Scientific Series

Displaying 3169 - 3180 of 5090

Last gasp ‎of a black hole: why unitary evaporation must be non-monotonic

Matteo Smerlak Capital Fund Management S.A.
May 29, 2014

PIRSA:14050027
General Relativity & Quantum Cosmology
Phenomenology of charge order in underdoped cuprates

Andrea Allais Harvard University

May 27, 2014

PIRSA:14050147
A mechanism for vortex annihilation in two dimensional superfluid turbulence

Andrew Lucas University of Colorado Boulder
May 22, 2014

PIRSA:14050139
General Relativity & Quantum Cosmology
Are the recent IceCube events hinting at O(100) TeV decaying dark matter?

Atri Bhattacharya University of Liège
May 22, 2014

PIRSA:14050118
High Energy Physics
Equality

Tobias Fritz Universität Innsbruck

May 21, 2014

PIRSA:14050063
Local quanta, unitary inequivalence, and vacuum entanglement

Hans Westman
May 20, 2014

PIRSA:14050117
Quantum Physics
Designing exotic circuitry with non-Abelian anyons
May 20, 2014

PIRSA:14050029
Condensed Matter
M-strings and their orbifolds

Babak Haghighat Harvard University
May 20, 2014

PIRSA:14050005
High Energy Physics
Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake

Brian Dolan Maynooth University
May 20, 2014

PIRSA:14050093
Astrophysics
From locally covariant QFT to quantum gravity

Katarzyna Rejzner University of York
May 15, 2014

PIRSA:14050004
General Relativity & Quantum Cosmology
Gravity waves from Kerr/CFT

Achilleas Porfyriadis Harvard University
May 15, 2014

PIRSA:14050009
General Relativity & Quantum Cosmology
A polynomial-time algorithm for the ground state of 1D gapped local Hamiltonians

Thomas Vidick Weizmann Institute of Science

May 14, 2014

PIRSA:14050039

Last gasp ‎of a black hole: why unitary evaporation must be non-monotonic

Matteo Smerlak Capital Fund Management S.A.
May 29, 2014

PIRSA:14050027
General Relativity & Quantum Cosmology
I will describe the relationship between radiated energy and entanglement entropy of massless fields at future null infinity (the "Page curve") in two-dimensional models of black hole evaporation. ‎I will use this connection to derive a general feature of any unitary-preserving evaporation scenario: the Bondi mass of the hole must be non-monotonic. Time permitting, I will comment on time scales in such scenarios.
Phenomenology of charge order in underdoped cuprates

Andrea Allais Harvard University

May 27, 2014

PIRSA:14050147

In the past few years substantial evidence has been collected that points to coexistence of charge correlations with long range superconductivity in underdoped cuprate superconductors. In this talk I will review some of this evidence, then show that a charge density wave with precisely the same signatures is a natural instability of an antiferromagnetic metal, and finally derive some phenomenological consequences, with special focus on quantum oscillation experiments.
A mechanism for vortex annihilation in two dimensional superfluid turbulence

Andrew Lucas University of Colorado Boulder
May 22, 2014

PIRSA:14050139
General Relativity & Quantum Cosmology
Recent numerical simulations [1] have suggested that two dimensional superfluid turbulence is characterized by a direct cascade of energy to small length scales, in contrast to the inverse cascade of normal fluids, where energy is transported to large length scales. This direct cascade is characterized by many vortex-antivortex annihilation events. Recent experimental work [2] on Bose-Einstein condensates appears to demonstrate qualitatively similar physics. I will discuss recent work in progress towards identifying the physical mechanism underlying this direct cascade, using techniques of effective field theory.
Are the recent IceCube events hinting at O(100) TeV decaying dark matter?

Atri Bhattacharya University of Liège
May 22, 2014

PIRSA:14050118
High Energy Physics
The IceCube detector has recently reported the observation of 28 events at previously unexplored energies. While the statistics of the observed events are still low, these events hint at the existence of a neutrino flux over and above the atmospheric neutrino background. We investigate the possibility that a significant component of the additional neutrino flux originates due to the decay of a very heavy dark matter (VHDM) particle via several possible channels into standard model particles. We show that a combination of a power law astrophysical neutrino spectrum and the neutrino flux from the decay of a DM species of mass in the range 150-400 TeV improves the fit to the observed neutrino events than that obtained from a best-fit astrophysical flux alone. Assuming the existence of an astrophysical background described by the IC best-fit, we also show that, for the decay of even heavier DM particles ($m_{\text{DM}} \sim 1$ PeV), the same observations impose significant constraints on the decay lifetimes. Allowing the astrophysical flux normalization to vary leads to modifications of these limits; however, there is still a range of dark matter mass and lifetime that is excluded by the IC results.
Equality

