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Articles 1  30 of 234
FullText Articles in Physics
Exotic Statistics For Strings In 4d Bf Theory, John C. Baez, Derek K. Wise, Alissa S. Crans
Exotic Statistics For Strings In 4d Bf Theory, John C. Baez, Derek K. Wise, Alissa S. Crans
Alissa Crans
After a review of exotic statistics for point particles in 3d BF theory, and especially 3d quantum gravity, we show that stringlike defects in 4d BF theory obey exotic statistics governed by the 'loop braid group'. This group has a set of generators that switch two strings just as one would normally switch point particles, but also a set of generators that switch two strings by passing one through the other. The first set generates a copy of the symmetric group, while the second generates a copy of the braid group. Thanks to recent work of XiaoSong Lin, we can ...
Toy Blocks And Rotational Physics, Gabriele U. Varieschi, Isabel R. Jully
Toy Blocks And Rotational Physics, Gabriele U. Varieschi, Isabel R. Jully
Gabriele Varieschi
Have you ever observed a child playing with toy blocks? A favorite game is to build towers and then make them topple like falling trees. To the eye of a trained physicist this should immediately look like an example of the physics of “falling chimneys,” when tall structures bend and break in midair while falling to the ground. The game played with toy blocks can actually reproduce well what is usually seen in photographs of falling towers, such as the one that appeared on the cover of the September 1976 issue of The Physics Teacher.1 In this paper we ...
Kerr Metric, Geodesic Motion, And Flyby Anomaly In FourthOrder Conformal Gravity, Gabriele U. Varieschi
Kerr Metric, Geodesic Motion, And Flyby Anomaly In FourthOrder Conformal Gravity, Gabriele U. Varieschi
Gabriele Varieschi
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 spacetime based on this geometry is indeed separable and that a fourth constant of motion—similar to Carter’s constant—can ...
Intonation And Compensation Of Fretted String Instruments, Gabriele U. Varieschi, Christina M. Gower
Intonation And Compensation Of Fretted String Instruments, Gabriele U. Varieschi, Christina M. Gower
Gabriele Varieschi
We discuss theoretical and physical models that are useful for analyzing the intonation of musical instruments such as guitars and mandolins and can be used to improve the tuning on these instruments. The placement of frets on the fingerboard is designed according to mathematical rules and the assumption of an ideal string. The analysis becomes more complicated when we include the effects of deformation of the string and inharmonicity due to other string characteristics. As a consequence, perfect intonation of all the notes on the instrument cannot be achieved, but complex compensation procedures can be introduced to minimize the problem ...
Simulating A Guitar With A Conventional Sonometer, Zily Burstein, Christina M. Gower, Gabriele U. Varieschi
Simulating A Guitar With A Conventional Sonometer, Zily Burstein, Christina M. Gower, Gabriele U. Varieschi
Gabriele Varieschi
In this paper we present a simple way to convert a conventional sonometer into a simulated fretted instrument, such as a guitar or similar, by adding a fingerboard to the sonometer. In particular, we use this modified apparatus in relation to the problem of the instrument intonation, i.e., how to obtain correctly tuned notes on these string instruments. The experimental procedures presented in this study can become a more structured laboratory activity to be used in general physics courses or acoustics classes.
Astrophysical Tests Of Kinematical Conformal Cosmology In FourthOrder Conformal Weyl Gravity, Gabriele U. Varieschi
Astrophysical Tests Of Kinematical Conformal Cosmology In FourthOrder Conformal Weyl Gravity, Gabriele U. Varieschi
Gabriele Varieschi
In this work we analyze kinematical conformal cosmology (KCC), an alternative cosmological model based on conformal Weyl gravity (CG), and test it against current type Ia supernova (SNIa) luminosity data and other astrophysical observations. Expanding upon previous work on the subject, we revise the analysis of SNIa data, confirming that KCC can explain the evidence for an accelerating expansion of the Universe without using dark energy or other exotic components. We obtain an independent evaluation of the Hubble constant, H0 = 67:53 kms1 Mpc1, very close to the current best estimates. The main KCC and CG parameters are reevaluated and ...
