# No-boundary proposal

1. Sep 4, 2010

### MrQG

What are everyone's thoughts on the (Hawking's) no-boundary proposal of the universe? Thank you in advance.

2. Sep 5, 2010

### Dmitry67

As I understand, it is Wick's rotation of the whole Universe.
It makes sense to me.

3. Sep 8, 2010

### MrQG

And what about its use of imaginary time?

4. Sep 8, 2010

### Dmitry67

The funny thing is imaginary time is represented by real numbers while real time is represented by imaginary numbers.
Our world is 4D sphere with metric ++++, Wick rotation of one of the spacial dimensions (which one? I dont understand) makes it infinitely expanding and with metric +++-
So our 'real' time we observe is imaginary (because it has "i" multiplier, - metric). Our time is a reflection of what Hawking calls "imaginary" time, but mathematically that time is real one because it is a part of ++++ metric.

5. Sep 8, 2010

### MrQG

I've heard some people criticize the proposal claiming that the use of imaginary time is simply for mathematical convenience. What do you think? I appreciate your thoughts.

6. Sep 8, 2010

### Dmitry67

I dont think there is a difference between physics and mathematics.
Also, it explains for example why our metrics is +++-,
and why Schrodinger equation is Wick rotation of fundamental solution of heat equation.
so it explains why Wicks roation is not just mathematics trick but has deep and fundamental physical meaning.

7. Sep 9, 2010

### MrQG

So, would you say that Hawking is actually postulating that "imaginary" time is something real, as in, actually there? Is he saying that this proposal actually describes reality or is it merely a mathematical model meant to make accurate predictions? Does he somehow "refuse" to convert back "real" time? Thanks.

8. Sep 10, 2010

### Dmitry67

I dont know if Hawking accepts, implicitly or explictly, Max Tegmark's Mathematical Universe Hypotesis (MUH). But IMHO the way of thinking you need to come to the idea of No boundary proposal requires MUH. Based on MUH, your question

does not make any sense, because MUH postulates that mathematics does not describe the reality, it is reality

9. Sep 10, 2010

### MrQG

That's an interesting hypothesis. Does it have much support? However, it sounds more like a metaphysical theory than a scientific one.

10. Sep 10, 2010

### Dmitry67

The proof of MUH it simple: it predicts that one will be able to express TOE in a form of mathematical equations, without any "word baggage". You won't need words like "t stands for time" etc. Just pure formulas. So MUH is falsifiable.