DRUM Collection: Physics Research Works
http://hdl.handle.net/1903/1597
2015-03-29T03:07:12ZProblems with the Newton–Schrödinger equations
http://hdl.handle.net/1903/16000
Title: Problems with the Newton–Schrödinger equations
Authors: Anastopoulos, C; Hu, B.L.
Abstract: We examine the origin of the Newton–Schrödinger equations (NSEs) that play an important role in alternative quantum theories (AQT), macroscopic quantum mechanics and gravity-induced decoherence. We show that NSEs for individual particles do not follow from general relativity (GR) plus quantum field theory (QFT). Contrary to what is commonly assumed, the NSEs are not the weak-field (WF), non-relativistic (NR) limit of the semi-classical Einstein equation (SCE) (this nomenclature is preferred over the ‘Moller–Rosenfeld equation’) based on GR+QFT. The wave-function in the NSEs makes sense only as that for a mean field describing a system of N particles as N → ∞, not that of a single or finite many particles. From GR+QFT the gravitational self-interaction leads to mass
renormalization, not to a non-linear term in the evolution equations of some AQTs. The WF-NR limit of the gravitational interaction in GR+QFT involves no dynamics. To see the contrast, we give a derivation of the equation (i) governing the many-body wave function from GR+QFT and (ii) for the nonrelativistic limit of quantum electrodynamics. They have the same structure, being linear, and very different from NSEs. Adding to this our earlier consideration that for gravitational decoherence the master equations based on GR +QFT lead to decoherence in the energy basis and not in the position basis, despite some AQTs desiring it for the ‘collapse of the wave function’, we conclude that the origins and consequences of NSEs are very different, and should be clearly demarcated from those of the SCE equation, the only legitimate representative of semiclassical gravity, based on GR+QFT.
Description: Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.2014-08-01T00:00:00ZGlobal Inequality in Energy Consumption from 1980 to 2010
http://hdl.handle.net/1903/15855
Title: Global Inequality in Energy Consumption from 1980 to 2010
Authors: Lawrence, Scott; Liu, Qin; Yakovenko, Victor M.
Abstract: We study the global probability distribution of energy consumption per capita
around the world using data from the U.S. Energy Information Administration (EIA) for
1980–2010. We find that the Lorenz curves have moved up during this time period, and the
Gini coefficient, G, has decreased from 0.66 in 1980 to 0.55 in 2010, indicating a decrease
in inequality. The global probability distribution of energy consumption per capita in 2010 is
close to the exponential distribution with G = 0.5. We attribute this result to the globalization
of the world economy, which mixes the world and brings it closer to the state of maximal
entropy. We argue that global energy production is a limited resource that is partitioned
among the world population. The most probable partition is the one that maximizes entropy,
thus resulting in the exponential distribution function. A consequence of the latter is the law
of 1/3: the top 1/3 of the world population consumes 2/3 of produced energy. We also find
similar results for the global probability distribution of CO2 emissions per capita.
Description: Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.2013-12-16T00:00:00ZRealization and Modeling of Metamaterials Made of rf Superconducting Quantum-Interference Devices
http://hdl.handle.net/1903/15853
Title: Realization and Modeling of Metamaterials Made of rf Superconducting Quantum-Interference Devices
Authors: Trepanier, M.; Zhang, Daimeng; Mukhanov, Oleg; Anlage, Steven M.
Abstract: We have prepared meta-atoms based on radio-frequency superconducting quantum-interference devices
(rf SQUIDs) and examined their tunability with dc magnetic field, rf current, and temperature. rf SQUIDs
are superconducting split-ring resonators in which the usual capacitance is supplemented with a Josephson
junction, which introduces strong nonlinearity in the rf properties. We find excellent agreement between
the data and a model that regards the Josephson junction as the resistively and capacitively shunted
junction. A magnetic field tunability of 80 THz=G at 12 GHz is observed, a total tunability of 56% is
achieved, and a unique electromagnetically induced transparency feature at intermediate excitation
powers is demonstrated for the first time. An rf SQUID metamaterial is shown to have qualitatively
the same behavior as a single rf SQUID with regard to dc flux and temperature tuning.
Description: Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.2013-12-18T00:00:00ZFast Prediction and Evaluation of Gravitational Waveforms Using Surrogate Models
http://hdl.handle.net/1903/15849
Title: Fast Prediction and Evaluation of Gravitational Waveforms Using Surrogate Models
Authors: Field, Scott E.; Galley, Chad R.; Hesthaven, Jan S.; Kaye, Jason; Tiglio, Manuel
Abstract: We propose a solution to the problem of quickly and accurately predicting gravitational waveforms within any given physical model. The method is relevant for both real-time applications and more traditional scenarios where the generation of waveforms using standard methods can be prohibitively expensive. Our approach is based on three offline steps resulting in an accurate reduced order model in both parameter and physical dimensions that can be used as a surrogate for the true or fiducial waveform family. First, a set of m parameter values is determined using a greedy algorithm from which a reduced basis representation is constructed. Second, these m parameters induce the selection of m time values for interpolating a waveform time series using an empirical interpolant that is built for the fiducial waveform family. Third, a fit in the parameter dimension is performed for the waveform’s value at each of these m times. The cost of predicting L waveform time samples for a generic parameter choice is of order O(mL+mcfit) online operations, where cfit denotes the fitting function operation count and, typically, m≪L. The result is a compact, computationally efficient, and accurate surrogate model that retains the original physics of the fiducial waveform family while also being fast to evaluate. We generate accurate surrogate models for effective-one-body waveforms of nonspinning binary black hole coalescences with durations as long as 105M, mass ratios from 1 to 10, and for multiple spherical harmonic modes. We find that these surrogates are more than 3 orders of magnitude faster to evaluate as compared to the cost of generating effective-one-body waveforms in standard ways. Surrogate model building for other waveform families and models follows the same steps and has the same low computational online scaling cost. For expensive numerical simulations of binary black hole coalescences, we thus anticipate extremely large speedups in generating new waveforms with a surrogate. As waveform generation is one of the dominant costs in parameter estimation algorithms and parameter space exploration, surrogate models offer a new and practical way to dramatically accelerate such studies without impacting accuracy. Surrogates built in this paper, as well as others, are available from GWSurrogate, a publicly available python package.
Description: Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.2014-07-14T00:00:00Z