Bulletin of the American Physical Society
2007 Joint Spring Meeting of the Texas Sections of APS, AAPT, and SPS
Volume 52, Number 2
Thursday–Saturday, March 22–24, 2007; Abilene, Texas
Session APS1: APS I - Gravitation, Astrophysics, and Theory |
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Chair: Josh Willis, Abilene Christian University Room: Biblical Studies Building 114 |
Friday, March 23, 2007 11:00AM - 11:12AM |
APS1.00001: Efficient computation of Lorentzian 6J symbols Joshua Willis Spin foam models are a proposal for a quantum theory of gravity, and an important open question is whether they reproduce classical general relativity in the low energy limit. One approach to tackling that problem is to simulate spin-foam models on the computer, but this is hampered by the high computational cost of evaluating the basic building block of these models, the so-called 10J symbol. For Euclidean models, Christensen and Egan have developed an efficient algorithm, but for Lorentzian models this problem remains open. In this talk we describe an efficient method developed for Lorentzian 6J symbols, and we also report on recent work in progress to use this efficient algorithm in calculating the 10J symbols that are of real interest. [Preview Abstract] |
Friday, March 23, 2007 11:12AM - 11:24AM |
APS1.00002: Testing Alternative Theories of Gravity Using Pulsar Timing Kejia Lee, Fredrick Jenet, Richard Price Pulsar timing observations can be used to directly detect gravitational waves. The measured statistics of the timing data strongly depends on the gravitational wave polarization properties. General relativity allows for two purely transverse modes, while a general metric gravity theory could have up to four additional modes. By constraining the amplitudes of all six polarization modes, pulsar timing data could be used to test various theories of gravity. Previously, only the general relativistic transverse modes have been considered. Here, we calculate the effect of the additional four polarization modes. Sensitivity curves of all six gravitational wave modes are derived and it is shown that pulsar timing techniques are particularly sensitive to the longitudinal gravitational wave mode. [Preview Abstract] |
Friday, March 23, 2007 11:24AM - 11:36AM |
APS1.00003: Probability and Entanglement in Quantum Mechanics James Espinosa The subject of entangled states in quantum mechanics offers a paradoxical situation that to this day appears quite mysterious. But paradoxes are the result of not having enough understanding of a given state of affairs. The proper interpretation of the theory of probability as applied to quantum mechanics appears to be the best way to remove the mystery that appears to be involved with the entanglement of states. [Preview Abstract] |
Friday, March 23, 2007 11:36AM - 11:48AM |
APS1.00004: Charge, from EM fields only. R.L. Collins Purely electromagnetic particle (PEP) models of an electron have until now failed because they do not account for ''charge''. A model of the electron, built from EM fields only, has been found that generates a \textbf {vxB} inverse square field that resembles the electric field \textbf {E} we associate with charge. Does this model contain charge? Not really. Gauss' law says yes, but div \textbf {vxB} finds no charge density. ``Charge'' is a mathematical fiction, useful but not fundamental. This model begins with a magnetic flux quantum configured as a magnetic dipole, $\mu$, spinning at $\sqrt{3}$ times the Compton frequency $ \nu_C = mc^2 /h$. As it decays, energy is transferred to a toroidal displacement current. Oscillation between these configurations proceeds at $\nu_C$. The EM assembly carries angular momentum \textbf {L}, spinning about $\mu$. Spinning \textbf {B} leads to \textbf {vxB}, an electric field that arises everywhere in space from spinning \textbf {B} and not from some compact central ``charge''. Elastic Coulomb scattering must find the electron to be a point particle, without size even though the EM structure itself is huge. $\mu$ undulates but does not reverse polarity. Faraday's static \textbf {E} field does not exist in nature. The electric field about an electron is \textbf {vxB}, inverse square and undulating at $1.24x10^{20} $ Hz. [Preview Abstract] |
Friday, March 23, 2007 11:48AM - 12:00PM |
APS1.00005: Cumulative Jets Produced by Laser-Ablation Driven Implosion of Hollow Cones and Wedges Charles Manka, Sergei Nikitin, Jacob Grun, Yefim Aglitskiy, Sasha Velikovich We observe and diagnose cumulative plasma jets formed by hollow cones and wedges imploded via laser ablation of their outer surfaces. The velocity, shape, and density of the jets are measured with monochromatic 0.65 keV x-ray imaging. Depending on cone geometry, cumulative jets of ion density $\sim $ 2 10$^{20}$ cm$^{-3}$ and propagation velocities $>$ 10 km/sec are formed. An initial dense plasma temperature of 7-8 eV and an average ion charge Z = 2 to 3 is inferred. We observe that a critical cone angle required for jet formation by our nickel cones is 2$\alpha \quad \sim$ 100$^{o}$. Similar jets are formed by both cones and wedges. Such jets can be used for laboratory simulation of the hydrodynamics of astrophysical jets interacting with stellar or interstellar matter. [Preview Abstract] |
Friday, March 23, 2007 12:00PM - 12:12PM |
APS1.00006: How Can Brane World Physics be reconciled to early universe applications of relic thermal input as given by LQG to inflationary cosmology? Andrew Beckwith We are investigating how LQG and brane world physics predictions can be reconciled. As it stands, Brane world models exclude the quantum bounce dynamics seen in LQG; in particular Akshenkhars construction of a prior universe collapsing to a singularity is undoable in contemporary Sundrum brane world physics. The author presents how answering Sean Carrolls supposition of a pre inflation state of low temperature-low entropy pre inflation state as given in 2005 provides a bridge between two models with radically different predictions. I.e. Loop quantum gravity may be giving us a template as to thermal input which answers relic graviton production issues, and CMB production which are presently unanswerable via brane world physics. This is also a way of getting around the get around the fact that conventional cosmological CMB is limited by a barrier as of a red shift limit of about z = 1000, i.e. when the universe was about 1000 times smaller and 100,000 times younger than today as to photons, and to come up with a working model of quintessence scalar fields which permits relic generation of dark matter/dark energy. [Preview Abstract] |
Friday, March 23, 2007 12:12PM - 12:24PM |
APS1.00007: In The Light of The Dark Matter Sunil Thakur Recent successful mapping of dark matter has clearly brought out some important facts about the dark matter and raises several important questions but a careful analysis also allows us to resolve numerous unresolved issues of physics. We need to explain how the expansion of universe affects distribution of dark matter and dark energy. All the experiments have shown that predictions of Newton's law of gravitation and theory of relativity hold good even though these theories do not take presence of dark matter and dark energy into account. We need to resolve this anomaly. This paper suggests that dark matter constitutes Higgs Field. Difference in the age of the dark matter suggest that universe was not created with 96{\%} of the imperceptible matter or in other words universe was not created with just 4{\%} perceptible matter. Only mechanism through which we can resolve this issue is by conversion of perceptible matter into imperceptible matter. Energy absorbed by the Higgs field gets converted to Higgs particles resulting in its expansion. Expanse of the Higgs field is the expanse of our universe. Almost homogenous distribution of Higgs field cancels the gravitational pull exerted by it except in the regions where Higgs field gets distorted due to presence of substance and energy as theorized by the Einstein. This theory resolves some long-standing unresolved issues like loss of energy, wave-particle duality, expansion of universe, and unification of four fundamental forces. [Preview Abstract] |
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