
Concept explainers
(a)
To analyze: The slowing down of the expansion of the universe in the absence of a cosmological constant. The expansion of the universe can be expressed in terms of the deceleration parameter, given by
(a)

Explanation of Solution
Given data:
The expansion of the universe can be expressed in terms of the deceleration parameter. It is denoted by
Formula used:
The given formula is written as,
Here,
Explanation:
If the dark density is zero, then there is no cosmological constant,
Recall the given formula.
Substitute 0 for
Conclusion:
Therefore, the expansion of the universe has slowed down because
(b)
The present day universe has a deceleration parameter which can be evaluated using the value of
(b)

Answer to Problem 52Q
Solution:
Explanation of Solution
Given data:
Use table 25-2 to get,
Formula used:
The provided relation can be written as:
Here,
Explanation:
Recall the provided relation.
Substitute 0.76 for
Conclusion:
Therefore, the expansion of the universe is speeding up because
(c)
The value of
(c)

Answer to Problem 52Q
Solution:
0.12, matter dominant.
Explanation of Solution
Given data:
The universe is expanding at a constant rate.
Formula used:
The provided relation can be written as:
Here,
Explanation:
The expansion of the universe is happening at a constant rate. So, the value of
Recall the provided relation.
Rearrange as,
Substitute 0 for
Conclusion:
Therefore, the dark density parameter is small. So, the universe is matter dominant.
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Chapter 25 Solutions
Universe
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