cianfa72's latest activity
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cianfa72 reacted to PeterDonis's post in the thread I Is a Gravitational Field Real or Just a Coordinate Transformation Artifact? with
Agree.
I don't think this is a good way to put it. As most other textbooks use the term "locally flat", it means that you an always find a... -
cianfa72 reacted to Dale's post in the thread I Is a Gravitational Field Real or Just a Coordinate Transformation Artifact? with
Like.
The connection between the two is tidal gravity. Spacetime curvature cannot be removed by a coordinate transformation and tidal effects... -
cianfa72 reacted to PeterDonis's post in the thread I How do non-diagonal indices of a metric allow for local flatness? with
Informative.
Not the way you mean. The Minkowski metric is diagonal when you choose a particular coordinate chart. But you can also choose a chart on... -
cianfa72 reacted to Ibix's post in the thread I How do non-diagonal indices of a metric allow for local flatness? with Agree.
Another way to look at it is that it's always possible to pick a timelike vector and three spacelike vectors that are mutually...
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cianfa72 reacted to PeterDonis's post in the thread I Transformation for Lemaitre coordinates with Like.
This will be true in general for any transformation between the Schwarzschild chart and a chart that doesn't have a coordinate...
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cianfa72 reacted to Dale's post in the thread I Deriving Einstein's Relativity Postulates from Minkowski Spacetime with Like.
You need to say a little more than just "Minkowski spacetime metric" for it to follow naturally. The Minkowski metric is just a...
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cianfa72 replied to the thread I How do non-diagonal indices of a metric allow for local flatness?.In Anderson coordinates the expression of the flat spacetime metric ##ds^2## includes mixed term in ##\kappa dtdx##. For ##\kappa=0##...
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cianfa72 reacted to Dale's post in the thread I How do non-diagonal indices of a metric allow for local flatness? with Like.
Yes. Also, any four-velocity is a 4D tangent vector to a worldline. So that vector is the same vector in different frames, although its...
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cianfa72 replied to the thread I How do non-diagonal indices of a metric allow for local flatness?.Ah ok, I think what I put in bold is the key point. What is actually invariant are the light cones and therefore the light's velocity as...
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cianfa72 reacted to Dale's post in the thread I How do non-diagonal indices of a metric allow for local flatness? with Like.
As @PeterDonis mentioned also the coordinate two way speed of light can vary in non-inertial charts. Although that does also depend on...
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cianfa72 replied to the thread I How do non-diagonal indices of a metric allow for local flatness?.I think you actually mean the one-way speed of light (OWSOL) is only invariant in the standard inertial coordinates (assuming of course...
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cianfa72 reacted to Ibix's post in the thread I Conventionality of the One-Way Speed of Light with Agree.
It's not necessarily the one-way speed, but it is necessarily the two-way speed of light. What your maths tells you, in short, is that...
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cianfa72 reacted to renormalize's post in the thread I Transformation for Lemaitre coordinates with Like.
Yes you can! Inspired by https://en.wikipedia.org/wiki/Lema%C3%AEtre_coordinates, note that your two...
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cianfa72 replied to the thread I 2-sphere intrinsic definition by gluing disks' boundaries.Of course the relevant gluing map glues "corresponding points" on disks ' boundary (e.g. point ##(1,0)## of ##D_{+}## is glued with...
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cianfa72 reacted to lavinia's post in the thread I 2-sphere intrinsic definition by gluing disks' boundaries with Like.
@cianfa72 Your thoughts brought to mind a few considerations that I thought would be of interest to you. You start out by saying that...