1,013 research outputs found
Massless D-Branes on Calabi-Yau Threefolds and Monodromy
We analyze the link between the occurrence of massless B-type D-branes for
specific values of moduli and monodromy around such points in the moduli space.
This allows us to propose a classification of all massless B-type D-branes at
any point in the moduli space of Calabi-Yau's. This classification then
justifies a previous conjecture due to Horja for the general form of monodromy.
Our analysis is based on using monodromies around points in moduli space where
a single D-brane becomes massless to generate monodromies around points where
an infinite number become massless. We discuss the various possibilities within
the classification.Comment: 29 pages, LaTeX2e, 3 figures, author order fixe
The Breakdown of Topology at Small Scales
We discuss how a topology (the Zariski topology) on a space can appear to
break down at small distances due to D-brane decay. The mechanism proposed
coincides perfectly with the phase picture of Calabi-Yau moduli spaces. The
topology breaks down as one approaches non-geometric phases. This picture is
not without its limitations, which are also discussed.Comment: 12 pages, 2 figure
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
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
C^2/Z_n Fractional branes and Monodromy
We construct geometric representatives for the C^2/Z_n fractional branes in
terms of branes wrapping certain exceptional cycles of the resolution. In the
process we use large radius and conifold-type monodromies, and also check some
of the orbifold quantum symmetries. We find the explicit Seiberg-duality which
connects our fractional branes to the ones given by the McKay correspondence.
We also comment on the Harvey-Moore BPS algebras.Comment: 34 pages, v1 identical to v2, v3: typos fixed, discussion of
Harvey-Moore BPS algebras update
Type IIB Flux Vacua from M-theory via F-theory
We study in detail some aspects of duality between type IIB and M-theory. We
focus on the duality between type IIB string theory on K3 x T^2/Z_2 orientifold
and M-theory on K3 x K3, in the F-theory limit. We give the explicit map
between the fields and in particular between the moduli of compactification,
studying their behavior under the F-theory limit. Turning on fluxes generates a
potential for the moduli both in type IIB and in M-theory. We verify that the
type IIB analysis gives the same results of the F-theory analysis. In
particular, we check that the two potentials match.Comment: 24 pages; reference correcte
Recommended from our members
Natural convection heat transfer effects with micro finned structures
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Micro-scale natural convection plays an important role in heat removal from microelectronic components and Micro-Electro-Mechanical Systems (MEMS) devices. Natural convection of macrofin arrays has been extensively studied by many researchers over the past several decades; however analysis of free convection around microfin arrays is less well researched. The objective of this work was to experimentally investigate the effects of micro fin height and spacing for a horizontally mounted heat sink on heat transfer coefficient when operating under steady state natural convection conditions. An array of micro finned copper heat sinks was fabricated using micro-electro discharge wire machining (μ-EDWM) with fin height ranging from 0.25 to 1.0mm and fin spacing from 0.5 to 1.0mm respectively. Results showed that values of the convective heat transfer coefficient increased with increased fin spacing and decreased as fin height increased.This study is funded by Advantage West Midlands (AWM)
Quantum symmetries and exceptional collections
We study the interplay between discrete quantum symmetries at certain points
in the moduli space of Calabi-Yau compactifications, and the associated
identities that the geometric realization of D-brane monodromies must satisfy.
We show that in a wide class of examples, both local and compact, the monodromy
identities in question always follow from a single mathematical statement. One
of the simplest examples is the Z_5 symmetry at the Gepner point of the
quintic, and the associated D-brane monodromy identity
Generalized Calabi-Yau Manifolds and the Mirror of a Rigid Manifold
We describe the mirror of the Z orbifold as a representation of a class of
generalized Calabi-Yau manifolds that can be realized as manifolds of dimension
five and seven. Despite their dimension these correspond to superconformal
theories with and so are perfectly good for compactifying the heterotic
string to the four dimensions of space-time. As a check of mirror symmetry we
compute the structure of the space of complex structures of the mirror and
check that this reproduces the known results for the Yukawa couplings and
metric appropriate to the Kahler class parameters on the Z orbifold together
with their instanton corrections.Comment: 39 pages, plain Te
Flavour from partially resolved singularities
In this letter we study topological open string field theory on D--branes in
a IIB background given by non compact CY geometries on with a singular point at which an extra fiber sits. We wrap
D5-branes on and effective D3-branes at singular points, which
are actually D5--branes wrapped on a shrinking cycle. We calculate the
holomorphic Chern-Simons partition function for the above models in a deformed
complex structure and find that it reduces to multi--matrix models with
flavour. These are the matrix models whose resolvents have been shown to
satisfy the generalized Konishi anomaly equations with flavour. In the
case, corresponding to a partial resolution of the singularity, the
quantum superpotential in the unitary SYM with one adjoint and
fundamentals is obtained. The case is also studied and shown to give rise
to two--matrix models which for a particular set of couplings can be exactly
solved. We explicitly show how to solve such a class of models by a quantum
equation of motion technique
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