arXiv subjects

C. M. Savage

Publications and source records attributed to C. M. Savage.

At least 19 recordsLinked to original sources

arXiv2016

Developing an Action Concept Inventory

We report on progress towards the development of an Action Concept Inventory (ACI), a test that measures student understanding of action principles in introductory mechanics and optics. The ACI also covers key concepts of many-paths quantum mechanics, from which classical action physics arises. We used a multi-stage iterative development cycle for incorporating expert and student feedback into successive revisions of the ACI. The student feedback, including think-aloud interviews, enabled us to identify their misconceptions about action physics.

physics.ed-ph↗

arXiv2016

Optomechanical tests of a Schrödinger-Newton equation for gravitational quantum mechanics

We show that optomechanical systems can test the Schrödinger-Newton equation of gravitational quantum mechanics due to Yang et al. This equation is motivated by semiclassical gravity, a widely used theory of interacting gravitational and quantum fields. From the many-body Schrödinger-Newton equation follows an approximate equation for the center-of-mass dynamics of macroscopic objects. This predicts a distinctive double-peaked signature in the output optical quadrature power spectral density of certain optomechanical systems. Since the Schrödinger-Newton equation lacks free parameters, these will allow its experimental confirmation or refutation.

gr-qc↗

arXiv2016

Action Physics

More than a decade ago Edwin Taylor issued a "call to action" that presented the case for basing introductory university mechanics teaching around the principle of stationary action. We report on our response to that call in the form of an investigation of the teaching and learning of the stationary action formulation of physics in a first-year university course. Our action physics instruction proceeded from the many-paths approach to quantum physics through to ray optics, classical mechanics, and relativity. Despite the challenges presented by action physics, students reported it to be accessible, interesting, motivational and valuable.

physics.ed-ph↗

arXiv2013

The Relativity Concept Inventory: development, analysis and results

We report on a concept inventory for special relativity: the development process, data analysis methods, and results from an introductory relativity class. The Relativity Concept Inventory tests understanding of kinematic relativistic concepts. An unusual feature is confidence testing for each question. This can provide additional information; for example high confidence correlated with incorrect answers suggests a misconception. A novel aspect of our data analysis is the use of Monte Carlo simulations to determine the significance of correlations. This approach is particularly useful for small sample sizes, such as ours. Our results include a gender bias that was not present in other assessment, similar to that reported for the Force Concept Inventory.

physics.ed-ph↗

arXiv2012

Nonlocal signaling in the configuration space model of quantum-classical interactions

When interactions are turned off, the theory of interacting quantum and classical ensembles due to Hall and Reginatto is shown to suffer from a nonlocal signaling effect that is effectively action at a distance. This limits the possible applicability of the theory. In its present form, it is restricted to those situations in which interactions are always on, such as classical gravity interacting with quantized matter.

quant-ph↗

arXiv2011

Interacting classical and quantum particles

We apply Hall and Reginatto's theory of interacting classical and quantum ensembles to harmonically coupled particles, with a view to understanding its experimental implications. This hybrid theory has no free parameters and makes distinctive predictions that should allow it to be experimentally distinguished from quantum mechanics. It also bears on the questions of quantum measurement and quantum gravity.

quant-ph↗

arXiv2011

Bosenova and three-body loss in a Rb-85 Bose-Einstein condensate

Collapsing Bose-Einstein condensates are rich and complex quantum systems for which quantitative explanation by simple models has proved elusive. We present new experimental data on the collapse of high density Rb-85 condensates with attractive interactions and find quantitative agreement with the predictions of the Gross-Pitaevskii equation. The collapse data and measurements of the decay of atoms from our condensates allow us to put new limits on the value of the Rb-85 three-body loss coefficient K_3 at small positive and negative scattering lengths.

cond-mat.quant-gas↗

arXiv2011

Causality in classical electrodynamics

Causality in electrodynamics is a subject of some confusion, especially regarding the application of Faraday's law and the Ampere-Maxwell law. This has led to the suggestion that we should not teach students that electric and magnetic fields can cause each other, but rather focus on charges and currents as the causal agents. In this paper I argue that fields have equal status as casual agents, and that we should teach this. Following a discussion of causality in classical physics I will use a numerical solution of Maxwell's equations to inform a field based causal explanation in electrodynamics.

physics.ed-ph↗

arXiv2009

Student experiences of virtual reality - a case study in learning special relativity

We present a study of student learning through the use of virtual reality. A software package is used to introduce concepts of special relativity to students in a game-like environment where users experience the effects of travelling at near light speeds. From this new perspective, space and time are significantly different to that experienced in everyday life. The study explores how students have worked with this environment and how these students have used this experience in their study of special relativity. A mixed method approach has been taken to evaluate the outcomes of separate implementations of the package at two universities. Students found the simulation to be a positive learning experience and described the subject area as being less abstract after its use. Also, students were more capable of correctly answering concept questions relating to special relativity, and a small but measurable improvement was observed in the final exam.

physics.ed-ph↗

arXiv2009

Teaching Physics Using Virtual Reality

We present an investigation of game-like simulations for physics teaching. We report on the effectiveness of the interactive simulation "Real Time Relativity" for learning special relativity. We argue that the simulation not only enhances traditional learning, but also enables new types of learning that challenge the traditional curriculum. The lessons drawn from this work are being applied to the development of a simulation for enhancing the learning of quantum mechanics.

