  There is great interest in the construction of brane worlds, where matter and
gravity are forced to be effective only in a lower dimensional surface , the
brane . How these could appear as a consequence of string theory is a crucial
question and this has been widely discussed. Here we will examine a distinct
scenario that appears in dynamical tension theories and where string tension is
positive between two surfaces separated by a short distance and at the two
surfaces themselves the string tensions become infinite, therefore producing an
effective confinement of the strings and therefore of all matter and gravity to
the space between these to surfaces, which is in fact a new type of stringy
brane world scenario. The basic formulation for obtaining this scenario consist
of assuming two types of strings characterized by a different constant of
integration related to the spontaneous string tension generation. These string
tension multiplied by the embedding metric define conformally related metrics
that both satisfy Einsteins equation. The braneworlds appear very naturally
when these two metrics are both flat spaces related by a special conformal
transformation. The two types of string tensions are determined and they blow
up at two close expanding surfaces. A puzzling aspect appears then: the
construction is based on flat spaces, but then there are also strings with very
large tension near the boundaries of the braneworld,so can the back reaction
from the infinite tension strings destroy the flat space background?.
Fortunatelly that can be resolved using the mechanism Universe creation from
almost flat (or empty) spaces, which incorporates a gas of very large string
tensions in a membrane, studied before in 1+1 membranes in a 2+1 embedding
space and now is generalized for a 1+(D-2) membrane moving in a 1+(D-1) space.
