Extra Dimensions and the strong CP problem.

Area of Science:

• Theoretical Physics
• High-Energy Physics
• String Theory

Background:

• Higher dimensional theories, like brane world models, introduce complexities in vacuum structure.
• Non-Abelian gauge fields and their behavior at large distances are crucial for understanding fundamental forces.
• The strong CP problem in quantum chromodynamics (QCD) remains a significant unsolved issue.

Purpose of the Study:

• To investigate the vacuum structure of higher dimensional theories with quasilocalized non-Abelian gauge fields.
• To determine if the strong CP problem is resolved in these specific brane world models.
• To analyze the impact of higher dimensions and topology on CP-violating theta terms.

Main Methods:

• Analysis of vacuum structure in higher dimensional brane world models.
• Topological analysis of the 'infinity' in a (4+delta)-dimensional spacetime.
• Investigation of finite action instantonic and solitonic configurations.

Main Results:

• The vacuum structure in these models is found to be trivial.
• The topology of infinity is S(3+delta), which does not support finite action instantonic configurations.
• The CP-violating theta term vanishes on the brane world volume, and solitonic contributions are absent.

Conclusions:

• The strong CP problem is absent in brane world models with quasilocalized gluons.
• The higher dimensional nature and topology inherently prevent CP violation.
• These findings offer a potential resolution to the strong CP problem within specific theoretical frameworks.