The cosmological background and the “external field” in modified gravity (MOG)

AbstractWe investigate the contributions of the Friedmann–Lemaître–Robertson–Walker metric of the standard cosmology as an asymptotic boundary condition on the first-order approximation of the gravitational field in Moffat’s theory of modified gravity (MOG). We also consider contributions due to the fact that the MOG theory does not satisfy the shell theorem or Birkhoff’s theorem, resulting in what is known as the “external field effect” (EFE). We show that while both these effects add small contributions to the radial acceleration law, the result is orders of magnitude smaller than the radial acceleration in spiral galaxies.

Download Full-text

Improved first-order approximation of eigenvalues and eigenvectors

AIAA Journal ◽

10.2514/3.14028 ◽

1998 ◽

Vol 36 ◽

pp. 1721-1727

Author(s):

Prasanth B. Nair ◽

Andrew J. Keane ◽

Robin S. Langley

Keyword(s):

Order Approximation ◽

Eigenvalues And Eigenvectors ◽

First Order ◽

First Order Approximation

Download Full-text

Analytical solution for unsteady flow behind ionizing shock wave in a rotational axisymmetric non-ideal gas with azimuthal or axial magnetic field

Zeitschrift für Naturforschung A ◽

10.1515/zna-2020-0248 ◽

2021 ◽

Vol 76 (3) ◽

pp. 265-283

Author(s):

G. Nath

Keyword(s):

Magnetic Field ◽

Shock Wave ◽

Analytical Solution ◽

Axial Magnetic Field ◽

Order Approximation ◽

Ideal Gas ◽

Field Region ◽

First Order ◽

First Order Approximation ◽

Flow Variables

Abstract The approximate analytical solution for the propagation of gas ionizing cylindrical blast (shock) wave in a rotational axisymmetric non-ideal gas with azimuthal or axial magnetic field is investigated. The axial and azimuthal components of fluid velocity are taken into consideration and these flow variables, magnetic field in the ambient medium are assumed to be varying according to the power laws with distance from the axis of symmetry. The shock is supposed to be strong one for the ratio C 0 V s 2 ${\left(\frac{{C}_{0}}{{V}_{s}}\right)}^{2}$ to be a negligible small quantity, where C 0 is the sound velocity in undisturbed fluid and V S is the shock velocity. In the undisturbed medium the density is assumed to be constant to obtain the similarity solution. The flow variables in power series of C 0 V s 2 ${\left(\frac{{C}_{0}}{{V}_{s}}\right)}^{2}$ are expanded to obtain the approximate analytical solutions. The first order and second order approximations to the solutions are discussed with the help of power series expansion. For the first order approximation the analytical solutions are derived. In the flow-field region behind the blast wave the distribution of the flow variables in the case of first order approximation is shown in graphs. It is observed that in the flow field region the quantity J 0 increases with an increase in the value of gas non-idealness parameter or Alfven-Mach number or rotational parameter. Hence, the non-idealness of the gas and the presence of rotation or magnetic field have decaying effect on shock wave.

Download Full-text

FIRST-ORDER APPROXIMATION OF THE NUMBER-PROJECTED SO(2N) TAMM-DANCOFF EQUATION AND ITS REDUCTION BY THE SCHUR FUNCTION

International Journal of Modern Physics E ◽

10.1142/s0218301399000318 ◽

1999 ◽

Vol 08 (05) ◽

pp. 461-483

Author(s):

SEIYA NISHIYAMA

Keyword(s):

Wave Function ◽

Order Approximation ◽

Approximate Equation ◽

Variation Principle ◽

Schur Function ◽

Soliton Theory ◽

First Order ◽

Fermion Systems ◽

Group Manifold ◽

First Order Approximation

First-order approximation of the number-projected (NP) SO(2N) Tamm-Dancoff (TD) equation is developed to describe ground and excited states of superconducting fermion systems. We start from an NP Hartree-Bogoliubov (HB) wave function. The NP SO(2N) TD expansion is generated by quasi-particle pair excitations from the degenerate geminals in the number-projected HB wave function. The Schrödinger equation is cast into the NP SO(2N) TD equation by the variation principle. We approximate it up to first order. This approximate equation is reduced to a simpler form by the Schur function of group characters which has a close connection with the soliton theory on the group manifold.

