law of thermodynamics does not capture all of the constraints on thermodynamic transitions. Finally, I will show that both asymmetry and athermality are informational resources, and that rehabilitated versions of Noether's theorem and the second law can both be understood as constraints on data processing. Considerations such as these---as well as evidence from other fronts of the invasion---make a compelling case for the revolutionary cause of reconceiving physics from an information-theoretic perspective.
GeV Gamma-Rays from the Central Milky Way and the Case for Annihilating Dark Matter

Tracy Slatyer
Massachusetts Institute of Technology (MIT) - Department of Physics
March 26, 2014

PIRSA:14030120
Particle Physics
Past studies have identified a spatially extended excess of ~1-3 GeV gamma rays from the Galactic Center and inner Galaxy, consistent with the emission expected from annihilating thermal relic dark matter. I will describe recent improvements in the characterization of this signal, which demonstrate that it is spherically symmetric, centered on the Galactic Center, and with a spatial profile consistent with annihilation from a cusped NFW profile. The excess can be detected out to 10 degrees from the Galactic Center, which poses challenges for a millisecond pulsar origin; I will discuss the implications of a dark matter interpretation.
Far from equilibrium energy flow in quantum critical systems
March 25, 2014

PIRSA:14030089
Quantum Fields and Strings
We investigate far from equilibrium energy transport in strongly coupled quantum critical systems. Combining results from gauge-gravity duality, relativistic hydrodynamics, and quantum field theory, we argue that long-time energy transport after a local thermal quench occurs via a universal steady-state for any spatial dimensionality. This is described by a boosted thermal state. We determine the transport properties of this emergent steady state, including the average energy flow and its long-time fluctuations.
Naturalness and the Weak Gravity Conjecture

Clifford Cheung
California Institute of Technology (Caltech) - Physics Office
March 25, 2014

PIRSA:14030119
Particle Physics
The weak gravity conjecture (WGC) asserts a powerful consistency condition on gauge theories coupled to quantum gravity: an Abelian, long-range force requires a state of charge q and mass m such that q > m/mPl. Failure of this condition implies the existence of stable black hole remnants and is in tension with no-hair theorems. In this paper, we argue that the WGC creates a non- perturbative obstruction to naturalness, which is the notion that dimensionless coefficients should take on O(1) values in the absence of enhanced symmetry. As an illustration, we show that for scalar quantum electrodynamics, a natural spectrum can actually be forbidden by the WGC, which bounds a radiatively unstable quantity, m, by a radiatively stable quantity, q. More generally, the WGC can be at odds with naturalness in any theory containing charged fundamental scalars. We extend the conditions of the WGC to more complicated theories with multiple gauge symmetries and particles. Finally, we discuss implications for the hierarchy problem and construct a simple model in which the natural value of the electroweak scale—at the cutoff—is forbidden by the WGC.
Cosmic initial conditions and the CMB

Daniel Grin
California Institute of Technology
March 25, 2014

PIRSA:14030112
Cosmology
One new frontier in cosmology is the frequency spectrum of the CMB. Future instruments may be precise enough to measure deviations from the nearly-perfect blackbody, measuring a chemical potential and thus probing energy injection at extremely high redshift. I will discuss ($\mu$ and $y$-type) CMB spectral distortions from the dissipation of entropy (isocurvature)-sourced acoustic modes. I will then discuss how a high-energy phase transition could also source such distortions. I will then switch gears and talk about the possibility of measuring a spatial fluctuation in the baryon/DM ratio using the CMB, including recent observational results. I may also muse on the surprising possible connection between these compensated isocurvature modes and the anomalously low large-scale scalar power hinted at by Planck observations of the CMB temperature power spectrum and the recent claimed BICEP2 detection of primordial tensor modes
Ambiguities in order-theoretic formulations of thermodynamics

Harvey Brown
University of Oxford
March 21, 2014

PIRSA:14030093
Quantum Foundations
Since the 1909 work of Carathéodory, an axiomatic approach to thermodynamics has gained ground which highlights the role of the the binary relation of adiabatic accessibility between equilibrium states. A feature of Carathédory's system is that the version therein of the second law contains an ambiguity about the nature of irreversible adiabatic processes, making it weaker than the traditional Kelvin-Planck statement of the law. This talk attempts first to clarify the nature of this ambiguity, by defining the arrow of time in thermodynamics by way of the Equilibrium Principle (``Minus First Law''). It then examines the extent to which the 1989 axiomatisation of Lieb and Yngvason shares the same ambiguity, despite proposing a very different approach to the second law.
Universal topological quantum computation from a superconductor/Abelian quantum Hall heterostructure