Toy Models For The Falling Chimney, Gabriele U. Varieschi, Kaoru Kamiya
Toy Models For The Falling Chimney, Gabriele U. Varieschi, Kaoru Kamiya
Gabriele Varieschi
In this paper we review the theory of the ‘‘falling chimney,’’ which deals with the breaking in midair of tall structures when they fall to the ground. We show that these ruptures can be caused by either shear forces typically developing near the base, or by the bending of the structure which is caused primarily by the internal bending moment. In the latter case the breaking is more likely to occur between onethird and onehalf of the height of the chimney. Small scale toy models are used to reproduce the dynamics of the falling chimney. By examining photos taken during ...
Wormhole Geometries In FourthOrder Conformal Weyl Gravity, Gabriele U. Varieschi, Kellie L. Ault
Wormhole Geometries In FourthOrder Conformal Weyl Gravity, Gabriele U. Varieschi, Kellie L. Ault
Gabriele Varieschi
We present an analysis of the classic wormhole geometries based on conformal Weyl gravity, rather than standard general relativity. The main characteristics of the resulting traversable wormholes remain the same as in the seminal study by Morris and Thorne, namely, that effective superluminal motion is a viable consequence of the metric. Improving on previous work on the subject, we show that for particular choices of the shape and redshift functions the wormhole metric in the context of conformal gravity does not violate the main energy conditions at or near the wormhole throat. Some exotic matter might still be needed at ...
Conformal Gravity And The Alcubierre Warp Drive Metric, Gabriele U. Varieschi, Zily Burstein
Conformal Gravity And The Alcubierre Warp Drive Metric, Gabriele U. Varieschi, Zily Burstein
Gabriele Varieschi
We present an analysis of the classic Alcubierre metric based on conformal gravity, rather than standard general relativity. The main characteristics of the resulting warp drive remain the same as in the original study by Alcubierre, that is, effective superluminal motion is a viable outcome of the metric. We show that for particular choices of the shaping function, the Alcubierre metric in the context of conformal gravity does not violate the weak energy condition, as was the case of the original solution. In particular, the resulting warp drive does not require the use of exotic matter. Therefore, if conformal gravity ...
Transport And Optical Conductivity In The Hubbard Model: A HighTemperature Expansion Perspective, Edward Perepelitsky, Andrew Galatas, Jernej Mravlje, Rok Žitko, Ehsan Khatami, B. Sriram Shastry, Antoine Georges
Transport And Optical Conductivity In The Hubbard Model: A HighTemperature Expansion Perspective, Edward Perepelitsky, Andrew Galatas, Jernej Mravlje, Rok Žitko, Ehsan Khatami, B. Sriram Shastry, Antoine Georges
Ehsan Khatami
Connecting SelfEfficacy And Views About Nature Of Science In Undergraduate Research Experiences, Gina M. Quan, Andrew Elby
Connecting SelfEfficacy And Views About Nature Of Science In Undergraduate Research Experiences, Gina M. Quan, Andrew Elby
Gina Quan
Fluctuations In A Cosmology With A Spacelike Singularity And Their Gauge Theory Dual Description, Robert H. Brandenberger, Elisa G.M. Ferreira, Ian A. Morrison, YiFu Cai, Sumit R. Das, Yi Wang
Fluctuations In A Cosmology With A Spacelike Singularity And Their Gauge Theory Dual Description, Robert H. Brandenberger, Elisa G.M. Ferreira, Ian A. Morrison, YiFu Cai, Sumit R. Das, Yi Wang
Ian Morrison
We consider a timedependent deformation of anti–de Sitter (AdS) spacetime which contains a spacelike “singularity”—a spacelike region of high curvature. Making use of the AdS/CFT correspondence we can map the bulk dynamics onto the boundary. The boundary theory has a time dependent coupling constant which becomes small at times when the bulk spacetime is highly curved. We investigate the propagation of small fluctuations of a test scalar field from early times before the bulk singularity to late times after the singularity. Under the assumption that the AdS/CFT correspondence extends to deformed AdS spacetimes, we can map ...
