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Articles 31 - 60 of 808
Full-Text Articles in Physics
Prospects For Determination Of Thermal History After Inflation With Future Gravitational Wave Detectors, Sachiko Kuroyanagi, Kazunori Nakayama, Shun Saito
Prospects For Determination Of Thermal History After Inflation With Future Gravitational Wave Detectors, Sachiko Kuroyanagi, Kazunori Nakayama, Shun Saito
Physics Faculty Research & Creative Works
Thermal history of the Universe between inflation and big-bang nucleosynthesis has not yet been revealed observationally. It will be probed by the detection of primordial gravitational waves generated during inflation, which contain information on the reheating temperature as well as the equation of state of the Universe after inflation. Based on the Fisher information formalism, we examine how accurately the tensor-to-scalar ratio and reheating temperature after inflation can be simultaneously determined with space-based gravitational wave detectors such as the DECI-hertz Interferometer Gravitational-wave Observatory and the Big-Bang Observer. We show that the reheating temperature is best determined if it is around …
Directional Limits On Persistent Gravitational Waves Using Ligo S5 Science Data, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Directional Limits On Persistent Gravitational Waves Using Ligo S5 Science Data, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.
Physics Faculty Research & Creative Works
The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence level (C.L.) upper-limit maps of GW strain power with typical values between 2 - 20 x 10-50 strain2 Hz-1 and 5 - 35 x 10-49 strain2Hz-1sr-1 for pointlike and extended sources, respectively. The latter result is the …
Highly Resistive And Ultrafast Fe‐Ion Implanted Ingaas For The Applications Of Thz Photomixer And Photoconductive Switch, J. H. Shin, K. H. Park, N. Kim, C. W. Lee, Eunsup Daniel Shim, Y. C. Kim, D. S. Yee, J. O. Kim, S. J. Lee, S. K. Noh
Highly Resistive And Ultrafast Fe‐Ion Implanted Ingaas For The Applications Of Thz Photomixer And Photoconductive Switch, J. H. Shin, K. H. Park, N. Kim, C. W. Lee, Eunsup Daniel Shim, Y. C. Kim, D. S. Yee, J. O. Kim, S. J. Lee, S. K. Noh
WCBT Faculty Publications
We develop highly‐resistive (i.e. low‐carrier‐density) and ultrafast Fe‐ion implanted InGaAs layers for the applications of THz photomixer and photoconductive switch. The measured Hall mobility, sheet resistance, carrier density, and carrier lifetime of the optimized 1.2‐μm‐thick Fe‐implanted InGaAs layer are 3.4×102 cm2/Vs, 0.24 MΩ, 6.5×1014 cm−3, and 0.13ps, respectively.
Sufficient Conditions For Uniqueness Of The Weak Value, Justin Dressel, Andrew N. Jordan
Sufficient Conditions For Uniqueness Of The Weak Value, Justin Dressel, Andrew N. Jordan
Mathematics, Physics, and Computer Science Faculty Articles and Research
We review and clarify the sufficient conditions for uniquely defining the generalized weak value as the weak limit of a conditioned average using the contextual values formalism introduced in Dressel, Agarwal and Jordan (2010 Phys. Rev. Lett. 104 240401). We also respond to criticism of our work by Parrott (arXiv:1105.4188v1) concerning a proposed counter-example to the uniqueness of the definition of the generalized weak value. The counter-example does not satisfy our prescription in the case of an underspecified measurement context. We show that when the contextual values formalism is properly applied to this example, a natural interpretation of the …
Revisiting Two-Step Forbush Decreases, Andrew P. Jordan, Harlan E. Spence, J. B. Blake, D. N. A. Shaul
Revisiting Two-Step Forbush Decreases, Andrew P. Jordan, Harlan E. Spence, J. B. Blake, D. N. A. Shaul
Physics & Astronomy