Download Full-text

The first-order approximation of non-Kirchhoff-Love theory for elastic circular plate with fixed boundary under uniform surface loading (III)—Numerical results

Applied Mathematics and Mechanics ◽

10.1007/bf02453737 ◽

1997 ◽

Vol 18 (5) ◽

pp. 411-419

Author(s):

Chien Weizang ◽

Sheng Shangzhong

Keyword(s):

Circular Plate ◽

Order Approximation ◽

Numerical Results ◽

Surface Loading ◽

Fixed Boundary ◽

First Order ◽

Elastic Circular Plate ◽

First Order Approximation

Download Full-text

First order approximation for quadratic dispersive equations by the renormalization group approach

Journal of Mathematical Physics ◽

10.1063/1.4903001 ◽

2014 ◽

Vol 55 (12) ◽

pp. 123503

Author(s):

Lin Wang

Keyword(s):

Renormalization Group ◽

Order Approximation ◽

Dispersive Equations ◽

Group Approach ◽

First Order ◽

Renormalization Group Approach ◽

First Order Approximation

Download Full-text

Chaotic Amplitude Dynamics for Parametrically Excited Systems With Quadratic Nonlinearities

Volume 3A: 15th Biennial Conference on Mechanical Vibration and Noise — Vibration of Nonlinear, Random, and Time-Varying Systems ◽

10.1115/detc1995-0284 ◽

1995 ◽

Author(s):

Bappaditya Banerjee ◽

Anil K. Bajaj

Keyword(s):

Harmonic Balance ◽

Chaotic Dynamics ◽

Degrees Of Freedom ◽

Order Approximation ◽

Amplitude Equations ◽

Analytical Technique ◽

First Order ◽

Numerical Studies ◽

Quadratic Nonlinearities ◽

First Order Approximation

Abstract Dynamical systems with two degrees-of-freedom, with quadratic nonlinearities and parametric excitations are studied in this analysis. The 1:2 superharmonic internal resonance case is analyzed. The method of harmonic balance is used to obtain a set of four first-order amplitude equations that govern the dynamics of the first-order approximation of the response. An analytical technique, based on Melnikov’s method is used to predict the parameter range for which chaotic dynamics exist in the undamped averaged system. Numerical studies show that chaotic responses are quite common in these quadratic systems and chaotic responses occur even in presence of damping.

Download Full-text

Analytical quality assessment of iteratively reweighted least-squares (IRLS) method

Boletim de Ciências Geodésicas ◽

10.1590/s1982-21702014000100009 ◽

2014 ◽

Vol 20 (1) ◽

pp. 132-141 ◽

Cited By ~ 1

Author(s):

Jianfeng Guo

Keyword(s):

Least Squares ◽

Order Approximation ◽

Diagnostic Tools ◽

Iteratively Reweighted Least Squares ◽

First Order ◽

Iterative Reweighting ◽

First Order Approximation ◽

Detectable Bias ◽

Theoretical Analyses ◽

Exact Analytical Method

The iteratively reweighted least-squares (IRLS) technique has been widely employed in geodetic and geophysical literature. The reliability measures are important diagnostic tools for inferring the strength of the model validation. An exact analytical method is adopted to obtain insights on how much iterative reweighting can affect the quality indicators. Theoretical analyses and numerical results show that, when the downweighting procedure is performed, (1) the precision, all kinds of dilution of precision (DOP) metrics and the minimal detectable bias (MDB) will become larger; (2) the variations of the bias-to-noise ratio (BNR) are involved, and (3) all these results coincide with those obtained by the first-order approximation method.

Download Full-text