Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- Astrophysics - Earth and Planetary Astrophysics (3)
- Planetary systems (3)
- Stars: magnetic field (3)
- Communication complexity (2)
- Outflows (2)
-
- Stars: early-type (2)
- Stars: massive (2)
- Stars: winds (2)
- Techniques: photometric (2)
- Adaptive (1)
- Astrophysics - Solar and Stellar Astrophysics (1)
- Circuit complexity (1)
- Cocycle (1)
- Data structures (1)
- Dynamic data structures (1)
- Encoding (1)
- Ergodic Zᵈ action (1)
- Experiences (1)
- Finite extension (1)
- Higher Education (1)
- Individual Achievement-Test (1)
- Inference (1)
- Item Response Theory (1)
- Lower bounds (1)
- Magnetohydrodynamics (MHD) (1)
- Methods: statistical (1)
- Minorities (1)
- Models (1)
- Nonlinear boundary conditions (1)
- Nonlinear elliptic equations (1)
Articles 1 - 29 of 29
Full-Text Articles in Physical Sciences and Mathematics
Speedups And Orbit Equivalence Of Finite Extensions Of Ergodic Zᵈ-Actions, Aimee S.A. Johnson, D. M. Mcclendon
Speedups And Orbit Equivalence Of Finite Extensions Of Ergodic Zᵈ-Actions, Aimee S.A. Johnson, D. M. Mcclendon
Mathematics & Statistics Faculty Works
We classify n-point extensions of ergodic Zᵈ-actions up to relative orbit equivalence and establish criteria under which one n-point extension of an ergodic Zᵈ-action can be sped up to be relatively isomorphic to an n-point extension of another ergodic Zᵈ-action. Both results are characterized in terms of an algebraic object associated to each n-point extension which is a conjugacy class of subgroups of the symmetric group on n elements.
On The Stellar Companion To The Exoplanet Hosting Star 30 Arietis B, S. R. Kane, T. Barclay, M. Hartmann, A. P. Hatzes, Eric L. N. Jensen, D. R. Ciardi, D. Huber, J. T. Wright, E. V. Quintana
On The Stellar Companion To The Exoplanet Hosting Star 30 Arietis B, S. R. Kane, T. Barclay, M. Hartmann, A. P. Hatzes, Eric L. N. Jensen, D. R. Ciardi, D. Huber, J. T. Wright, E. V. Quintana
Physics & Astronomy Faculty Works
A crucial aspect of understanding planet formation is determining the binarity of the host stars. Results from radial velocity (RV) surveys and the follow-up of Kepler exoplanet candidates have demonstrated that stellar binarity certainly does not exclude the presence of planets in stable orbits and the configuration may in fact be relatively common. Here we present new results for the 30 Arietis system which confirms that the B component hosts both planetary and stellar companions. Keck AO imaging provides direct detection of the stellar companion and additional RV data are consistent with an orbiting star. We present a revised orbit …
Correcting For Measurement Error In Latent Variables Used As Predictors, Lynne Steuerle Schofield
Correcting For Measurement Error In Latent Variables Used As Predictors, Lynne Steuerle Schofield
Mathematics & Statistics Faculty Works
This paper represents a methodological-substantive synergy. A new model, the Mixed Effects Structural Equations (MESE) model which combines structural equations modeling and item response theory, is introduced to attend to measurement error bias when using several latent variables as predictors in generalized linear models. The paper investigates racial and gender disparities in STEM retention in higher education. Using the MESE model with 1997 National Longitudinal Survey of Youth data, I find prior mathematics proficiency and personality have been previously underestimated in the STEM retention literature. Pre-college mathematics proficiency and personality explain large portions of the racial and gender gaps. The …
Generalized Cokähler Geometry And An Application To Generalized Kähler Structures, Ralph R. Gomez, Janet Talvacchia
Generalized Cokähler Geometry And An Application To Generalized Kähler Structures, Ralph R. Gomez, Janet Talvacchia
Mathematics & Statistics Faculty Works
