Eric Sembrat's Test Bonanza

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There is much impressive observational evidence, mainly from the cosmic microwave background (CMB), for an enormously hot and dense early stage of the universe referred to as the Big Bang. Observations of the CMB are now very detailed, but this very detail presents new puzzles of various kinds, one of the most blatant being an apparent paradox in relation to the second law of thermodynamics. The hypothesis of inflationary cosmology has long been argued to explain away some of these puzzles, but it does not resolve some key issues, including that raised by the second law. In this talk, I describe a quite different proposal, which posits a succession of universe aeons prior to our own. The expansion of the universe never reverses in this scheme, but the space-time geometry is nevertheless made consistent through a novel geometrical conception. Some very recent analysis of the CMB data, obtained from the WMAP satellite, will be described, this having a profound but tantalizing bearing on these issues.

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We'll look at two novel experiments that are looking for ultrahigh energy neutrinos in the Antarctic ice. ANITA is a balloon-borne experiment which has twice flown over Antarctica making observations of ultrahigh energy cosmic rays and neutrinos. ARA is a new englacial project, under construction at the South Pole with similar goals. Both utilize the Askaryan Effect, coherent radio Cherenkov emission from particle cascades in matter, for neutrino detection.

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We consider the Universe to be fundamentally quantum and statistical, the many-paths/many-worlds information-theoretic story. This lecture uses Cosmic Information Theory and Analysis, CITA, as a unifying theme to explore the vast sweep  of our current ideas of the Universe and the experiments we use to probe them, ranging from the ultra-early beginnings to our far-future fate. I describe the intimate entanglement of theory with precision "first-light"  and other cosmic data, in particular from the satellite Planck and the Andes-based ACT. Such data are the BITs in IT informing us of the physics that defines the BIT of the Universe accessible to us from which we hope to learn of that vast IT which encodes all Cosmic Information.
 

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Measuring an event in time seems to require a shorter one. As a result, the development of a technique for measuring ultrashort laser pulses—the shortest events ever created—has been particularly difficult. We have, however, developed simple methods for fully characterizing these events, that is, for measuring a pulse's intensity and phase vs. time. One involves making an optical spectrogram of the pulse by using nonlinear optic. The mathematics involved is equivalent to the two-dimensional phase-retrieval problem—a problem that’s solvable because the Fundamental Theorem of Algebra fails for polynomials of two variables.  We call this method Frequency-Resolved Optical Gating (FROG), and it’s simple, rigorous, intuitive, and general. FROG has been used to measure pulses as short as 80 attoseconds (8×10-17s), and it has also measured the most complex ultrashort pulse ever generated. And we have recently developed simple methods (also with frivolous acronyms: SEA TADPOLE, MUD TADPOLE, and STRIPED FISH) for measuring the complete spatio-temporal field of an arbitrary laser pulse, making ultrashort laser pulses the best characterized form of light known to humankind.

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We study wetting and filling of patterned surfaces by a nematic liquid crystal. We focus on three important classes of periodic surfaces: saw-toothed, sinusoidal and stepwise, which have been considered in the literature as promising candidates to develop less-consuming zenithal bistable switches for practical applications. For saw-toothed substrates, geometry induces the nucleation of disclination lines on the wedges and apexes of the substrate, so  the nematic surface free energy density develops an elastic contribution which scales as qlnq (with q being the wavenumber associated with the substrate periodicity). This leads to a large departure from Wenzel's prediction for the wetting transition. For the sinusoidal substrate, the interplay of geometry, surface and elastic energies can lead to the suppression of either filling or wetting, which are observed for a same substrate only for a narrow range of roughness parameters. Finally, periodic stepwise surface displays re-entrant transitions, with a sequence dry-filled-wet-filled, in the relevant region of parameter space.

