Riemann Curvature Scalar Differs in Landau & MTW

[zn5252]

hello
For the same Friedmann metric, Landau (Classical theory of fields) finds a value for the Riemann curvature scalar which is given in section 107 :
R = 6/a³( a + d²(a)/dt²)
whereas in MTW , in box 14.5 , equation 6 , its value is :

R = 6(a^-1 d²(a)/dt² + a^-2 (1 + (d(a)/dt)² ) )

The metric is the same ! how come ? this could not be related to the fact that Landau does the replacement :
cd$\tau$ = ad$\eta$

 

[Bill_K]

The metric is the same ! how come ? this could not be related to the fact that Landau does the replacement : cd$\tau$ = ad$\eta$

Yes, that's it exactly. the difference is that in Landau & Lifgarbagez, the dot means d/dη, not d/dt.

 

[zn5252]

I see Bill Thanks. Not so obvious though .