Scientific Series

Displaying 3193 - 3204 of 5012

Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice

Gang Chen
Fudan University
December 06, 2013

PIRSA:13120055
Condensed Matter
BBN and the Unnatural Weak Scale

David Pinner
University of California, Berkeley
December 05, 2013

PIRSA:13120058
Particle Physics
From spin foams to anyons and back again - Joint Condensed Matter/Quantum Gravity Seminar

Bianca Dittrich
Perimeter Institute for Theoretical Physics
December 05, 2013

PIRSA:13120048
Quantum Gravity
Using the Higgs as a Direct Probe of New Physics

Michael Park
Rutgers University
December 05, 2013

PIRSA:13120050
Particle Physics
Supersymmetry, Non-thermal Dark Matter and Precision Cosmology

Scott Watson
Syracuse University
December 05, 2013

PIRSA:13120054
Cosmology
Direct Detection of Classically Undetectable Dark Matter through Quantum Decoherence

Jess Riedel
NTT Research
December 04, 2013

PIRSA:13120053
Quantum Information
The Galactic Real Estate Market: The Physics and Chemistry of Habitability

Penelope Boston
National Cave and Karst Research Institute

December 04, 2013

PIRSA:13120044
Jets Without Jets

Daniele Bertolini
Massachusetts Institute of Technology (MIT)
December 04, 2013

PIRSA:13120052
Particle Physics
Quantum Mechanics as Classical Physics

Charles Sebens
University of Michigan–Ann Arbor
December 03, 2013

PIRSA:13120006
Quantum Foundations
Fully exploring exotic production of the 125 GeV Higgs

Felix Yu
Fermi National Accelerator Laboratory (Fermilab)
December 03, 2013

PIRSA:13120047
Particle Physics
Acceleration, Then and Now

Cliff Burgess
McMaster University
December 03, 2013

PIRSA:13120059
Cosmology
Cornering Gluinos at the LHC

Jared Evans
Rutgers University
December 02, 2013

PIRSA:13120057
Particle Physics

Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice

Gang Chen
Fudan University
December 06, 2013

PIRSA:13120055
Condensed Matter
Quantum spin liquid (QSL) is an exotic phase of matter and provides an interesting example of emergent non-locality. Even though many materials have been proposed as candidates for QSLs, there is no direct confirmation of QSLs in any of these systems. Quantum spin ice (QSI) is a physical realization of U(1) QSLs on the pyrochlore lattice. We consider a class of electron systems in which dipolar-octupolar Kramers doublets arise on the pyrochlore lattice. In the localized limit, the Kramers doublets are described by the effective spin 1/2 pseudospins. The most general nearest-neighbor exchange model between these pseudospins is the XYZ model. We show that this XYZ model exhibit two distinct symmetry enriched QSI phases, that we dub dipolar QSI and octupolar QSI. This XYZ model is absent from the notorious sign problem for a quantum Monte Carlo simmulation. We also discuss the potential relevance to real material systems.
BBN and the Unnatural Weak Scale

David Pinner
University of California, Berkeley
December 05, 2013

PIRSA:13120058
Particle Physics
The discovery of a perturbatively-coupled, 125 GeV Higgs, together with the absence of LHC signals for supersymmetry, places the principle of naturalness under tension. In this talk I will discuss the possibility that the weak scale is unnatural, with its value determined environmentally in the landscape. In particular, this environmental selection may be driven by BBN: as the weak scale is increased, the abundance of Hydrogen in the early universe is rapidly depleted. That our own universe contains an O(1) fraction of primordial Helium arises as a conspiracy among the weak scale, the neutron-proton mass difference, and the planck scale.
From spin foams to anyons and back again - Joint Condensed Matter/Quantum Gravity Seminar

Bianca Dittrich
Perimeter Institute for Theoretical Physics
December 05, 2013

PIRSA:13120048
Quantum Gravity
Spin foams provide models for quantum gravity and hence quantum space time. One of the key outstanding questions is to show that they reproduce smooth space time manifolds in a continuum limit.I will start with a very short introduction to spin foams and the structure of quantum space time they encode. I will explain how the investigation of the continuum limit via coarse graining and renormalization techniques led as to consider anyonic spin chains and a classification of ground states in systems with quantum group symmetries.I will then present new results on the continuum limit of spin net models, that allow us to draw first conclusions about the large scale dynamics of spin foams.
Based on: B.D., W. Kaminski, Topological lattice field theories from intertwiner dynamics, arXiv:1311.1798, B.D., S. Steinhaus, Time evolution as refining, coarse graining and entangling, to appear, B.D. M. Martin-Benito, S. Steinhaus, The refinement limit of quantum group spin net models, to appear
Using the Higgs as a Direct Probe of New Physics

