Questions tagged [general-relativity]
Questions about relativistic theory of gravity. General relativity describes gravity as a geometrical property of space and time.
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What is called following two metric's signature if they are not Lorentz signatures?
I make two different substitutions (m(r)=m1(r), m2(r)) to the modified Schwarzschild metrics:
$${\it m1} \left( r \right) =1/2\,r{c}^{2} \left( 1+\sqrt {{\frac {r{c}^
{2}-2\,MG}{r{c}^{2}}}} \right) {G}...
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Help me figure out how to solve the gravitational lens equations
I want to simulate gravitational lensing. In the article LENSINGGW: a PYTHON package for lensing of gravitational waves there is this fragment [page 3]:
My research: As far as I understand, this is a ...
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What does the upper and lower indices in metric tensor means?
When we have metric g that can be written as $$\begin{vmatrix}g_1 & g_2 & g_3\\
g_4 & g_5 & g_6 \\ g_7 & g_8 & g_9\end{vmatrix}$$ What does the $g^{\alpha\beta}$ and $g_{\alpha\...
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Is the hypothetical '(Don) Page curve' of evaporating black holes equal in time, so to speak, on both sides of the curve?
I have heard that Hawking radiation is slow at first, but rapidly increases when the black hole becomes much smaller... (I forget the formula...)
Does that mean that the second half of Page's curve, ...
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What exactly is a 'gravastar'? How is it different from a 'regular' black hole?
The Wikipedia article on gravastar says that it has a 'regular' black hole metric (Schwarzschild, I presume?) on the outside, but a de Sitter metric on the inside....
What exactly does that mean?
Don'...
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Does an infalling observer ever cross the black hole event horizon in finite proper time?
I am interested in how an infalling observer perceives the plunge into a black hole.
Let me assume that actually we have three spaceships: C being at a constant distance to the event horizon, and A ...
user56648
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Cosmic massive graviton bounds
In the paper, Relativistic theory of gravitation and the graviton rest mass. Theoretical and Mathematical Physics, 65(1), 971–979. doi:10.1007/bf01028629, the mass bound
$$m_g<6.4\cdot 10^{-66}g=6....
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Expanding voids ending being collapsed?
According to some papers I've found 1, 2 expanding voids can be foun inside clouds of denser materials that can cause them to eventually collapse. I have two questions about this:
Overdensities ...
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Is gravitational lensing "additive" in a line of sight?
As usually depicted, gravitational lensing implies, at least, three objects: a distant source, an observer, and a "massive enough" object in the middle, where enough is the mass needed to ...
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Shouldn't the Friedmann equation take into account the massive extra distance traveled during the time for gravity to travel across the universe? [closed]
I’ve got a question that has been bothering me for the past few years that of the few sources that are only somewhat related to this, none of them say anything about this should be wrong so I can’t ...
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Can we measure how fast space is expanding from how quickly gravitationally lensed galaxies or stars are blurring or getting sharper?
A galaxy that lenses another celestial body should as it moves away from Earth alter the sharpness of what it lenses by gravity. Could this be used to determine how quickly space is expanding?
user54398
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Is the difference of redshift parameter z able to prove expansion is accelerating in flat FLRW universe model?
Sorry for my bad english, this is not my mother tongue.
Recently, I've encountered a problem in cosmology class that is about FLRW universe.
Assuming that the universe we inhabit is composed of non-...
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Does dark matter exist because as Einstein said the laws of physics should be the same inside and outside a black hole?
Spacetime is said to be time like inside a black hole ( two events can happen at the same place at different times). Spacetime is called space- like outside a black hole ( two events can happen ...
user53017
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$v_{GW}$ near a binary star?
In empty space, at large distances from masses and at small amplitudes, GWs propagate at the speed of light. This does not apply near the source, because there is a large mass and the amplitude of the ...
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How can Kerr black holes have a 'speed limit' to how fast they can spin?
Obviously, the speed of light is a presumed limit, at least for 'physical' objects moving 'within' ('through'?) spacetime, but...
In recent news some scientists believe they have figured out the ...
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