- #1

m_brain

## Main Question or Discussion Point

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]

--

m_brain

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"_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]

--

m_brain

------------------------------------------------------------------------

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View this thread: https://www.physicsforums.com/showthread.php?t=66834

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