The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Weng Cho Chew - One of the best experts on this subject based on the ideXlab platform.
-
Generalized Solver Hybridization Using Equivalence Principle Algorithm
IEEE Transactions on Antennas and Propagation, 2020Co-Authors: Joseph M. Rutherford, Weng Cho ChewAbstract:The simulation of antennas often necessitates modeling the effect of nearby electrically large structures. Such structures are often unsuitable for modeling with the same technique as used on the antenna because of the prohibitive required unknown count. First-Principles models of antennas (or other key features) must then be augmented with approximate models of the larger auxiliary structures, usually with high-frequency asymptotic models. The surface Equivalence Principle is applied to linear-media multiple scattering without regard to the formulations used for each contained domain. A Schur complement is then applied to convert the homogeneous medium equivalent problem into a inhomogeneous medium equivalent problem. The Schur complement form supports application of approximate models and makes the scattering physics plain. The results are provided for two cases modeled with the Equivalence Principle algorithm (EPA) hybridized with physical optics (PO) approximation.
-
Hybrid Solver Via Equivalence Principle Algorithm
2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, 2019Co-Authors: Joseph M. Rutherford, Weng Cho ChewAbstract:The challenges of predicting wireless device performance may be addressed by constructing hybrid solutions with rigorous models around sensitive regions and approximate methods over electrically-large smooth structures. The surface Equivalence Principle supports constructing multiple scattering problems with per-domain scattering algorithms, but discretization over electrically large surfaces is prohibitively expensive. A Schur complement applied to the equations expresses a generalized hybrid method with clear physical interpretation. An example case with results is presented.
-
Fast Direct Equivalence Principle Algorithm for Multi-scale Electromagnetic Problems
2018 IEEE International Symposium on Antennas and Propagation & USNC URSI National Radio Science Meeting, 2018Co-Authors: Li Jun Jiang, Weng Cho ChewAbstract:The Equivalence Principle algorithm is proposed to integrated with hierarchical matrix based fast direct solver in order to solve deep multi-scale problem accurately and efficiently. Additionally, model order reduction techniques are applied to the Equivalence Principle algorithm to further reduce the computational complexities.
-
Solving array structures using single-source Equivalence Principle algorithm
2013 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2013Co-Authors: Hanru Shao, Jun Hu, Weng Cho ChewAbstract:In this paper, a new single-source Equivalence Principle algorithm (EPA) is proposed to solve array structures. In the traditional Equivalence Principle algorithm, the unknown currents of the scatterers are replaced by equivalent electric and magnetic currents on the virtual Equivalence surface. In single-source EPA, a single electric/magnetic current on the Equivalence surface is used to generate the scattered field. Similar to generalized impedance boundary condition (GIBC), a relation between the Equivalence electric current and magnetic current can be established by using the extinction theorem. Therefore, only the electric/magnetic current is the unknown in the final EPA formulation. Numerical results for the array structures are obtained to demonstrate the accuracy and efficiency of the proposed method.
-
Complex Structures Modeling Using Equivalence Principle Algorithm
2006 IEEE Electrical Performane of Electronic Packaging, 2006Co-Authors: Maokun Li, Weng Cho ChewAbstract:A Equivalence Principle algorithm using the method moments is introduced. Complex structures can be decomposed into smaller, simpler structures using simpler Equivalence surface which will help the electromagnetic modeling of complex structures in electrical packages
Thibault Damour - One of the best experts on this subject based on the ideXlab platform.
-
Equivalence Principle violations and couplings of a light dilaton
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2010Co-Authors: Thibault Damour, Jacqueline Faye DonoghueAbstract:We consider possible violations of the Equivalence Principle through the exchange of a light `dilaton-like' scalar field. Using recent work on the quark-mass dependence of nuclear binding, we find that the dilaton-quark-mass coupling induces significant Equivalence-Principle-violating effects varying like the inverse cubic root of the atomic number - A^{-1/3}. We provide a general parameterization of the scalar couplings, but argue that two parameters are likely to dominate the Equivalence-Principle phenomenology. We indicate the implications of this framework for comparing the sensitivities of current and planned experimental tests of the Equivalence Principle.
-
The Equivalence Principle and the constants of nature
Space Science Reviews, 2009Co-Authors: Thibault DamourAbstract:We briefly review the various contexts within which one might address the issue of ``why'' the dimensionless constants of Nature have the particular values that they are observed to have. Both the general historical trend, in physics, of replacing a-priori-given, absolute structures by dynamical entities, and anthropic considerations, suggest that coupling ``constants'' have a dynamical nature. This hints at the existence of observable violations of the Equivalence Principle at some level, and motivates the need for improved tests of the Equivalence Principle.
-
Equivalence Principle and Clocks
arXiv: General Relativity and Quantum Cosmology, 1999Co-Authors: Thibault DamourAbstract:String theory suggests the existence of gravitational-strength scalar fields ("dilaton" and "moduli") whose couplings to matter violate the Equivalence Principle. This provides a new motivation for high-precision clock experiments, as well as a generic theoretical framework for analyzing their significance.