Interplanetary coronal mass ejections (ICMEs) and their shocks can sweep out galactic cosmic rays (GCRs), thus creating Forbush decreases (FDs). The traditional model of FDs predicts that an ICME and its shock decrease the GCR intensity in a two-step profile. This model, however, has been the focus of little testing. Thus, our goal is to discover whether a passing ICME and its shock inevitably lead to a two-step FD, as predicted by the model. We use cosmic ray data from 14 neutron monitors and, when possible, high time resolution GCR data from the spacecraft International Gamma Ray Astrophysical Laboratory (INTEGRAL). …
Dipole-Dipole Interaction Between Rubidium Rydberg Atoms, Emily Altiere, Donald P. Fahey, Michael W. Noel, Rachel J. Smith, Thomas J. Carroll
Dipole-Dipole Interaction Between Rubidium Rydberg Atoms, Emily Altiere, Donald P. Fahey, Michael W. Noel, Rachel J. Smith, Thomas J. Carroll
Physics and Astronomy Faculty Publications
Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (F¨orster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that …
Dipole-Dipole Interaction Between Rubidium Rydberg Atoms, Emily Altiere, Donald Fahey, Michael Noel, Rachel J. Smith, Thomas J. Carroll
Dipole-Dipole Interaction Between Rubidium Rydberg Atoms, Emily Altiere, Donald Fahey, Michael Noel, Rachel J. Smith, Thomas J. Carroll
Physics Faculty Research and Scholarship
Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (Forster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that …
Modeling Free-Carrier Absorption And Avalanching By Ultrashort Laser Pulses, Jeremy R. Gulley
Modeling Free-Carrier Absorption And Avalanching By Ultrashort Laser Pulses, Jeremy R. Gulley
Faculty and Research Publications
In the past decade it was demonstrated experimentally that negatively-chirped laser pulses can lower the surface LIDT for wide band-gap materials by decreasing the number of photons required for photoionization on the leading edge of the pulse. Similarly, simulations have shown that positively-chirped pulses resulting from selffocusing and self-phase modulation in bulk dielectrics can alter the onset of laser-induced material modifications by increasing the number of photons required for photoionization on the leading edge of the pulse. However, the role of multi-chromatic effects in free-carrier absorption and avalanching has yet to be addressed. In this work a frequency-selective model of …
Temperature Dependence Of Sio2 Electron-Induced Luminescence, Amberly Evans Jensen, Gregory Wilson, Jr Dennison
Temperature Dependence Of Sio2 Electron-Induced Luminescence, Amberly Evans Jensen, Gregory Wilson, Jr Dennison
Presentations
No abstract provided.
Scaling Of Losses With Size And Wavelength In Nanoplasmonics And Metamaterials, Jacob B. Khurgin, Greg Sun
Scaling Of Losses With Size And Wavelength In Nanoplasmonics And Metamaterials, Jacob B. Khurgin, Greg Sun
Physics Faculty Publications
We show that, for the resonant metal-dielectric structures with sub-wavelength confinement of light in all three dimensions, the loss cannot be reduced considerably below the loss of the metal itself unless one operates in the far IR and THz regions of the spectrum or below. Such high losses cannot be compensated by introducing gain due to Purcell-induced shortening of recombination times. The only way low loss optical meta-materials can be engineered is with, as yet unknown, low loss materials with negative permittivity.
De Sitter Gravity From Lattice Gauge Theory, Simon Catterall, Daniel Ferrante, Arwen Nicholson
De Sitter Gravity From Lattice Gauge Theory, Simon Catterall, Daniel Ferrante, Arwen Nicholson
Physics - All Scholarship
We investigate a lattice model for Euclidean quantum gravity based on discretization of the Palatini formulation of General Relativity. Using Monte Carlo simulation we show that while a naive approach fails to lead to a vacuum state consistent with the emergence of classical spacetime, this problem may be evaded if the lattice action is supplemented by an appropriate counter term. In this new model we find regions of the parameter space which admit a ground state which can be interpreted as (Euclidean) de Sitter space.
