The universe is an anti de-sitter space within an all but equal and opposite de sitter space.
The zero point energy density of the vacuum is masked by the zero point curvature of space-time.
The universe has three uniform dimensions of space and a minimally non-uniform dimension of time.
Taking

as the co-ordinate of the fourth dimension and

as a measure of pure time then, in natural units,

is defined by

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Derivatives of u and t
from

it follows that

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Change Of Co-ordinates
The general formula for a change of co-ordinate of a tensor
Ft is

since
t is only dependant on
u, and is fully dependant on
u, this simplifies to

likewise for

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Einstein's field equations
Einstein's field equations may be written

alternatively, using zero point values we get

Subtracting the second equation from the first we get

Thus ahowing the cosmological constant to be the difference of the two zero point values.
If we assume that the curvature components are in the fourth dimension and that the energy components are in proper time then
incorporating the cosmological constant
and adding together
So the vacuum solution is
Assuming the cosmological constant to be negligable, we derive the Friedman equation for the vacuum.

for an intrinsic curvature of zero
Assuming that in fundamental units
So there we have it. Inflation, slow roll, with a graceful exit, straight from the vacuum; providing that
in natural units is more than three.
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What is the value of
in natural units?
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Time Has A Begining, The Fourth Dimension Does Not.
The universe has three uniform dimensions of space and a minimally non-uniform dimension of time.
Taking

as the co-ordinate of the fourth dimension and

as a measure of cosmological time i.e. proper time for all things cosmological, then in natural units,

is defined by

If we look at the universe with all the dimensions of space "edge-on"
then we will simply see a line representing the fourth dimension.
Here we see a line representing the fourth dimension with all the dimensions of space seen "edge on".
The line is continuous, it does not have a beggining or an end.
The graph shows the relationship between the fourth dimension and pure time.
Time does have a beggining.
At the south pole every direction is north.
At u=0 every direction is forwards in time.
When space and time are added together the square of the result is
equal to the difference of the squares of the parts. If there is more
time added than space then the result is time. If there is more space
added than time then the result is space. If the amount of time is equal
to the amount of space then the result is Null, neither time nor space.
Note 1 second is equivalent to 299 792 458 metres. The fourth dimension
is a dimension of time at all points except u=0, where it is Null, and
proper time changes direction.
A universe in two halves. Not the big bounce.