Research Experience for Undergraduates

Prof. Brett Altschul — Theoretical Analysis of Atomic Clock Comparison Studies

The reconciliation of quantum field theory with general relativity is probably the greatest outstanding problem in fundamental physics. This is an old problem, and it has inspired a tremendous amount of fascinating work; however, the basic conflict between quantum mechanics and general relativity has not been resolved, and there is a natural expectation that quantum gravity effects should only become important in reactions where single-particle energies are comparable to the Planck scale, far beyond what could possibly be generated at any accelerators in the foreseeable future. Therefore, if experimental evidence of quantum gravity is to be found, a different approach is needed. One way to look for evidence of quantum gravity effects is to search for phenomena that cannot occur in either the standard model or general relativity, such as violations of fundamental symmetries like Lorentz and CPT invariances. If either of these symmetries are found to be violated in nature, that would represent an incredibly important clue about what quantum gravity should look like.

Many of the most stringent tests of these symmetries come from comparisons made with multiple atomic clocks. Dr. Altschul can mentor a student working on a project related to the analysis of existing and future atomic clock experiments. The project involves an analysis of the sensitivity of atomic clock experiments that have already been performed or are ongoing. While there have been numerous after-the-fact analyses of radio frequency clock experiments, there has been far less work on similarly precise optical frequency atomic clock experiments. Using an established formalism, the REU student will look at one or more of these optical clock experiments and develop expressions describing the sensitivities of these experiments to the various forms of Lorentz and CPT violation that might exist in nature.

Prof. Thomas Crawford — Pattern Transfer Nanomanufacturing With Magnetically Recorded Nanotemplates

Dr. Crawford's laboratory works on nanotechnology projects related to nanomanufacturing and magnetically-directed self-assembly. One REU project employs bright-field and fluorescence microscopy to visualize in real-time, in fluid, the assembly of magnetic nanoparticles onto magnetically-recorded nanotemplates. By studying the dynamics of the assembly and the velocity distribution of nanoparticle motion, the student will assess how this distribution changes dynamically, as the nanoparticles are pulled from the fluid to the surface and assemble into sub-micrometer patterns. This project will assess experimentally the relative importance of diffusive and thermal nanoparticle transport in comparison with motion driven by nano-patterned magnetic forces. It is self-contained and optimal for completion over the timescale of a summer research experience, while presenting a challenging experience for an undergraduate student.

A second REU project involves nanomanufacturing diffractive optical elements and using a combination of light sources to study spectral responses of the nanomanufactured films. Here an undergraduate will nanomanufacture a standalone diffraction grating built entirely from magnetic nanoparticles, and will then test that grating in an optical spectrograph test-bed. In addition to studying diffracted spectra and how the spectra depend on the nanomanufacturing process, the student could move on to study changes in the film's optical properties in response to both thermal and magnetic stimuli.

Prof. Scott Crittneden — Atomic Force Microscopy of Surface Proteins

The ability of a protein to function depends on its form, that form depends on the forces experienced by the protein, the immediate environment of most proteins is liquid, and liquids exert considerable forces at the nanoscale. The study of these surface-solvent forces with sub-nanometer resolution is the focus of a multi-University, DoD-funded project. The mechanical and electro-mechanical dynamics of the liquid environment is complex and difficult to measure at the single-molecule scale. We are investigating these forces and their dependence on the properties of the solution (pH, ionic concentration, temperature, etc.) and on the properties of the molecule (isoelectric point, dipole moment, etc.) via an Atomic Force Microscope (AFM). An AFM is a surface measurement instrument capable of measuring sub-nanoNewton forces with sub-nanometer resolution and our system has been able to resolve individual atoms on a surface in solution.

The REU student will be involved in every step of the project, under the guidance of the graduate student and postdoctoral researcher who currently work on it full time. This will involve preparing the samples, which will require learning how to make gold surfaces atomically flat over areas of a micron or more, learning how to encourage molecules to form single-molecule-thick crystal structures on these surfaces, employing the AFM to interrogate a wide variety of physical properties of the resulting sample systems, and analyzing the results.

Prof. Timir Datta — Mechanical and Electrical Complexity in This Films

In the last decade or so an unexpectedly rich complexity has been discovered in nonlinear systems giving rise to the so-called deterministic chaos. Dr. Datta's group is studying a number of non-linear chaotic behaviors in high temperature superconductors and mechanical oscillators. His laboratory is equipped with three superconducting quantum interference device (SQUID) susceptometers and magnetometers. Several SQUID measurement electronic, liquid helium cryogenics, and magneto-transport apparatus are also available. It also have high and ultra high vacuum chambers for thin film, multi-layer growth, and patterning in the laboratory. A scanning tunneling microscope (STM) with a temperate and magnetic field state is used to study quantum mesoscopic transport in nano-scale conductors. REU students working in Dr. Datta's laboratory will be involved in these studies of nonlinear dynamics in surface structures through studies of ultraviolet and visual light transmission and electronic structures of thin photovoltaic films and studies of the nanoscale electronic and magnetic morphologies of semiconductors surfaces.

