4,836 research outputs found
Tachyon condensation in unstable type I D-brane systems
Type I string theory provides eight classes of unstable D-brane systems. We
determine the gauge group and tachyon spectrum for each one, and thereby
describe the gauge symmetry breaking pattern in the low-energy world-volume
field theory. The topologies of the resulting coset vacuum manifolds are
related to the real K-theory groups KO^{-n}, extending the known relations
between the Type II classifying spaces BU and U and the complex K-theory groups
K^0 and K^{-1}. We also comment on the role of the background D9-branes.Comment: 14 pages, LaTex; footnote regarding bosonic D-branes has been
corrected, references adde
Stable Non-BPS Dyons in N=2 SYM
As a novel application of string junctions, we provide evidence for the
existence of stable non-BPS dyons with magnetic charge greater than 1 in (the
semiclassical regime of) N=2 SU(2) Super-Yang-Mills theory. In addition, we
find a new curve of marginal stability. Moduli space is therefore divided into
four regions, each containing a different stable particle spectrum.Comment: 12 pages LaTex, 5 figures; Added comments in both section 3 and the
conclusions regarding the applicability of the string web picture in the
field theory limi
Aharonov-Bohm Scattering, Contact Interactions and Scale Invariance
We perform a perturbative analysis of the Aharonov-Bohm problem to one loop
in a field-theoretic formulation, and show that contact interactions are
necessary for renormalizability. In general, the classical scale invariance of
this problem is broken quantum mechanically. There exists however a critical
point for which this anomaly disappears.Comment: 9 pages, TEX, CTP#218
Stable non-BPS D-particles
It is shown that the orbifold of type IIB string theory by (-1)^{F_L} I_4
admits a stable non-BPS Dirichlet particle that is stuck on the orbifold fixed
plane. It is charged under the SO(2) gauge group coming from the twisted
sector, and transforms as a long multiplet of the D=6 supersymmetry algebra.
This suggests that it is the strong coupling dual of the perturbative stable
non-BPS state that appears in the orientifold of type IIB by \Omega I_4.Comment: 10 pages, LaTe
Dualities of Type 0 Strings
It is conjectured that the two closed bosonic string theories, Type 0A and
Type 0B, correspond to certain supersymmetry breaking orbifold
compactifications of M-theory. Various implications of this conjecture are
discussed, in particular the behaviour of the tachyon at strong coupling and
the existence of non-perturbative fermionic states in Type 0A. The latter are
shown to correspond to bound states of Type 0A D-particles, thus providing
further evidence for the conjecture. We also give a comprehensive description
of the various Type 0 closed and open string theories.Comment: 23 pages LaTex, 1 figure. Error corrected in table 1. Version to
appear in JHE
Non-BPS States in Heterotic - Type IIA Duality
The relation between some perturbative non-BPS states of the heterotic theory
on T^4 and non-perturbative non-BPS states of the orbifold limit of type IIA on
K3 is exhibited. The relevant states include a non-BPS D-string, and a non-BPS
bound state of BPS D-particles (`D-molecule'). The domains of stability of
these states in the two theories are determined and compared.Comment: 17 pages LaTex, 1 figure; Minor correction in subsection 4.
Easy on that trigger dad: a study of long term family photo retrieval
We examine the effects of new technologies for digital photography on people's longer term storage and access to collections of personal photos. We report an empirical study of parents' ability to retrieve photos related to salient family events from more than a year ago. Performance was relatively poor with people failing to find almost 40% of pictures. We analyze participants' organizational and access strategies to identify reasons for this poor performance. Possible reasons for retrieval failure include: storing too many pictures, rudimentary organization, use of multiple storage systems, failure to maintain collections and participants' false beliefs about their ability to access photos. We conclude by exploring the technical and theoretical implications of these findings
Supersymmetric Quantum Mechanics for String-Bits
We develop possible versions of supersymmetric single particle quantum
mechanics, with application to superstring-bit models in view. We focus
principally on space dimensions , the transverse dimensionalities of
superstring in space-time dimensions. These are the cases for which
``classical'' superstring makes sense, and also the values of for which
Hooke's force law is compatible with the simplest superparticle dynamics. The
basic question we address is: When is it possible to replace such harmonic
force laws with more general ones, including forces which vanish at large
distances? This is an important question because forces between string-bits
that do not fall off with distance will almost certainly destroy cluster
decomposition. We show that the answer is affirmative for , negative for
, and so far inconclusive for .Comment: 17 pages, Late
Orientifolds, RR Torsion, and K-theory
We analyze the role of RR fluxes in orientifold backgrounds from the point of
view of K-theory, and demonstrate some physical implications of describing
these fluxes in K-theory rather than cohomology. In particular, we show that
certain fractional shifts in RR charge quantization due to discrete RR fluxes
are naturally explained in K-theory. We also show that some orientifold
backgrounds, which are considered distinct in the cohomology classification,
become equivalent in the K-theory description, while others become unphysical.Comment: 30 pages, 5 figures; typos corrected and references adde
The Stringy Quantum Hall Fluid
Using branes in massive Type IIA string theory, and a novel decoupling limit,
we provide an explicit correspondence between non-commutative Chern-Simons
theory and the fractional quantum Hall fluid. The role of the electrons is
played by D-particles, the background magnetic field corresponds to a RR 2-form
flux, and the two-dimensional fluid is described by non-commutative D2-branes.
The filling fraction is given by the ratio of the number of D2-branes and the
number of D8-branes, and therefore by the ratio rank/level of the Chern-Simons
gauge theory. Quasiparticles and quasiholes are realized as endpoints of
fundamental strings on the D2-branes, and are found to possess fractional
D-particle charges and fractional statistics.Comment: 24 pages, 2 figures; references adde
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