# Need to find the Ricci scalar curvature of this metric

1. May 27, 2012

### chinared

Need to find the Ricci scalar curvature of this metric:

ds2 = e2a(z)(dx2 + dy2) + dz2 − e2b(z)dt2

I tried to find the solution, but failed to pass the calculation of Riemann curvature tensor:

<The Christoffel connection> Here a'(z) denotes the first derivative of a(z) respect to z.
$\Gamma\stackrel{x}{xz}$=$\Gamma\stackrel{x}{zx}$=a'(z)
$\Gamma\stackrel{y}{yz}$=$\Gamma\stackrel{y}{zy}$=a'(z)
$\Gamma\stackrel{z}{tt}$=b'(z)e2b(z)
$\Gamma\stackrel{z}{xx}$=$\Gamma\stackrel{z}{yy}$=-a'(z)e2a(z)
$\Gamma\stackrel{t}{tz}$=$\Gamma\stackrel{t}{zt}$=b'(z)
$\Gamma\stackrel{}{either}$=0

<The Riemann curvature tensor>
$R\stackrel{x}{zxz}$=$R\stackrel{y}{zyz}$=-a''(z)-[a'(z)]2
$R\stackrel{z}{tzt}$=b''(z)+[b'(z)]2

I tried to find the Ricci scalar curvature(R) from current result, but it gave a function depend on z. Is there any problem in my calculation?

2. May 27, 2012

### phyzguy

I didn't check your calculation, but why do you think the Ricci scalar shouldn't depend on z?

3. May 27, 2012

### Staff: Mentor

I got the same for the Christoffel symbols, but I got a lot more non-zero elements for the Riemann curvature tensor.

4. May 27, 2012

### chinared

Sorry for that I did not write down the other non-zero terms of Riemann curvature tensor which can be deduced by symmetry and anti-symmetry properties.
However, I still have a contradiction that
Rt _ztz-b''(z)-[b'(z)]2
but
Rz_tzt=[b''(z)+[b'(z)]2]e2b(z)

Did you also get the same result?

5. May 28, 2012

### Mentz114

I get

Rztzt = -[b''(z)+[b'(z)]2]e2b(z)

Last edited: May 28, 2012
6. May 28, 2012

### chinared

Thank you, I will check my result again