Open Access. Powered by Scholars. Published by Universities.®

Physics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2009

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 121 - 150 of 907

Full-Text Articles in Physics

Structural Development In Ge-Rich Ge-S Glasses, Y. Sakaguchi, Dmitri Tenne, Maria Mitkova Oct 2009

Structural Development In Ge-Rich Ge-S Glasses, Y. Sakaguchi, Dmitri Tenne, Maria Mitkova

Physics Faculty Publications and Presentations

The Raman spectra of Ge-S glasses in the Ge-rich region from Ge 33 to 46 % have been investigated in order to know the structural development of the network glasses. From the detailed curve fits, we have found that there is an unassigned peak at 410 cm-1 and it becomes larger with increasing Ge composition. To clarify the structural origin of the peak, we virtually constructed the atomic arrangement of the glassy state starting from the crystalline state through the liquid state and changed the composition gradually depleting the medium in sulfur. From the consideration of the structural modeling …

Go to article

Nonlinear Power Spectrum In The Presence Of Massive Neutrinos: Perturbation Theory Approach, Galaxy Bias, And Parameter Forecasts, Shun Saito, Masahiro Takada, Atsushi Taruya Oct 2009

Nonlinear Power Spectrum In The Presence Of Massive Neutrinos: Perturbation Theory Approach, Galaxy Bias, And Parameter Forecasts, Shun Saito, Masahiro Takada, Atsushi Taruya

Physics Faculty Research & Creative Works

Future or ongoing galaxy redshift surveys can put stringent constraints on neutrinos masses via the high-precision measurements of galaxy power spectrum, when combined with CMB information. In this paper we develop a method to model galaxy power spectrum in the weakly nonlinear regime for a mixed dark matter [cold dark matter (CDM) plus finite-mass neutrinos] model, based on perturbation theory (PT) whose validity is well tested by simulations for a CDM model. In doing this we carefully study various aspects of the nonlinear clustering (nonlinear neutrino perturbations and the higher-order growth functions), and then arrive at a useful approximation allowing …

Go to article

Isomeric Effects With Di-Iodobenzene (C6H4I2) On Adsorption On Graphite, Keisuke Fukutani, Ning Wu, Peter A. Dowben Oct 2009

Isomeric Effects With Di-Iodobenzene (C6H4I2) On Adsorption On Graphite, Keisuke Fukutani, Ning Wu, Peter A. Dowben

Peter Dowben Publications

Differences are seen in the adsorption of 1,2-di-iodobenzene, 1,3-di-iodobenzene, and 1,4-di-iodobenzene on graphite, as a function of exposure, using core level photoemission. The isomer 1,3-di-iodobenzene exhibits significant differences from 1,2-di-iodobenzene, and 1,4-di-iodobenzene in apparent sticking coefficients and core level binding energies. 1,3-Di-iodobenzene adsorb on graphite at 110 K in a strongly Stranski–Krastanov or Volmer–Weber (island) growth mode. The implication is that, even for small molecules adsorption, the adsorbate dipole in the plane of surface and the choice of isomer may matter.

Go to article

Subjet Distributions In Deep Inelastic Scattering At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann Oct 2009

Subjet Distributions In Deep Inelastic Scattering At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann

Faculty Publications

Subjet distributions were measured in neutral current deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 81.7 pb-1. Jets were identified using the k T cluster algorithm in the laboratory frame. Subjets were defined as jet-like substructures identified by a reapplication of the cluster algorithm at a smaller value of the resolution parameter ycut. Measurements of subjet distributions for jets with exactly two subjets for ycut=0.05 are presented as functions of observables sensitive to the pattern of parton radiation and to the colour coherence between the initial and final states. Perturbative QCD predictions give …

Go to article

Image Registration Using Conformal Log Polar Mapping, Bala Krishna Vadapally Oct 2009

Image Registration Using Conformal Log Polar Mapping, Bala Krishna Vadapally

Electrical & Computer Engineering Theses & Dissertations

Image Registration is the process of aligning, or overlaying two images of the same scene that were taken at different times and/or from different viewing angles and/or by sensors with different modalities or resolutions. The variations in the imaging environment induce the difference between the images of the same scene. In our situation, we have two images of the same scene taken with two sensors, one in the visible and the other in the infrared (IR) domain. The cameras are placed adjacent to each other on a stable platform, and the images are captured almost simultaneously. This means that the …

