cianfa72's latest activity
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cianfa72 posted the thread Undergrad Do existing EFE solutions support Closed Timelike Curves? in Cosmology.Hi, I'm curious about the following: taking the point of view of the standard physics of spacetime including EFE's solutions, are there... -
cianfa72 reacted to PAllen's post in the thread Undergrad Question about Parallel Transport with
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I am not sure that is always true. Consider, by analogy, a 3-sphere embedded in Euclidean 4 space. It can contain a geodesic of the... -
cianfa72 reacted to PAllen's post in the thread Undergrad Question about Parallel Transport with Like.
I am saying this is not necessarily true. True is that you can find a hypersurface containing it such it is a geodesic of the...
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cianfa72 replied to the thread Undergrad Question about Parallel Transport.No, maybe I wasn't clear. For any geodesic of the 4D Euclidean space you can always find an hypersurface containing it (on this...
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cianfa72 replied to the thread Undergrad Question about Parallel Transport.This raises the following point. Let's take a spacelike geodesic of the 4D Lorentzian spacetime. There exists a spacelike hypersurface...
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cianfa72 replied to the thread Undergrad Question about Parallel Transport.You mean, taking a spacelike hypersurface (endowed with the induced metric) is basically a recipe to build a 3D Riemannian manifold.
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cianfa72 reacted to PAllen's post in the thread Undergrad Question about Parallel Transport with Like.
Actually, if you take any small part of the geodesic, and a small neighborhood around that part, then that geodesic segment is minimal -...
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cianfa72 reacted to PAllen's post in the thread Undergrad Question about Parallel Transport with Like.
True, but that is just a recipe for constructing a pure Riemannian manifold, that happens to a submanifold. So it is actually covered in...
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cianfa72 replied to the thread Undergrad Question about Parallel Transport.As far as I can understand, in GR, the spacelike geodesics are (always) saddle points when considering them in the overall 4D spacetime...
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cianfa72 reacted to PAllen's post in the thread Undergrad Question about Parallel Transport with Like.
No, not longest distance - you can deviate from a non minimal great circle path and make it longer - by any amount with squiggles. In...
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cianfa72 reacted to Nugatory's post in the thread Undergrad Synchronizing clocks at different locations to measure speed of light with Like.
Simultaneity is a property of pairs of events not objects even in classical physics where there is no relativity of simultaneity.
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cianfa72 replied to the thread Undergrad Can a Gyroscope in a Satellite Detect Orbit?.Ok, this is similar to the Langevin congruence: take the worldline at the center of the rotating disk as "reference/fiducial" worldline...
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cianfa72 reacted to PeterDonis's post in the thread Undergrad Can a Gyroscope in a Satellite Detect Orbit? with Like.
The vorticity isn't a cause, it's a description. As I understand it, the rotation of the ISS wrt the gyroscope's axis is maintained by...
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cianfa72 replied to the thread Undergrad Can a Gyroscope in a Satellite Detect Orbit?.Yes the vorticity is small, however it suffices to provide the rotation of the ISS w.r.t. the gyroscope's axis.
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cianfa72 reacted to PeterDonis's post in the thread Undergrad Can a Gyroscope in a Satellite Detect Orbit? with Like.
Strictly speaking, I suppose this is true, but the proper acceleration will be extremely small, because the only reasons it would be...