How Does the Singularity Behave as t Approaches 0 in the Kasner Solution?

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Homework Help Overview

The discussion revolves around the behavior of the singularity as time approaches zero in the context of the Kasner solution in general relativity. Participants explore the implications of the metric and the Einstein equations related to this solution.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the need to specify the form of the Kasner solution and the conditions on the exponents derived from Einstein's equations. There are attempts to understand the implications of substituting the metric into the equations and the behavior of the scale factors as time approaches zero. Questions arise regarding the positivity of the exponents and the nature of different Kasner solutions.

Discussion Status

The discussion is active, with participants providing insights into the relationships between the parameters of the Kasner solution and exploring various scenarios. Some guidance has been offered regarding the algebraic conditions that must be satisfied, and there is a recognition of the complexity of the behavior of the scale factors.

Contextual Notes

Participants note the constraints of the problem, including the requirement to describe the behavior of the singularity without deriving the Kasner solution itself. There is also mention of the potential errors in the source material being referenced.

  • #31
I'll work on this, though I've been studying for 12 hours now. ;) If that's all I need to know then thanks for your help.
 
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  • #32
Take a break and good luck with the rest.
 
  • #33
I think I will need some help with the rest aswell. ;) No MatLab installed here...
 
  • #34
Unless I can use p_1p_2+p_2p_3+p_3p_1=0 aswell?
 
  • #35
Sure you can. It's a consequence of the other two relations between the p's.
 
  • #36
I get

p_1 = -\frac{p_3}{2} \pm \frac{1}{2} \sqrt{-3p_3^2+2p_3+1} + \frac{1}{2}

and

p_2 = \frac{1}{2} \left(-p_3 \pm \sqrt{-3p_3^2+3p_3+1} + 1 \right)

but what does this tell me? They cannot have the same sign but then what?
 
  • #37
Logarythmic said:
Unless I can use p_1p_2+p_2p_3+p_3p_1=0 aswell?

You are working way too hard. What does this say about the possibility that all of the p's are positive or all are negative?
 
  • #38
They cannot all be positive nor negative, but one positive and two negative or two positive and one negative. Is that right?
 
  • #39
Almost. Except you can't have two negative p's either.
p_1+p_2+p_3=1. What would this tell you about p3 if p1 and p2 are negative?
 
  • #40
Then p_3 > 1?
 
  • #41
You're catching on. But the sum of the squares should be one too!
 
  • #42
There we are. So it's either [1,0,0] or [+,+,-] and the behavior is strange. ;)
 
  • #43
Yes. If you want to see an attempt to use this strange behavior look up Mixmaster cosmologies sometime.
 
  • #44
Can you briefly tell me something about it?
 
  • #45
Sorry, better get to work here. Besides, other people tell the story better than I.
 
  • #46
I'll look it up tomorrow, now I need some sleep. Thanks for all your help.
 

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