Michael Park
Rutgers University
December 05, 2013

PIRSA:13120050
Particle Physics
The discovery of the Higgs boson marks the first direct probe into the mechanism of electroweak symmetry breaking. All evidence currently points to the fact that electroweak symmetry is broken by at least one fundamental scalar, and naturalness remains the most compelling reason to expect additional degrees of freedom at the weak scale. This talk will describe some ideas for how to utilize powerful and proven experimental techniques, in conjunction with the fact that observables directly related to the Higgs boson are now experimentally accessible, to make concrete statements about the existence of possible new degrees of freedom at the weak scale.
Supersymmetry, Non-thermal Dark Matter and Precision Cosmology

Scott Watson
Syracuse University
December 05, 2013

PIRSA:13120054
Cosmology
Within the Minimal Supersymmetric Standard Model (MSSM), LHC bounds suggest that scalar superpartner masses are far above the electroweak scale. Given a high superpartner mass, nonthermal dark matter is a viable alternative to WIMP dark matter generated via freezeout. In the presence of moduli fields nonthermal dark matter production is associated with a long matter dominated phase, modifying the spectral index and primordial tensor amplitude relative to those in a thermalized primordial universe. Nonthermal dark matter can have a higher self-interaction cross-section than its thermal counterpart, enhancing astrophysical bounds on its annihilation signals. I will review recent progress in this program, and discuss how we can constrain the contributions to the neutralino mass from the bino, wino and higgsino using existing astrophysical bounds and direct detection experiments for models with nonthermal neutralino dark matter. Using these constraints we will then see how expected changes to inflationary observables result from the nonthermal phase.
Direct Detection of Classically Undetectable Dark Matter through Quantum Decoherence

Jess Riedel
NTT Research
December 04, 2013

PIRSA:13120053
Quantum Information
Although various pieces of indirect evidence about the nature of dark matter have been collected, its direct detection has eluded experimental searches despite extensive effort. If the mass of dark matter is below 1 MeV, it is essentially imperceptible to conventional detection methods because negligible energy is transferred to nuclei during collisions. Here I propose directly detecting dark matter through the quantum decoherence it causes rather than its classical effects such as recoil or ionization. I show that quantum spatial superpositions are sensitive to low-mass dark matter that is inaccessible to classical techniques. This provides new independent motivation for matter interferometry with large masses, especially on spaceborne platforms. The apparent dark matter wind we experience as the Sun travels through the Milky Way ensures interferometers and related devices are directional detectors, and so are able to provide unmistakable evidence that decoherence has galactic origins.
The Galactic Real Estate Market: The Physics and Chemistry of Habitability

Penelope Boston
National Cave and Karst Research Institute

December 04, 2013

PIRSA:13120044

Exoplanets, planets circling distant stars, are proving to be an extraordinary source of new thinking about the potential for life beyond Earth. Until recently, we have assumed that our Solar System and its planets were probably representative of such systems elsewhere. But the amazing array of very odd exoplanets that are being uncovered have stimulated a renaissance of thought on the subject of potential homes for life in the universe. Combined with work on extreme lifeforms here on Earth and intensive study of Mars and several other planets and moons in our system, new paradigms for life search missions are emerging. Science fiction has long drawn from and extrapolated out from science, but the cross-fertilization has gone both ways. Some of the more outrageous planets incorporated into fiction in the past may not be so outrageous after all. I will discuss what we think we know about exoplanets so far, how they are detected, how we are beginning to characterize their environments, and ideas about what this means for our search for living neighbors in our galaxy, whether they be microbes or folks we can actually chat with some day.
Jets Without Jets

Daniele Bertolini
Massachusetts Institute of Technology (MIT)
December 04, 2013

PIRSA:13120052
Particle Physics
Jets are key tools for physics at the LHC. Usually, jets are identified through a jet algorithm. In this talk, I will present an alternative way of thinking about jets, by showing how a broad class of inclusive jet-based observables can be replaced by event shapes. These event shapes do not require any jet clustering, but they still implement a jet-like pT cut on "jets" with an R-like radius. I will discuss various applications, including event selection at trigger-level, event-wide trimming, and alternative definitions for boosted objects identifiers.
Quantum Mechanics as Classical Physics

Charles Sebens
University of Michigan–Ann Arbor
December 03, 2013

PIRSA:13120006
Quantum Foundations
On the face of it, quantum physics is nothing like classical physics. Despite its oddity, work in the foundations of quantum theory has provided some palatable ways of understanding this strange quantum realm. Most of our best theories take that story to include the existence of a very non-classical entity: the wave function. Here I offer an alternative which combines elements of Bohmian mechanics and the many-worlds interpretation to form a theory in which there is no wave function. According to this theory, all there is at the fundamental level are particles interacting via Newtonian forces. In this sense, the theory is classical. However, it is still undeniably strange as it posits the existence of many worlds. Unlike the many worlds of the many-worlds interpretation, these worlds are fundamental, not emergent, and are interacting, not causally isolated. The theory will be presented as a fusion of the many-worlds interpretation and Bohmian mechanics, but can also be seen as a foundationally clear version of quantum hydrodynamics. A key strength of this theory is that it provides a simple and compelling story about the connection between the amplitude-squared of the wave function and probability. The theory also gives a natural explanation of the way the wave function transforms under time reversal and Galilean boosts.
Fully exploring exotic production of the 125 GeV Higgs

