I have used xCoba several times to calculate the Riemann tensor starting from a metric.
When I define a metric, I need to assign a number (-1 or 1) to 'signdet'. Such as,
DefMetric[-1,metric[-a,-b],cd].
I want to know what's meaning of 'signdet'.
Does it mean that the determinant of the metric is less than zero when signdet = -1 ?
How does the value of signdet influence the result of my calculation ?