Abstract: I work on the Muon g-2 experiment, a precision particle physics experiment which is being built at Fermilab. We plan to measure the anomalous magnetic moment of the muon to 0.14 ppm precision, a factor of four improvement over the current experimental value. Our measurement is desirable from the standpoint of particle physics because it will be a fine probe of the standard model, as well as various beyond-the-standard-model scenarios. I will give an overview of the experiment -- its purpose, method, and progress so far. I will also talk about my own work simulating the response of the electromagnetic calorimeters. Finally, I will share some thoughts about what it's like to be a graduate student in experimental particle physics, and how I ended up doing this work.

Abstract: Turbulence in classical fluids may readily be found in the mixing of a cup of coffee or the intricate patters in the atmosphere. While such examples are commonplace, fluids cooled to temperatures near absolute zero exhibit turbulent phenomena that differ from their classical counterparts, owing to quantum effects. Quantum fluids, such as superfluid helium-4, are typically described as a mixture of two interpenetrating fluids with distinct velocity fields: a viscous normal fluid akin to water and an inviscid superfluid. In this “two-fluid model,” there is no conventional viscous dissipation in the superfluid component. While vortices in classical fluids can be any size and strength, from whirlpools in a bathtub to tornadoes, every vortex in superfluid helium-4 is atomically thin and has quantized circulation. Our group discovered that micron-sized particles of frozen hydrogen may be used for flow visualization in superfluid helium-4. The particles can trace the motions of the normal fluid or be trapped by the quantized vortices, which enables one to characterize the dynamics of both the normal fluid and superfluid components for the first time. By directly observing and tracking these particles, we have confirmed the two-fluid nature of quantum fluids, observed vortex rings and quantized vortex reconnection, characterized thermal counterflows, and observed the very peculiar nature of quantum turbulence.

Abstract: Here are two ways to look at quantum mechanics: (i) as a dynamical theory with a fairly standard mathematical structure, but a strange probabilistic interpretation; (ii) as a probabilistic theory with a fairly standard interpretation, but a strange mathematical structure. The first point of view has to deal with the measurement problem. The second wants a convincing account of how the Hilbert space structure of quantum theory emerges from deeper operational, probabilistic or information-theoretic principles. In fact, there is a long history of attempts to give such an account. After briefly surveying some of these, I'll sketch a recent approach that is particularly simple and economical.

Abstract: Stars form via the gravitational collapse of large diffuse molecular clouds that occupy much of the disk of our galaxy. However, not all of this cloud material participates in the collapse process, mostly because energy injected on a range of size scales “stirs up” the cloud material. The competition between gravitational attraction and dynamical support ultimately determines how many stars form from any cloud. I'll discuss some of the basic ideas behind the process, and describe how astronomers measure the amount and dynamical state of cloud material using radio wavelength astronomical observations.

Abstract: Phase field models are widely used in computational physics and materials science. These models are capable of spontaneously generating interfaces with desired thermodynamic properties, and then evolving them in time without the need for interface tracking. Unfortunately, phase field models come with a cost: they become numerically unstable unless the time step size is held below a rather small threshhold value. I will introduce phase field modelling, demonstrate some important examples, and illustrate the problem associated with numerical instability. Then I will describe recent work in developing stable integration methods that will allow us to keep the benefits of phase field models without paying the cost.

Abstract: The answer to the question “What is Light?” has always been fraught with difficulties in attempts to explain its behavior by placing it into the category of either particle-like or wave-like. Historically this characterization has vacillated between these two categories several times. In this talk I will show the results of some experiments that demonstrate the rather bizarre behavior of light and imply that an understanding of light is even trickier than a simple hybridization of particle-wave concepts.

Abstract: The advent of multi-dimensional NMR, grounded in the use of the Fast-Fourier Transform (FFT) algorithm, ignited decades of innovation and discovery in studying the structures and dynamics of molecules. A modified method for acquiring multi-dimensional NMR data, termed non-uniform sampling (NUS), can informally be described as “skipping” certain data points. Although offering several advantages, NUS data can not take advantage of the FFT and the theorems associated with its use. We have been developing exact analytic expressions, with extensive experimental verification, that place some of the advantages of NUS methods on stronger theoretical foundations. We recently solved the exact sensitivity of NUS-NMR of decaying signals, showing that NUS leads to significant and predictable sensitivity enhancements that enable new science. In particular: NUS can simultaneously improve resolution and sensitivity, a statement that cannot be applied to conventional data acquisition. The theory also indicates road maps for further optimizations of NUS resolution and sensitivity that are currently being developed in our lab.

Abstract: Generally, different fundamental physics theories lead to different predictions about the existence and nature of topological defects such as domain walls and cosmic strings. Thus, observing the properties of such objects would open a window on higher-energy physics than we can access with experiments. However, we find that some interesting non-standard theories can have defect solutions that are identical to those of a standard theory. In this talk, I will introduce topological defects and their importance in cosmology, explain the motivation for studying non-standard fundamental theories, and explore the implications for defect solutions.