61 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
New Dimensions for Wound Strings: The Modular Transformation of Geometry to Topology
We show, using a theorem of Milnor and Margulis, that string theory on
compact negatively curved spaces grows new effective dimensions as the space
shrinks, generalizing and contextualizing the results in hep-th/0510044.
Milnor's theorem relates negative sectional curvature on a compact Riemannian
manifold to exponential growth of its fundamental group, which translates in
string theory to a higher effective central charge arising from winding
strings. This exponential density of winding modes is related by modular
invariance to the infrared small perturbation spectrum. Using self-consistent
approximations valid at large radius, we analyze this correspondence explicitly
in a broad set of time-dependent solutions, finding precise agreement between
the effective central charge and the corresponding infrared small perturbation
spectrum. This indicates a basic relation between geometry, topology, and
dimensionality in string theory.Comment: 28 pages, harvmac big. v2: references and KITP preprint number added,
minor change
The Scaling of the No Scale Potential and de Sitter Model Building
We propose a variant of the KKLT (A)dS flux vacuum construction which does
not require an antibrane to source the volume modulus. The strategy is to find
nonzero local minima of the no-scale potential in the complex structure and
dilaton directions in moduli space. The corresponding no-scale potential
expanded about this point sources the volume modulus in the same way as does
the antibrane of the KKLT construction. We exhibit explicit examples of such
nonzero local minima of the no-scale potential in a simple toroidal orientifold
model.Comment: 11 pages, harvmac big. v2: trivial typos fixe
On the Matrix Description of Calabi-Yau Compactifications
We point out that the matrix description of M-theory compactified on
Calabi-Yau threefolds is in many respects simpler than the matrix description
of a compactification. This is largely because of the differences between
D6 branes wrapped on Calabi-Yau threefolds and D6 branes wrapped on six-tori.
In particular, if we define the matrix theory following the prescription of Sen
and Seiberg, we find that the remaining degrees of freedom are decoupled from
gravity.Comment: 12 pages, harvmac big; comment on 4d N=1 theories change
Adventures in Holographic Dimer Models
We abstract the essential features of holographic dimer models, and develop
several new applications of these models. First, semi-holographically coupling
free band fermions to holographic dimers, we uncover novel phase transitions
between conventional Fermi liquids and non-Fermi liquids, accompanied by a
change in the structure of the Fermi surface. Second, we make dimer vibrations
propagate through the whole crystal by way of double trace deformations,
obtaining nontrivial band structure. In a simple toy model, the topology of the
band structure experiences an interesting reorganization as we vary the
strength of the double trace deformations. Finally, we develop tools that would
allow one to build, in a bottom-up fashion, a holographic avatar of the Hubbard
model.Comment: 22 pages, 8 figures; v2: brief description of case of pure D5 lattice
added in sec.3; v3: minor typo fixed; v4: minor change
Moduli Stabilization from Fluxes in a Simple IIB Orientifold
We study novel type IIB compactifications on the T^6/Z_2 orientifold. This
geometry arises in the T-dual description of Type I theory on T^6, and one
normally introduces 16 space-filling D3-branes to cancel the RR tadpoles. Here,
we cancel the RR tadpoles either partially or fully by turning on three-form
flux in the compact geometry. The resulting (super)potential for moduli is
calculable. We demonstrate that one can find many examples of N=1
supersymmetric vacua with greatly reduced numbers of moduli in this system. A
few examples with N>1 supersymmetry or complete supersymmetry breaking are also
discussed.Comment: 49 pages, harvmac big; v2, corrected some typo
Orientifolds, RG Flows, and Closed String Tachyons
We discuss the fate of certain tachyonic closed string theories from two
perspectives. In both cases our approach involves studying directly
configurations with finite negative tree-level cosmological constant. Closed
string analogues of orientifolds, which carry negative tension, are argued to
represent the minima of the tachyon potential in some cases. In other cases, we
make use of the fact, noted in the early string theory literature, that strings
can propagate on spaces of subcritical dimension at the expense of introducing
a tree-level cosmological constant. The form of the tachyon vertex operator in
these cases makes it clear that a subcritical-dimension theory results from
tachyon condensation. Using results of Kutasov, we argue that in some
Scherk-Schwarz models, for finely-tuned tachyon condensates, a minimal model
CFT times a subcritical dimension theory results. In some instances, these two
sets of ideas may be related by duality.Comment: 15 pages, 2 figures, uses harvmac; v2: references adde
Brane/Flux Annihilation and the String Dual of a Non-Supersymmetric Field Theory
We consider the dynamics of p anti-D3 branes inside the Klebanov-Strassler
geometry, the deformed conifold with M units of RR 3-form flux around the S^3.
We find that for p<<M the system relaxes to a nonsupersymmetric NS 5-brane
``giant graviton'' configuration, which is classically stable, but quantum
mechanically can tunnel to a nearby supersymmetric vacuum with M-p D3 branes.
This decay mode is exponentially suppressed and proceeds via the nucleation of
an NS 5-brane bubble wall. We propose a dual field theory interpretation of the
decay as the transition between a nonsupersymmetric ``baryonic'' branch and a
supersymmetric ``mesonic'' branch of the corresponding SU(2M-p)x SU(M-p) low
energy gauge theory. The NS 5-brane tunneling process also provides a simple
explanation of the geometric transition by which D3-branes can dissolve into
3-form flux.Comment: 27 pages, 4 figures, typo correcte
Vacuum Energy Cancellation in a Non-supersymmetric String
We present a nonsupersymmetric orbifold of type II string theory and show
that it has vanishing cosmological constant at the one and two loop level. We
argue heuristically that the cancellation persists at higher loops.Comment: 31 pages harvmac big, 6 figures. New version includes the 2-loop
analysis of hep-th/9810129 and elimination of one of the two heuristic
arguments for higher loop cancellatio
AdS Bubbles, Entropy and Closed String Tachyons
We study the conjectured connection between AdS bubbles (AdS solitons) and
closed string tachyon condensations. We confirm that the entanglement entropy,
which measures the degree of freedom, decreases under the tachyon condensation.
The entropies in supergravity and free Yang-Mills agree with each other
remarkably. Next we consider the tachyon condensation on the AdS twisted circle
and argue that its endpoint is given by the twisted AdS bubble, defined by the
double Wick rotation of rotating black 3-brane solutions. We calculated the
Casimir energy and entropy and checked the agreements between the gauge and
gravity results. Finally we show an infinite boost of a null linear dilaton
theory with a tachyon wall (or bubble), leads to a solvable time-dependent
background with a bulk tachyon condensation. This is the simplest example of
spacetimes with null boundaries in string theory.Comment: 45 pages, 6 figures, harvmac, eq.(2.16) corrected, references adde
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