Spring 2013 Colloquium Series
Colloquia are at 4pm, Thursdays, in 100 Willamette Hall and are preceded by coffee, tea, and cookies at 3:40 in the Willamette Atrium.
The organizer of the Spring Term Colloquia is: Steven van Enk
Establishing a path to mathematization in introductory physics
Sense-making in physics involves translating non-mathematical understanding into conceptualized mathematics, and formal mathematical statements into narrative explanations.
These processes, referred to as mathematization, have been studied in mid- to upper-level undergraduate physics courses (Bing & Redish, Sherin).
Successful students actively attribute meaning to equations and generate mathematical relationships to describe physical situations.
This mathematical understanding becomes integral to their physics knowledge.
Mexico State University, we seek to promote mathematization in the much larger population of high school and college students in introductory physics.
Unlike the successful upper level students, these students tend to view math in physics as a process of memorizing and mastering algorithms, devoid of creative and generative power for building understanding.
Increasing the frequency and quality of student mathematization is a desired outcome of our introductory courses, but there is strong evidence that this is generally not realized for most students.
To explicitly teach mathematization, we are developing curricular materials and methods based on invention instruction. Invention tasks serve as preparation for an initial exposure to the use of math in a variety of physics contexts.
Through creative thinking and struggle, students construct mathematically sensible ways to characterize physical situations and reason numerically about them.
Because socioeconomically disadvantaged school districts often have weak mathematics programs in the middle and high school levels, these invention tasks may be particularly beneficial to students from some underrepresented groups. In coordination with the development and testing of instructional materials, we are formulating assessments to measure student reasoning about the proportional relationships ubiquitous in introductory physics.
We present early results on this work with mathematically underprepared students as well as mainstream students.
This work is supported by NSF DUE-1045227,
NSF DUE-1045231, and NSF DUE-10452
Host: Stan Micklavzina
Department of Physics, Oregon State University
A tale of two E’s: Energy and entropy in aqueous interfaces
Water is a rather important liquid to most of us. All of biology and most of chemistry involves interfaces with water, and yet aqueous interfaces continue to present a challenge to understand theoretically. I will introduce the structure of liquid water, and will present a new method using classical density functional theory for treating aqueous interfaces.
Host: van Enk
Department of Physics, University of Portland
Are Quantum States Really Real?
Quantum mechanics is our most successful theory, yet its conceptual
foundations and interpretation are as hotly debated as ever. A central
question is the meaning of quantum states (“wave functions”). Quantum
states predict only probabilities of what we will find in a
measurement, yet quantum states are also said to be a complete
description of the physical state of a system. So, are quantum states
just calculational tools, or do they represent physical properties? A
recent theorem has made big waves by claiming that to avoid
contradictions with the predictions of quantum mechanics, quantum
states must be real. I will show that while the theorem does establish
something interesting, its conclusion is too hasty and its sting
Host: van Enk
Department of Physics, University of California, Santa Barbara and Huygens Laboratory, Leiden University
Quantum mechanics has been formulated over hundred years ago and many experiments have supported this extraordinary theory. It remains however unclear how quantum mechanics can be combined with general relativity in a 4 dimensional space-time structure. Furthermore the emergence of the classical world from the underlying quantum mechanics, often discussed in connection with the collapse of the quantum wavefunction, leaves open questions. Prof. R. Penrose has been one of the leading theorists in the past 50 years who addressed these fundamental issues. I will discuss some of his ideas leading to far reaching predictions that could be tested in experiments. In particular I will discuss two quantum optomechanical experiments that are designed to test the notion of quantum superpositions for macroscopic objects. The goal is to bring a tiny optical mirror into a quantum superposition and to investigate its decoherence. An essential aspect of the experiments is to perform optical cooling to the quantum ground state of a low frequency resonator.
Host: van Enk
Pacific Northwest National Laboratory
In-Situ TEM: From High Spatial Resolution to High Temporal Resolution
The last few years have seen a paradigm change in (scanning) transmission electron microscopy ((S)TEM) with unprecedented improvements in spatial, spectroscopic and temporal resolution being realized by aberration correctors, monochromators and pulsed photoemission sources. Spatial resolution now extends to the sub-angstrom level, spectroscopic resolution into the sub-100meV regime and temporal resolution for single shot imaging is now on the nanosecond timescale (stroboscopic imaging extends this even further to femtoseconds). The challenge now in performing experiments in an (S)TEM is to implement the in-situ capabilities that will allow both engineering and biological systems to be studied under realistic environmental conditions. Performing experiments using in-situ stages or full environmental microscopes presents numerous challenges to the traditional means of analyzing samples in an electron microscope – we are now dealing with the variability of dynamic process rather than a more straightforward static structure. In this presentation, I will discuss the recent developments in the design and implementation of in-situ stages being pursued at the Pacific Northwest National laboratory (PNNL). Examples of the use of these capabilities for the direct imaging of oxidation and reduction in metals, ceramics and catalytic systems and to identify the fundamental processes involved in nucleation and growth of nanostructures from solution will be presented. As the in-situ stages have been designed to be incorporated into both high spatial resolution aberration corrected (S)TEM as well as into high temporal resolution Dynamic TEM (DTEM), the potential for future experiments to study dynamics, including those in live biological structures, will also be discussed.