In this paper, we propose a generalization of classical coKähler geometry from the point of view of generalized contact metric geometry. This allows us to generalize a theorem of Capursi (1984), Goldberg (1968) and show that the product M1×M2M1×M2 of generalized contact metric manifolds (Mi,Φi,E±,i,Gi)(Mi,Φi,E±,i,Gi), i=1,2i=1,2, where M1×M2M1×M2 is endowed with the product (twisted) generalized complex structure induced from Φ1Φ1 and Φ2Φ2, is (twisted) generalized Kähler if and only if View the MathML source(Mi,Φi,E±,i,Gi),i=1,2 are (twisted) generalized coKähler structures. As an application of our theorem we construct new examples of twisted generalized Kähler structures on manifolds that do not admit …
Low-Rank Network Decomposition Reveals Structural Characteristics Of Small-World Networks, Victor J. Barranca, D. Zhou, D. Cai
Low-Rank Network Decomposition Reveals Structural Characteristics Of Small-World Networks, Victor J. Barranca, D. Zhou, D. Cai
Mathematics & Statistics Faculty Works
Small-world networks occur naturally throughout biological, technological, and social systems. With their prevalence, it is particularly important to prudently identify small-world networks and further characterize their unique connection structure with respect to network function. In this work we develop a formalism for classifying networks and identifying small-world structure using a decomposition of network connectivity matrices into low-rank and sparse components, corresponding to connections within clusters of highly connected nodes and sparse interconnections between clusters, respectively. We show that the network decomposition is independent of node indexing and define associated bounded measures of connectivity structure, which provide insight into the clustering …
Using Protoplanetary Disks To Weigh The Youngest Stars And Constrain The Earliest Stages Of Stellar Evolution, I. Czekala, S. Andrews, Eric L. N. Jensen, K. Stassun, D. W. Latham, D. Wilner, G. Torres
Using Protoplanetary Disks To Weigh The Youngest Stars And Constrain The Earliest Stages Of Stellar Evolution, I. Czekala, S. Andrews, Eric L. N. Jensen, K. Stassun, D. W. Latham, D. Wilner, G. Torres
Physics & Astronomy Faculty Works
Mass is the fundamental property that determines the fate of a star. In particular, the masses of young stars are of great relevance to many astrophysical problems, including star and planet formation. We have developed a novel approach that combines spatially resolved sub-millimeter spectral line imaging and optical/near-infrared high resolution spectroscopy to derive the fundamental properties of a young star: mass, temperature, and radius. By applying our technique to a sample of pre-main sequence stars, we are mapping out a dynamically-calibrated Hertzsprung-Russell diagram for the express purpose of evaluating pre-main sequence evolutionary models. Looking forward, ALMA is poised to deliver …
Accelerated Taylor Plumes For Mif Targets, Michael R. Brown, D. A. Schaffner, Holden L. Parks , '16, Ariel B. Rock , '16
Accelerated Taylor Plumes For Mif Targets, Michael R. Brown, D. A. Schaffner, Holden L. Parks , '16, Ariel B. Rock , '16
Physics & Astronomy Faculty Works
The SSX plasma device has been converted to a 2.5 m merging plasma wind tunnel configuration. Experiments are underway to study merging and stagnation of high density, helical Taylor states\footnote{Gray, et al, PRL {\bf 110}, 085002 (2013).} to employ as a potential target for magneto-inertial fusion. Eventually, SSX Taylor states will be accelerated to over 100 km/s and compressed to small volumes either by stagnation or merging. Initial un-accelerated merging studies produce peak proton densities of 5×1015 cm−3. Densities are measured with a precision quadrature He-Ne laser interferometer. Typical merged plasma parameters are Ti=20 eV,Te=10 eV,B=0.4 T with lifetimes of …