Roger Mong
University of Pittsburgh
March 19, 2014

PIRSA:14030118
Quantum Information
Non-Abelian anyons promise to reveal spectacular features of quantum mechanics that could ultimately provide the foundation for a decoherence-free quantum computer. The Moore-Read quantum Hall state and a (relatively simple) two-dimensional p+ip superconductor both support Ising non-Abelian anyons, also referred to as Majorana zero modes. Here we construct a novel two-dimensional superconductor in which charge-2e Cooper pairs are built from fractionalized quasiparticles, and like the Z3 Read-Rezayi state, harbors Fibonacci anyons that--unlike Ising anyons--allow for universal topological quantum computation solely through braiding.
Exact results in supersymmetric gauge theories in various dimensions

Sara Pasquetti
University of Milan
March 19, 2014

PIRSA:14030084
Particle Physics
One of the central challenges in theoretical physics is to develop non-perturbative methods to describe quantitatively the dynamics of strongly coupled quantum fields. Much progress in this direction has been made for theories with a higher degree of symmetry, such as conformal symmetry or supersymmetry. In recent years the method of localisation has allowed to obtain a great deal of exact results for supersymmetric gauge theories in various dimensions which has led to the discovery of new surprising correspondences such as the celebrated Alday-Gaiotto-Tachikawa correspondence. I will review some recent results which indicate that partition functions of supersymmetric theories formulated on compact manifolds can be expressed in terms of a small set of fundamental building blocks.
A histories perpective on bounding quantum correlations

Joe Henson
BNP Paribas Asset Management London
March 18, 2014

PIRSA:14030111
Quantum Foundations
There has recently been much interest in finding simple principles that explain the particular sets of experimental probabilities that are possible with quantum mechanics in Bell-type experiments. In the quantum gravity community, similar questions had been raised, about whether a certain generalisation of quantum mechanics allowed more than quantum mechanics in this regard. We now bring these two strands of work together to see what can be learned on both sides.
Before the Bang

Raman Sundrum
University of Maryland, College Park
March 18, 2014

PIRSA:14030113
Particle Physics
The simplest black hole solution in asymptotic AdS spacetime, the eternal 3-dimensional BTZ black hole, is studied from the viewpoint of AdS/CFT duality. We identify a class of non-local correlators on the CFT side that allow us to generalize the notion of quantum gravity "S-matrix" to scattering inside the horizon. Since the interior of the horizon is a cosmological spacetime with a big bang/crunch-like singularity, our construction can be interpreted as identifying generally coordinate invariant observables of quantum gravity in a simple cosmology. We show in a certain precise sense, that these holographic observables lie "before the big bang" in a region of spacetime containing closed timelike curves. A central tool in our analysis is the realization of BTZ as a quotient of 3-dimensional AdS.

Title	Speaker(s)	Date	Talk Type	Info link
Possible Astrophysical Observables of Quantum Gravity Effects near Black Holes	Ue-Li Pen	2014-03-27	Scientific Series	View details
Bungee jumping of black holes in AdS universe		2014-03-27	Scientific Series	View details
The invasion of physics by information theory	Robert Spekkens	2014-03-26	Scientific Series	View details
GeV Gamma-Rays from the Central Milky Way and the Case for Annihilating Dark Matter	Tracy Slatyer	2014-03-26	Scientific Series	View details
Far from equilibrium energy flow in quantum critical systems		2014-03-25	Scientific Series	View details
Naturalness and the Weak Gravity Conjecture	Clifford Cheung	2014-03-25	Scientific Series	View details
Cosmic initial conditions and the CMB	Daniel Grin	2014-03-25	Scientific Series	View details
Ambiguities in order-theoretic formulations of thermodynamics	Harvey Brown	2014-03-21	Scientific Series	View details
Universal topological quantum computation from a superconductor/Abelian quantum Hall heterostructure	Roger Mong	2014-03-19	Scientific Series	View details
Exact results in supersymmetric gauge theories in various dimensions	Sara Pasquetti	2014-03-19	Scientific Series	View details
A histories perpective on bounding quantum correlations	Joe Henson	2014-03-18	Scientific Series	View details
Before the Bang	Raman Sundrum	2014-03-18	Scientific Series	View details

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