Transition From Static To Dynamic Macroscopic Friction In The Framework Of The Frenkel-Kontorova Model, Naum I. Gershenzon, Gust Bambakidis
Transition From Static To Dynamic Macroscopic Friction In The Framework Of The Frenkel-Kontorova Model, Naum I. Gershenzon, Gust Bambakidis
Physics Faculty Publications
A new generation of experiments on dry macroscopic friction has revealed that the transition from static to dynamic friction is essentially a spatially and temporally non-uniform process, initiated by a rupture-like detachment front. We show the suitability of the Frenkel-Kontorova model for describing this transition. The model predicts the existence of two types of detachment fronts, explaining both the variability and abrupt change of velocity observed in experiments. The quantitative relation obtained between the velocity of the detachment front and the ratio of shear to normal stress is consistent with experiments. The model provides a functional dependence between slip velocity …
Circular And Near-Circular Polarization States Of Evanescent Monochromatic Light Fields In Total Internal Reflection, R. M. A Azzam
Circular And Near-Circular Polarization States Of Evanescent Monochromatic Light Fields In Total Internal Reflection, R. M. A Azzam
Electrical Engineering Faculty Publications
Conditions for the production of near-circular polarization states of the evanescent field present in the rarer medium in total internal reflection of incident monochromatic p-polarized light at a dielectric-dielectric planar interface are determined. Such conditions are satisfied if high-index (>3.2) transparent prism materials (e.g., GaP and Ge) are used at angles of incidence well above the critical angle but sufficiently below grazing incidence. Furthermore, elliptical polarization of incident light with nonzero p and s components can be tailored to cause circular polarization of the resultant tangential electric field in the plane of the interface or circular polarization of the …
Enhanced Quantum Dot Emission For Luminescent Solar Concentrators Using Plasmonic Interaction, Subhash Chandra, Manus Kennedy, John Doran, Sarah Mccormack, A. J. Chatten
Enhanced Quantum Dot Emission For Luminescent Solar Concentrators Using Plasmonic Interaction, Subhash Chandra, Manus Kennedy, John Doran, Sarah Mccormack, A. J. Chatten
Articles
Plasmonic excitation enhanced fluorescence of CdSe/ZnS core-shell quantum dots (QDs) in the presence of Au nanoparticles (NPs) has been studied for application in quantum dot solar concentrator (QDSC) devices. We observe that there is an optimal concentration of Au NPs that gives a maximum 53% fluorescence emission enhancement for the particular QD/Au NP composite studied. The optimal concentration depends on the coupling and spacing between neighboring QDs and Au NPs. We show the continuous transition from fluorescence enhancement to quenching, depending on Au NP concentration. The locally enhanced electromagnetic field induced by the surface plasmon resonance in the Au NPs …
Thermodynamic Limit To Photonic-Plasmonic Light-Trapping In Thin Films On Metals, Eric A. Schiff
Thermodynamic Limit To Photonic-Plasmonic Light-Trapping In Thin Films On Metals, Eric A. Schiff
Physics - All Scholarship
We calculate the maximum optical absorptance enhancements in thin semiconductor films on metals due to structures that diffuse light and couple it to surface plasmon polaritons. The calculations can be used to estimate plasmonic effects on light-trapping in solar cells. The calculations are based on the statistical distribution of energy in the electromagnetic modes of the structure, which include surface plasmon polariton modes at the metal interface as well as the trapped waveguide modes in the film. The enhancement has the form 4n2+nλ/h (n – film refractive index, λ – optical wavelength, h …
Exploring The Universe… One Electron At A Time, Jr Dennison
Exploring The Universe… One Electron At A Time, Jr Dennison
Presentations
No abstract provided.
Electron Energy Dependent Charging Effects Of Multilayered Dielectric Materials, Gregory Wilson, Amberly Evans Jensen, Jr Dennison
Electron Energy Dependent Charging Effects Of Multilayered Dielectric Materials, Gregory Wilson, Amberly Evans Jensen, Jr Dennison
Presentations
No abstract provided.