Tobias Fritz Universität Innsbruck

May 21, 2014

PIRSA:14050063

Equality of two mathematical objects is a seemingly simple and well-understood concept. In this talk, I will do three things to explain why this is a misconception: I will survey different notions of equality, explain how revising the notion of equality has led to an emerging alternative foundation of mathematics called "homotopy type theory", and try to convince you that thinking about equality is relevant to your research in quantum field theory, quantum gravity or quantum foundations.
Local quanta, unitary inequivalence, and vacuum entanglement

Hans Westman
May 20, 2014

PIRSA:14050117
Quantum Physics
In this work we develop a formalism for describing localised quanta for a real-valued Klein-Gordon field in a one-dimensional box [0, R]. We quantise the field using non-stationary local modes which, at some arbitrarily chosen initial time, are completely localised within the left or the right side of the box. In this concrete set-up we directly face the problems inherent to a notion of local field excitations, usually thought of as elementary particles. Specifically, by computing the Bogoliubov coefficients relating local and standard (global) quantizations, we show that the local quantisation yields a Fock space F^L which is unitarily inequivalent to the standard one F^G. In spite of this, we find that the local creators and annihilators remain well defined in the global Fock space F^G, and so do the local number operators associated to the left and right partitions of the box. We end up with a useful mathematical toolbox to analyse and characterise local features of quantum states in F^G . Specifically, an analysis of the global vacuum state |0_G> ∈ F^G in terms of local number operators shows, as expected, the existence of entanglement between the left and right regions of the box. The local vacuum |0_L> ∈ F^L , on the contrary, has a very different character. It is neither cyclic nor separating and displays no entanglement. Further analysis shows that the global vacuum also exhibits a distribution of local excitations reminiscent, in some respects, of a thermal bath. We discuss how the mathematical tools developed herein may open new ways for the analysis of fundamental problems in local quantum field theory.
Designing exotic circuitry with non-Abelian anyons
May 20, 2014

PIRSA:14050029
Condensed Matter
Non-Abelian anyons are widely sought for the exotic fundamental physics they harbor as well as for their possible applications for quantum information processing. Currently, there are numerous blueprints for stabilizing the simplest type of non-Abelian anyon, a Majorana zero energy mode bound to a vortex or a domain wall. One such candidate system, a so-called "Majorana wire" can be made by judiciously interfacing readily available materials; the experimental evidence for the viability of this approach is presently emerging.
Following this idea, we introduce a device fabricated from conventional fractional quantum Hall states, s-wave superconductors and insulators with strong spin-orbit coupling. Similarly to a Majorana wire, the ends of our “quantum wire” would bind "parafermions", exotic non-Abelian anyons which can be viewed as fractionalised Majorana zero modes.
I will discuss their properties and describe how such parafermions can be used to construct new and potentially useful circuit elements which include current and voltage mirrors, transistors for fractional charge currents and "flux capacitors".
M-strings and their orbifolds

Babak Haghighat Harvard University
May 20, 2014

PIRSA:14050005
High Energy Physics
We consider M-theory in the presence of M parallel M5-branes probing a transverse A_{N-1} singularity. This leads to a superconformal theory with (1,0) supersymmetry in six dimensions. We compute the supersymmetric partition function of this theory on a two-torus, with arbitrary supersymmetry preserving twists, using the topological vertex formalism. Alternatively, we show that this can also be obtained by computing the elliptic genus of an orbifold of recently studied M-strings. The resulting 2d theory is a (4,0) supersymmetric quiver gauge theory whose Higgs branch corresponds to strings propagating on the moduli space of SU(N)^(M-1) instantons on R^4 where the right-moving fermions are coupled to a particular bundle.
Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake

Brian Dolan Maynooth University
May 20, 2014

PIRSA:14050093
Astrophysics
The thermodynamics of black holes will be reviewed and recent developments incorporating pressure into the first law described. The asymptotically AdS Kerr metric has a van der Waals type critical point with a line of first order phase transitions terminating at a critical point with mean field exponents. The phase structure and stability of black holes in higher dimensions will also be described.
From locally covariant QFT to quantum gravity

Katarzyna Rejzner University of York
May 15, 2014

PIRSA:14050004
General Relativity & Quantum Cosmology
Locally covariant quantum field theory (LCQFT) has proven to be a very successful framework for QFT on curved spacetimes. It is natural to ask, how far these ideas can be generalized and if one can learn something about quantum gravity, using LCQFT methods. In particular, one can use the relative Cauchy evolution to formulate the notion of background independence. Recently we have proven that background independence in this sense holds for effective quantum gravity, formulated as a perturbative QFT. Remarkably, the formalism of LCQFT can be extended to structures more general than spacetimes. The essential feature is the presence of the causal structure. An example application would be QFT on causal sets (work in progress).
Gravity waves from Kerr/CFT

