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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Notation for vector density in Lagrangian density
Consider a manifold $M$ and a Lagrangian density $\mathcal{L} \equiv \mathcal{L}(\phi, \nabla \phi)$. By varying the action, one obtains the equation
$$\int_M \, dV \; \Big( \frac{\partial \mathcal{L}}...
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History Of The Equivalence Principle [closed]
The problem of the equivalence of inertial mass and gravitational mass was an outstanding problem since the time of Galileo. History shows that multiple thinkers will attempt to solve a problem even ...
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Can perfectly stable orbits exist in GR?
Defining "stable orbit" between two bodies as one where, in the absence of other bodies or non-gravitational forces, the distance stays between some value pair $r_{min}>0$ and $r_{max}$. ...
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Gravitoelectromagnetism (GEM) and Planck's constant [closed]
I've studied physics mainly on my own, having earned a degree in geology (in Italy). Almost by chance, I realized that applying the GEM equations (gravitoelectromagnetic; an approximation of the ...
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Are de Sitter, Anti-de Sitter and Minkowski spaces spatially infinite?
I am not someone who has studied general relativity, however have recently developed an interest in it. From what I have seen online, de Sitter, Minkowski and Anti-de Sitter spaces are often compared ...
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How to derive Smarr formula for Kerr Black Hole?
Following is the Smarr formula for Kerr Black Hole
$$M=\frac{\kappa A}{4\pi}+2 \Omega J $$
where $\kappa, \Omega$, $J$ and $A$ are surface gravity, angular velocity, angular momentum and surface area ...
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On time arrow and coordinate change in General relativity
This may be a silly question but I would like to have things cleared up once and for all in my head.
I will take the example of a Schwarzschild black hole as a solution to vacuum Einstein Field ...
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Necessity of Singularity in General Relativity
The Schwarzschild solution is the standard example used to describe a black hole, its important points being the event horizon and the central singularity. But this solution is derived by assuming an ...
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What is the cause of gravity according to general relativity? [duplicate]
The question is based on general relativity and it can help big bang theory.
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End points of event horizon
I am reading The Nature of Space and Time by S. W. Hawking. In the last paragraph on page 16 he said that:
event horizon may have past end points but don't have any future end points
I understand ...
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Clarification of Weinberg's cosmology book eqns 5.1.44-5.1.47 for scalar perturbation
Has anyone clarified the equations in Weinberg's cosmology book for scalar perturbation for nonzero $F$ and $B$, eqns 5.1.44-5.1.47. I am not sure why there are terms with $\nabla^2 \dot{B}$ and $\...
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Probabilistic curvature of spacetime [duplicate]
I was wondering since matter tells space-time how to curve, and since matter is probabilistic in position (say hydrogen atom) is the curvature also probabilistic?
black holes slowly shrink by ...
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Has anyone thought about the idea that our reality is only operating in a certain "speed range"? [closed]
I am not a physicist so I hope that this is the right place to ask.
The other night after reading some of The Grand Design I was dreaming about a unified string theory type of universe where there is ...
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Cause of Coordinate Acceleration in Free Fall [duplicate]
So I understand that objects in free fall are in an inertial frame, at rest in terms of relativity. However, from a person on the surface of earth, a falling apple is accelerating constantly until it ...
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Is the size of a black hole singularity smaller than a fundamental particle?
I am wondering about the size of a black hole singularity. We know that a classical black hole is infinitely dense. I am not asking about size of event horizon. I am asking about actual size of the ...
