A mechanical analog of quantum bradyons and tachyons

We present a mechanical analog of a quantum wave-particle duality: a vibrating string threaded through a freely moving bead or `masslet'. For small string amplitudes, the particle movement is governed by a set of non-linear dynamical equations that couple the wave field to the masslet dynamics. Under specific conditions, the particle achieves a regime of {\it transparency} in which the field and the particle's dynamics appear decoupled. In that special case, the particle conserves its momentum and a guiding wave obeying a Klein-Gordon equation, with real or imaginary mass, emerges. Similar to the double-solution theory of de Broglie, this guiding wave is locked in phase with a modulating group-wave co-moving with the particle. Interestingly, both subsonic and supersonic particles can fall into a quantum regime as with the slower-than-light bradyons and hypothetical, faster-than-light tachyons of particle physics.Comment: 10 pages, 3 figures, 1 video (Supp. Mat

Maximally Localized Dynamical Quantum Embedding for Solving Many-Body Correlated Systems

We present a quantum embedding methodology to resolve the Anderson impurity model in the context of dynamical mean-field theory, based on an extended exact diagonalization method. Our method provides a maximally localized quantum impurity model, where the non-local components of the correlation potential remain minimal. This method comes at a large benefit, as the environment used in the quantum embedding approach is described by propagating correlated electrons and hence offers a polynomial increase $O(N^4)$ of the number of degrees of freedom for the embedding mapping without adding bath sites. We report that quantum impurity models with as few as 3 bath sites can reproduce both the Mott transition and the Kondo physics, thus opening a more accessible route to the description of time-dependent phenomena. Finally, we obtain excellent agreement for dynamical magnetic susceptibilities, poising this approach as a candidate to describe 2-particle excitations such as excitons in correlated systems. We expect that our approach will be highly beneficial for the implementation of embedding algorithms on quantum computers, as it allows for a fine description of the correlation in materials with a reduced number of required qubits

A review of protocols for Fiducial Reference Measurements of downwelling irradiance for the validation of satellite remote sensing data over water

This paper reviews the state of the art of protocols for the measurement of downwelling irradiance in the context of Fiducial Reference Measurements (FRM) of water reflectance for satellite validation. The measurement of water reflectance requires the measurement of water-leaving radiance and downwelling irradiance just above water. For the latter, there are four generic families of method, using: (1) an above-water upward-pointing irradiance sensor; (2) an above-water downward-pointing radiance sensor and a reflective plaque; (3) a Sun-pointing radiance sensor (sunphotometer); or (4) an underwater upward-pointing irradiance sensor deployed at different depths. Each method-except for the fourth, which is considered obsolete for the measurement of above-water downwelling irradiance-is described generically in the FRM context with reference to the measurement equation, documented implementations, and the intra-method diversity of deployment platform and practice. Ideal measurement conditions are stated, practical recommendations are provided on best practice, and guidelines for estimating the measurement uncertainty are provided for each protocol-related component of the measurement uncertainty budget. The state of the art for the measurement of downwelling irradiance is summarized, future perspectives are outlined, and key debates such as the use of reflectance plaques with calibrated or uncalibrated radiometers are presented. This review is based on the practice and studies of the aquatic optics community and the validation of water reflectance, but is also relevant to land radiation monitoring and the validation of satellite-derived land surface reflectance

Integrating inland and coastal water quality data for actionable knowledge

Water quality measures for inland and coastal waters are available as discrete samples from professional and volunteer water quality monitoring programs and higher-frequency, near-continuous data from automated in situ sensors. Water quality parameters also are estimated from model outputs and remote sensing. The integration of these data, via data assimilation, can result in a more holistic characterization of these highly dynamic ecosystems, and consequently improve water resource management. It is becoming common to see combinations of these data applied to answer relevant scientific questions. Yet, methods for scaling water quality data across regions and beyond, to provide actionable knowledge for stakeholders, have emerged only recently, particularly with the availability of satellite data now providing global coverage at high spatial resolution. In this paper, data sources and existing data integration frameworks are reviewed to give an overview of the present status and identify the gaps in existing frameworks. We propose an integration framework to provide information to user communities through the the Group on Earth Observations (GEO) AquaWatch Initiative. This aims to develop and build the global capacity and utility of water quality data, products, and information to support equitable and inclusive access for water resource management, policy and decision making.Additional co-authors: Anders Knudby, Camille Minaudo, Nima Pahlevan, Ils Reusen, Kevin C. Rose, John Schalles and Maria Tzortzio

Nonlinear atmospheric variability in the winter northeast Pacific associated with the Madden-Julian oscillation

The Madden-Julian Oscillation (MJO), the primary mode of large-scale intraseasonal variability in the tropics, is known to relate to the mid-latitude atmospheric variability. Using neural network techniques, a nonlinear projection of the MJO onto the precipitation and 200-hPa wind anomalies in the northeast Pacific during January–March shows asymmetric atmospheric patterns associated with different phases of the MJO. For precipitation, the strength of the nonlinear effect to the linear effect was 0.94 (in terms of the squared anomalies and averaged over all phases of the MJO), indicating strong nonlinearity, while for the 200-hPa wind, the ratio was 0.55, indicating moderate nonlinearity. In general, anomalous winds blowing from the north or from land were associated with negative precipitation anomalies, while winds from the south or from the open ocean, with positive precipitation anomalies. The nonlinear effects generally induced positive precipitation anomalies during all phases of the MJO. An edited version of this paper was published by AGU. Copyright 2005 American Geophysical Union.Science, Faculty ofEarth and Ocean Sciences, Department ofReviewedFacult

