43 research outputs found
Type IIA D-Branes, K-Theory, and Matrix Theory
We show that all supersymmetric Type IIA D-branes can be constructed as bound
states of a certain number of unstable non-supersymmetric Type IIA D9-branes.
This string-theoretical construction demonstrates that D-brane charges in Type
IIA theory on spacetime manifold are classified by the higher K-theory
group , as suggested recently by Witten. In particular, the system
of D0-branes can be obtained, for any , in terms of sixteen Type IIA
D9-branes. This suggests that the dynamics of Matrix theory is contained in the
physics of magnetic vortices on the worldvolume of sixteen unstable D9-branes,
described at low energies by a U(16) gauge theory.Comment: 32 pages (published version
On QCD String Theory and AdS Dynamics
The AdS/CFT correspondence of elementary string theory has been recently
suggested as a ``microscopic'' approach to QCD string theory in various
dimensions. We use the microscopic theory to show that the ultraviolet regime
on the string world-sheet is mapped to the ultraviolet effects in QCD. In the
case of QCD_2, a world-sheet path integral representation of QCD strings is
known, in terms of a topological rigid string theory whose world-sheet
supersymmetry is reminiscent of Parisi-Sourlas supersymmetry. We conjecture
that the supersymmetric rigid string theory is dual to the elementary Type IIB
string theory in the singular AdS background that corresponds to the large-N
limit of QCD_2. We also generalize the rigid string with world-sheet
Parisi-Sourlas supersymmetry to dimensions greater than two, and argue that the
theory is asymptotically free, a non-zero string tension is generated
dynamically through dimensional transmutation, and the theory is topological
only asymptotically in the ultraviolet.Comment: 29pp. v2: typos corrected, final version to appear in JHE
Probable Values of the Cosmological Constant in a Holographic Theory
We point out that for a large class of universes, holography implies that the
most probable value of the cosmological constant is zero. In four spacetime
dimensions, the probability distribution takes the Baum-Hawking form,
.Comment: 8 pages, harvmac (b
Emergent Gravity at a Lifshitz Point from a Bose Liquid on the Lattice
We propose a model with quantum bosons on the fcc lattice, which has a stable
algebraic Bose liquid phase at low energy. We show that this phase is described
by emergent quantum gravity at the Gaussian z = 3 Lifshitz fixed point in 3+1
dimensions. The stability of this algebraic Bose liquid phase is guaranteed by
the gauge symmetry of gravitons and self-duality of the low energy field
theory. By tuning one parameter in the lattice boson model we can drive a phase
transition between the z = 3 Lifshitz gravity and another algebraic Bose liquid
phase, described by gravity at the z = 2 Lifshitz point.Comment: 8 pages, 1 figur
Closed-String Tachyon Condensation and the Worldsheet Super-Higgs Effect
Alternative gauge choices for worldsheet supersymmetry can elucidate
dynamical phenomena obscured in the usual superconformal gauge. In the
particular example of the tachyonic heterotic string, we use a judicious
gauge choice to show that the process of closed-string tachyon condensation can
be understood in terms of a worldsheet super-Higgs effect. The worldsheet
gravitino assimilates the goldstino and becomes a dynamical propagating field.
Conformal, but not superconformal, invariance is maintained throughout.Comment: 4 pages; v2: typos corrected, a reference added; v3: final version,
to appear in Phys. Rev. Lett. (abstract and intro modified for a broader
audience
Topology Changing Transitions in Bubbling Geometries
Topological transitions in bubbling half-BPS Type IIB geometries with SO(4) x
SO(4) symmetry can be decomposed into a sequence of n elementary transitions.
The half-BPS solution that describes the elementary transition is seeded by a
phase space distribution of fermions filling two diagonal quadrants. We study
the geometry of this solution in some detail. We show that this solution can be
interpreted as a time dependent geometry, interpolating between two asymptotic
pp-waves in the far past and the far future. The singular solution at the
transition can be resolved in two different ways, related by the particle-hole
duality in the effective fermion description. Some universal features of the
topology change are governed by two-dimensional Type 0B string theory, whose
double scaling limit corresponds to the Penrose limit of AdS_5 x S^5 at
topological transition. In addition, we present the full class of geometries
describing the vicinity of the most general localized classical singularity
that can occur in this class of half-BPS bubbling geometries.Comment: 24 pages, 8 figure