Physics Commons^™

Linked-Cluster Expansion For The Green's Function Of The Infinite-U Hubbard Model, Ehsan Khatami, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry

Faculty Publications

We implement a highly efficient strong-coupling expansion for the Green's function of the Hubbard model. In the limit of extreme correlations, where the onsite interaction is infinite, the evaluation of diagrams simplifies dramatically enabling us to carry out the expansion to the eighth order in powers of the hopping amplitude. We compute the finite-temperature Green's function analytically in the momentum and Matsubara frequency space as a function of the electron density. Employing Padé approximations, we study the equation of state, Kelvin thermopower, momentum distribution function, quasiparticle fraction, and quasiparticle lifetime of the system at temperatures lower than, or of the …

Kerr Metric, Geodesic Motion, And Flyby Anomaly In Fourth-Order Conformal Gravity, Gabriele U. Varieschi

Physics Faculty Works

In this paper we analyze the Kerr geometry in the context of Conformal Gravity, an alternative theory of gravitation, which is a direct extension of General Relativity (GR). Following previous studies in the literature, we introduce an explicit expression of the Kerr metric in Conformal Gravity, which naturally reduces to the standard GR Kerr geometry in the absence of Conformal Gravity effects. As in the standard case, we show that the Hamilton–Jacobi equation governing geodesic motion in a space-time based on this geometry is indeed separable and that a fourth constant of motion—similar to Carter’s constant—can also be introduced in …

Nonlinear Internal Waves, Internal Bores, And Turbulent Mixing In The Nearshore Coastal Environment, Ryan K. Walter

Physics

The nearshore coastal environment is generally taken to be one of the most productive and ecologically important parts of the ocean. The nearshore is also a complex environment from a physical standpoint, due in large part to the widespread and often irregular occurrence of nonlinear internal waves (NLIWs) that frequently appear more bore-like than wave-like. Indeed, this region of the ocean can be thought of as the “swash zone” for larger-scale internal wave fields on the continental shelf. These nearshore NLIWs and bores have considerable implications for the cross-shelf exchange and transport of nutrients, sediments, contaminants, larvae, and other scalars; …

Rubidium-Based Atomic Clock, Kate Miles

Physics

In this paper we will explore the process of building an atomic clock from a function generator, go into an in-depth introductory discussion of the Datum LPRO, and examine how rubidium function generators work.

Introduction To Ligo And An Experiment Regarding The Quality Factor Of Crystalline Silicon, Edward Taylor

Physics

Third generation LIGO detectors will be limited by thermal noise at a low frequency band where gravitational wave signals are expected to exist. A large contribution to thermal noise is caused by internal friction of the mirror and suspension elements. In order to meet the quantum mechanical sensitivity limits of the detector, it will be necessary to further push down the contribution of thermal noise. Future detectors will require new materials with extremely high mechanical quality. Silicon at cryogenic temperatures shows the promise to provide the required mechanical quality due to its vanishing expansion coefficient at 120 K. The fluctuation …

Exploring The Relationship Between A Fluid Container's Geometry And When It Will Balance On Edge, Ryan J. Moriarty

Physics

At some point while consuming a beverage, many people will idly try to balance its container on edge. The act itself is physically straightforward, merely involving the system's center of mass and achieving a static equilibrium between the opposing torques caused by gravity and the normal force between the container and the surface on which it balances. Further analysis of the act, however, illuminates the richness of the exercise.

These nuances are apparent even in simplified two-dimensional models because of the depth of the relationship between a container's geometry and achieving balance. The purpose of such analysis is threefold: first, …

Optical Properties Of De Vries Liquid Crystals And A Look At Ultra Thin Freely Suspended Smectic Films, Joshua P. Fankhauser

Physics

Liquid crystals exist as a fourth state of matter. They are anisotropic and due to this order, they affect light that passes through them, making them ideal candidates for optical study. By employing a basic technique for measuring a liquid crystal's birefringence and tilt angle, one is able to study a number of other properties such as the electroclinic effect. In addition, smectic liquid crystals have been studied intently because of their ability to create stable ultra-thin films of quantized layer thickness. These thin films have been studied due to the fact that they are an ideal system for investigating …

Laser Doppler Velocimetry: Flow Measurement Using A Digital Micromirror Device, Dawei Kuo

Physics

In this experiment we utilize a Texas Instruments Digital Micromirror Device to impart a phase shift to the beams of a laser Doppler velocimeter. The advantages of this approach include low cost, low power consumption, a precisely known phase-stepping frequency, and the capability of working with a broad range of optical wavelengths. The velocities measured with the set up shown here are of order 1 cm/s.