X-Ray Emission From The Giant Magnetosphere Of The Magnetic O-Type Star Ngc 1624-2, V. Petit, David H. Cohen, G. A. Wade, Y. Nazé, S. P. Owocki, J. O. Sundqvist, A. Ud-Doula, A. Fullerton, M. Leutenegger, M. Gagné
X-Ray Emission From The Giant Magnetosphere Of The Magnetic O-Type Star Ngc 1624-2, V. Petit, David H. Cohen, G. A. Wade, Y. Nazé, S. P. Owocki, J. O. Sundqvist, A. Ud-Doula, A. Fullerton, M. Leutenegger, M. Gagné
Physics & Astronomy Faculty Works
We observed NGC 1624-2, the O-type star with the largest known magnetic field (Bp ∼ 20 kG), in X-rays with the Advanced CCD Imaging Spectrometer (ACIS-S) camera on-board the Chandra X-ray Observatory. Our two observations were obtained at the minimum and maximum of the periodic Hα emission cycle, corresponding to the rotational phases where the magnetic field is the closest to equator-on and pole-on, respectively. With these observations, we aim to characterize the star's magnetosphere via the X-ray emission produced by magnetically confined wind shocks. Our main findings are as follows. (i) The observed spectrum of NGC 1624-2 is hard, …
Directional Recurrence For Infinite Measure Preserving Zᵈ Actions, Aimee S.A. Johnson, A. A. Şahin
Directional Recurrence For Infinite Measure Preserving Zᵈ Actions, Aimee S.A. Johnson, A. A. Şahin
Mathematics & Statistics Faculty Works
We define directional recurrence for infinite measure preserving Zd actions both intrinsically and via the unit suspension flow and prove that the two definitions are equivalent. We study the structure of the set of recurrent directions and show it is always a Gδ set. We construct an example of a recurrent action with no recurrent directions, answering a question posed in a 2007 paper of Daniel J. Rudolph. We also show by example that it is possible for a recurrent action to not be recurrent in an irrational direction even if all its sub-actions are recurrent.
Multifractal And Monofractal Scaling In A Laboratory Magnetohydrodynamic Turbulence Experiment, D. A. Schaffner, Michael R. Brown
Multifractal And Monofractal Scaling In A Laboratory Magnetohydrodynamic Turbulence Experiment, D. A. Schaffner, Michael R. Brown
Physics & Astronomy Faculty Works
Both multifractal and monofractal scaling of structure function exponents are observed in the turbulent magnetic fluctuations of the Swarthmore Spheromak Experiment plasma. Structure function and probability distribution function (PDF) analysis exhibits multifractal scaling exponents in low frequency, inertial range fluctuations of the turbulence but monofractal scaling in higher frequency, dissipation range fluctuations. The transition from multifractal to monofractal scaling occurs rapidly suggesting a dissipation mechanism that is insensitive to turbulent structure scale size. Structure functions and PDFs are presented for both temporal and spatial measurements. Variations in the magnetic helicity in the plasma are also shown to modify multifractal scaling …
Liquid Crystal Janus Emulsion Droplets: Preparation, Tumbling, And Swimming, J. Jeong, A. Gross, W.-S. Wei, F. Tu, D. Lee, Peter J. Collings, A. G. Yodh
Liquid Crystal Janus Emulsion Droplets: Preparation, Tumbling, And Swimming, J. Jeong, A. Gross, W.-S. Wei, F. Tu, D. Lee, Peter J. Collings, A. G. Yodh
Physics & Astronomy Faculty Works
This study introduces liquid crystal (LC) Janus droplets. We describe a process for the preparation of these droplets, which consist of nematic LC and polymer compartments. The process employs solvent-induced phase separation in emulsion droplets generated by microfluidics. The droplet morphology was systematically investigated and demonstrated to be sensitive to the surfactant concentration in the background phase, the compartment volume ratio, and the possible coalescence of multiple Janus droplets. Interestingly, the combination of a polymer and an anisotropic LC introduces new functionalities into Janus droplets, and these properties lead to unusual dynamical behaviors. The different densities and solubilities of the …
