On 4/24/2019 4:11 PM, [email protected] wrote:


On Wednesday, April 24, 2019 at 3:34:28 PM UTC-6, Brent wrote:



    On 4/21/2019 7:35 PM, [email protected] <javascript:> wrote:


    On Sunday, April 21, 2019 at 8:07:28 PM UTC-6, Brent wrote:



        On 4/21/2019 6:31 PM, [email protected] wrote:
        *Here's something odd. At 9:45 in Susskind's Lecture 2 on
        GR, he says the metric tensor is a Kronecker delta function.
        But I could swear that the diagonal of -1,1,1,1 represents
        flat space in SR. AG??*

        What's odd about that??? Flat space is just special case of
        curved space in which the curvature is zero.

        Brent


    *Sure, but he seems to be saying that the Kronecker delta is the
    metric tensor for curved space. Isn't that how you interpret his
    comment?*

    No.?? After he goes thru the derivation with delta function in it,
    then he says it's different for a curve?? space.

    Brent


*I just reviewed it again. That's not my reading. In any event, it's not clear what he means, and using Bruno's suggestion, t' --> it,?? doesn't really help either since you end up with the Lorentz metric which is far from Euclidean intuition for demonstrating deviations from flatness. *

It was NOT demonstrating deviation from flatness.?? I don't know what the guy was intending to demonstrate but he started with assuming flatness, got a metric, and then remarked that it's different for curve space.?? So what's your problem??? Read

arXiv:1608.05752v1 [physics.hist-ph] 19 Aug 2016

and stop fussing about some video.

Brent
*Further, there are transformations that keep spacetime flat with NON-zero off diagonal elements, such as a simple rotation. AG *
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