Felix Yu
Fermi National Accelerator Laboratory (Fermilab)
December 03, 2013

PIRSA:13120047
Particle Physics
I consider the effects of exotic production modes of the 125 GeV Higgs and their impact on Higgs searches and the Higgs discovery. I emphasize that new production modes have been largely overlooked in contemporary tests of the Standard Model nature of the Higgs boson but experimental tests of exotic production modes are viable now or will be soon. I present a couple explicit examples of exotic production arising from chargino-neutralino associated production in the MSSM. As a corollary of this work, I point out that current Higgs coupling fits do not adequately explore the complete space of new physics deviations possible in Higgs measurements.
Acceleration, Then and Now

Cliff Burgess
McMaster University
December 03, 2013

PIRSA:13120059
Cosmology
There is good evidence that the universe underwent an epoch of accelerated expansion sometime in its very early history, and that it is entering a similar phase now. This talk is in two parts. The first part describes what I believe to be the take-home message about inflationary models, coming both from the recent Planck results and from attempts to embed inflation within a UV completion (string theory). I will argue that both point to a particularly interesting class of inflationary models that also evade many of the tuning problems of inflation. These models also turn out to make the tantalizing prediction that the scalar-to-tensor ratio, r, could be just out of reach, being predicted to be proportional to (n_s - 1)^2, where n_s ~ 0.96 is the spectral tilt of the scalar spectrum. The second part provides an update on an approach to solving the "cosmological constant problem", which asks why the vacuum energy seems to gravitate so little. This is the main theoretical obstruction that makes it so difficult to understand the origins of the present epoch of acceleration. In the approach described - Supersymmetric Large Extra Dimensions - observations can be reconciled with a large vacuum energy because the vacuum energy curves the extra dimensions and not the ones measured in cosmology. It leads to a picture of very supersymmetric gravity sector coupled to a completely non-supersymmetric particle-physics sector (which predicts in particular no superpartners to be found at the LHC). The update presented here summarizes the underlying mechanism whereby supersymmetry in the extra dimensions acts to suppress the gravitational effects of quantum fluctuations. Because the large quantum contributions are under control it becomes possible to estimate the size of to be expected of the observed dark energy. For the simplest configuratin the result is of order C (m Mg/4 pi Mp)^4, where m is the heaviest particle on the branes (and so no smaller than the top quark mass), Mg is the extra-dimensional gravity scale (no smaller than 10 TeV due to astrophysical constraints, implying two extra dimensions that are of order a micron in size) and Mp is the 4D Planck mass. C is a constant unsuppressed by symmetry-breaking effects, and C = 6 x 10^6 gives the observed dark energy density, using the smallest values given above for m and Mg. If there is time I will sketch arguments as to why there must be other light degrees of freedom in the theory as well, whose implications might ultimately be used to test the picture.
Cornering Gluinos at the LHC

Jared Evans
Rutgers University
December 02, 2013

PIRSA:13120057
Particle Physics
Gluinos are expected to be light for a natural electroweak scale, but the LHC has not seen them yet. Many possibilities have been proposed to hide natural gluinos in the LHC data, but are these methods really effective? In this talk, I will discuss the current status of kinematically accessible gluinos. By noting the most common features - MET, tops, and high multiplicity - which pervade natural gluino decays, I will argue that there are few places left to hide. I will briefly discuss the remaining weaknesses in LHC coverage and how to bolster them.

Title	Speaker(s)	Date	Talk Type	Info link
Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice	Gang Chen	2013-12-06	Scientific Series	View details
BBN and the Unnatural Weak Scale	David Pinner	2013-12-05	Scientific Series	View details
From spin foams to anyons and back again - Joint Condensed Matter/Quantum Gravity Seminar	Bianca Dittrich	2013-12-05	Scientific Series	View details
Using the Higgs as a Direct Probe of New Physics	Michael Park	2013-12-05	Scientific Series	View details
Supersymmetry, Non-thermal Dark Matter and Precision Cosmology	Scott Watson	2013-12-05	Scientific Series	View details
Direct Detection of Classically Undetectable Dark Matter through Quantum Decoherence	Jess Riedel	2013-12-04	Scientific Series	View details
The Galactic Real Estate Market: The Physics and Chemistry of Habitability	Penelope Boston	2013-12-04	Scientific Series	View details
Jets Without Jets	Daniele Bertolini	2013-12-04	Scientific Series	View details
Quantum Mechanics as Classical Physics	Charles Sebens	2013-12-03	Scientific Series	View details
Fully exploring exotic production of the 125 GeV Higgs	Felix Yu	2013-12-03	Scientific Series	View details
Acceleration, Then and Now	Cliff Burgess	2013-12-03	Scientific Series	View details
Cornering Gluinos at the LHC	Jared Evans	2013-12-02	Scientific Series	View details

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