References:

[1]  P. Patricio, C.-T. Pham and J. M. Romero-Enrique, Eur. Phys. J. E 26, 97 (2008).
[2] J. M. Romero-Enrique, C.-T. Pham and P. Patricio, Phys. Rev. E 82, 011707 (2010)
[3] P. Patrício, J. M. Romero-Enrique, N. M. Silvestre; N. R. Bernardino and M.M. Telo da Gama, Molec. Phys. 109, 1067-1075 (2011)
[4] P. Patrício, N. M. Silvestre, C.-T. Pham and J. M. Romero-Enrique, accepted for publication in Phys. Rev. E (2011).

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“Cogito ergo sum.”  In the physical sciences, there is a long history of thinking about thinking, going back at least as far as René Descartes' famous pronouncement. Much more recently, a combination of neuroscientists and physicists have realized that it is possible to explore the dynamics of interacting neurons using ideas borrowed from nonlinear dynamics and statistical mechanics. The nervous system contains many reasonably small collections of neurons that collectively generate a well-defined pattern of electrical activity, which continues even when those collections of cells are removed from the animal. These functional groups of neurons are now termed central pattern generators. While understanding such restricted systems does not necessarily elucidate such sublime questions as those regarding the nature of consciousness, these studies do provide an intriguing example of an application of statistical mechanics to biology. They also admit quantitative comparisons to experiment!

In this talk I present a minimal model for one such central pattern generator, based on the interaction of nonlinear dynamical systems interacting on a quenched random network. No biological background will be assumed and, fortunately, very little will be required for exploring how a simple model of coupled excitatory neurons can produce collective and metronomic bursts of activity that control the breathing rhythm in mammals. I will focus on how topological properties of the random network of neuronal connections controls the collective dynamical phase diagram of the system.  I will conclude with some new extensions of this work to the building of similarly simple models of the global and rhythmic dynamics of the neocortex, the seat of consciousness and the paragon of complexity that produced “Cogito ergo sum.”

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Bose-Einstein condensates (BECs) have revolutionized atomic physics, a revolution which, sixteen years after their discovery, shows little sign of stopping.  The attention of the quantum gases community has increasingly shifted from studies of broad features of the many-body condensed state to more specific realizations based upon control of spin state, trapping geometry, dimensionality and temporal behavior.  In many regards quantum gases have no direct counterpart in condensed matter, although many parallels do exist, and these serve to guide efforts at the interface between disciplines.  Experiments in our laboratory investigate the spinor nature of a sodium BEC, an example of a quantum antiferromagnet.  The interplay between the quadratic Zeeman effect and spin-spin interactions gives rise to a rich phase diagram of possibilities.  In this talk I will describe experiments that explore the dynamical behavior of such a BEC in the vicinity of a quantum phase transition.  Our work highlights the experimental knobs and probes that are available to explore these fascinating quantum systems.

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Computational models of the Earth system lie at the heart of modern climate science. Concerns about their predictions have been illegitimately used to undercut the case that the climate is changing and this has put dynamical modelling in an awkward position. I will discuss ways that we, as a community, can contribute by highlighting some of the major outstanding questions that drive climate science, and I will outline their mathematical dimensions. I will put a particular focus on the issue of simultaneously handling the information coming from data and models, and argue that this balancing act will impact the way in which we formulate problems in nonlinear science.

 

 

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Two important advances have occurred in recent years which have brought us closer to the goal of observing and interpreting gravitational waves from coalescing compact objects: the successful construction and operation of a world-wide network of ground-based gravitational-wave detectors and the impressive success of numerical relativity in successfully simulating the merger phase of Binary Black Hole (BBH) coalescence. The aim of the Numerical INjection Analysis (NINJA) project is to study the sensitivity of gravitational-wave analysis pipelines to numerical simulations of waveforms and foster close collaboration between numerical relativists and data analysts.  NINJA-1 was a huge success, over 75 numerical relativists and data
analysis participated in the contribution of a simulated data set containing numerical waveforms, analysis of this data and interpreting the results of this analysis. We present some results from NINJA-1 and the goals, status, and preliminary results of the followup project, NINJA-2, which is currently ongoing.

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