Go to article

Plasmonic Enhancement Of Forster Energy Transfer Between Two Molecules In The Vicinity Of A Metallic Nanoparticle: Nonlocal Optical Effects, P.T. Leung, H. Y. Xie, H. Y. Chung, D. P. Tsai Oct 2009

Plasmonic Enhancement Of Forster Energy Transfer Between Two Molecules In The Vicinity Of A Metallic Nanoparticle: Nonlocal Optical Effects, P.T. Leung, H. Y. Xie, H. Y. Chung, D. P. Tsai

Physics Faculty Publications and Presentations

The problem of Forster resonance energy transfer (FRET) between two molecules in the vicinity of a metallic nanoparticle such as a nanoshell is studied within a phenomenological model which takes into account the nonlocal optical response of the metal. This model allows for arbitrary locations and orientations of the two molecular dipoles with respect to the metal particle which can be of ultrasmall sizes (nm) and for which nonlocal effects are of high significance. In particular, for the nanoshell case, the molecules can be located both outside, both inside, or one inside and one outside the shell. Also, the case …

Go to article

Two-Loop Soft Anomalous Dimensions With Massive And Massless Quarks, Nikolaos Kidonakis Oct 2009

Two-Loop Soft Anomalous Dimensions With Massive And Massless Quarks, Nikolaos Kidonakis

Faculty Articles

I present results for two-loop soft anomalous dimensions, which are derived from dimensionally regularized diagrams with eikonal quark lines and control soft-gluon emission in hard-scattering processes. Detailed results for the UV poles of the eikonal integrals are shown for massive quarks, and the massless limit is also taken. The construction of soft anomalous dimensions at two-loops allows soft-gluon resummations at NNLL accuracy.

Go to article

Galaxy Zoo: ‘Hanny's Voorwerp’, A Quasar Light Echo?, Chris J. Lintott, Kevin Schawinski, William Keel, Hanny Van Arkel, Nicola Bennert, Edward Edmondson, Daniel Thomas, Daniel J.B. Smith, Peter D. Herbert, Matt J. Jarvis, Shanil Virani, Dan Andreescu, Steven P. Bamford, Kate Land, Phil Murray, Robert C. Nichol, M. Jordan Raddick, Anže Slosar, Alex Azalay, Jan Vandenberg Oct 2009

Galaxy Zoo: ‘Hanny's Voorwerp’, A Quasar Light Echo?, Chris J. Lintott, Kevin Schawinski, William Keel, Hanny Van Arkel, Nicola Bennert, Edward Edmondson, Daniel Thomas, Daniel J.B. Smith, Peter D. Herbert, Matt J. Jarvis, Shanil Virani, Dan Andreescu, Steven P. Bamford, Kate Land, Phil Murray, Robert C. Nichol, M. Jordan Raddick, Anže Slosar, Alex Azalay, Jan Vandenberg

Physics

We report the discovery of an unusual object near the spiral galaxy IC 2497, discovered by visual inspection of the Sloan Digital Sky Survey (SDSS) as part of the Galaxy Zoo project. The object, known as Hanny's Voorwerp, is bright in the SDSS g band due to unusually strong [O iii]4959, 5007 emission lines. We present the results of the first targeted observations of the object in the optical, ultraviolet and X-ray, which show that the object contains highly ionized gas. Although the line ratios are similar to extended emission-line regions near luminous active galactic nucleus (AGN), the source of …

Go to article

Thermodynamics Of The Quantum Critical Point At Finite Doping In The Two-Dimensional Hubbard Model Studied Via The Dynamical Cluster Approximation, K. Mikelsons, Ehsan Khatami, D. Galanakis, A. Macridin, J. Moreno, M. Jarrell Oct 2009

Thermodynamics Of The Quantum Critical Point At Finite Doping In The Two-Dimensional Hubbard Model Studied Via The Dynamical Cluster Approximation, K. Mikelsons, Ehsan Khatami, D. Galanakis, A. Macridin, J. Moreno, M. Jarrell

Faculty Publications

We study the thermodynamics of the two-dimensional Hubbard model within the dynamical cluster approximation. We use continuous time quantum Monte Carlo as a cluster solver to avoid the systematic error which complicates the calculation of the entropy and potential energy (double occupancy). We find that at a critical filling, there is a pronounced peak in the entropy divided by temperature, S/T, and in the normalized double occupancy as a function of doping. At this filling, we find that specific heat divided by temperature, C/T, increases strongly with decreasing temperature and kinetic and potential energies vary like T2 ln T. These …

