1,332 research outputs found
Stable non-BPS D-branes of type I
We review the boundary state description of the non-BPS D-branes in the type
I string theory and show that the only stable configurations are the D-particle
and the D-instanton. We also compute the gauge and gravitational interactions
of the non-BPS D-particles and compare them with the interactions of the dual
non-BPS particles of the heterotic string finding complete agreement. In this
way we provide further dynamical evidence of the heterotic/type I duality.Comment: 8 pages, 1 figure.eps, JHEP.cls, talk given by A. Lerda at the TMR
Conference "Quantum aspects of gauge theories, supersymmetry and
unification", Paris, September 199
Anyonic Realization of the Quantum Affine Lie Superalgebra U_q(A(M,N)^{(1)})
We give a realization of the quantum affine Lie superalgebras U_q(A(M,N))^(1)
in terms of anyons defined on a one or two-dimensional lattice, the deformation
parameter q being related to the statistical parameter of the anyons by q
= exp(i\pi\nu). The construction uses anyons contructed from usual fermionic
oscillators and deformed bosonic oscillators. As a byproduct, realization
deformed in any sector of the quantum superalgebras U_q(A(M,N)) is obtained.Comment: 14p LaTeX Document (should be run twice
Chemical Differentiation toward the Pipe Nebula Starless Cores
We used the new IRAM 30-m FTS backend to perform an unbiased ~15 GHz wide
survey at 3 mm toward the Pipe Nebula young diffuse starless cores. We found an
unexpectedly rich chemistry. We propose a new observational classification
based on the 3 mm molecular line emission normalized by the core visual
extinction (Av). Based on this classification, we report a clear
differentiation in terms of chemical composition and of line emission
properties, which served to define three molecular core groups. The "diffuse"
cores, Av<~15, show poor chemistry with mainly simple species (e.g. CS and
CCH). The "oxo-sulfurated" cores, Av~15--22, appear to be abundant in species
like SO and SO2, but also in HCO, which seem to disappear at higher densities.
Finally, the "deuterated" cores, Av>~22, show typical evolved chemistry prior
to the onset of the star formation process, with nitrogenated and deuterated
species, as well as carbon chain molecules. Based on these categories, one of
the "diffuse" cores (Core 47) has the spectral line properties of the
"oxo-sulfurated" ones, which suggests that it is a possible failed core.Comment: Accepted for publication in A&A. 5 pages, 2 figure
Anyonic Realization of the Quantum Affine Lie Algebra U_q(A_N)
We give a realization of quantum affine Lie algebra in
terms of anyons defined on a two-dimensional lattice, the deformation parameter
being related to the statistical parameter of the anyons by . In the limit of the deformation parameter going to one we recover
the Feingold-Frenkel fermionic construction of undeformed affine Lie algebra.Comment: 13p LaTeX Document (should be run twice
The Lorentz force between D0 and D6 branes in string and M(atrix) theory
We use different techniques to analyze the system formed by a D0 brane and a
D6 brane (with background gauge fields) in relative motion. In particular,
using the closed string formalism of boosted boundary states, we show the
presence of a term linear in the velocity, corresponding to the Lorentz force
experienced by the D0 brane moving in the magnetic background produced by the
D6 brane. This term, that was missed in previous analyses of this system, comes
entirely from the R-R odd spin structure and is also reproduced by a M(atrix)
theory calculation.Comment: 13 pages, plain LaTeX; some clarifying comments and a reference adde
Is a classical description of stable non-BPS D-branes possible?
We study the classical geometry produced by a stack of stable (i.e. tachyon
free) non-BPS D-branes present in K3 compactifications of type II string
theory. This classical representation is derived by solving the equations of
motion describing the low-energy dynamics of the supergravity fields which
couple to the non-BPS state. Differently from what expected, this configuration
displays a singular behaviour: the space-time geometry has a repulson-like
singularity. This fact suggests that the simplest setting, namely a set of
coinciding non-interacting D-branes, is not acceptable. We finally discuss the
possible existence of other acceptable configurations corresponding to more
complicated bound states of these non-BPS branes.Comment: Latex file: 41 pages, 5 figures; some minor corrections and
references adde
Stable non-BPS D-branes in Type I string theory
We use the boundary state formalism to study, from the closed string point of
view, superpositions of branes and anti-branes which are relevant in some
non-perturbative string dualities. Treating the tachyon instability of these
systems as proposed by A. Sen, we show how to incorporate the effects of the
tachyon condensation directly in the boundary state. In this way we manage to
show explicitly that the D1 -- anti-D1 pair of Type I is a stable non-BPS
D-particle, and compute its mass. We also generalize this construction to
describe other non-BPS D-branes of Type I. By requiring the absence of tachyons
in the open string spectrum, we find which configurations are stable and
compute their tensions. Our classification is in complete agreement with the
results recently obtained using the K-theory of space-time.Comment: 31 pages, plain LaTeX, final version to be published in Nucl. Phys.
Microscopic string analysis of the D0-D8 brane system and dual R-R states
Using the boundary state formalism, we perform a microscopic string analysis
of the interaction between two D-branes and provide a local interpretation for
the R-R force in the D0-D8 brane system. To do so, we construct BRST invariant
vertex operators for the massless R-R states in the asymmetric picture that are
proportional to potentials rather than field strengths. The Hilbert space of
such R-R states contains combinations of two vectors that decouple from all
physical amplitudes, even in the presence of boundaries. Identifying these
vectors, we remove the null states and recover duality relations among R-R
potentials. If we specify to the D0-D8 brane system, this mechanism implies
that the R-R 1-form state has a non-zero overlap with both the D0-brane and the
D8-brane, thus explaining from a local point of view the non-vanishing R-R
contribution in the interaction for the D0-D8 brane system and those related to
it by duality.Comment: 31 pages, final version to be published in Nucl. Phys.
Structure constants in superconformal quiver theories at strong coupling and holography
In a four-dimensional superconformal quiver theory with gauge
group and bi-fundamental matter, we
analytically obtain the exact strong-coupling behavior of the normalized
3-point correlators of single-trace scalar operators in the large- limit
using localization techniques. We then obtain the same strong-coupling behavior
from the holographic dual using the AdS/CFT correspondence at the supergravity
level. This agreement confirms the validity of the analytic strong-coupling
results and of the holographic correspondence in a non-maximally supersymmetric
set-up in four dimensions.Comment: 5 pages, 2 figure
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