Achilleas Porfyriadis Harvard University
May 15, 2014

PIRSA:14050009
General Relativity & Quantum Cosmology
Astronomical observation suggests the existence of near-extreme Kerr black holes whose horizons spin at nearly the speed of light. Properties of diffeomorphisms imply that the dynamics of the high-redshift near-horizon region of near-extreme Kerr, which includes the innermost-stable-circular-orbit (ISCO), is governed by an infinite-dimensional emergent conformal symmetry. This symmetry may be exploited to analytically, rather than numerically, compute a variety of potentially observable processes. In this talk I will show how we compute and study the conformal transformation properties of the gravitational radiation emitted by an orbiting massive object in the large-redshift near-horizon region. I will also use conformal symmetry of the near-horizon region to compute the gravitational radiation produced during the plunge phase following the object's crossing of the ISCO.
A polynomial-time algorithm for the ground state of 1D gapped local Hamiltonians

Thomas Vidick Weizmann Institute of Science

May 14, 2014

PIRSA:14050039

Computing ground states of local Hamiltonians is a fundamental problem in condensed matter physics. We give the first randomized polynomial-time algorithm for finding ground states of gapped one-dimensional Hamiltonians: it outputs an (inverse-polynomial) approximation, expressed as a matrix product state (MPS) of polynomial bond dimension. The algorithm combines many ingredients, including recently discovered structural features of gapped 1D systems, convex programming, insights from classical algorithms for 1D satisfiability, and new techniques for manipulating and bounding the complexity of MPS. Our result provides one of the first major classes of Hamiltonians for which computing ground states is provably tractable despite the exponential nature of the objects involved. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-style-parent:""; font-size:11.0pt; font-family:"Calibri","sans-serif";}

Title	Speaker(s)	Date	Talk Type	Info link
Last gasp ‎of a black hole: why unitary evaporation must be non-monotonic	Matteo Smerlak	2014-05-29	Scientific Series	View details
Phenomenology of charge order in underdoped cuprates	Andrea Allais	2014-05-27	Scientific Series	View details
A mechanism for vortex annihilation in two dimensional superfluid turbulence	Andrew Lucas	2014-05-22	Scientific Series	View details
Are the recent IceCube events hinting at O(100) TeV decaying dark matter?	Atri Bhattacharya	2014-05-22	Scientific Series	View details
Equality	Tobias Fritz	2014-05-21	Scientific Series	View details
Local quanta, unitary inequivalence, and vacuum entanglement	Hans Westman	2014-05-20	Scientific Series	View details
Designing exotic circuitry with non-Abelian anyons		2014-05-20	Scientific Series	View details
M-strings and their orbifolds	Babak Haghighat	2014-05-20	Scientific Series	View details
Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake	Brian Dolan	2014-05-20	Scientific Series	View details
From locally covariant QFT to quantum gravity	Katarzyna Rejzner	2014-05-15	Scientific Series	View details
Gravity waves from Kerr/CFT	Achilleas Porfyriadis	2014-05-15	Scientific Series	View details
A polynomial-time algorithm for the ground state of 1D gapped local Hamiltonians	Thomas Vidick	2014-05-14	Scientific Series	View details

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Last gasp ‎of a black hole: why unitary evaporation must be non-monotonic

Phenomenology of charge order in underdoped cuprates

A mechanism for vortex annihilation in two dimensional superfluid turbulence

Are the recent IceCube events hinting at O(100) TeV decaying dark matter?

Equality

Local quanta, unitary inequivalence, and vacuum entanglement

Designing exotic circuitry with non-Abelian anyons

M-strings and their orbifolds

Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake

From locally covariant QFT to quantum gravity

Gravity waves from Kerr/CFT

A polynomial-time algorithm for the ground state of 1D gapped local Hamiltonians

Last gasp ‎of a black hole: why unitary evaporation must be non-monotonic

Phenomenology of charge order in underdoped cuprates

A mechanism for vortex annihilation in two dimensional superfluid turbulence

Are the recent IceCube events hinting at O(100) TeV decaying dark matter?

Equality

Local quanta, unitary inequivalence, and vacuum entanglement

Designing exotic circuitry with non-Abelian anyons

M-strings and their orbifolds

Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake

From locally covariant QFT to quantum gravity

Gravity waves from Kerr/CFT

A polynomial-time algorithm for the ground state of 1D gapped local Hamiltonians