Go to article

Beam Spin Asymmetries In Deeply Virtual Compton Scattering (Dvcs) With Clas At 4.8 Gev, G. Gavalian, Gerard P. Gilfoyle, Et. Al. Sep 2009

Beam Spin Asymmetries In Deeply Virtual Compton Scattering (Dvcs) With Clas At 4.8 Gev, G. Gavalian, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

We report measurements of the beam spin asymmetry in deeply virtual Compton scattering (DVCS) at an electron beam energy of 4.8 GeV using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The DVCS beam spin asymmetry has been measured in a wide range of kinematics, 1.0 < Q2 < 2.8 (GeV/c)2, 0.12 < xB < 0.48, and 0.1 < −t < 0.8 (GeV/c)2, using the reaction ep → e' p X. The number of H(e, e' γ p) and H(e, e'π0p) events are separated in each (Q2, xB, t …

Go to article

Extracting Black Hole Physics From The Lattice, Simon Catterall, Toby Wiseman Sep 2009

Extracting Black Hole Physics From The Lattice, Simon Catterall, Toby Wiseman

Physics - All Scholarship

We perform lattice simulations of N D0-branes at finite temperature in the decoupling limit, namely 16 supercharge SU(N) Yang-Mills quantum mechanics in the 't Hooft limit. At low temperature this theory is conjectured to be dual to certain supergravity black holes. We emphasize that the existence of a non-compact moduli space renders the partition function of the quantum mechanics theory divergent, and we perform one loop calculations that demonstrate this explicitly. In consequence we use a scalar mass term to regulate this divergence and argue that the dual black hole thermodynamics may be recovered in the appropriate large N limit …

Go to article

Perturbed S3 Neutrinos, Joseph Schechter, Renata Jora, M. Naeem Shahid Sep 2009

Perturbed S3 Neutrinos, Joseph Schechter, Renata Jora, M. Naeem Shahid

Physics - All Scholarship

We study the effects of the perturbation which violates the permutation symmetry of three Majorana neutrinos but preserves the well known (23) interchange symmetry. This is done in the presence of an arbitrary Majorana phase which serves to insure the degeneracy of the three neutrinos at the unperturbed level.

Go to article

The Hunt For New Physics At The Large Hadron Collider, Joseph Schechter, Pran Nath Sep 2009

The Hunt For New Physics At The Large Hadron Collider, Joseph Schechter, Pran Nath

Physics - All Scholarship

We study the effects of the perturbation which violates the permutation symmetry of three Majorana neutrinos but preserves the well known (23) interchange symmetry. This is done in the presence of an arbitrary Majorana phase which serves to insure the degeneracy of the three neutrinos at the unperturbed level.

Go to article

First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone Sep 2009

First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

We report on a matched-filter search for gravitational wave bursts from cosmic string cusps using LIGO data from the fourth science run (S4) which took place in February and March 2005. No gravitational waves were detected in 14.9 days of data from times when all three LIGO detectors were operating. We interpret the result in terms of a frequentist upper limit on the rate of gravitational wave bursts and use the limits on the rate to constrain the parameter space (string tension, reconnection probability, and loop sizes) of cosmic string models. Many grand unified theory-scale models (with string tension ��⁢��/��2≈10−6) …

Go to article

Detections Of Water Ice, Hydrocarbons, And 3.3 ΜM Pah In Z ~ 2 Ulirgs, Anna Sajina, Henrik Spoon, Lin Yan, Masatoshi Imanishi, Dario Fadda, Moshe Elitzur Sep 2009

Detections Of Water Ice, Hydrocarbons, And 3.3 ΜM Pah In Z ~ 2 Ulirgs, Anna Sajina, Henrik Spoon, Lin Yan, Masatoshi Imanishi, Dario Fadda, Moshe Elitzur

Physics and Astronomy Faculty Publications

We present the first detections of the 3 μm water ice and 3.4 μm amorphous hydrocarbon (HAC) absorption features in z ~ 2 ULIRGs. These are based on deep rest-frame 2-8 μm Spitzer Infrared Spectrograph spectra of 11 sources selected for their appreciable silicate absorption. The HAC-to-silicate ratio for our z ~ 2 sources is typically higher by a factor of 2-5 than that observed in the Milky Way. This HAC “excess” suggests compact nuclei with steep temperature gradients as opposed to predominantly host obscuration. Beside the above molecular absorption features, we detect the 3.3 μm …

