<p>I describe the theory and construction of a new bichromatic optical superlattice to study the pairing and thermodynamics of spin $\frac{1}{2}$-up and spin $\frac{1}{2}$-down atoms in periodic double well potentials. Our bichromatic lattice contains $\lambda_1=1064$ nm and $\lambda_2=532$ nm standing wave lattices. With tunable depth and relative phase between the two lattices, periodic double well potentials of arbitrary local symmetry can be constructed. </p><p>I present the first systematic experimental study of a two-component ultracold $^6$Li atomic Fermi gas in a single color 1064 nm lattice, which is continuously tuned from 2D to quasi-2D. A system is 2D if it is free to move in two dimensions while tightly confined in the third direction, such that only the ground state is occupied. Conversely, it is quasi-2D if higher states in the tightly confined direction are also occupied. I describe both radio frequency spectra and radial cloud profiles measured under identical conditions for each regime. Our results confirm predictions that the mean-field theory is not valid throughout the 2D to quasi-2D dimensional crossover. We also clarify that there is no transition between 2D and quasi-2D systems.</p><p>I also present the first study of pairing in a periodic double well potential. A Green's function method is developed to compute the pairing energies in the lattice. Although further understanding of the results are needed, I provide some preliminary rf spectra measurements supporting the theoretical approach and implying the existence of two types of pairing.</p> / Dissertation

Optical nanostructures are becoming an increasingly important aspect of modern technology. As a result high-resolution experimental techniques as well as nanoscale computational methods have become increasingly important in materials science to access the nanoscale effects. From the theoretical side atomistic density functional theory calculations are used to quantitatively determine interface absorption effects in multilayer heterostructures. From the experimental side, scanning transmission electron microscopy coupled with cathodoluminescence and electron energy loss spectroscopy are used to probe complex optical systems with nanoscale precision, specifically focusing on plasmonic nanostructures with unique optical responses. The combination of the two allows for in depth investigations into the optical response of complex nanostructures directly at the nanoscale.

Detection of signals is critical for the function of eukaryotic cells. D. discoideum cells are particularly adept at responding chemical gradients, sensing single percent concentration changes across their body. We measure the ability of the cells to sense gradients through this developmental transition as they change their internal machinery. Additionally, we impair the ability of the cells to modulate the speed of the receptors and measure the effect of a single receptor state on gradient sensing over development. We find a novel link between mechanotransduction and autophagy through the actin-rich microvillar protrusions lining the gut. These protrusions on the apical cell surface share structural similarities to the mechanosensitive stereocilia in the inner hair cells of the ear. Intestinal epithelial monolayers with microvilli, when exposed to persistent fluid shear stress, developed large vacuoles lined with autophagy associated proteins LC3 and LAMP1. The size and number of vacuoles were suppressed by perturbations to the autophagy pathway, including small molecule inhibitors and LC3 knockdown as well as through perturbations to the microvilli. Our results establish a link between apical shear and autophagic trafficking in intestinal epithelial monolayers.

We present three experiments designed to explore the physics of nanostructured materials in nonlinear optics. We utilize both photon and electron-beam excitations on systems with local densities of states specifically designed to generate small mode volumes. The first experiment uses planar arrays of gold Archimedean nanospirals to create asymmetric electric-field profiles for efficient second-harmonic generation (SHG). This nanostructure exhibits two-dimensional chirality and record SHG efficiency per unit volume. In the optical-field-induced second harmonic experiment, we employ an array of serrated gold nanogaps coupled to a polymer film to temporally resolve the change in the second-order nonlinear susceptibility of the polymer with 100 attosecond time resolution while separaing the nonlinear signals from the polymer and plasmonic emission using a spatial light modulator. Finally, we report the first demonstration of a quantum emitter in a dressed state using an electron beam to excite neutral nitrogen-vacancy (NV0) centers in a diamond nanocrystal. We deduce the presence of Rabi oscillations from the ensemble of NV0 centers at room temperature by measuring the second-order autocorrelation function of the cathodoluminescence signal that arises from the beam-induced plasmon interaction with the NV0 centers. The effects of phonon scattering on the autocorrelation amplitudes are revealed by subtracting the zero-phonon contribution to the cathodoluminescence spectrum. In summary, we have demonstrated three unique approaches for generating strong nonlinearities in nanoscale systems by manipulating the local density of states and following the dynamical evolution of these states in the time domain.

Neutrinos play a significant role in the Standard Model and the recent discovery of high energy cosmic neutrinos at IceCube has signified the beginning of neutrino astroparticle physics. The cosmic neutrinoâs direction and energy are preserved, and its flavor is altered in a calculable way. We study how to use the inverse propagation matrix to infer the cosmic neutrino injection models using observed flavor ratios at the Earth. This is possible after the discovery of broken symmetry which guarantees a non-vanishing determinant. Moreover, we demonstrate how to use neutrino telescope experiments to study mass hierarchy in beyond standard scenarios. We calculate the predicted Glashow Resonant (GR) events rate to explain the absence of GR events at IceCube. The flavor triangle is a powerful tool to connect the mixing parameters, cosmic sources, and observed Earthly ratios. We prove some useful theorems regarding the flavor triangles and discuss how to use these theorems to make inference.

