Large extra dimension

Encyclopedia

In particle physics

, models with

by assuming that all fields propagate universally in the extra dimensions; in contrast, the ADD model requires that the fields of the Standard Model

are confined to a four-dimensional membrane, while only gravity propagates in the extra dimensions.

The universal extra dimensions are assumed to be compactified with radii much larger than the traditional Planck length, although smaller than in the ADD model, ~10

The strictest experimental lower bounds on the inverse size of one or two universal extra dimensions comes from electroweak precision measurements at the Z pole, the muon's magnetic moment, and limits on flavor changing neutral currents. The most conservative lower limit on the compactification scale of a single extra dimension is several hundred GeV. Using universal extra dimensions to explain dark matter yields an upper limit on the compactification scale of several TeV.

Particle physics

Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...

, models with

**universal extra dimensions**propose that there are one or more additional dimensions beyond the three spatial dimensions and one temporal dimension that are observed. These models differ from the ADD modelLarge extra dimension

In particle physics, models with universal extra dimensions propose that there are one or more additional dimensions beyond the three spatial dimensions and one temporal dimension that are observed...

by assuming that all fields propagate universally in the extra dimensions; in contrast, the ADD model requires that the fields of the Standard Model

Standard Model

The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the current formulation was finalized in the mid 1970s upon...

are confined to a four-dimensional membrane, while only gravity propagates in the extra dimensions.

The universal extra dimensions are assumed to be compactified with radii much larger than the traditional Planck length, although smaller than in the ADD model, ~10

^{−18}m, and a few claim that experimental bounds on their size are loose. Generically, the - so far unobserved - Kaluza-Klein resonances of the Standard Model fields in such a theory would appear at an energy scale that is directly related to the inverse size of the extra dimension,The strictest experimental lower bounds on the inverse size of one or two universal extra dimensions comes from electroweak precision measurements at the Z pole, the muon's magnetic moment, and limits on flavor changing neutral currents. The most conservative lower limit on the compactification scale of a single extra dimension is several hundred GeV. Using universal extra dimensions to explain dark matter yields an upper limit on the compactification scale of several TeV.

## See also

- Large extra dimensionLarge extra dimensionIn particle physics, models with universal extra dimensions propose that there are one or more additional dimensions beyond the three spatial dimensions and one temporal dimension that are observed...

s - Kaluza-Klein theory
- Randall-Sundrum modelRandall-Sundrum modelIn physics, Randall–Sundrum models imagine that the real world is a higher-dimensional Universe described by warped geometry...
- DGP modelDGP modelThe DGP model is a model of gravity proposed by Gia Dvali, Gregory Gabadadze, and Massimo Porrati in 2000. The model is popular among some model builders, but has resisted being embedded into string theory....