Detection Of 610-Mhz Radio Emission From Hot Magnetic Stars, P. Chandra, G. A. Wade, J. O. Sundqvist, D. Oberoi, J. H. Grunhut, A. Ud-Doula, V. Petit, David H. Cohen, M. E. Oksala, A. David-Uraz
Detection Of 610-Mhz Radio Emission From Hot Magnetic Stars, P. Chandra, G. A. Wade, J. O. Sundqvist, D. Oberoi, J. H. Grunhut, A. Ud-Doula, V. Petit, David H. Cohen, M. E. Oksala, A. David-Uraz
Physics & Astronomy Faculty Works
We have carried out a study of radio emission from a small sample of magnetic O- and B-type stars using the Giant Metrewave Radio Telescope, with the goal of investigating their magnetospheres at low frequencies. These are the lowest frequency radio measurements ever obtained of hot magnetic stars. The observations were taken at random rotational phases in the 1390 and the 610 MHz bands. Out of the eight stars, we detect five B-type stars in both the 1390 and the 610 MHz bands. The three O-type stars were observed only in the 1390 MHz band, and no detections were obtained. …
Predictive Inference Using Latent Variables With Covariates, Lynne Steuerle Schofield, B. Junker, L. J. Taylor, D. A. Black
Predictive Inference Using Latent Variables With Covariates, Lynne Steuerle Schofield, B. Junker, L. J. Taylor, D. A. Black
Mathematics & Statistics Faculty Works
Plausible values (PVs) are a standard multiple imputation tool for analysis of large education survey data, which measures latent proficiency variables. When latent proficiency is the dependent variable, we reconsider the standard institutionally generated PV methodology and find it applies with greater generality than shown previously. When latent proficiency is an independent variable, we show that the standard institutional PV methodology produces biased inference because the institutional conditioning model places restrictions on the form of the secondary analysts’ model. We offer an alternative approach that avoids these biases based on the mixed effects structural equations model of Schofield (Modeling measurement …
Kelt-8b: A Highly Inflated Transiting Hot Jupiter And A New Technique For Extracting High-Precision Radial Velocities From Noisy Spectra, B. J. Fulton, K. A. Collins, B. S. Gaudi, K. G. Stassun, J. Pepper, T. G. Beatty, R. J. Siverd, K. Penev, A. W. Howard, C. Baranec, G. Corfini, J. D. Eastman, J. Gregorio, N. M. Law, M. B. Lund, T. E. Oberst, M. T. Penny, R. Riddle, J. E. Rodriguez, D. J. Stevens, R. Zambelli, C. Ziegler, A. Bieryla, G. D'Ago, D. L. Depoy, Eric L.N. Jensen, J. F. Kielkopf, D. W. Latham, M. Manner, J. Marshall, K. K. Mcleod, P. A. Reed
Kelt-8b: A Highly Inflated Transiting Hot Jupiter And A New Technique For Extracting High-Precision Radial Velocities From Noisy Spectra, B. J. Fulton, K. A. Collins, B. S. Gaudi, K. G. Stassun, J. Pepper, T. G. Beatty, R. J. Siverd, K. Penev, A. W. Howard, C. Baranec, G. Corfini, J. D. Eastman, J. Gregorio, N. M. Law, M. B. Lund, T. E. Oberst, M. T. Penny, R. Riddle, J. E. Rodriguez, D. J. Stevens, R. Zambelli, C. Ziegler, A. Bieryla, G. D'Ago, D. L. Depoy, Eric L.N. Jensen, J. F. Kielkopf, D. W. Latham, M. Manner, J. Marshall, K. K. Mcleod, P. A. Reed
Physics & Astronomy Faculty Works
We announce the discovery of a highly inflated transiting hot Jupiter by the KELT-North survey. A global analysis including constraints from isochrones indicates that the V = 10.8 host star (HD 343246) is a mildly evolved, G dwarf with {T}{eff}={5754}-55+54 K, {log} g={4.078}-0.054+0.049, [{Fe}/{{H}}]=0.272+/- 0.038, an inferred mass {M}*={1.211}-0.066+0.078 {M}☉ , and radius {R}*={1.67}-0.12+0.14 {R}☉ . The planetary companion has a mass {M}{{P}}={0.867}-0.061+0.065 MJ, radius {R}{{P}}={1.86}-0.16+0.18 RJ, surface gravity {log} {g} …