As astronomy expands into the era of Big Data, with increased data capture and storage capabilities and enhanced computing power, the large data sets that will become accessible need to be properly understood to maximize their scientific yield. Some of this data will be generated by upcoming missions, such as the Large Synoptic Survey Telescope (LSST). For this telescope we demonstrate that while it was not specifically designed for it, LSST can recover transiting exoplanets for several archetypal planetary systems. We also provide a set of tools built upon the LSST Metric Analysis Framework (MAF) that quantify how the LSST time sampling will impact observing both periodic and non-periodic variable sources. Other data will be the large data sets generated from archival data, such as from Digital Access to a Sky Century @ Harvard (DASCH), a database of digitized photographic plates over a century. We take a sample of F2 stars from the DASCH archive, and use a series of statistical tests to determine that there are large-scale systematics. After accounting for a large break in the data, we find that most F2 stars do not appear to change in brightness on century timescales, however we also provide a handful of stars that do seem to be changing over long timescales.

The focus of this dissertation is the interaction of gold (Au) plasmonic structures and the phase change material vanadium dioxide (VO2). Vanadium dioxide modifies the local surface plasmon resonance of an Au nanoparticles and the local surface plasmon can also act as a probe of the VO2 optical properties. Heterostructures combining plasmonic and phase-change materials create platforms with tunable optical properties that provide access to a cornucopia of optical-physics phenomena. In this thesis we specifically look at three such phenomena. First, we demonstrate active plasmon-induced transparency via finite-difference time-domain simulations and investigate an experimental realization of the relevant structure that exhibit plasmon-induced transparency. Second, we observe a novel pattern of coexisting metallic and insulating domains in a VO2 single crystal using plasmonic antennas in a scattering scanning near-field optical microscope, and thus show that even single VO2 crystals are not homogeneous. Third, we employ the optical resonance shifts of plasmonic monomers and dimers embedded in VO2 films to probe the kinetics and dynamics of atomic hydrogen diffusion and its effects on the phase transition. In addition, the challenges inherent in fabricating these complex structures are discussed, illuminating the ways in which the choice of thin-film deposition method influence the resulting VO2 material properties. This work demonstrates the versatility of hybrid material platforms that combine the exquisite optical sensitivity of the surface plasmon resonance with the tunable dielectric functions in phase-changing materials to study the kinetics and dynamics of strong correlations, doping interactions, and classical analogs of atomic phenomena in solid-state systems.

Ultra high energy cosmic rays (UHECRs) are accelerated by the most energetic processes in the universe. Upon entering Earthâs atmosphere they produce particle showers known as extensive air showers (EASs). Observatories like the Pierre Auger Observatory sample the particles and light produced by the EASs through large particle detector arrays or nitro- gen fluorescence detectors to ascertain the fundamental properties of UHECRs. The large sample of high quality data provided by the Pierre Auger Observatory can be attributed to the hybrid technique which utilizes the two aforementioned techniques simultaneously; however, the limitation of only being able to observe nitrogen fluorescence from EASs on clear moonless nights yields a limited 10% duty cycle for the hybrid technique. One pro- posal for providing high quality data at increased statistics is the observation of isotropic microwave emission from EAS, as such emission would be observed with a 100% duty cycle. Measurements of microwave emission from laboratory air plasmas conducted by Gorham et al. (2008) produced promising results indicating that the microwave emission should be observable using inexpensive detectors. The Microwave Detection of Air Showers (MIDAS) experiment was built at the University of Chicago to characterize the isotropic microwave emission from EASs and has collected 359 days of observational data at the location of the Pierre Auger experiment. We have performed a time coincidence analysis between this data and data from Pierre Auger and we report a null result. This result places stringent limits on microwave emission from EASs and demonstrates that the laboratory measure- ments of Gorham et al. (2008) are not applicable to EASs, thus diminishing the feasibility of using isotropic microwave emission to detect EASs.

In the series of morphogenetic events that are required for Drosophila development, some of the most dramatic are those that involve the coordinated movement of the germband and amnioserosa, two epithelia that remain contiguous through the first thirteen hours of morphogenesis until the amnioserosaâs death. The importance of the amnioserosa in ensuring the germbandâs proper shape and position has been established, but its exact role as a signaling source and force generator and the balance between amnioserosal and germband forces are not fully understood. Pursuing this question from the germband side of the balance, a new angle-measurement method has yielded information from germband cell edges about the tensions and stresses acting during germband retraction. These results show that the amnioserosa pulls on the germband to produce cell and segment elongation, while the germband cell-edge tensions are polarized to resist elongation, acting in the same direction that they do during the preceding stage of germband extension. The degree of force anisotropy varies in different germband segments, indicating that a more detailed analysis of the entire germband is required to understand the amnioserosa-germband force balance. Other avenues of research support vertical germband polarization and the general picture of the amnioserosa as an essential player in morphogenesis, exerting forces on the germband that are instrumental in proper development.

<p> In this thesis I present the theoretical work on Fermionic surface states, and %the bulk Bosonic collective excitations in topological superfluids and superconductors. Broken symmetries %Bulk-edge correspondence in topological condensed matter systems have implications for the spectrum of Fermionic excitations confined on surfaces or topological defects. (Abstract shortened by ProQuest.) </p>