Questions tagged [post-newtonian]
65 questions
27
votes
4 answers
Why do gravitational waves circularize a binary?
I understand that a binary orbiting around one another will circularize due to the emission of GWs due to Peters equations and that highly eccentric binaries evolve faster.
But GW emission also removes energy and angular momentum (wouldn’t the…
Warrenmovic
- 508
15
votes
1 answer
What's wrong with Abraham's proposed force law in Nordström's first theory of gravity?
Nordström's 1912 proposed theory of relativistic gravity posited that the gravitational potential field $\phi$ and the matter density field $\rho$ are both scalar fields, simply related by the wave equation $\partial^2 \phi = 4 \pi G \rho$.
The…
tparker
- 51,104
11
votes
1 answer
What is the current status of the convergence of the post-Newtonian approximation?
In the very well written article by C. Will, On the Unreasonable Effectiveness of the post-Newtonian Approximation in Gravitational Physics, he states:
The one question that remains open is the nature of the post-Newtonian sequence; we still do not…
Daddy Kropotkin
- 2,790
11
votes
1 answer
Post-Minkowskian expansion of some quantities in Post-Newtonian theory
I'm studying Post-Newtonian theory on the book "Gravity" by Poisson and Will and I found a few formulas that I can't obtain by myself. I'm pretty sure it must be quite simple, but can't find the right method to get the result.
First of all, a really…
GRB
- 1,451
8
votes
3 answers
Does General Relativity predict Mercury's orbital precession without other planets?
From Newtonian mechanics, the precession of Mercury can be calculated by taking into account the gravitational pull of other planets. From that, I assume that in the absence of external planets, Newtonian mechanics predicts that the elliptical orbit…
Stallmp
- 879
7
votes
1 answer
Extreme Mass Ratio Inspirals and GWs cycles
I was reading through the following paper GRMHD study of accreting massive black hole binaries in astrophysical environment: A review. Therein, we have the following image
It is not quite clear how long Post-Newtonian (PN) theory remains adequate…
RKerr
- 1,367
6
votes
1 answer
Lagrangian of a system of relativistic charged particles
I was studying Landau's Classical Field Theory: Volume 2 and came across the Lagrangian for a system of charged particles, up to first-order post-Newtonian corrections ($65), which can be expressed as:
\begin{equation}
\mathcal{L} = \mathcal{L_{0}}…
RKerr
- 1,367
6
votes
4 answers
How do we interpret measurements of Mercury's position?
When scientists measured the position of Mercury in the 18th century, they interpreted the results assuming a Euclidean background, because they did not know general relativity. So they measured $r$ and $\phi$ in function of time attributing to…
Giovanni
- 61
6
votes
2 answers
As of 2021 in how many binary systems has the period decrease due to gravitational waves been measured?
I am searching for data for the period decrease of binary systems due to gravitational waves. I am aware of three systems in which it was possible to measure this period decrease:
The Hulse-Taylor binary PSR 1913+16
the double pulsar PSR…
Benito McLanbeck
- 580
5
votes
1 answer
General relativity modifies Newton's inverse square law of gravity. Why do many people do experiments to test the inverse square law?
General relativity may induce the so-called post-Newtonian correction to the inverse square law of gravity. For details, please refer to chapter 9 of Weinberg's Gravitation and Cosmology.
However, there are many research papers about testing the…
lewton
- 303
5
votes
1 answer
What's the difference between a post-Minkowskian approximation and a post-Newtonian one?
I'm studying the book Gravity by Poisson & Will. Specifically, I'm interested in the post-Newtonian and post-Minkowskian approximations showed in chapters 6-10. The problem I'm having is conceptual, I understand the calculations but I don't get the…
P. C. Spaniel
- 4,476
5
votes
1 answer
What are modern solar system applications of GR where approximation methods fail?
It is often stated that general relativity (GR) provides the most accurate description of gravitational phenomenon. In most undergraduate and even graduate textbooks this idea is reinforced by discussing various applications of GR i.e. the…
Rumplestillskin
- 2,008
- 1
- 15
- 33
5
votes
2 answers
Light dispersion in gravitational theories
GR predicts no Ricci curvature in vacuum (or at least when we can ignore the cosmological constant). Would theories that violate this lead to observable light dispersion in solar system tests of gravity, or in light lensed around a galaxy?
The field…
JJMalone
- 175
5
votes
8 answers
Is relativity necessary for the existence of life?
If the universe didn't have the relativity principle, would it be able to support life?
Life consists of very complicated organisms. The operation of these organisms depends on the laws of physics.
If the laws of physics depended on absolute…
Carl Brannen
- 13,059
5
votes
1 answer
Derivation of Post-Newtonian (PN) expression for acceleration in Schwarzschild geometry
The expression for the acceleration of a near-earth satellite as presented in the IERS Technical note is given by
\begin{equation} \label{eq:problemeq} \tag{1}
\frac{d^2\mathbf{r}}{dt^2} = \frac{GM_E}{c^2r^3}…
Rumplestillskin
- 2,008
- 1
- 15
- 33