# String theory allows chiral gauge coupling

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In Polchinski String Vol 1:

Chiral gauge couplings. The gauge interactions in nature are parity asymmetric (chiral). This has been a stumbling block for a number of previous unifying ideas: they required parity symmetric gauge couplings. String theory allows chiral gauge couplings.

What are the approaches from String theory allowing chiral gauge couplings?

Can experts sketch and enumerate all of the different ideas?

This post imported from StackExchange Physics at 2020-12-07 19:34 (UTC), posted by SE-user annie marie heart
The gauge interactions in nature are parity asymmetric (chiral). Is there parity asymmetry in QCD?

This post imported from StackExchange Physics at 2020-12-07 19:34 (UTC), posted by SE-user G. Smith
>> parity asymmetry in QCD. Ans: No

This post imported from StackExchange Physics at 2020-12-07 19:34 (UTC), posted by SE-user annie marie heart
So I don’t understand this sweeping statement about “the gauge interactions in nature”, which seems plainly wrong. Why didn’t Polchinski write “some gauge interactions in nature”? Is there some context that you omitted?

This post imported from StackExchange Physics at 2020-12-07 19:34 (UTC), posted by SE-user G. Smith
He meant the whole gauge interaction violates P. I just copy paste

This post imported from StackExchange Physics at 2020-12-07 19:34 (UTC), posted by SE-user annie marie heart

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Is there a classification of all theories belonging to the string landscape with chiral gauge couplings? No, we are far from such a precise knowledge of the string theory landscape.

Nevertheless, a sample of representative approaches can be mentioned:

1) Heterotic string compactifications on Calabi-Yau: See Chiral four-dimensional heterotic strings from self-dual lattices.

2) Four-dimensional $$N=1$$ superconformal quiver gauge theories: See brane tillings and their applications. The simplest cases of this class of theories are dicussed in the case of local Calabi-Yau, however, they model the local behaviour of a wide class of semi-realistic theories.

3) Intersecting branes setups: See the excellent review https://arxiv.org/abs/hep-th/0502005.

4) F-theory compactifications: See the outstanding A Quadrillion Standard Models from F-theory.

5) Strings on orbifold geometries: See strings on orbifolds.

Just to mention a few.

This post imported from StackExchange Physics at 2020-12-07 19:34 (UTC), posted by SE-user Ramiro Hum-Sah
answered Oct 18, 2020 by (80 points)

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