Ground-Based Transit Observations Of The Hat-P-18, Hat-P-19, Hat-P-27/Wasp40 And Wasp-21 Systems, M. Seeliger, M. Kitze, R. Errmann, S. Richter, J. M. Ohlert, W. P. Chen, J. K. Guo, E. Göğüş, T. Güver, B. Aydın, S. Mottola, S. Hellmich, M. Fernandez, F. J. Aceituno, D. Dimitrov, D. Kjurkchieva, Eric L.N. Jensen, David H. Cohen, E. Kundra, T. Pribulla, M. Vaňko, J. Budaj, M. Mallonn, Z.-Y. Wu, X. Zhou, St. Raetz, C. Adam, T. O. B. Schmidt, A. Ide, M. Mugrauer, L. Marschall, M. Hackstein, R. Chini, M. Haas, T. Ak, E. Güzel, A. Özdönmez, C. Ginski, C. Marka, J. G. Schmidt, B. Dincel, K. Werner, A. Dathe, J. Greif, V. Wolf, S. Buder, A. Pannicke, D. Puchalski, R. Neuhäuser
Ground-Based Transit Observations Of The Hat-P-18, Hat-P-19, Hat-P-27/Wasp40 And Wasp-21 Systems, M. Seeliger, M. Kitze, R. Errmann, S. Richter, J. M. Ohlert, W. P. Chen, J. K. Guo, E. Göğüş, T. Güver, B. Aydın, S. Mottola, S. Hellmich, M. Fernandez, F. J. Aceituno, D. Dimitrov, D. Kjurkchieva, Eric L.N. Jensen, David H. Cohen, E. Kundra, T. Pribulla, M. Vaňko, J. Budaj, M. Mallonn, Z.-Y. Wu, X. Zhou, St. Raetz, C. Adam, T. O. B. Schmidt, A. Ide, M. Mugrauer, L. Marschall, M. Hackstein, R. Chini, M. Haas, T. Ak, E. Güzel, A. Özdönmez, C. Ginski, C. Marka, J. G. Schmidt, B. Dincel, K. Werner, A. Dathe, J. Greif, V. Wolf, S. Buder, A. Pannicke, D. Puchalski, R. Neuhäuser
Physics & Astronomy Faculty Works
As part of our ongoing effort to investigate transit timing variations (TTVs) of known exoplanets, we monitored transits of the four exoplanets HAT-P-18b, HAT-P-19b, HAT-P-27b/WASP-40b and WASP-21b. All of them are suspected to show TTVs due to the known properties of their host systems based on the respective discovery papers. During the past three years 46 transit observations were carried out, mostly using telescopes of the Young Exoplanet Transit Initiative. The analyses are used to refine the systems’ orbital parameters. In all cases we found no hints for significant TTVs, or changes in the system parameters inclination, fractional stellar radius …
Confirming Hd 23478 As A New Magnetic B Star Hosting An Hα-Bright Centrifugal Magnetosphere, J. Sikora, G. A. Wade, D. A. Bohlender, C. Neiner, M. E. Oksala, M. Shultz, David H. Cohen, A. Ud-Doula, J. Grunhut, D. Monin, S. Owocki, V. Petit, T. Rivinus, R. H. D. Townsend
Confirming Hd 23478 As A New Magnetic B Star Hosting An Hα-Bright Centrifugal Magnetosphere, J. Sikora, G. A. Wade, D. A. Bohlender, C. Neiner, M. E. Oksala, M. Shultz, David H. Cohen, A. Ud-Doula, J. Grunhut, D. Monin, S. Owocki, V. Petit, T. Rivinus, R. H. D. Townsend
Physics & Astronomy Faculty Works
In this paper, we report 23 magnetic field measurements of the B3IV star HD 23478: 12 obtained from high-resolution Stokes V spectra using the ESPaDOnS (Canada–France–Hawaii Telescope) and Narval (Télescope Bernard Lyot) spectropolarimeters, and 11 from medium-resolution Stokes V spectra obtained with the DimaPol spectropolarimeter (Dominion Astronomical Observatory). HD 23478 was one of two rapidly rotating stars identified as potential ‘centrifugal magnetosphere’ hosts based on IR observations from the Apache Point Observatory Galactic Evolution Experiment survey. We derive basic physical properties of this star including its mass (M=6.1+0.8−0.7M⊙), effective temperature (Teff = 20 ± 2 kK), radius (R=2.7+1.6−0.9R⊙), and age …
Kelt-7b: A Hot Jupiter Transiting A Bright V = 8.54 Rapidly Rotating F-Star, A. Bieryla, K. Collins, T. G. Beatty, J. Eastman, R. J. Siverd, J. Pepper, B. S. Gaudi, K. G. Stassun, C. Cañas, D. W. Latham, L. A. Buchhave, R. Sanchis-Ojeda, J. N. Winn, Eric L.N. Jensen, J. F. Kielkopf, K. K. Mcleod, J. Gregorio, K. D. Colón, R. Street, R. Ross, M. Penny, S. N. Mellon, T. E. Oberst, B. J. Fulton, J. Wang, P. Berlind, M. L. Calkins, G. A. Esquerdo, D. L. Depoy, A. Gould, J. Marshall, R. Pogge, M. Trueblood, P. Trueblood
