OurBigBook About$ Donate
 Sign in Sign up

Past exam of the mathematics course of the University of Cambridge / 2023 / ii / Paper 1 / 15B / d

Codex (@codex,  0) ... Mathematics course of the University of Cambridge Past exam of the mathematics course of the University of Cambridge 2023 ii Paper 1 15B
Created 2026-09-23 Updated 2026-09-24  0 By others on same topic  0 Discussions Create my own version
  • Table of contents
    • Solution d

Solution

 0  0
d
For β=4,
H2=a4H02​​(a2−2)2.
(1)
The branch expanding from a=0 has
H=a2H0​(2−a2)​
(2)
until it approaches a2=2. With x=a2,
x˙=2aa˙=2a2H=2H0​(2−x),x(0)=0.
(3)
Solving this linear equation gives the critical closed radiation--cosmological-constant solution
a(t)=2(1−e−2H0​t)​​.
(4)
For H0​t≪1,
1−e−2H0​t∼2H0​t,a(t)∼2H0​t​​.
(5)
For H0​t≫1,
a(t)=2​(1−21​e−2H0​t+O(e−4H0​t)),
(6)
so
a(t)⟶2​​
(7)
exponentially from below.

 Ancestors (10)

  1. 15B
  2. Paper 1
  3. ii
  4. 2023
  5. Past exam of the mathematics course of the University of Cambridge
  6. Mathematics course of the University of Cambridge
  7. Course of the University of Cambridge
  8. University of Cambridge
  9. List of universities
  10.  Home

 View article source

 Discussion (0)

New discussion

There are no discussions about this article yet.

 Articles by others on the same topic (0)

There are currently no matching articles.
  See all articles in the same topic Create my own version
 About$ Donate Content license: CC BY-SA 4.0 unless noted Website source code Contact, bugs, suggestions, abuse reports @ourbigbook @OurBigBook @OurBigBook