Department of Physics, Massachusetts Institute of Technology
The Shape of Jets to Come: Boosting the Search for New Physics at the LHC
Collision events at the Large Hadron Collider (LHC) are dominated by jets — collimated sprays of particles arising from the fragmentation of underlying quarks and gluons. Jets are a crucial probe of possible new physics beyond the standard model, but the high energy and high luminosity of the LHC pose serious challenges for precision jets studies. In this colloquium, I will report on recent advances in using jet substructure to maximize the discovery potential of the LHC. These advances include new methods to extract properties of the Higgs boson, new observables to identify boosted resonances from high energy collisions, and new insights into the physics of hadronization.
Department of Physics, Boise State University
Using DNA to arrange matter at the nanoscale
DNA has proven to be a versatile tool for arranging and manipulating matter on the nanoscale. I will describe work that I have been involved in that uses DNA to make molecular motors and active materials as well as to arrange nanoscale components into devices.
Host: Raymer, van Enk
Department of Physics, University of Chicago
Adapting granular materials through artificial evolution
Despite research dating back more than 200 years, it is still unknown how to connect the mechanical response of an amorphous granular material unambiguously to the shape of its constituents. From a practical point of view, this is problematic since granular materials like sand, grain, and pharmaceuticals are essential in engineering and industry. At a fundamental level, granular systems represent prototypes for far-from-equilibrium behavior. Thus, understanding the relationship between microscopic shape and macroscopic response can shed light on other amorphous systems like foams, dense colloids and molecular glasses. A key difficulty arises from the vast range of possible shapes, making it seem infeasible to isolate which candidates generate a particular response. In this talk I will demonstrate that particle shape can, however, be explored efficiently when viewed in a fresh context: artificial evolution. Representing arbitrary particle shapes by “granular molecules” consisting of bonded spheres, we have used simulations to evolve these shapes and 3D printing to verify the results experimentally. Using this approach, we find predictive motifs linking particle shape to packing stiffness and have discovered a particle shape that self-confines to produce granular packings that stiffen, rather than weaken, under compression. I will discuss opportunities to explore particle shape for effective jamming and to design granular matter with optimized properties for applications ranging from soft robotics to architecture.
Oregon State University
Complementarity of information and the emergence of the classical world
Hilbert space is a big place. Quite often, however, systems explore only a tiny fraction of the space available to them. The limited sampling of the Hilbert space can be implicated in the emergence of the objective, classical world from the ultimately quantum substrate. Quantum Darwinism is a framework for describing and quantifying what distinguishes quasi-classical states awash in the enormous sea of Hilbert space. Typical macroscopic observers do not directly interact with a system. Instead, they sample a (small) fragment of its environment in order to infer its state, using the environment as a communication channel. Thus, when we measure the position of a chair by looking at it, our eyes do not directly interact with the chair. By opening our eyes, we merely allow them (and hence, our neurons) to become correlated with some of the photons scattered by the chair (and hence, its position).
I will discuss the proliferation of information from a system into its surrounding environment during decoherence, as well as bounds (based on the Quantum Chernoff Information and Fidelity) on an observer’s ability to extract information communicated by the environment. The amount of quantum information about a system’s observable deposited in a fragment of the environment plus the amount of classical information yields an observable-independent total given by the quantum mutual information. In the quantum-to-classical transition, this split naturally delineates information about quantum systems accessible to observers – information that is redundantly transmitted by the environment – while showing that it is maximized for the quasi-classical pointer observable. Other observables are accessible only via correlations with the pointer observable. Further, I will prove an anti-symmetry property relating accessible, classical information and quantum information. It shows that information becomes objective – accessible to many observers – only as quantum information is relegated to correlations with the global environment, and, therefore, locally inaccessible. The resulting complementarity explains why, in a quantum Universe, we perceive objective classical reality, and supports Bohr’s intuition that quantum phenomena acquire classical reality only when communicated.
Host: van Enk
University of Illinois at Urbana-Champaign
Flipping the Classroom in Introductory Physics Courses at the University of Illinois
Students’ unprecedented access to content on the web is providing a unique opportunity to transform the role of lectures in education, moving the focus from content delivery to helping students synthesizes the content into knowledge. We have introduced a variety of activities to facilitate this transformation at the University of Illinois, including web-based preflight assessments of student understanding before lecture, peer instruction (clickers) to assess and facilitate student understanding during lecture, and web-based multimedia pre-lectures designed to provide students with content before lecture. In this talk I will discuss the pedagogical motivation for introducing these activities, and the impact they have had at the University of Illinois.
Host: Stan Micklavzina