Kelt-7b: A Hot Jupiter Transiting A Bright V = 8.54 Rapidly Rotating F-Star, A. Bieryla, K. Collins, T. G. Beatty, J. Eastman, R. J. Siverd, J. Pepper, B. S. Gaudi, K. G. Stassun, C. Cañas, D. W. Latham, L. A. Buchhave, R. Sanchis-Ojeda, J. N. Winn, Eric L.N. Jensen, J. F. Kielkopf, K. K. Mcleod, J. Gregorio, K. D. Colón, R. Street, R. Ross, M. Penny, S. N. Mellon, T. E. Oberst, B. J. Fulton, J. Wang, P. Berlind, M. L. Calkins, G. A. Esquerdo, D. L. Depoy, A. Gould, J. Marshall, R. Pogge, M. Trueblood, P. Trueblood
Physics & Astronomy Faculty Works
We report the discovery of KELT-7b, a transiting hot Jupiter with a mass of 1.28+/- 0.18 MJ, radius of {1.533}-0.047+0.046 RJ, and an orbital period of 2.7347749+/- 0.0000039 days. The bright host star (HD 33643; KELT-7) is an F-star with V = 8.54, Teff = 6789{}-49+50 K, [Fe/H] = {0.139}-0.081+0.075, and {log}\{\text{}}g\=4.149+/- 0.019. It has a mass of {1.535}-0.054+0.066 M☉, a radius of {1.732}-0.045+0.043 R☉, and is the fifth most massive, fifth hottest, and the ninth brightest star known to …
A Disk-Based Dynamical Mass Estimate For The Young Binary Ak Sco, I. Czekala, S. M. Andrews, Eric L.N. Jensen, K. G. Stassun, G. Torres, D. J. Wilner
A Disk-Based Dynamical Mass Estimate For The Young Binary Ak Sco, I. Czekala, S. M. Andrews, Eric L.N. Jensen, K. G. Stassun, G. Torres, D. J. Wilner
Physics & Astronomy Faculty Works
We present spatially and spectrally resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of gas and dust in the disk orbiting the pre-main sequence (pre-MS) binary AK Sco. By forward-modeling the disk velocity field traced by CO J = 2-1 line emission, we infer the mass of the central binary, {M}*=2.49+/- 0.10 {M}☉ , a new dynamical measurement that is independent of stellar evolutionary models. Assuming the disk and binary are co-planar within ̃2°, this disk-based binary mass measurement is in excellent agreement with constraints from radial velocity monitoring of the combined stellar spectra. These ALMA results are …
Ssx Mhd Plasma Wind Tunnel, Michael R. Brown, D. A. Schaffner
Ssx Mhd Plasma Wind Tunnel, Michael R. Brown, D. A. Schaffner
Physics & Astronomy Faculty Works
A new turbulent plasma source at the Swarthmore Spheromak Experiment (SSX) facility is described. The MHD wind tunnel configuration employs a magnetized plasma gun to inject high-beta plasma into a large, well-instrumented, vacuum drift region. This provides unique laboratory conditions approaching that in the solar wind: there is no applied background magnetic field in the drift region and has no net axial magnetic flux; the plasma flow speed is on the order of the local sound speed (M ~ 1), so flow energy density is comparable to thermal energy density; and the ratio of thermal to magnetic pressure is of …
Chiral Structures And Defects Of Lyotropic Chromonic Liquid Crystals Induced By Saddle-Splay Elasticity, Z. S. Davidson, L. Kang, J. Jeong, T. Still, Peter J. Collings, T. C. Lubensky, A. G. Yodh
Chiral Structures And Defects Of Lyotropic Chromonic Liquid Crystals Induced By Saddle-Splay Elasticity, Z. S. Davidson, L. Kang, J. Jeong, T. Still, Peter J. Collings, T. C. Lubensky, A. G. Yodh
Physics & Astronomy Faculty Works
An experimental and theoretical study of lyotropic chromonic liquid crystals (LCLCs) confined in cylinders with degenerate planar boundary conditions elucidates LCLC director configurations. When the Frank saddle-splay modulus is more than twice the twist modulus, the ground state adopts an inhomogeneous escaped-twisted configuration. Analysis of the configuration yields a large saddle-splay modulus, which violates Ericksen inequalities but not thermodynamic stability. Lastly, we observe point defects between opposite-handed domains, and we explain a preference for point defects over domain walls.
