11-Dimensional Chirality?

[m_brain]

I just read a book by Davies and Brown entitled
"_Superstrings:_A_Theory_of_Everything_?"

They dismiss 11D theory as having a fatal flaw: -"A distinctive element
of the weak interaction is that it breaks left-right mirror symmetry.
This implies that elementary particles must be endowed with a definite
handedness, or 'chirality'...It turns out that definite chirality only
exists in spaces with an odd number of dimensions. This means that
space must have an odd number of dimensions, and hence spacetime must
have an even number of dimensions, otherwise there would be no
chirality in the laws of nature. In short, eleven spacetime dimensions
won't work."-

Any thoughts?

[Moderator's note: While it's true that M-theory on smooth spaces gives
left-right symmetric physics, M-theory compactified on singular spaces
generically leads to asymmetric, chiral theories. This is why M-theory
on singular G_2 manifolds offers realistic backgrounds that may match
reality. Another way how chiral, asymmetric theories can occur from
M-theory is in the context of M-theory on two-torus which is not a
9-dimensional symmetric theory but a 10-dimensional asymmetric one. LM]

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[Crosson]

There are better reasons for why 11 dimensional spacetime is rediculous.

[Moderator's note: The word should be spelled "ridiculous". But strictly
speaking, it is not impossible that someone learns how to judge ideas
about quantum gravity before he learns how to write. LM]

Sure Einstein overthrew classical space and time single handedly, but
he was guided by evidence and physical principles.

Remember that scientific theories are not "correct", they only serve to
organize our observations (according to organizational principles.)
Therefore, its not that the universe has 11 dimensions, its that the
best way to explain the universe is using 11 dimensions. And to me, 11
dimensions is not a very good way to explain anything (begs more
questions than it resolves).


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[m_brain]

What are some of the better reasons?

Crosson Wrote:

> There are better reasons for why 11 dimensional spacetime is rediculous.
>
>
> Sure Einstein overthrew classical space and time single handedly, but
> he was guided by evidence and physical principles.
>
> Remember that scientific theories are not "correct", they only serve to
> organize our observations (according to organizational principles.)
> Therefore, its not that the universe has 11 dimensions, its that the
> best way to explain the universe is using 11 dimensions. And to me, 11
> dimensions is not a very good way to explain anything (begs more
> questions than it resolves).


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