-
Gravity, Equivalence Principle and Clocks
arXiv: General Relativity and Quantum Cosmology, 1997Co-Authors: Thibault DamourAbstract:String theory suggests the existence of gravitational-strength scalar fields (``dilaton'' and ``moduli'') whose couplings to matter violate the Equivalence Principle. This provides a new motivation for high-precision clock experiments, as well as a generic theoretical framework for analyzing their significance.
-
Equivalence Principle and the Moon
Physical Review D, 1996Co-Authors: Thibault Damour, David VokrouhlickýAbstract:The perturbation of the lunar motion caused by a hypothetical violation of the Equivalence Principle is analytically worked out in terms of power series in the manner of Hill and Brown. The interaction with the quadrupolar tide is found to amplify the leading order term in the synodic range oscillation by more than 62%. Confirming a recent finding of Nordtvedt, we show that this amplification has a pole singularity for an orbit beyond the lunar orbit. This singularity is shown to correspond to the critical prograde orbit beyond which, as
Natalia K. Nikolova - One of the best experts on this subject based on the ideXlab platform.
-
Reduction of the Line-of-Sight Equivalence Principle
Electronics, 2020Co-Authors: Nagula Tharma Sangary, Natalia K. NikolovaAbstract:An improvement to the line-of-sight (LoS) approximation of the Equivalence Principle used in far-field computations is presented. In the original LoS approximation of the Equivalence Principle, the integral equation uses only the surface currents on the LoS surface, as well as the edge currents on the contour of the LoS surface, which is the replacement of the surface integrals over the shadow part of the surface. Here, we show that the integration over one type of surface current on the LoS surface and edge currents is sufficient, which reduces the resources required for the LoS radiation pattern computations by half. The proposed theory is a rigorous analysis of Love’s Equivalence theory with an introduction of the point-of-symmetry concept. The proposed method makes use of the vector-potential field representation to derive the improved LoS Equivalence Principle. The proposed approach is validated with the calculation of the far-field radiation pattern of a patch antenna using the Finite Difference Time Domain (FDTD) simulations.
-
Line-of-sight approximation to the Equivalence Principle
IEEE Transactions on Antennas and Propagation, 2004Co-Authors: Nagula Tharma Sangary, Natalia K. NikolovaAbstract:A line-of-sight (LoS) approximation to the Equivalence Principle used in far-field computations is proposed. In the LoS Equivalence, only the surface currents at the virtual surface and the edge currents at its contour, which are on the LoS with the observation point, are used in the calculation of the radiated field. It is a far more efficient alternative to the standard Equivalence Principle, which requires integration over the entire closed virtual surface. We present the theory associated with the LoS Equivalence approach, examine the error due to the approximation, and demonstrate its accuracy via the radiation of dipole antennas.
Holger Muller - One of the best experts on this subject based on the ideXlab platform.
-
Equivalence Principle and bound kinetic energy
Physical Review Letters, 2013Co-Authors: Michael Hohensee, Holger Muller, R B WiringaAbstract:: We consider the role of the internal kinetic energy of bound systems of matter in tests of the Einstein Equivalence Principle. Using the gravitational sector of the standard model extension, we show that stringent limits on Equivalence Principle violations in antimatter can be indirectly obtained from tests using bound systems of normal matter. We estimate the bound kinetic energy of nucleons in a range of light atomic species using Green's function Monte Carlo calculations, and for heavier species using a Woods-Saxon model. We survey the sensitivities of existing and planned experimental tests of the Equivalence Principle, and report new constraints at the level of between a few parts in 10(6) and parts in 10(8) on violations of the Equivalence Principle for matter and antimatter.
-
Equivalence Principle and gravitational redshift
Physical Review Letters, 2011Co-Authors: Michael Hohensee, Achim Peters, Holger MullerAbstract:We investigate leading order deviations from general relativity that violate the Einstein Equivalence Principle in the gravitational standard model extension. We show that redshift experiments based on matter waves and clock comparisons are equivalent to one another. Consideration of torsion balance tests, along with matter-wave, microwave, optical, and Moessbauer clock tests, yields comprehensive limits on spin-independent Einstein Equivalence Principle-violating standard model extension terms at the 10{sup -6} level.
James D Phillips - One of the best experts on this subject based on the ideXlab platform.
-
a weak Equivalence Principle test on a suborbital rocket
Classical and Quantum Gravity, 2010Co-Authors: Robert D Reasenberg, James D PhillipsAbstract:We describe a Galilean test of the weak Equivalence Principle, to be conducted during the free fall portion of a sounding rocket flight. The test of a single pair of substances is aimed at a measurement uncertainty of ?(?) < 10?16 after averaging the results of eight separate drops. The weak Equivalence Principle measurement is made with a set of four laser gauges that are expected to achieve 0.1 pm Hz?1/2. The discovery of a violation (? ? 0) would have profound implications for physics, astrophysics and cosmology.