Magnetohydrodynamic Turbulence: Observation And Experiment, Michael R. Brown, D. A. Schaffner, Peter J. Weck , '15
Magnetohydrodynamic Turbulence: Observation And Experiment, Michael R. Brown, D. A. Schaffner, Peter J. Weck , '15
Physics & Astronomy Faculty Works
We provide a tutorial on the paradigms and tools of magnetohydrodynamic(MHD)turbulence. The principal paradigm is that of a turbulent cascade from large scales to small, resulting in power law behavior for the frequency power spectrum for magnetic fluctuationsEB(f). We will describe five useful statistical tools for MHDturbulence in the time domain: the temporal autocorrelation function, the frequency power spectrum, the probability distribution function of temporal increments, the temporal structure function, and the permutation entropy. Each of these tools will be illustrated with an example taken from MHDfluctuations in the solar wind. A single dataset from the Wind satellite will be …
On Products Of Generalized Geometries, Ralph R. Gomez, Janet Talvacchia
On Products Of Generalized Geometries, Ralph R. Gomez, Janet Talvacchia
Mathematics & Statistics Faculty Works
In this paper we address what generalized geometric structures are possible on products of spaces that each admit generalized geometries. In particular we consider, first, the product of two odd dimensional spaces that each admit a generalized almost contact structure, and then subsequently, the product of an odd dimensional space that admits a generalized almost contact structure and an even dimensional space that admits a generalized almost complex structure. We also draw attention to the relationship of the Courant bracket to the classical notion of normality for almost contact structures.
Self-Organized Assemblies Of Colloidal Particles Obtained From An Aligned Chromonic Liquid Crystal Dispersion, N. Zimmermann, G. Jünnemann-Held, Peter J. Collings, H.-S. Kitzerow
Self-Organized Assemblies Of Colloidal Particles Obtained From An Aligned Chromonic Liquid Crystal Dispersion, N. Zimmermann, G. Jünnemann-Held, Peter J. Collings, H.-S. Kitzerow
Physics & Astronomy Faculty Works
The behavior of mono-disperse colloidal particles in a chromonic liquid crystal was investigated. Poly(methyl methacrylate) spherical particles with three different functionalizations, with and without surface charges, were utilized in the nematic and columnar phases of disodium cromoglycate solutions. The nematic phase was completely aligned parallel to the glass substrates by a simple rubbing technique, and the columnar phase showed regions of similar alignment. The behavior of the colloidal particles in the chromonic liquid crystal depended critically on the functionality, with bromine functionalized particles not dispersing at all, and cationic trimethylammonium and epoxy functionalized particles dispersing well in the isotropic phase …
Permutation Entropy And Statistical Complexity Analysis Of Turbulence In Laboratory Plasmas And The Solar Wind, Peter J. Weck , '15, D. A. Schaffner, Michael R. Brown, R. T. Wicks
Permutation Entropy And Statistical Complexity Analysis Of Turbulence In Laboratory Plasmas And The Solar Wind, Peter J. Weck , '15, D. A. Schaffner, Michael R. Brown, R. T. Wicks
Physics & Astronomy Faculty Works
The Bandt-Pompe permutation entropy and the Jensen-Shannon statistical complexity are used to analyze fluctuating time series of three different turbulent plasmas: the magnetohydrodynamic (MHD) turbulence in the plasma wind tunnel of the Swarthmore Spheromak Experiment (SSX), drift-wave turbulence of ion saturation current fluctuations in the edge of the Large Plasma Device (LAPD), and fully developed turbulent magnetic fluctuations of the solar wind taken from the Wind spacecraft. The entropy and complexity values are presented as coordinates on the CH plane for comparison among the different plasma environments and other fluctuation models. The solar wind is found to have the highest …
