8,520 research outputs found
Don't Panic! Closed String Tachyons in ALE Spacetimes
We consider closed string tachyons localized at the fixed points of
noncompact nonsupersymmetric orbifolds. We argue that tachyon condensation
drives these orbifolds to flat space or supersymmetric ALE spaces. The decay
proceeds via an expanding shell of dilaton gradients and curvature which
interpolates between two regions of distinct angular geometry. The string
coupling remains weak throughout. For small tachyon VEVs, evidence comes from
quiver theories on D-branes probes, in which deformations by twisted couplings
smoothly connect non-supersymmetric orbifolds to supersymmetric orbifolds of
reduced order. For large tachyon VEVs, evidence comes from worldsheet RG flow
and spacetime gravity. For \IC^2/\IZ_n, we exhibit infinite sequences of
transitions producing SUSY ALE spaces via twisted closed string condensation
from non-supersymmetric ALE spaces. In a -dual description this provides a
mechanism for creating NS5-branes via {\it closed} string tachyon condensation
similar to the creation of D-branes via {\it open} string tachyon condensation.
We also apply our results to recent duality conjectures involving fluxbranes
and the type 0 string.Comment: 48 pages, harvmac big; 13 figures. v2: added references; comment on
gravity regime added to section 5.2. v3: added reference
Tension is Dimension
We propose a simple universal formula for the tension of a D-brane in terms
of a regularized dimension of the associated conformal field theory statespace.Comment: 18 pages, harvmac (b), one ref added, one typo fixe
Matrix Description of Interacting Theories in Six Dimensions
We propose descriptions of interacting (2,0) supersymmetric theories without
gravity in six dimensions in the infinite momentum frame. They are based on the
large limit of quantum mechanics or 1+1 dimensional field theories on the
moduli space of instantons in \IR^4.Comment: 10 pages, harvmac bi
Monodromy in the CMB: Gravity Waves and String Inflation
We present a simple mechanism for obtaining large-field inflation, and hence
a gravitational wave signature, from string theory compactified on twisted
tori. For Nil manifolds, we obtain a leading inflationary potential
proportional to phi^(2/3) in terms of the canonically normalized field phi,
yielding predictions for the tilt of the power spectrum and the
tensor-to-scalar ratio, and with 60
e-foldings of inflation; we note also the possibility of a variant with a
candidate inflaton potential proportional to phi^(2/5). The basic mechanism
involved in extending the field range -- monodromy in D-branes as they move in
circles on the manifold -- arises in a more general class of compactifications,
though our methods for controlling the corrections to the slow-roll parameters
require additional symmetries.Comment: 43 pages, latex. 4 figure
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