Salvio, AlbertoShaposhnikov, Mikhail2010-09-072010-09-072010-09-07200710.1088/1126-6708/2007/11/0372-s2.0-36849035026https://infoscience.epfl.ch/handle/20.500.14299/53006An intriguing feature of the Standard Model is that the representations of the unbroken gauge symmetries are vector-like whereas those of the spontaneously broken gauge symmetries are chiral. Here we provide a toy model which shows that a natural explanation of this property could emerge in higher dimensional field theories and discuss the difficulties that arise in the attempt to construct a realistic theory. An interesting aspect of this type of models is that the 4D low energy effective theory is not generically gauge invariant. However, the non-invariant contributions to the observable quantities are very small, of the order of the square of the ratio between the light particle mass scale and the Kaluza-Klein mass scale. Remarkably, when we take the unbroken limit both the chiral asymmetry and the non-invariant terms disappear. © SISSA 2007.field theories in higher dimensionsspontaneous symmetry breakinggauge symmetrySpace-Time DimensionsKaluza-Klein TheoriesExtra DimensionsInternal SpacesBrane WorldsDomain-WallsFermionsCompactificationReductionAnomaliestext::journal::journal article::research article