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Astrophysics and Astronomy

2004

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Articles 151 - 160 of 160

Full-Text Articles in Physical Sciences and Mathematics

Riemann Tensor Of The Ambient Universe, The Dilaton, And Newton’S Constant, Rossen Ivanov, Emil Prodanov Jan 2004

Riemann Tensor Of The Ambient Universe, The Dilaton, And Newton’S Constant, Rossen Ivanov, Emil Prodanov

Articles

We investigate a four-dimensional world, embedded into a five-dimensional spacetime, and find the five-dimensional Riemann tensor via generalisation of the Gauss (--Codacci) equations. We then derive the generalised equations of the four-dimensional world and also show that the square of the dilaton field is equal to the Newton's constant. We find plausable constant and non-constant solutions for the dilaton. Comment: 5 pages, revtex

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Setting Upper Limits On The Strength Of Periodic Gravitational Waves From Psr J1939+2134 Using The First Science Data From The Geo 600 And Ligo Detectors, B. P. Abbott, R. Abbott, Mario C. Diaz, Wm. R. Johnston, Joseph D. Romano, Cristina V. Torres Jan 2004

Setting Upper Limits On The Strength Of Periodic Gravitational Waves From Psr J1939+2134 Using The First Science Data From The Geo 600 And Ligo Detectors, B. P. Abbott, R. Abbott, Mario C. Diaz, Wm. R. Johnston, Joseph D. Romano, Cristina V. Torres

Physics and Astronomy Faculty Publications and Presentations

Data collected by the GEO 600 and LIGO interferometric gravitational wave detectors during their first observational science run were searched for continuous gravitational waves from the pulsar J1939+2134 at twice its rotation frequency. Two independent analysis methods were used and are demonstrated in this paper: a frequency domain method and a time domain method. Both achieve consistent null results, placing new upper limits on the strength of the pulsar’s gravitational wave emission. A model emission mechanism is used to interpret the limits as a constraint on the pulsar’s equatorial ellipticity.

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Probing Molecular Free Energy Landscapes By Periodic Loading, Oliver Braun, Andreas Hanke, Udo Seifert Jan 2004

Probing Molecular Free Energy Landscapes By Periodic Loading, Oliver Braun, Andreas Hanke, Udo Seifert

Physics and Astronomy Faculty Publications and Presentations

Single molecule pulling experiments provide information about interactions in biomolecules that cannot be obtained by any other method. However, the reconstruction of the molecule’s free energy profile from the experimental data is still a challenge, in particular, for the unstable barrier regions. We propose a new method for obtaining the full profile by introducing a periodic ramp and using Jarzynski’s relation for obtaining equilibrium quantities from nonequilibrium data. Our simulated experiments show that this method delivers significant more accurate data than previous methods, under the constraint of equal experimental effort.

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Coalescence Remnant Of Spinning Binary Black Holes, J Baker, M. Campanelli, C. O. Lousto, R. Takahashi Jan 2004

Coalescence Remnant Of Spinning Binary Black Holes, J Baker, M. Campanelli, C. O. Lousto, R. Takahashi

Physics and Astronomy Faculty Publications and Presentations

We compute the gravitational radiation generated in the evolution of a family of close binary black hole configurations, using a combination of numerical and perturbative approximation methods. We evolve the binaries with spins s aligned or counteraligned with the orbital angular momentum from near the innermost stable circular orbit down to the final single rotating black hole. For the moderately spinning holes studied here the remnant Kerr black holes formed at the end of an inspiral process have rotation parameters a/M≈0.72+0.32(s/mH), suggesting it is difficult (though not excluded) to end up with near maximally rotating holes from such scenarios.