physics.ed-ph↗

arXiv2008

Directional spatial structure of dissociated elongated molecular condensates

Ultra-cold clouds of dimeric molecules can dissociate into quantum mechanically correlated constituent atoms that are either bosons or fermions. We theoretically model the dissociation of cigar shaped molecular condensates, for which this difference manifests as complementary geometric structures of the dissociated atoms. For atomic bosons beams form along the long axis of the molecular condensate. For atomic fermions beams form along the short axis. This directional beaming simplifies the measurement of correlations between the atoms through relative number squeezing.

cond-mat.other↗

arXiv2007

Spatial pair correlations of atoms in molecular dissociation

We perform first-principles quantum simulations of dissociation of trapped, spatially inhomogeneous Bose-Einstein condensates of molecular dimers. Specifically, we study spatial pair correlations of atoms produced in dissociation after time of flight. We find that the observable correlations may significantly degrade in systems with spatial inhomogeneity compared to the predictions of idealized uniform models. We show how binning of the signal can enhance the detectable correlations and lead to the violation of the classical Cauchy-Schwartz inequality and relative number squeezing.

cond-mat.other↗

arXiv2007

Quantum-field dynamics of expanding and contracting Bose-Einstein condensates

We analyze the dynamics of quantum statistics in a harmonically trapped Bose-Einstein condensate, whose two-body interaction strength is controlled via a Feshbach resonance. From an initially non-interacting coherent state, the quantum field undergoes Kerr squeezing, which can be qualitatively described with a single mode model. To render the effect experimentally accessible, we propose a homodyne scheme, based on two hyperfine components, which converts the quadrature squeezing into number squeezing. The scheme is numerically demonstrated using a two-component Hartree-Fock-Bogoliubov formalism.

cond-mat.other↗

arXiv2007

Quantum depletion of collapsing Bose-Einstein condensates

We perform the first numerical three-dimensional studies of quantum field effects in the Bosenova experiment on collapsing condensates by E. Donley et al. [Nature 415, 39 (2002)] using the exact experimental geometry. In a stochastic truncated Wigner simulation of the collapse, the collapse times are larger than the experimentally measured values. We find that a finite temperature initial state leads to an increased creation rate of uncondensed atoms, but not to a reduction of the collapse time. A comparison of the time-dependent Hartree-Fock-Bogoliubov and Wigner methods for the more tractable spherical trap shows excellent agreement between the uncondensed populations. We conclude that the discrepancy between the experimental and theoretical values of the collapse time cannot be explained by Gaussian quantum fluctuations or finite temperature effects.

cond-mat.other↗

arXiv2007

Limits to the analogue Hawking temperature in a Bose-Einstein condensate

Quasi-one dimensional outflow from a dilute gas Bose-Einstein condensate reservoir is a promising system for the creation of analogue Hawking radiation. We use numerical modeling to show that stable sonic horizons exist in such a system under realistic conditions, taking into account the transverse dimensions and three-body loss. We find that loss limits the analogue Hawking temperatures achievable in the hydrodynamic regime, with sodium condensates allowing the highest temperatures. A condensate of 30,000 atoms, with transverse confinement frequency omega_perp=6800*2*pi Hz, yields horizon temperatures of about 20 nK over a period of 50 ms. This is at least four times higher than for other atoms commonly used for Bose-Einstein condensates.

cond-mat.other↗

arXiv2007

Real Time Relativity: exploration learning of special relativity

Real Time Relativity is a computer program that lets students fly at relativistic speeds though a simulated world populated with planets, clocks, and buildings. The counterintuitive and spectacular optical effects of relativity are prominent, while systematic exploration of the simulation allows the user to discover relativistic effects such as length contraction and the relativity of simultaneity. We report on the physics and technology underpinning the simulation, and our experience using it for teaching special relativity to first year university students.

physics.ed-ph↗

arXiv2006

First-principles quantum simulations of dissociation of molecular condensates: Atom correlations in momentum space

We investigate the quantum many-body dynamics of dissociation of a Bose-Einstein condensate of molecular dimers into pairs of constituent bosonic atoms and analyze the resulting atom-atom correlations. The quantum fields of both the molecules and atoms are simulated from first principles in three dimensions using the positive-P representation method. This allows us to provide an exact treatment of the molecular field depletion and s-wave scattering interactions between the particles, as well as to extend the analysis to nonuniform systems. In the simplest uniform case, we find that the major source of atom-atom decorrelation is atom-atom recombination which produces molecules outside the initially occupied condensate mode. The unwanted molecules are formed from dissociated atom pairs with non-opposite momenta. The net effect of this process -- which becomes increasingly significant for dissociation durations corresponding to more than about 40% conversion -- is to reduce the atom-atom correlations. In addition, for nonuniform systems we find that mode-mixing due to inhomogeneity can result in further degradation of the correlation signal. We characterize the correlation strength via the degree of squeezing of particle number-difference fluctuations in a certain momentum-space volume and show that the correlation strength can be increased if the signals are binned into larger counting volumes.

cond-mat.other↗

arXiv2006

Real Time Relativity

Real Time Relativity is a computer program that allows the user to fly through a virtual world governed by relativistic physics. The user controls a 'rocket' carrying a 'camera'. The rocket may be accelerated and steered, and the camera may be pointed in any direction. It takes advantage of the fact that video cards provide inexpensive data-parallel processing and are designed to perform rapid arithmetic on four-dimensional vectors.

physics.ed-ph↗