On Wednesday, April 24, 2019 at 6:04:43 PM UTC-6, Brent wrote: > > > > On 4/24/2019 4:11 PM, [email protected] <javascript:> wrote: > > > > On Wednesday, April 24, 2019 at 3:34:28 PM UTC-6, Brent wrote: >> >> >> >> On 4/21/2019 7:35 PM, [email protected] 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 know. He just offered a final comment that deviations from flatness corresponds to non-zero off diagonal elements, so it got me wondering how flatness is mathematically defined for a Lorentz metric. I agree I should focus on the reference I posted. AG* > 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??* > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > To post to this group, send email to [email protected] > <javascript:>. > Visit this group at https://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