Overlap Statistics Of Cumuliform Boundary-Layer Cloud Fields In Large-Eddy Simulations, Roel A.J. Neggers, Thijs Heus, A. Pier Siebesma
Overlap Statistics Of Cumuliform Boundary-Layer Cloud Fields In Large-Eddy Simulations, Roel A.J. Neggers, Thijs Heus, A. Pier Siebesma
Physics Faculty Publications
Overlap statistics of cumuliform boundary-layer clouds are studied using large-eddy simulations at high resolutions. The cloud overlap is found to be highly inefficient, due to the typical irregularity of cumuliform clouds over a wide range of scales. The detection of such inefficient overlap is enabled in this study by i) applying fine enough discretizations and ii) by limiting the analysis to exclusively cumuliform boundary-layer cloud fields. It is argued that these two factors explain the differences with some previous studies on cloud overlap. In contrast, good agreement exists with previously reported observations of cloud overlap as derived from lidar measurements …
Equation Of State From The Potts-Percolation Model Of A Solid, Miron Kaufman
Equation Of State From The Potts-Percolation Model Of A Solid, Miron Kaufman
Physics Faculty Publications
We expand the Potts-percolation model of a solid to include stress and strain. Neighboring atoms are connected by bonds. We set the energy of a bond to be given by the Lennard-Jones potential. If the energy is larger than a threshold the bond is more likely to fail, whereas if the energy is lower than the threshold, the bond is more likely to be alive. In two dimensions we compute the equation of state: stress as a function of interatomic distance and temperature by using renormalization-group and Monte Carlo simulations. The phase diagram, the equation of state, and the isothermal …
Hubble Space Telescope Imaging Of Post-Starburst Quasars, S. L. Cales, M. S. Brotherton, Zhaohui Shang, Vardha N. Bennert, G. Canalizo, R. Stoll, R. Ganguly, D. Vanden Berk, C. Paul, A. Diamond-Stanic
Hubble Space Telescope Imaging Of Post-Starburst Quasars, S. L. Cales, M. S. Brotherton, Zhaohui Shang, Vardha N. Bennert, G. Canalizo, R. Stoll, R. Ganguly, D. Vanden Berk, C. Paul, A. Diamond-Stanic
Physics
We present images of 29 post-starburst quasars (PSQs) from a Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Wide Field Channel Snapshot program. These broadlined active galactic nuclei (AGNs) possess the spectral signatures of massive (M burst ~ 1010 M ☉), moderate-aged stellar populations (hundreds of Myr). Thus, their composite nature provides insight into the AGN-starburst connection. We measure quasar-to-host galaxy light contributions via semi-automated two-dimensional light profile fits of point-spread-function-subtracted images. We examine the host morphologies and model the separate bulge and disk components. The HST/ACS-F606W images reveal an equal number …
Electroproduction Of Hyperons At Low Momentum Transfer, Armando R. Acha
Electroproduction Of Hyperons At Low Momentum Transfer, Armando R. Acha
FIU Electronic Theses and Dissertations
A high resolution study of the H(e,e'K+)Λ,Σ0 reaction was performed at Hall A, TJNAF as part of the hypernuclear experiment E94-107. One important ingredient to the measurement of the hypernuclear cross section is the elementary cross section for production of hyperons, Λ and Σ0. This reaction was studied using a hydrogen (i.e. a proton) target. Data were taken at very low Q2 (∼0.07 (GeV/c)2) and W∼2.2 GeV. Kaons were detected along the direction of q, the momentum transferred by the incident electron (θCM~6°). In addition, there are few data available regarding electroproduction …
Experimental Study Of The Role Of Physicochemical Surface Processing On The In Ability Of Mineral Dust Particles, D. Niedermeier, S. Hartmann, T. Clauss, H. Wex, A. Kiselev, R. C. Sullivan, P. J. Demott, M. D. Petters, P. Reitz, J. Schneider, E. Mikhailov, B. Sierau, O. Stetzer, B. Reimann, U. Bundke, R. A. Shaw, A. Buchholz, T. F. Mentel, F. Stratmann