Hybrid Spatiotemporal Coherent Pulse Addition Of A Picosecond FlashlampPumped Ndyag Laser.Pdf, Ahmad Azim
Hybrid Spatiotemporal Coherent Pulse Addition Of A Picosecond FlashlampPumped Ndyag Laser.Pdf, Ahmad Azim
Ahmad Azim
Femtosecond Pulse Trains Of Polychromatic Inverse Compton ΓRays From Designer Electron Beams Produced By LaserPlasma Acceleration In Plasma Channels, Serge Y. Kalmykov, Isaac Ghebregziabher, X. Davoine, Remi Lehe, Agustin F. Lifschitz, Victor Malka, Bradley A. Shadwick
Femtosecond Pulse Trains Of Polychromatic Inverse Compton ΓRays From Designer Electron Beams Produced By LaserPlasma Acceleration In Plasma Channels, Serge Y. Kalmykov, Isaac Ghebregziabher, X. Davoine, Remi Lehe, Agustin F. Lifschitz, Victor Malka, Bradley A. Shadwick
Serge Youri Kalmykov
Accordion Effect Revisited: Generation Of CombLike Electron Beams In Plasma Channels, Serge Y. Kalmykov, X. Davoine, Remi Lehe, Agustin F. Lifschitz, Bradley A. Shadwick
Accordion Effect Revisited: Generation Of CombLike Electron Beams In Plasma Channels, Serge Y. Kalmykov, X. Davoine, Remi Lehe, Agustin F. Lifschitz, Bradley A. Shadwick
Serge Youri Kalmykov
Examination Of The Nonlinear Dynamics And Possible Chaos Encryption In A ZerothOrder AcoustoOptic Bragg Modulator With Feedback, Fares S. Almehmadi, Monish Ranjan Chatterjee
Examination Of The Nonlinear Dynamics And Possible Chaos Encryption In A ZerothOrder AcoustoOptic Bragg Modulator With Feedback, Fares S. Almehmadi, Monish Ranjan Chatterjee
Monish R. Chatterjee
Zerothorder chaos modulation in a Bragg cell is examined such that tracking problems due to spatial deflections of the firstorder AO beam at the receiver may be avoided by switching to the undeviated zerothorder beam.
Anisoplanatic Electromagnetic Image Propagation Through Narrow Or Extended Phase Turbulence Using AltitudeDependent Structure Parameter, Monish Ranjan Chatterjee, Ali Mohamed
Anisoplanatic Electromagnetic Image Propagation Through Narrow Or Extended Phase Turbulence Using AltitudeDependent Structure Parameter, Monish Ranjan Chatterjee, Ali Mohamed
Monish R. Chatterjee
The effects of turbulence on anisoplanatic imaging are often modeled through the use of a sequence of phase screens distributed along the optical path. We implement the splitstep wave algorithm to examine turbulencecorrupted images.
Volume Component Analysis For Classification Of Lidar Data, Nina M. Varney, Vijayan K. Asari
Volume Component Analysis For Classification Of Lidar Data, Nina M. Varney, Vijayan K. Asari
Vijayan K. Asari
One of the most difficult challenges of working with LiDAR data is the large amount of data points that are produced. Analysing these large data sets is an extremely time consuming process. For this reason, automatic perception of LiDAR scenes is a growing area of research. Currently, most LiDAR feature extraction relies on geometrical features specific to the point cloud of interest. These geometrical features are scenespecific, and often rely on the scale and orientation of the object for classification. This paper proposes a robust method for reduced dimensionality feature extraction of 3D objects using a volume component analysis (VCA ...
Multiple Object Detection In Hyperspectral Imagery Using Spectral FringeAdjusted Joint Transform Correlator, Paheding Sidike, Vijayan K. Asari, Mohammad S. Alam
Multiple Object Detection In Hyperspectral Imagery Using Spectral FringeAdjusted Joint Transform Correlator, Paheding Sidike, Vijayan K. Asari, Mohammad S. Alam
Vijayan K. Asari
Hyperspectral imaging (HSI) sensors provide plenty of spectral information to uniquely identify materials by their reflectance spectra, and this information has been effectively used for object detection and identification applications. Joint transform correlation (JTC) based object detection techniques in HSI have been proposed in the literatures, such as spectral fringeadjusted joint transform correlation (SFJTC) and with its several improvements. However, to our knowledge, the SFJTC based techniques were designed to detect only similar patterns in hyperspectral data cube and not for dissimilar patterns. Thus, in this paper, a new deterministic object detection approach using SFJTC is proposed to perform multiple ...