Modeling The Field Control Of The Surface Electroclinic Effect And Its Impact On Smectic Layer Strain, Kara M. Zappitelli

Physics

Chiral, smectic liquid crystal molecules align in layers and can be controlled by the application of an electric field, yielding a variety of implications for the quality of liquid crystal (LC) displays. Both the bulk electroclinic effect (BECE) and surface electroclinic effect (SECE) impact the angle at which the molecules tilt with respect to the layer normal in different areas of a LC cell due to dipole interactions. Certain LC’s exhibit a continuous Sm-A* to Sm-C* transition, where the angles of the surface and bulk molecules change continuously with electric field strength. Other LC’s exhibit first order transitions where we …

Lightweight Uav Launcher, Ben Miller, Christian Valoria, Corinne Warnock, Jake Coutlee

Mechanical Engineering

This report discusses the design, construction, and testing of a lightweight, portable UAV launcher. There is a current need for a small team of soldiers to launch a US Marine Tier II UAV in a remote location without transport. Research was conducted into existing UAV launcher designs and the pros and cons of each were recorded. This research served as a basis for concept generation during the initial design development stage. It was required that the design weigh less than 110 lbs, occupy a smaller volume than 48" x 24" 18" in its collapsed state, be portable by a single …

String Fluid Cosmological Model With Magnetic Field In Bimetric Theory Of Gravitation, M. S. Borkar, N. P. Gaikwad

Applications and Applied Mathematics: An International Journal (AAM)

In this paper, LRS Bianchi type I string fluid cosmological model with magnetic field in bimetric theory of gravitation is investigated by assuming barotropic equation of state for pressure and density and assuming the bulk viscosity to be inversely proportional to the scalar expansion. The source of energy momentum tensor is a bulk viscous fluid containing one dimensional string with electromagnetic field. The physical and geometrical properties of the model are discussed. The bulk viscosity affected the whole properties of the model.

Evaluation Of Schwarz Child’S Exterior And Interior Solutions In Bimetric Theory Of Gravitation, M. S. Borkar, P. V. Gayakwad

Applications and Applied Mathematics: An International Journal (AAM)

In this note, we have investigated Schwarz child’s exterior and interior solutions in bimetric theory of gravitation by solving Rosen’s field equations and concluded that the physical singularities at r = 0 and at r =2M do not appear in our solution. We have ruled out the discrepancies between physical singularity and mathematical singularity at r = 2M and proved that the Schwarzschild exterior solution is always regular and does not break-down at r = 2M. Further, we observe that the red shift of light in our model is much stronger than that of Schwarz child’s solution in general relativity …

Photovoltaic Effect In Single-Junction Organic Solar Cell Fabricated Using Vanadyl Phthalocyanine Soluble Derivative, Shahino Mah Abdullah

Shahino Mah Abdullah

Purpose: The purpose of this paper is to study the optical and electrical characteristics of a single‐junction solar cell based on a green-color dye Vanadyl 2,9,16, 23-tetraphenoxy-29H, 31H-phthalocyanine (VOPcPhO). The use of soluble vanadyl phthalocyanine derivative makes it very attractive for photovoltaic applications due to its tunable properties and high solubility. Design/methodology/approach: A photoactive layer of VOPcPhO has been sandwiched between indium tin oxide (ITO) and aluminum (Al) electrodes to produce ITO/PEDOT:PSS/VOPcPhO/Al photovoltaic device. The VOPcPhO thin film is deposited by a simple spin coating technique. In order to obtain the optimal thickness for the solar cell device, different thicknesses …

A Deep Chandra Acis Survey Of M83, Knox S. Long, Kip D. Kuntz, William P. Blair, Leith Godfrey, Paul P. Plucinsky, Roberto Soria, Christopher Stockdale, P. Frank Winkler

Physics Faculty Research and Publications

We have obtained a series of deep X-ray images of the nearby galaxy M83 using Chandra, with a total exposure of 729 ks. Combining the new data with earlier archival observations totaling 61 ks, we find 378 point sources within the D₂₅ contour of the galaxy. We find 80 more sources, mostly background active galactic nuclei (AGNs), outside of the D₂₅ contour. Of the X-ray sources, 47 have been detected in a new radio survey of M83 obtained using the Australia Telescope Compact Array. Of the X-ray sources, at least 87 seem likely to be supernova remnants …

Room-Temperature In-Situ Nanostructure Synthesis Using Electron Beam Irradiation, Mark H. Rümmeli

Special Session 5: Carbon and Oxide Based Nanostructured Materials (2014)

No abstract provided.

Silicon Carbide-Based One-Dimensional Nanostructures Growth: Towards Electronics And Biology Perspectives, Laurence Latu-Romain

Special Session 5: Carbon and Oxide Based Nanostructured Materials (2014)

No abstract provided.

Synthesis And Characterization: Low-Dimensional Carbon Nanomaterials On 3c-Sic/Si, John J. Boeckl, Weijie Lu, Hong Huang, Casey Strope, Li Wang, Neeraj Mishra, Francesca Iacopi

Special Session 5: Carbon and Oxide Based Nanostructured Materials (2014)

No abstract provided.

Field Emission Cathodes Made From Laser Cut Cnt Fibers And Films, Steven B. Fairchild, John Bulmer, Martin Sparkes, John J. Boeckl, Gregory Kozlowski

Special Session 5: Carbon and Oxide Based Nanostructured Materials (2014)

No abstract provided.

H(D)-Induced Nanotunnels Opening At Sic Sub-Surface And Graphene/Sic Grains Etching As A Path To Pahs' Formation In The Universe, Patrick Soukiassian

Special Session 5: Carbon and Oxide Based Nanostructured Materials (2014)

No abstract provided.

Intensity Interferometry Experiment, Christy Rose Pedraza

Physics

In this experiment we investigate the correlations in the intensity of diffracted light using an interferometer similar to Hanbury Brown and Twiss’. We use a pseudo-thermal light source composed of a laser and a rotating ground-glass screen with detection by silicon photodiodes. The experimental results agree with the theory that describes the correlation between spatially separated parts of the intensity field.