1,459 research outputs found
Decompactifications and Massless D-Branes in Hybrid Models
A method of determining the mass spectrum of BPS D-branes in any phase limit
of a gauged linear sigma model is introduced. A ring associated to monodromy is
defined and one considers K-theory to be a module over this ring. A simple but
interesting class of hybrid models with Landau-Ginzburg fibres over CPn are
analyzed using special Kaehler geometry and D-brane probes. In some cases the
hybrid limit is an infinite distance in moduli space and corresponds to a
decompactification. In other cases the hybrid limit is at a finite distance and
acquires massless D-branes. An example studied appears to correspond to a novel
theory of supergravity with an SU(2) gauge symmetry where the gauge and
gravitational couplings are necessarily tied to each other.Comment: PDF-LaTeX, 34 pages, 2 mps figure
String-String triality for d=4, Z_2 orbifolds
We investigate the perturbative and non-perturbative correspondence of a
class of four dimensional dual string constructions with N=4 and N=2
supersymmetry, obtained as Z_2 or Z_2 x Z_2 orbifolds of the type II, heterotic
and type I string. In particular, we discuss the heterotic and type I dual of
all the symmetric Z_2 x Z_2 orbifolds of the type II string, classified in
hep-th/9901123. .Comment: latex, 50 pages, figures, final published versio
The Landau-Ginzburg to Calabi-Yau Dictionary for D-Branes
Based on work by Orlov, we give a precise recipe for mapping between B-type
D-branes in a Landau-Ginzburg orbifold model (or Gepner model) and the
corresponding large-radius Calabi-Yau manifold. The D-branes in Landau-Ginzburg
theories correspond to matrix factorizations and the D-branes on the Calabi-Yau
manifolds are objects in the derived category. We give several examples
including branes on quotient singularities associated to weighted projective
spaces. We are able to confirm several conjectures and statements in the
literature.Comment: 24 pages, refs added + minor correctio
Moduli Spaces for D-branes at the Tip of a Cone
For physicists: We show that the quiver gauge theory derived from a
Calabi-Yau cone via an exceptional collection of line bundles on the base has
the original cone as a component of its classical moduli space. For
mathematicians: We use data from the derived category of sheaves on a Fano
surface to construct a quiver, and show that its moduli space of
representations has a component which is isomorphic to the anticanonical cone
over the surface.Comment: 8 page
N=1 String Duality
We discuss duality between Type IIA string theory, eleven-dimensional
supergravity, and heterotic string theory in four spacetime dimensions with
supersymmetry. We find theories whose infrared limit is trivial at
enhanced symmetry points as well as theories with supersymmetry but the
field content of theories which flow to the fixed line in the
infrared.Comment: 14 pages, harvma
Solitons in Seiberg-Witten Theory and D-branes in the Derived Category
We analyze the "geometric engineering" limit of a type II string on a
suitable Calabi-Yau threefold to obtain an N=2 pure SU(2) gauge theory. The
derived category picture together with Pi-stability of B-branes beautifully
reproduces the known spectrum of BPS solitons in this case in a very explicit
way. Much of the analysis is particularly easy since it can be reduced to
questions about the derived category of CP1.Comment: 20 pages, LaTex2
Strings, Junctions and Stability
Identification of string junction states of pure SU(2) Seiberg-Witten theory
as B-branes wrapped on a Calabi-Yau manifold in the geometric engineering limit
is discussed. The wrapped branes are known to correspond to objects in the
bounded derived category of coherent sheaves on the projective line \cp{1} in
this limit. We identify the pronged strings with triangles in the underlying
triangulated category using Pi-stability. The spiral strings in the weak
coupling region are interpreted as certain projective resolutions of the
invertible sheaves. We discuss transitions between the spiral strings and
junctions using the grade introduced for Pi-stability through the central
charges of the corresponding objects.Comment: 15 pages, LaTeX; references added. typos correcte
Quivers from Matrix Factorizations
We discuss how matrix factorizations offer a practical method of computing
the quiver and associated superpotential for a hypersurface singularity. This
method also yields explicit geometrical interpretations of D-branes (i.e.,
quiver representations) on a resolution given in terms of Grassmannians. As an
example we analyze some non-toric singularities which are resolved by a single
CP1 but have "length" greater than one. These examples have a much richer
structure than conifolds. A picture is proposed that relates matrix
factorizations in Landau-Ginzburg theories to the way that matrix
factorizations are used in this paper to perform noncommutative resolutions.Comment: 33 pages, (minor changes
Enhanced gauge symmetries on elliptic K3
We show that the geometry of K3 surfaces with singularities of type A-D-E
contains enough information to reconstruct a copy of the Lie algebra associated
to the given Dynkin diagram. We apply this construction to explain the
enhancement of symmetry in F and IIA theories compactified on singular K3's.Comment: 9 pages, Late
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