@ominazzoli @timhenke
@MisterRelativity

#EPS referring (of course) to ["Ehlers-Priani-Schild"](https://en.wikipedia.org/wiki/J%C3%BCrgen_Ehlers#cite_ref-27),
in [this case](https://mathstodon.xyz/@MisterRelativity/109718470425452510).

#SpaceTime #Relativity #Particle #CoincidenceDeterminations

@RefurioAnachro
> <em> hesitate to say acceleration is _the cause_ for #TD </em>

Alright!
Only a flat region or a (therefore so called) [[normal]] region allow this strong statement about paths connecting 1 initial and 1 final event:

exhibiting unequal lengths (durations) is then _sufficient + necessary_ for (all but 1 of) them exhibiting acceleration (bends, even kinks/knees).

But not more general.

> <em> already a property of the metric </em>

Primary in #RT are #CoincidenceDeterminations

@heafnerj
Joe Heafner wrote:
> <em> [...] concept of #InertialFrame in [... the ST] of #relativity https://arxiv.org/abs/2103.15570 </em>

So ... author Boris Čulina, who

- doesn't even acknowledge a distinction of "good #clock" vs. "bad #clock" (cmp. MTW, Fig. 1.9),

- much less #HowTo define + measure such a distinction by [#CoincidenceDeterminations](http://einsteinpapers.press.princeton.edu/vol6-trans/165?highlightText=coincidences),

is nevertheless https://arxiv.org/auth/show-endorsers/2103.15570 ?!? ...

Well, therefore, we have #mastodon