Experimental Study Of The Role Of Physicochemical Surface Processing On The In Ability Of Mineral Dust Particles, D. Niedermeier, S. Hartmann, T. Clauss, H. Wex, A. Kiselev, R. C. Sullivan, P. J. Demott, M. D. Petters, P. Reitz, J. Schneider, E. Mikhailov, B. Sierau, O. Stetzer, B. Reimann, U. Bundke, R. A. Shaw, A. Buchholz, T. F. Mentel, F. Stratmann
Michigan Tech Publications
During the measurement campaign FROST 2 (FReezing Of duST 2), the Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to investigate the influence of various surface modifications on the ice nucleating ability of Arizona Test Dust (ATD) particles in the immersion freezing mode. The dust particles were exposed to sulfuric acid vapor, to water vapor with and without the addition of ammonia gas, and heat using a thermodenuder operating at 250 °C. Size selected, quasi monodisperse particles with a mobility diameter of 300 nm were fed into LACIS and droplets grew on these particles such that each droplet contained a …
Dc Pulsed Atmospheric Pressure Plasma Jet Image Information, Denis P. Dowling, F T. O'Neill, Vladimir Milosavljevic, Victor J. Law
Dc Pulsed Atmospheric Pressure Plasma Jet Image Information, Denis P. Dowling, F T. O'Neill, Vladimir Milosavljevic, Victor J. Law
Articles
This paper presents optical imaging and optical emission spectroscopy (OES) data of an atmospheric-pressure plasma jet. It is shown how the visual information and OES information of the air discharge are related as the blown arc extends from the nozzle (2-4 mm) with a molecular nitrogen rotational temperature on the order of 1700 K and the flowing afterglow beyond this region is dominated by the cooler (300-K) NO-O chemiluminescent reaction that produces NO2 species.
Wave-Function Functionals For The Density, Marlina Slamet, Xiao-Yin Pan, Viraht Sahni
Wave-Function Functionals For The Density, Marlina Slamet, Xiao-Yin Pan, Viraht Sahni
Publications and Research
We extend the idea of the constrained-search variational method for the construction of wave-function functionals psi[chi] of functions chi. The search is constrained to those functions chi such that psi[chi] reproduces the density rho(r) while simultaneously leading to an upper bound to the energy. The functionals are thereby normalized and automatically satisfy the electron-nucleus coalescence condition. The functionals psi[chi] are also constructed to satisfy the electron-electron coalescence condition. The method is applied to the ground state of the helium atom to construct functionals psi[chi] that reproduce the density as given by the Kinoshita correlated wave function. The expectation of single-particle …
Search For A New Gauge Boson In Electron-Nucleus Fixed-Target Scattering By The Apex Experiment, S. Abrahamyan, Timothy Holmstrom, Jefferson Lab
Search For A New Gauge Boson In Electron-Nucleus Fixed-Target Scattering By The Apex Experiment, S. Abrahamyan, Timothy Holmstrom, Jefferson Lab
Chemistry & Physics Faculty Publications
We present a search at the Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling α′ to electrons. Such a particle A′ can be produced in electron-nucleus fixed-target scattering and then decay to an e+e- pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175–250 MeV, found no evidence for an A′→e+e- reaction, and set an upper limit of α′/α≃10-6. Our findings demonstrate that fixed-target searches can explore a new, …
The Polylogarithm And The Lambert W Functions In Thermoelectrics, Muralikrishna Molli, Kamisetty Venkataramaniah, Sree Ram Valluri
The Polylogarithm And The Lambert W Functions In Thermoelectrics, Muralikrishna Molli, Kamisetty Venkataramaniah, Sree Ram Valluri
Physics and Astronomy Publications
In this work, we determine the conditions for the extremum of the figure of merit, theta2, in a degenerate semiconductor for thermoelectric (TE) applications. We study the variation of the function theta2 with respect to the reduced chemical potential mu* using relations involving polylogarithms of both integral and nonintegral orders. We present the relevant equations for the thermopower, thermal, and electrical conductivities that result in optimizing theta2 and obtaining the extremum equations. We discuss the different cases that arise for various values of r, which depends on the type of carrier scattering mechanism present in the …