Go to article

Exact Lattice Supersymmetry, Simon Catterall, David B. Kaplan, Mithat Unsal Sep 2009

Exact Lattice Supersymmetry, Simon Catterall, David B. Kaplan, Mithat Unsal

Physics - All Scholarship

We provide an introduction to recent lattice formulations of supersymmetric theories which are invariant under one or more real supersymmetries at nonzero lattice spacing. These include the especially interesting case of {\cal N}=4 SYM in four dimensions. We discuss approaches based both on twisted supersymmetry and orbifold-deconstruction techniques and show their equivalence in the case of gauge theories. The presence of an exact supersymmetry reduces and in some cases eliminates the need for fine tuning to achieve a continuum limit invariant under the full supersymmetry of the target theory. We discuss open problems.

Go to article

On The Use Of The Proximity Force Approximation For Deriving Limits To Short-Range Gravitational-Like Interactions From Sphere-Plane Casimir Force Experiments, Diego A. R. Dalvit, Roberto Onofrio Sep 2009

On The Use Of The Proximity Force Approximation For Deriving Limits To Short-Range Gravitational-Like Interactions From Sphere-Plane Casimir Force Experiments, Diego A. R. Dalvit, Roberto Onofrio

Dartmouth Scholarship

We discuss the role of the proximity force approximation in deriving limits to the existence of Yukawian forces—predicted in the submillimeter range by many unification models—from Casimir force experiments using the sphere-plane geometry. Two forms of this approximation are discussed, the first used in most analyses of the residuals from the Casimir force experiments performed so far, and the second recently discussed in this context in R. Decca et al. [Phys. Rev. D 79, 124021 (2009)]. We show that the former form of the proximity force approximation overestimates the expected Yukawa force and that the relative deviation …

Go to article

The Influences Of Cell Type And Zno Nanoparticle Size On Immune Cell Cytotoxicity And Cytokine Induction, Cory Hanley, Aaron Thurber, Charles Hanna, Alex Punnoose, Jianhui Zhang, Denise G. Wingett Sep 2009

The Influences Of Cell Type And Zno Nanoparticle Size On Immune Cell Cytotoxicity And Cytokine Induction, Cory Hanley, Aaron Thurber, Charles Hanna, Alex Punnoose, Jianhui Zhang, Denise G. Wingett

Physics Faculty Publications and Presentations

Nanotechnology represents a new and enabling platform that promises to provide a range of innovative technologies for biological applications. ZnO nanoparticles of controlled size were synthesized, and their cytotoxicity towards different human immune cells evaluated. A differential cytotoxic response between human immune cell subsets was observed, with lymphocytes being the most resistant and monocytes being the most susceptible to ZnO nanoparticle-induced toxicity. Significant differences were also observed between previously activated memory lymphocytes and naive lymphocytes, indicating a relationship between cell-cycle potential and nanoparticle susceptibility. Mechanisms of toxicity involve the generation of reactive oxygen species, with monocytes displaying the highest levels, …

Go to article

Dynamical Quantum Error Correction Of Unitary Operations With Bounded Controls, Kaveh Khodjasteh, Lorenza Viola Sep 2009

Dynamical Quantum Error Correction Of Unitary Operations With Bounded Controls, Kaveh Khodjasteh, Lorenza Viola

Dartmouth Scholarship

Dynamically corrected gates were recently introduced [K. Khodjasteh and L. Viola, Phys. Rev. Lett. 102, 080501 (2009)] as a tool to achieve decoherence-protected quantum gates based on open-loop Hamiltonian engineering. Here, we further expand the framework of dynamical quantum error correction, with emphasis on elucidating under what conditions decoherence suppression can be ensured while performing a generic target quantum gate, using only available bounded-strength control resources. Explicit constructions for physically relevant error models are detailed, including arbitrary linear decoherence and pure dephasing on qubits. The effectiveness of dynamically corrected gates in an illustrative non-Markovian spin-bath setting is investigated numerically, …

Go to article

Exclusive Photoproduction Of ϒmesons At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann, E. Hilger Sep 2009

Exclusive Photoproduction Of ϒmesons At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann, E. Hilger

Faculty Publications

The exclusive photoproduction reaction γ p → Υ{hooked} p has been studied with the ZEUS experiment in ep collisions at HERA using an integrated luminosity of 468 pb-1. The measurement covers the kinematic range 60 < W < 220 GeV and Q2 < 1 GeV2, where W is the photon-proton centre-of-mass energy and Q2 is the photon virtuality. These results, which represent the analysis of the full ZEUS data sample for this channel, are compared to predictions based on perturbative QCD. © 2009 Elsevier B.V.

