### 5.2 Brane-world instanton

The creation of an inflating brane-world can be modelled as a de Sitter instanton in a way that closely
follows the 4D instanton, as shown in [154]. The instanton consists of two identical patches of AdS_{5} joined
together along a de Sitter brane (dS_{4}) with compact spatial sections. The instanton describes the
“birth” of both the inflating brane and the bulk spacetime, which are together “created from
nothing”, i.e., the point at the south pole of the de Sitter 4-sphere. The Euclidean AdS_{5} metric is
where is a 3-sphere, and . The Euclidean instanton interpolates between
(“nothing”) and (the created universe), which is a spherical brane of radius
After creation, the brane-world evolves according to the Lorentzian continuation, ,
(see Figure 7).