Directional Ringlet Intensity Feature Transform For Tracking, Evan Krieger, Paheding Sidike, Theus H. Aspiras, Vijayan K. Asari
Directional Ringlet Intensity Feature Transform For Tracking, Evan Krieger, Paheding Sidike, Theus H. Aspiras, Vijayan K. Asari
Vijayan K. Asari
The challenges existing for current intensitybased histogram feature tracking methods in wide area motion imagery include object structural information distortions and background variations, such as different pavement or ground types. All of these challenges need to be met in order to have a robust object tracker, while attaining to be computed at an appropriate speed for realtime processing. To achieve this we propose a novel method, Directional Ringlet Intensity Feature Transform (DRIFT), that employs Kirsch kernel filtering and Gaussian ringlet feature mapping. We evaluated the DRIFT on two challenging datasets, namely Columbus Large Image Format (CLIF) and Large Area Image ...
Histogram Of Oriented Phase (Hop): A New Descriptor Based On Phase Congruency, Hussin Ragb, Vijayan K. Asari
Histogram Of Oriented Phase (Hop): A New Descriptor Based On Phase Congruency, Hussin Ragb, Vijayan K. Asari
Vijayan K. Asari
In this paper we present a low level image descriptor called Histogram of Oriented Phase based on phase congruency concept and the Principal Component Analysis (PCA). Since the phase of the signal conveys more information regarding signal structure than the magnitude, the proposed descriptor can precisely identify and localize image features over the gradient based techniques, especially in the regions affected by illumination changes. The proposed features can be formed by extracting the phase congruency information for each pixel in the image with respect to its neighborhood. Histograms of the phase congruency values of the local regions in the image ...
A Robust FringeAdjusted Joint Transform Correlator For Efficient Object Detection, Paheding Sidike, Vijayan K. Asari, Mohammad S. Alam
A Robust FringeAdjusted Joint Transform Correlator For Efficient Object Detection, Paheding Sidike, Vijayan K. Asari, Mohammad S. Alam
Vijayan K. Asari
The fringeadjusted joint transform correlation (FJTC) technique has been widely used for realtime optical pattern recognition applications. However, the classical FJTC technique suffers from target distortions due to noise, scale, rotation and illumination variations of the targets in input scenes. Several improvements of the FJTC have been proposed in the literature to accommodate these problems. Some popular techniques such as synthetic discriminant function (SDF) based FJTC was designed to alleviate the problems of scale and rotation variations of the target, whereas wavelet based FJTC has been found to yield better performance for noisy targets in the input scenes. While these ...
Mechanical Properties Of SelfAssembled Nanoparticle Membranes: Stretching And Bending, Yifan Wang, Pongsakorn Kanjanaboos, Sean P. Mcbride, Edward Barry, XiaoMin Lin, Heinrich M. Jaeger
Mechanical Properties Of SelfAssembled Nanoparticle Membranes: Stretching And Bending, Yifan Wang, Pongsakorn Kanjanaboos, Sean P. Mcbride, Edward Barry, XiaoMin Lin, Heinrich M. Jaeger
Dr. Sean P. McBride
Monolayers composed of colloidal nanoparticles, with thickness less than ten nanometers, have remarkable mechanical strength and can suspend over micronsized holes to form freestanding membranes. We discuss experiments probing the tensile strength and bending stiffness of these selfassembled nanoparticle sheets. The fracture behavior of monolayers and multilayers is investigated by attaching them to elastomer substrates which are then stretched. For different applied strain the fracture patterns are imaged down to the scale of single particles. The resulting detailed information about the crack width distribution allows us to relate the measured overall tensile strength to the distribution of local bond strengths ...
Viscosity Dependent Liquid Slip At Molecularly Smooth Hydrophobic Surfaces, Sean P. Mcbride, Bruce M. Law
Viscosity Dependent Liquid Slip At Molecularly Smooth Hydrophobic Surfaces, Sean P. Mcbride, Bruce M. Law
Dr. Sean P. McBride
Colloidal probe atomic force microscopy is used to study the slip behavior of 18 Newtonian liquids from two homologous series, the nalkanes and nalcohols, at molecularly smooth hydrophobic nhexadecyltrichlorosilane coated surfaces. We find that the slip behavior is governed by the bulk viscosity η of the liquid, specifically, the slip length b∼ηx with x∼0.33. Additionally, the slip length was found to be shear rate independent, validating the use of Vinogradova slip theory in this work.