Go to article

Multi-Lepton Production At High Transverse Momentum At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann Sep 2009

Multi-Lepton Production At High Transverse Momentum At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann

Faculty Publications

A search for events containing two or more high-transverse-momentum isolated leptons has been performed in ep collisions with the ZEUS detector at HERA using the full collected data sample, corresponding to an integrated luminosity of 480 pb -1. The number of observed events has been compared with the prediction from the Standard Model, searching for possible deviations, especially for multi-lepton events with invariant mass larger than 100 GeV. Good agreement with the Standard Model has been observed. Total and differential cross sections for di-lepton production have been measured in a restricted phase space dominated by photon-photon collisions. © 2009 Elsevier …

Go to article

Photopolymers: Beyond The Standard Approach To Photosensitisation, Izabela Naydenova, Suzanne Martin, Vincent Toal Sep 2009

Photopolymers: Beyond The Standard Approach To Photosensitisation, Izabela Naydenova, Suzanne Martin, Vincent Toal

Articles

A photopolymerizable material for use in the visible normally consists of a dye sensitizer, a free radical generator, monomer/monomers and, optionally, a binder, and is prepared usually as a dry or liquid film. Upon illumination with light of appropriate wavelength, a photopolymerisation reaction is triggered, leading to a change in the film’s refractive index. Because the presence of the dye is essential, the film is usually made sensitive to light during its preparation. Here we separate the film preparation and the sensitisation processes. In this way the photopolymerisation process can be used to detect dye labelled analytes, providing an alternative …

Go to article

Dissecting Galaxy Formation. I. Comparison Between Pure Dark Matter And Baryonic Models, Emilio Romano-Diaz, Isaac Shlosman, Clayton Heller, Yehuda Hoffman Sep 2009

Dissecting Galaxy Formation. I. Comparison Between Pure Dark Matter And Baryonic Models, Emilio Romano-Diaz, Isaac Shlosman, Clayton Heller, Yehuda Hoffman

Physics & Astronomy: Faculty Publications

We compare assembly of dark matter (DM) halos with and without baryons from identical initial conditions, within the context of cosmological evolution in the ΛCDM WMAP3 Universe (baryons+DM, hereafter BDM model, and pure DM, PDM model). In representative PDM and BDM models, we find that baryons contribute decisively to the evolution of the central region, leading to an isothermal DM cusp, and thereafter to a flat DM density core—the result of heating by dynamical friction of the DM+baryon substructure during a quiescent evolution epoch. This process ablates the cold gas from an embedded disk, cutting the star formation rate by …

Go to article

Input To The Nas Ctbt Study, David Hafemeister Sep 2009

Input To The Nas Ctbt Study, David Hafemeister

Physics

No abstract provided.

Go to article

De Vries Behavior In Smectics Near A Biaxiality Induced Smectic A - Smectic C Tricritical Point, Karl Saunders Sep 2009

De Vries Behavior In Smectics Near A Biaxiality Induced Smectic A - Smectic C Tricritical Point, Karl Saunders

Physics

We show that a generalized Landau theory for the smectic A and C phases exhibits a biaxiality induced AC tricritical point. Proximity to this tricritical point depends on the degree of orientational order in the system; for sufficiently large orientational order the AC transition is 3D XY-like, while for sufficiently small orientational order, it is either tricritical or 1st order. We investigate each of the three types of AC transitions near tricriticality and show that for each type of transition, small orientational order implies de Vries behavior in the layer spacing, an unusually small layer contraction. This result is consistent …

Go to article

Signal Classification In Fading Channels Using Cyclic Spectral Analysis, Zhiqiang Wu, Eric C. Like, Vasu D. Chakravarthy, Paul Ratazzi Sep 2009

Signal Classification In Fading Channels Using Cyclic Spectral Analysis, Zhiqiang Wu, Eric C. Like, Vasu D. Chakravarthy, Paul Ratazzi

