Domain-wall brane models of an infinite extra dimension
Mar, 2009Citations per year
0 Citations
Abstract:
In this thesis we consider aspects related to the construction and phenomenology of domain-wall brane models of a single, infinite, extra spatial dimension. We discuss how gravity, gauge- and matter-fields become four-dimensional at low energies due to the dynamical formation of a topologicaldefect known as a brane. These ideas are amongst the leading candidates for extensions to the standard models of particle physics and cosmology.
We first examine a toy model where a pair of scalar fields, charged under a U(1)⊗U(1) gauge symmetry, form a background domain-wall configuration. This analysis demonstrates the general ideas of domain-wall formation
and stability, dimensional reduction and semi-confinement of gauge fields. Gravity is incorporated into this toy model, in the form of a regularised version of the Randall-Sundrum warped metric.
For the case of a single real scalar field, we show in detail how a domain wall can be obtained, and determine its relationship to the fundamental brane in the infinitely thin wall limit. Explicit expressions for the modes of such a domain wall are found, as well as the modes associate
d with coupled fermions and scalars. The symmetric modified P ̈oschl-Teller potential
arises in this context, and the analysis elucidates the reduction of a five-dimensional field to a tower of four-dimensional modes.
Adding gravity to the model alters the spectrum of four-dimensional
modes trapped to the wall. What were once discrete modes become resonances within a continuum, and low-energy modes are coupled to these continuum bulk modes. We show explicitly how this comes about, and use a toy model to demonstrate that this coupling can be made small enough to avoid experimental constraints.
The Dvali-Shifman mechanism for gauge field localisation is introduced, and we use it, along with the previously discussed techniques for constructing domain walls, to write down an SU(5) grand unified, single generation version of the standard model. Fermion mass relations and Higgs induced
proton decay are significantly improved from usual SU(5) models due to an inherent split fermion set-up. An extension of the gauge group to E6 is considered, naturally including the clash of symmetries mechanism, and it is shown that the field content can be simplified.
Cosmological implications of domain-wall branes are investigated, and we attempt to reproduce an effective four-dimensional Friedmann-Lemaˆıtre-Robertson-Walker metric for brane-localised matter. We find that for a domain wall of finite thickness it is not possible to define a common spacetime for all localised species of matter. As a consequence, different species experience a different effective four-dimensional scale factor, an unusual effect that is suppressed when the domain wall is made sufficiently thin.
We conclude that domain-wall brane models of an infinite extra dimension are viable extensions of the standard models of particle physics and cosmology. These models provide a rich set of phenomenology, and allow new ways to tackle existing theoretical problems.- domain wall: formation
- grand unified theory: SU(5)
- energy: low
- membrane model
- toy model
- gauge field theory: E(6)
- gravitation
- Randall-Sundrum model
- localization
- thesis
References(245)
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- [6]
- [7]
- [8]
- [9]
- [10]
- [11]
- [12]
- [13]
- [14]
- [15]
- [16]
- [17]
- [18]
- [19]
- [20]
- [21]
- [22]
- [23]
- [24]
- [25]