Questions tagged [gravity]
Gravity is an attractive force that affects and is affected by all mass and - in general relativity - energy, pressure, and stress. Prefer newtonian-gravity or general-relativity if sensible.
5,469 questions
5 votes
1 answer
185 views
In a stationary, asymptotically flat spacetime, when does a Killing horizon coincide with the event horizon?
In general relativity, the black hole region (B) of an asymptotically flat spacetime $M,g$ is defined globally as $$ B := M \setminus J^-(\mathscr I^+), $$ and the (future) event horizon is its ...
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0 votes
0 answers
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Does dissipation have different gravitational entropy effects depending on which mass dissipates in a bound system?
Consider a bound two-body system ($M>>m$) such as Earth–Moon. I'm trying to understand whether there's a meaningful asymmetry in how identical dissipation processes affect gravitational entropy ...
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What do we know about mass equivalence principle for non-nucleons, mass in e.g. neutrino oscillations?
While special relativity says inertial mass is equivalent with energy, there are at least two more types of mass, for which equivalence seems not so certain - let me briefly summarize and ask for more ...
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2 votes
0 answers
42 views
Collapse of a charged dust cloud to a Reissner–Nordström black hole
The Oppenheimer–Snyder_model models the collapse of an object into a black hole. But what if the object is strongly charged, is there a model for the collapse of a spherical cloud of charged matter ...
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-3 votes
0 answers
80 views
Black hole evaporation [duplicate]
“If mass and energy are equivalent, and black holes evaporate by losing energy via Hawking radiation, does that mean singularities never actually form — that they’re replaced by ultra-dense, finite ...
0 votes
0 answers
50 views
Induced metric on hypersurface of constant comoving radius in FLRW metric
I am currently looking at the Oppenheimer Snyder Collapse model analytically. The interior metric is described as the FLRW metric: $$ ds^2 = - d \tau^2 + a^2(\tau)(d \chi^2 + sin^2 \chi d\Omega^2) $$ ...
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0 votes
0 answers
59 views
Could the absence of local cosmological expansion be viewed as a balance of stresses in spacetime?
Cosmic expansion is described by the FLRW scale factor 𝑎(𝑡), while locally bound systems are well modelled by the Schwarzschild or Schwarzschild–de Sitter metric. The usual explanation is that ...
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5 votes
1 answer
348 views
Is it possible to deduce the density distribution only from the gravity field around it?
Is it possible to deduce the density distribution only from the gravity field around it? Apparently this cannot be done in Newtonian gravity or static cases of GR: in spherical symmetric cases of ...
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