Student Publications

Cognitive Radio (CR), a hierarchical Dynamic Spectrum Access (DSA) model, has been considered as a strong candidate for future communication systems improving spectrum efficiency utilizing unused spectrum of opportunity. However, to ensure the effectiveness of dynamic spectrum access, accurate signal classification in fading channels at low signal to noise ratio is essential. In this paper, a hierarchical cyclostationary-based classifier is proposed to reliably identify the signal type of a wide range of unknown signals. The proposed system assumes no a priori knowledge of critical signal statistics such as carrier frequency, carrier phase, or symbol rate. The system is designed with …

Go to article

A Non-Thermal Wimp Miracle, Scott Watson, Bobby Samir Acharya, Gordon Kane, Piyush Kumar Sep 2009

A Non-Thermal Wimp Miracle, Scott Watson, Bobby Samir Acharya, Gordon Kane, Piyush Kumar

Physics - All Scholarship

Light scalar fields with only gravitational strength couplings are typically present in UV complete theories of physics beyond the Standard Model. In the early universe it is natural for these fields to dominate the energy density, and their subsequent decay, if prior to BBN, will typically yield some dark matter particles in their decay products. In this paper we make the observation that a Non-thermal WIMP `Miracle' may result: that is, in the simplest solution to the cosmological moduli problem, non-thermally produced WIMPs can naturally account for the observed dark matter relic density. Such a solution may be generic in …

Go to article

M2-Factor Of Coherent And Partially Coherent Dark Hollow Beams Propagating In Turbulent Atmosphere, Yangsheng Yuan, Yangjian Cai, Jun Qu, Halil T. Eyyuboglu, Yahya Baykal, Olga Korotkova Sep 2009

M2-Factor Of Coherent And Partially Coherent Dark Hollow Beams Propagating In Turbulent Atmosphere, Yangsheng Yuan, Yangjian Cai, Jun Qu, Halil T. Eyyuboglu, Yahya Baykal, Olga Korotkova

Physics Articles and Papers

Analytical formula is derived for the M2-factor of coherent and partially coherent dark hollow beams (DHB) in turbulent atmosphere based on the extended Huygens-Fresnel integral and the second-order moments of the Wigner distribution function. Our numerical results show that the M2- factor of a DHB in turbulent atmosphere increases on propagation, which is much different from its invariant properties in free-space, and is mainly determined by the parameters of the beam and the atmosphere. The relative M2-factor of a DHB increases slower than that of Gaussian and flat-topped beams on propagation, which means a …

Go to article

Synthesis Of Znse/Cds/Znse Nanobarbells Showing Photoinduced Charge Separation, Maria Kirsanova, Alexander Nemchinov, Nishshanka N. Hewa-Kasakarage, Nicholas Schmall, Mikhail Zamkov Sep 2009

Synthesis Of Znse/Cds/Znse Nanobarbells Showing Photoinduced Charge Separation, Maria Kirsanova, Alexander Nemchinov, Nishshanka N. Hewa-Kasakarage, Nicholas Schmall, Mikhail Zamkov

Physics and Astronomy Faculty Publications

We report on it colloidal synthesis of barbell-shaped nanocrystals comprising a type II hetero-junction of ZnSe and US domains and showing compelling evidence of photoinduced charge separation at the interface of ZnSe and US materials. The nanobarbells were fabricated in a two-step procedure by growing ZnSe caps onto polar facets of US nanorods. Under present synthetic conditions, minimal growth of ZnSe shell in the lateral direction and focusing of the barbell length distribution were observed. Formation of epitaxial interfaces between nearly lattice-matched ZnSe and US crystal phases was primarily evidenced by the observation of "spatially indirect" fluorescence and long radiative …

Go to article

Self-Similar Nested Sequences On A Chaotic Attractor For Travelingwave Electrophoresis, Boyd F. Edwards Sep 2009

Self-Similar Nested Sequences On A Chaotic Attractor For Travelingwave Electrophoresis, Boyd F. Edwards

All Physics Faculty Publications

Oscillating electric potentials are applied to interdigitated arrays of cylindrical electrodes above and below a stationary conducting viscous fluid. The phases of these potentials are chosen to produce a longitudinal traveling wave that traps high-mobility ions and partially traps intermediate-mobility ions in periodic and narrowband chaotic attractors with average velocities that are commensurate with the wave speed. Stable periodic attractors have periods up to 101 times the wave period. Incommensurate broadband chaotic attractors are described by one-dimensional iterated contact-angle return maps, which feature self-similar nested sequences that converge geometrically at unstable trapped orbits. Sequences of singular angles and sequences of …

Go to article

First Prev Next Last