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Observations Of The Pulsating White Dwarf G 185-32, Bárbara Garcia Castanheira, Matt A. Wood Jan 2004

Observations Of The Pulsating White Dwarf G 185-32, Bárbara Garcia Castanheira, Matt A. Wood

Aerospace, Physics, and Space Science Faculty Publications

We observed the pulsating hydrogen atmosphere white dwarf G 185-32 with the Whole Earth Telescope in 1992. We report on a weighted Fourier transform of the data detecting 18 periodicities in its light curve. Using the Hubble Space Telescope Faint Object Spectrograph time resolved spectroscopy, and the wavelength dependence of the relative amplitudes, we identify the spherical harmonic degree (ℓ) for 14 pulsation signals. We also compare the determinations of effective temperature and surface gravity using the excited modes and atmospheric methods, obtaining Teff = 11960 ± 80 K, log g = 8.02 ± 0.04 and M = 0.617 ± …

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Rectification Of Thermal Fluctuations In Ideal Gases, Alejandro Garcia, P. Meurs, C. Van De Broeck Jan 2004

Rectification Of Thermal Fluctuations In Ideal Gases, Alejandro Garcia, P. Meurs, C. Van De Broeck

Alejandro Garcia

We calculate the systematic average speed of the adiabatic piston and a thermal Brownian motor, introduced by C. Van den Broeck, R. Kawai and P. Meurs [Phys. Rev. Lett. 93, 090601 (2004)], by an expansion of the Boltzmann equation and compare with the exact numerical solution.

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Bioinformatics: An Undergraduate Research/Teaching Tool., Abhishek Agrawal, Valgene L. Dunham Jan 2004

Bioinformatics: An Undergraduate Research/Teaching Tool., Abhishek Agrawal, Valgene L. Dunham

Journal of the South Carolina Academy of Science

No abstract provided.

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Lisa Time-Delay Interferometry Zero-Signal Solution: Geometrical Properties, Massimo Tinto, Shane L. Larson Jan 2004

Lisa Time-Delay Interferometry Zero-Signal Solution: Geometrical Properties, Massimo Tinto, Shane L. Larson

All Physics Faculty Publications

Time-delay interferometry (TDI) is the data processing technique needed for generating interferometric combinations of data measured by the multiple Doppler readouts available onboard the three Laser Interferometer Space Antenna (LISA) spacecraft. Within the space of all possible interferometric combinations TDI can generate, we have derived a specific combination that has zero response to the gravitational wave signal, and called it the zero-signal solution (ZSS). This is a two-parameter family of linear combinations of the generators of the TDI space, and its response to a gravitational wave becomes null when these two parameters coincide with the values of the angles of …

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Novel N-Body Orbits For Constrained Potentials Including The Unusual Figure Eight Three Body Orbit, Jan M. Dudzik Jan 2004

Novel N-Body Orbits For Constrained Potentials Including The Unusual Figure Eight Three Body Orbit, Jan M. Dudzik

Masters Theses

Recently new n-body planar orbits have been discovered which are known as choreographies. These orbits correspond to small n, generally n<20, and exhibit unexpected patterns with respect to given initial conditions. Here we shall examine numerical solutions to the three-body problem and the restricted three-body problem for three body potentials that are the sum of three two-body potentials. Then for an everywhere attractive three body potential with non-collinear and collision-less orbits with a strictly monotone decreasing potential function there exist bound states that are not chaotic that are choreographies. For the right initial conditions these orbits can be mapped numerically and visualized. We will display a number of these cases corresponding to the three body problem, restricted three body problem, the chaotic restricted three body problem and the new figure eight bound state choreography for the Kazalov potential orbits to exhibit some of their special features and to take note of a number of open questions dealing with simple orbital problems.

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H2s (22,0-21,1) Observations Toward The Sgr B2 Region, Young C. Minh, William M. Irvine, S J. Kim Dec 2003

H2s (22,0-21,1) Observations Toward The Sgr B2 Region, Young C. Minh, William M. Irvine, S J. Kim

William M. Irvine

The H2S 22,0-21,1 line emission is observed to be strongly localized toward Sgr B2(M), and emissions from other positions in the more extended SgrB2 region are almost negligible. H2S is thought to form effectively by the passage of the C-type shocks but to be quickly transformed to SO2 or other sulfur species (Pineau des Forêts et al. 1993). Such a shock may have enhanced the H2S abundance in Sgr B2(M), where massive star formation is taking place. But the negligible emission of H2S from other observed positions may indicate that these positions have not been affected by shocks enough to …

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