Questions tagged [general-relativity]
A theory that describes how matter interacts dynamically with the geometry of space and time. It was first published by Einstein in 1915 and is currently used to study the structure and evolution of the universe, as well as having practical applications like GPS.
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Definition of reference system in the context of General Relativity [closed]
I'm in trouble with the definition of reference system in the context of General Relativity intended as coordinate chart (i.e. no frame field).
Various sources define it as a one-to-one smooth mapping ...
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Why is the Hubble radius $R_H = \frac{c}{H}$ considered the relevant horizon scale in cosmology?
In cosmology, several characteristic horizon scales can be defined, including the particle horizon,
the event horizon, and the Hubble radius.
The Hubble radius is defined as
$R_H = \frac{c}{H}$
where $...
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How do gravitational waves propagate through spacetime without a medium? [duplicate]
How do gravitational waves propagate through spacetime without a medium?
I'm trying to understand gravitational waves at an introductory level, and I'm confused about how they propagate.
My confusion:
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Why do we conclude that gravity is fictitious force from equivalence principle?
I read about equivalence principle. I tried to understand Einstein's thought experiment with elevator and I can't understand why we compare elevator in the space and elevator on the surface of the ...
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How mass diverges at Cauchy Horizon in Kerr Black Hole?
I have just started studying this topic so maybe this question sounds very basic.
In General Relativity, Cauchy horizon is unstable because of the concept called mass inflation in which mass parameter ...
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Does the frequency of the (nominal) "10 MHz output signal" of a GPS-disciplined clock system vary (systematically) with altitude?
Preprint article https://arxiv.org/abs/1707.00171 ("Measurement of Gravitational Time Dilation: An Undergraduate Research Project", M. S. Burns et al.) reports having worked with Trimble ...
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Relation between the axioms of relativistic spacetime and the postulates of relativity
I am watching the course on general relativity by the WE Heraeus international winter school on gravity and light given by prof. Frederic Schuller, concretely on Lecture 13 on relativistic spacetimes ...
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Consider an infinite massive plate, with mass density $\sigma$. What will be the path of a photon, starting out parallel to the plate?
According to this article, the metric on both sides of an infinite plate with mass density $\sigma$ is:
$$ds^2=e^{2g|z|}(-dt^2+dx^2+dy^2)+dz^2,$$
where $g=2\pi G \sigma$, $G$ being the universal ...
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How would a tachyon gravitationally interact with a fermion? [closed]
Assuming that tachyons were real and we somehow managed to trap some, what would its gravitational field look like? I know they have imaginary mass, but I’m having a very hard time trying to figure ...
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Everything From bivalent Boolean logic? [closed]
If the notion of observer is defined properly, his logic then dictates, to a certain degree, general properties of the observable environment (GR-Friendly Description of Quantum Systems), like group ...
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Why can't you just go around the black hole to get to Quadrant III of the Kruskal-Szekeres diagram?
A Kruskal-Szekeres diagram (below) only shows one spatial dimension. If you extended it to cover two spatial dimensions, it seems like it should have a future and past cone meeting at their common ...
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Is there a typo in Wald General Relativity Theorem 8.1.6?
My contention is, didn't we just find out that $\lambda \subset I^+(C)$ contradicts that $p \in \dot{I}^+(C)$, which $p$ should fulfill by definition? Should this not be $\lambda \subset \dot{I}^+(C)$ ...
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Can cosmological horizons be consistently treated as thermodynamic systems with temperature and entropy?
in several areas of gravitational physics, horizons appear to exhibit thermodynamic properties. In
particular, black hole horizons are known to possess an entropy proportional to their area and a
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Radar coordinates and smooth structures
Consider a time-orientable spacetime $M$ and two timelike particles Alice and Bob.
Radar coordinates are usually defined (operationally) in terms of messages and echos:
a particle Alice sends a pulse ...
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On the definition of rest frame in special & general relativity
In the context of special & general relativity there exists the notion of "rest frame" w.r.t. an object or an observer.
The latter are represented in spacetime by a timelike worldline (...
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