Improved In Situ Spring Constant Calibration For Colloidal Probe Atomic Force Microscopy, Sean P. Mcbride, Bruce M. Law
Improved In Situ Spring Constant Calibration For Colloidal Probe Atomic Force Microscopy, Sean P. Mcbride, Bruce M. Law
Dr. Sean P. McBride
In colloidal probe atomic force microscopy (AFM) surface forces cannot be measured without an accurate determination of the cantilever spring constant. The effective spring constant k depends upon the cantilever geometry and therefore should be measured in situ; additionally, k may be coupled to other measurement parameters. For example, colloidal probe AFM is frequently used to measure the slip length b at solid/liquid boundaries by comparing the measured hydrodynamic force with Vinogradova slip theory (Vtheory). However, in this measurement k and b are coupled, hence, b cannot be accurately determined without knowing k to high precision. In this paper ...
Forces At Individual PseudopodFilament Adhesive Contacts, Govind Paneru, Prem S. Thapa, Sean P. Mcbride, David MooreNichols, Bruce M. Law, Bret N. Flanders
Forces At Individual PseudopodFilament Adhesive Contacts, Govind Paneru, Prem S. Thapa, Sean P. Mcbride, David MooreNichols, Bruce M. Law, Bret N. Flanders
Dr. Sean P. McBride
Onchip cellular force sensors are fabricated from cantilever poly(3,4ethylene dioxythiophene) filaments that visibly deflect under forces exerted at individual pseudopodfilament adhesive contacts. The shape of the deflected filaments and their ∼3 nN/μm spring constants are predicted by cantilever rod theory. Pulling forces exerted by Dictyostelium discoideumcells at these contacts are observed to reach ∼20 nN without breaking the contact.
Influence Of Line Tension On Spherical Colloidal Particles At LiquidVapor Interfaces, Sean P. Mcbride, Bruce M. Law
Influence Of Line Tension On Spherical Colloidal Particles At LiquidVapor Interfaces, Sean P. Mcbride, Bruce M. Law
Dr. Sean P. McBride
Atomic force microscopy (AFM) imaging of isolated submicron dodecyltrichlorosilane coated silica spheres, immobilized at the liquid polystyrene (PS) air interface at the PS glass transition temperature, Tg , allows for determination of the contact angle θ versus particle radius R . At Tg , all θ versus R measurements are well described by the modified Young’s equation for a line tension τ=0.93 nN . The AFM measurements are also consistent with a minimum contact angle θmin and minimum radius Rmin , below which single isolated silica spheres cannot exist at the PSair interface.
Hydrolysis Of PNitrophenyl Esters Promoted By SemiFluorinated Quaternary Ammonium Polymer Latexes And Films, Baljinder Kaur, Sean P. Mcbride, Warren T. Ford
Hydrolysis Of PNitrophenyl Esters Promoted By SemiFluorinated Quaternary Ammonium Polymer Latexes And Films, Baljinder Kaur, Sean P. Mcbride, Warren T. Ford
Dr. Sean P. McBride
Semifluorinated polymer latexes were prepared by emulsion polymerization of 2.525% of a fluoroalkyl methacrylate, 25% chloromethylstyrene, 1% styrylmethyl(trimethyl)ammonium chloride, and the remainder 2ethylhexyl methacrylate under surfactantfree conditions. The chloromethylstyrene units were converted to quaternary ammonium ions with trimethylamine. In aqueous dispersions at particle concentrations of less than 1 mg mL1 the quaternary ammonium ion latexes promoted hydrolyses of pnitrophenyl hexanoate (PNPH) in pH 9.4 borate buffer and of diethyl pnitrophenyl phosphate (Paraoxon) in 0.1 M NaOH at 30 oC with halflives of less than 10 minutes. Thin 0.72 μm films of the latexes on ...
Electron Acceleration And Generation Of HighBrilliance XRay Radiation In Kilojoule, Subpicosecond LaserPlasma Interactions, Serge Y. Kalmykov, X. Davoine
Electron Acceleration And Generation Of HighBrilliance XRay Radiation In Kilojoule, Subpicosecond LaserPlasma Interactions, Serge Y. Kalmykov, X. Davoine
Serge Youri Kalmykov
Observation Of Spatial Charge And Spin Correlations In The 2d FermiHubbard Model, Lawrence W. Cheuk, Matthew A. Nichols, Katherine R. Lawrence, Melih Okan, Hao Zhang, Ehsan Khatami, Nandini Trivedi, Thereza Paiva, Marcos Rigol, Martin W. Zwierlein