Prof. Yordanka Ilieva — Tests of a Maximum Log-Likelihood Estimators of Polarization Observables

An REU student working with Dr. Ilieva will support a research program in studies of the hyperon-nucleon interaction by extracting a large set of observables for final-state interaction events in the production of spin-polarized Lambda hyperons. The Lambda particle differs from protons and neutrons (nucleons which form the atomic nucleus) in that it contains a strange quark, while the nucleons contain only the lightest quarks, the up and down quarks. While the strong force between nucleons is relatively well understood at low energies, the force between hyperons and nucleons is poorly known. The hyperon-nucleon potentials have many parameters which are not well constrained. Mostly, this is due to the lack of high-quality data on hyperon-nucleon elastic scattering. Hyperons decay in a very short amount of time, and it is very difficult to produce hyperon beams or targets.

The ten-week undergraduate REU project will involve analysis of data taken with the CLAS detector at the Thomas Jefferson Accelerator Facility (JLab). The undergraduate student will become part of the Experimental Nuclear Physics Group at USC. They will attend weekly group meetings and give regular status reports. They will also be encouraged to attend the CLAS Collaboration meeting in June where they will have the opportunity to establish contacts with faculty and students from across the U.S. During the internship, the student will be trained in LINUX and C/C++, statistical methods for data analysis, modern software analysis tools such as PAW or ROOT, and concepts of basic experimental nuclear physics. She/he will receive training in technical writing of experimental paper, in preparing an oral presentation of their research to a group of peers, and will learn the established standards for such presentations in modern experimental nuclear physics research.

Prof. Varsha Kulkarni — Observational Tests of Galaxy Evolution Models

Dr. Kulkarni will mentor one or two REU students on projects in astrophysics, an area of great fascination for many students. Kulkarni's research is in observational extragalactic astrophysics. Her group uses primarily optical, infrared, and ultraviolet telescope facilities to study distant galaxies, quasars, and intergalactic matter. The group uses a number of ground-based state-of-the-art telescopes, such as Keck, Gemini, Subaru, Magellan, Multiple Mirror Telescope, and the Very Large Telescope. One of the goals of these studies is to chart the evolution of chemical elements in galaxies, i.e., to understand how the universe went from an essentially primordial chemical composition shortly after the Big Bang to one with the currently seen diversity and abundances of chemical elements.

To address these questions, the group uses observations of bright background sources such as quasars, whose spectra show absorption signatures imprinted by intervening galaxies. One of the REU students will work on analyzing spectra and images of quasar fields with foreground absorption lines to determine the chemical compositions and luminosities of the galaxies producing the absorption lines. These will be compared with observations of other quasar absorbers, data for nearby galaxies, and with predictions of galaxy chemical evolution models. This project will provide the student training in a number of topics, ranging from astrophysical spectroscopy to image processing.

Another related focus area of Kulkarni's research is the structural evolution of galaxies, and the cosmic star formation history. As part of this work, she has recently started studying a unique class of galaxies known as polar ring galaxies. These are a fascinating type of galaxies that show a ring of star formation in a plane orthogonal to the major axis of the main host galaxy. Besides providing insight into a unique star-forming environment, polar rings can also be used to map the distribution of dark matter in galaxies. The second REU student will work on analyzing images of polar ring galaxies in multiple filters that Kulkarni and group have obtained recently with the Gemini telescope. This project will provide training in image processing and galactic structure.

Prof. Yuriy Pershin — Circuit Elements with Memory

Dr. Pershin will supervise a project in the area of memory circuit elements. Memory circuit elements---resistors, capacitors and inductors with memory---are two-terminal electronic devices with great potential in a wide range of applications. While the operation of such electronic devices is based on a variety of physical phenomena, their mathematical description is universal, thus allowing identification of general features without regard to specific physical processes that lead to memory.

The area of research of memory resistors (memristors) is more advanced both technologically and theoretically than that of memory capacitors (memcapacitors) and memory inductors (meminductors). In fact, although some experimental systems have been identified as memcapacitive and meminductive, their number is still small and possible applications for them are less developed. This project will study dynamics of electronic circuits with memcapacitors. Specifically, an adaptable LC contour, namely, the oscillating circuit that tunes its frequency of oscillations to the frequency of the input signal, will be investigated. The adaptive behavior is an important feature of many biological systems and may find useful applications if implemented electronically. Several existing models of memcapacitive systems will be used in our computer simulations that will focus on circuit performance characteristics, energy flow, similarities with biological systems, and possible experimental implementations.

Prof. Steffen Strauch — Analysis of Precision Electron-Muon Comparisons

Steffen Strauch, a member of the Experimental Nuclear Physics group, will mentor an REU student in work related to muon scattering experiments. The proposed Muon-Proton Scattering Experiment (MUSE) at the Paul Scherrer Institute (PSI) in German is intended to resolve the large discrepancy found in proton radius measurements. The apparent proton radius measured in muonic hydrogen spectroscopy and electron-proton scattering are quite different. MUSE is expected to measure the scattering of electrons and muons off protons in the same apparatus at the same time, to see whether differences between electron and muon behavior (known as violations of lepton universality) could be responsible for the discrepancy.

Lepton universality, which requires the identical coupling constant of the three lepton generations is a basic assumption in the Standard Model (SM). Violation of lepton universality will clearly indicate the existence of physics beyond the SM. There is also an opportunity to work on the TREK experiment, approved at the Japan Proton Accelerator Research Complex (J-PARC), which will also test lepton universality. Both of these experiments aim to have high-precision results and require a detailed understanding of the experimental apparatuses. One tool to gain such an understanding and to help optimizing the setup is a full simulation of the experiment. Together with, collaborators, Dr. Strauch's group is developing a full Monte Carlo simulation of both of these experiments, in which the REU students will participate. The software is written in C++ and proficiency in C++ programming is a plus.