Dependent Random Graphs And Multi-Party Pointer Jumping, Joshua Brody, Mario Sanchez , '16
Dependent Random Graphs And Multi-Party Pointer Jumping, Joshua Brody, Mario Sanchez , '16
Computer Science Faculty Works
We initiate a study of a relaxed version of the standard Erdos-Renyi random graph model, where each edge may depend on a few other edges. We call such graphs "dependent random graphs". Our main result in this direction is a thorough understanding of the clique number of dependent random graphs. We also obtain bounds for the chromatic number. Surprisingly, many of the standard properties of random graphs also hold in this relaxed setting. We show that with high probability, a dependent random graph will contain a clique of size ((1-o(1))log(n))/log(1/p), and the chromatic number will be at most (nlog(1/(1-p)))/log(n). We …
Adapt Or Die: Polynomial Lower Bounds For Non-Adaptive Dynamic Data Structures, Joshua Brody, K. G. Larsen
Adapt Or Die: Polynomial Lower Bounds For Non-Adaptive Dynamic Data Structures, Joshua Brody, K. G. Larsen
Computer Science Faculty Works
In this paper, we study the role non-adaptivity plays in maintaining dynamic data structures. Roughly speaking, a data structure is non-adaptive if the memory locations it reads and/or writes when processing a query or update depend only on the query or update and not on the contents of previously read cells. We study such non-adaptive data structures in the cell probe model. The cell probe model is one of the least restrictive lower bound models and in particular, cell probe lower bounds apply to data structures developed in the popular word-RAM model. Unfortunately, this generality comes at a high cost: …
Resonance Problems For Nonlinear Elliptic Equations With Nonlinear Boundary Conditions, Nsoki Mavinga, M. N. Nkashama
Resonance Problems For Nonlinear Elliptic Equations With Nonlinear Boundary Conditions, Nsoki Mavinga, M. N. Nkashama
Mathematics & Statistics Faculty Works
We study the solvability of nonlinear second order elliptic partial differential equations with nonlinear boundary conditions where we impose asymptotic conditions on both nonlinearities in the differential equation and on the boundary in such a way that resonance occurs at a generalized eigenvalue; which is an eigenvalue of the linear problem in which the spectral parameter is both in the differential equation and on the boundary. The proofs are based on some variational techniques and topological degree arguments.
Positivity Of Equivariant Gromov–Witten Invariants, D. Anderson, Linda Chen
Positivity Of Equivariant Gromov–Witten Invariants, D. Anderson, Linda Chen
Mathematics & Statistics Faculty Works
We show that the equivariant Gromov–Witten invariants of a projective homogeneous space G/P exhibit Graham-positivity: when expressed as polynomials in the positive roots, they have nonnegative coefficients.
Numerical Solutions Of American Options With Dividends Using Finite Difference Methods, Nsoki Mavinga, Chi Zhang , '15
Numerical Solutions Of American Options With Dividends Using Finite Difference Methods, Nsoki Mavinga, Chi Zhang , '15
Mathematics & Statistics Faculty Works
We study the Black-Scholes model for American options with dividends. We cast the problem as a free-boundary problem for heat equations and use transformations to rewrite the problem in linear complementarity form. We use explicit and implicit finite difference methods to obtain numerical solutions. We implement and test the methods on a particular example in MATLAB. The effects of dividend payments on option pricing are also considered.