OLE: A Novel Oceanic Lidar Emulator

International audienc

Disruptive Imaginings - Artist Roundtable (A.RT): New Economies

Can art challenge us to shift our economy to one that embraces sustainability, equality, and justice? Can we create local and global economies that are not only resilient and thriving but inclusive of everyone? The Artist Round Table (A.RT) on New Economies brought together a diverse group of panellists who have provocative ideas about art, economy, and transformative change. Set within a staged 1983 corporate boardroom, the A.RT kickoff with a presentation by artist Marilou Lemmens about her collaborative, multidisciplinary practice with Richard Ibghy. Lemmens presented artistic projects that explore the ways in which the economic system pervades nearly every facet of our daily lives. In response, panellists from various fields engaged in a lively discussion, digging deeply into the issues at the heart of the duo’s practice. The panelists draw on their experiences in the realms of art and culture, activism and citizenship, and sustainability and radical urbanism as they tell stories, debate ideas, and challenge each other and the audience with thought-provoking questions. The audience was invited into a discourse on the emergence of a new economy and how art can be a driving force for social change. FEATURING: Marilou Lemmens is a visual artist based in Durham-Sud and Montreal, Quebec where she works in collaboration with Richard Ibghy. Spanning various media, including video, performance, and installation, their work explores the material, affective, and sensory dimensions of experience that cannot be fully translated into signs or systems. For several years, they have examined the rationale upon which economic actions are described and represented, and how the logic of economy has come to infiltrate the most intimate aspects of life. Their work has been shown nationally and internationally, including at La Biennale de Montréal (Montreal, 2014), 27th Images Festival (Toronto, 2014), La Filature, Scène Nationale (Mulhouse, France, 2013-14), Centre for Contemporary Arts (Glasgow, 2012), and the 10th Sharjah Biennial (Sharjah, UAE, 2011), among others. WITH PANELISTS: Community organizer, writer, and activist Matt Hern teaches at UBC and is known for his work in radical urbanism, community development, and alternative forms of education. He is founder of the Purple Thistle Centre, Car-Free Vancouver Day, and Groundswell: Grassroots Economic Alternatives. Cédric Jamet is a Project Manager at the Montreal Urban Ecology Centre and a Curator at Cities for People. His work explores the relationship between the urban imaginary, active citizenship, and the co-creation of sustainable cities. Artist and cultural producer Todd Lester has dedicated his career to supporting and enabling socially engaged artists around the world. He is a senior fellow at the World Policy Institute and founder of both freeDimensional and Lanchonete.org

Disentangling the role of bond lengths and orbital symmetries in controlling TcT_c in YBa2_2Cu3_3O7_7

Optimally doped YBCO (YBa$_{2}$Cu$_{3}$O$_{7}$) has a high critical temperature, at 92 K. It is largely believed that Cooper pairs form in YBCO and other cuprates because of spin fluctuations, the issue and the detailed mechanism is far from settled. In the present work, we employ a state-of-the-art \emph{ab initio} ability to compute both the low and high energy spin fluctuations in optimally doped YBCO. We benchmark our results against recent inelastic neutron scattering and resonant inelastic X-ray scattering measurements. Further, we use strain as an external parameter to modulate the spin fluctuations and superconductivity. We disentangle the roles of Barium-apical Oxygen hybridization, the interlayer coupling and orbital symmetries by applying an idealized strain, and also a strain with a fully relaxed structure. We show that shortening the distance between Cu layers is conducive for enhanced Fermi surface nesting, that increases spin fluctuations and drives up $T_{c}$. However, when the structure is fully relaxed electrons flow to the d$_{z^2}$ orbital as a consequence of a shortened Ba-O bond which is detrimental for superconductivityComment: 5 pages, 4 figure

Early Warning from Space for a Few Key Tipping Points in Physical, Biological, and Social-Ecological Systems

In this review paper, we explore latest results concerning a few key tipping elements of the Earth system in the ocean, cryosphere, and land realms, namely the Atlantic overturning circulation and the subpolar gyre system, the marine ecosystems, the permafrost, the Greenland and Antarctic ice sheets, and in terrestrial resource use systems. All these different tipping elements share common characteristics related to their nonlinear nature. They can also interact with each other leading to synergies that can lead to cascading tipping points. Even if the probability of each tipping event is low, they can happen relatively rapidly, involve multiple variables, and have large societal impacts. Therefore, adaptation measures and management in general should extend their focus beyond slow and continuous changes, into abrupt, nonlinear, possibly cascading, high impact phenomena. Remote sensing observations are found to be decisive in the understanding and determination of early warning signals of many tipping elements. Nevertheless, considerable research still remains to properly incorporate these data in the current generation of coupled Earth system models. This is a key prerequisite to correctly develop robust decadal prediction systems that may help to assess the risk of crossing thresholds potentially crucial for society. The prediction of tipping points remains difficult, notably due to stochastic resonance, i.e. the interaction between natural variability and anthropogenic forcing, asking for large ensembles of predictions to correctly assess the risks. Furthermore, evaluating the proximity to crucial thresholds using process-based understanding of each system remains a key aspect to be developed for an improved assessment of such risks. This paper finally proposes a few research avenues concerning the use of remote sensing data and the need for combining different sources of data, and having long and precise-enough time series of the key variables needed to monitor Earth system tipping elements