Nonlinear Progressive Wave Equation For Stratified Atmospheres, B. Edward Mcdonald, Andrew A. Piacsek
Nonlinear Progressive Wave Equation For Stratified Atmospheres, B. Edward Mcdonald, Andrew A. Piacsek
All Faculty Scholarship for the College of the Sciences
The nonlinear progressive wave equation (NPE) [McDonald and Kuperman, J. Acoust. Soc. Am. 81, 1406–1417 (1987)] is expressed in a form to accommodate changes in the ambient atmospheric density, pressure, and sound speed as the time-stepping computational window moves along a path possibly traversing significant altitude differences (in pressure scale heights). The modification is accomplished by the addition of a stratification term related to that derived in the 1970s for linear range-stepping calculations and later adopted into Khokhlov-Zabolotskaya-Kuznetsov-type nonlinear models. The modified NPE is shown to preserve acoustic energy in a ray tube and yields analytic similarity solutions for …
Understanding The Molecular Information Contained In Principal Component Analysis Of Vibrational Spectra Of Biological Systems, Franck Bonnier, Hugh Byrne
Understanding The Molecular Information Contained In Principal Component Analysis Of Vibrational Spectra Of Biological Systems, Franck Bonnier, Hugh Byrne
Articles
K-means clustering followed by Principal Component Analysis (PCA) is employed to analyse Raman spectroscopic maps of single biological cells. K-means clustering successfully identifies regions of cellular cytoplasm, nucleus and nucleoli, but the mean spectra do not differentiate their biochemical composition. The loadings of the principal components identified by PCA shed further light on the spectral basis for differentiation but they are complex and, as the number of spectra per cluster is imbalanced, particularly in the case of the nucleoli, the loadings under-represent the basis for differentiation of some cellular regions. Analysis of pure bio-molecules, both structurally and spectrally distinct, in …
Thermodynamics Of Strongly Interacting Fermions In Two-Dimensional Optical Lattices, Ehsan Khatami, Marcos Rigol
Thermodynamics Of Strongly Interacting Fermions In Two-Dimensional Optical Lattices, Ehsan Khatami, Marcos Rigol
Faculty Publications
We study finite-temperature properties of strongly correlated fermions in two-dimensional optical lattices by means of numerical linked cluster expansions, a computational technique that allows one to obtain exact results in the thermodynamic limit. We focus our analysis on the strongly interacting regime, where the on-site repulsion is of the order of or greater than the band width. We compute the equation of state, double occupancy, entropy, uniform susceptibility, and spin correlations for temperatures that are similar to or below the ones achieved in current optical lattice experiments. We provide a quantitative analysis of adiabatic cooling of trapped fermions in two …
Poincaré Sphere Representation Of The Fixed-Polarizer Rotating-Retarder Optical System, R. M.A. Azzam
Poincaré Sphere Representation Of The Fixed-Polarizer Rotating-Retarder Optical System, R. M.A. Azzam
Electrical Engineering Faculty Publications
The trajectory of the polarization state of a monochromatic light beam after it passes through a fixed linear polarizer and a rotating linear retarder of arbitrary retardance Δ is determined on the Poincaré sphere. The three-dimensional figure-8 contour is shown to be the line of intersection of a right-circular cylinder with the sphere. The cylinder is parallel to the polar (s3) axis, touches the sphere at the equator (at the point that represents the linear polarization transmitted by the fixed polarizer), and has a radius r=sin2(Δ/2). Projections of the trajectory in the coordinate planes of the …