11,609 research outputs found
Fundamental strings and NS5-branes from unstable D-branes in supergravity
By using the non-supersymmetric -brane solutions delocalized in arbitrary
number of transverse directions in type II supergravities, we show how they can
be regarded as interpolating solutions between unstable D-branes (a non-BPS
D-brane or a pair of coincident D-brane-antiD-brane) and fundamental strings
and also between unstable D-branes and NS5-branes. We also show that some of
these solutions can be regarded as interpolating solutions between
NS5/5 and D-branes (for ). This gives a closed
string description of the tachyon condensation and lends support to the
conjecture that the open string theory on unstable D-branes at the tachyonic
vacuum has soliton solutions describing not only the lower dimensional BPS
D-branes, but also the fundamental strings as well as the NS5-branes.Comment: 11 pages, LaTeX, one statement corrected and one reference added, v3:
more details of the solution used is given, version to appear in Phys. Lett.
Non-SUSY -branes delocalized in two directions, tachyon condensation and T-duality
We here generalize our previous construction [hep-th/0409019] of
non-supersymmetric -branes delocalized in one transverse spatial direction
to two transverse spatial directions in supergravities in arbitrary dimensions
(). These solutions are characterized by five parameters. We show how these
solutions in interpolate between D()-anti-D() brane system,
non-BPS D-branes (delocalized in one direction) and BPS D-branes by
adjusting and scaling the parameters in suitable ways. This picture is very
similar to the descent relations obtained by Sen in the open string effective
description of non-BPS D brane and BPS D-brane as the respective
tachyonic kink and vortex solutions on the D-anti-D brane system
(with some differences). We compare this process with the T-duality
transformation which also has the effect of increasing (or decreasing) the
dimensionality of the branes by one.Comment: 19 pages, late
Non-SUSY -branes, bubbles and tubular branes
We consider non-supersymmetric -brane solutions of type II string theories
characterized by three parameters. When the charge parameter vanishes and one
of the other two takes a specific value, the corresponding chargeless solutions
can be regular and describe ``bubbles'' in static (unstable) equilibrium when
lifted to . In appropriate coordinates, they represent D6 branes with a
tubular topology R S when reduced to , called
the tubular D6 branes, held in static equilibrium by a fixed magnetic flux
(fluxbrane). Moreover, a `rotation parameter' can be introduced to either of
the above two eleven dimensional configurations, giving rise to a generalized
configuration labelling by the parameter. As such, it brings out the relations
among non-supersymmetric -branes, bubbles and tubular D6 branes. Given our
understanding on tubular D6 branes, we are able to reinforce the interpretation
of the chargeless non-supersymmetric -branes as representing
-brane-anti-brane (or non-BPS -brane) systems, and understand the
static nature and various singularities of these systems in a classical
supergravity approximation.Comment: 18 pages, footnote 7 removed due to some erro
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