1,299 research outputs found
Tachyon Vacuum in Cubic Superstring Field Theory
In this paper we give an exact analytic solution for tachyon condensation in
the modified (picture 0) cubic superstring field theory. We prove the absence
of cohomology and, crucially, reproduce the correct value for the D-brane
tension. The solution is surprising for two reasons: First, the existence of a
tachyon vacuum in this theory has not been definitively established in the
level expansion. Second, the solution {\it vanishes} in the GSO sector,
implying a ``tachyon vacuum'' solution exists even for a {\it BPS} D-brane.Comment: 16 pages, 2 figure
The Tachyon Potential in the Sliver Frame
We evaluate the tachyon potential in the Schnabl gauge through off-shell
computations in the sliver frame. As an application of the results of our
computations, we provide a strong evidence that Schnabl's analytic solution for
tachyon condensation in open string field theory represents a saddle point
configuration of the full tachyon potential. Additionally we verify that
Schnabl's analytic solution lies on the minimum of the effective tachyon
potential.Comment: v1: 19 pages, 1 figure, 1 table; v2: 20 pages, 1 figure, 2 tables, 1
reference added, comments added; v3: 21 pages, 1 figure, 2 tables, 4
references added, comments adde
Superstring field theory equivalence: Ramond sector
We prove that the finite gauge transformation of the Ramond sector of the
modified cubic superstring field theory is ill-defined due to collisions of
picture changing operators.
Despite this problem we study to what extent could a bijective classical
correspondence between this theory and the (presumably consistent)
non-polynomial theory exist. We find that the classical equivalence between
these two theories can almost be extended to the Ramond sector: We construct
mappings between the string fields (NS and Ramond, including Chan-Paton factors
and the various GSO sectors) of the two theories that send solutions to
solutions in a way that respects the linearized gauge symmetries in both sides
and keeps the action of the solutions invariant. The perturbative spectrum
around equivalent solutions is also isomorphic.
The problem with the cubic theory implies that the correspondence of the
linearized gauge symmetries cannot be extended to a correspondence of the
finite gauge symmetries. Hence, our equivalence is only formal, since it
relates a consistent theory to an inconsistent one. Nonetheless, we believe
that the fact that the equivalence formally works suggests that a consistent
modification of the cubic theory exists. We construct a theory that can be
considered as a first step towards a consistent RNS cubic theory.Comment: v1: 24 pages. v2: 27 pages, significant modifications of the
presentation, new section, typos corrected, references adde
A perturbative analysis of tachyon condensation
Tachyon condensation in the open bosonic string is analyzed using a
perturbative expansion of the tachyon potential around the unstable D25-brane
vacuum. Using the leading terms in the tachyon potential, Pad\'e approximants
can apparently give the energy of the stable vacuum to arbitrarily good
accuracy. Level-truncation approximations up to level 10 for the coefficients
in the tachyon potential are extrapolated to higher levels and used to find
approximants for the full potential. At level 14 and above, the resulting
approximants give an energy less than -1 in units of the D25-brane tension, in
agreement with recent level-truncation results by Gaiotto and Rastelli. The
extrapolated energy continues to decrease below -1 until reaching a minimum
near level 26, after which the energy turns around and begins to approach -1
from below. Within the accuracy of this method, these results are completely
consistent with an energy which approaches -1 as the level of truncation is
taken to be arbitrarily large.Comment: 8 pages, 3 eps figures, Latex; v2: typo correcte
Ghost story. II. The midpoint ghost vertex
We construct the ghost number 9 three strings vertex for OSFT in the natural
normal ordering. We find two versions, one with a ghost insertion at z=i and a
twist-conjugate one with insertion at z=-i. For this reason we call them
midpoint vertices. We show that the relevant Neumann matrices commute among
themselves and with the matrix representing the operator K1. We analyze the
spectrum of the latter and find that beside a continuous spectrum there is a
(so far ignored) discrete one. We are able to write spectral formulas for all
the Neumann matrices involved and clarify the important role of the integration
contour over the continuous spectrum. We then pass to examine the (ghost) wedge
states. We compute the discrete and continuous eigenvalues of the corresponding
Neumann matrices and show that they satisfy the appropriate recursion
relations. Using these results we show that the formulas for our vertices
correctly define the star product in that, starting from the data of two ghost
number 0 wedge states, they allow us to reconstruct a ghost number 3 state
which is the expected wedge state with the ghost insertion at the midpoint,
according to the star recursion relation.Comment: 60 pages. v2: typos and minor improvements, ref added. To appear in
JHE
Conservation laws and tachyon potentials in the sliver frame
Conservation laws have provided an elegant and efficient tool to evaluate the
open string field theory interaction vertex, they have been originally
implemented in the case where the string field is expanded in the Virasoro
basis. In this work we derive conservation laws in the case where the string
field is expanded in the so-called sliver -basis. As an
application of these conservation laws derived in the sliver frame, we compute
the open string field action relevant to the tachyon condensation and in order
to present not only an illustration but also an additional information, we
evaluate the action without imposing a gauge choice.Comment: 26 pages, some typos fixed, comments added, references adde
Ghost story. III. Back to ghost number zero
After having defined a 3-strings midpoint-inserted vertex for the bc system,
we analyze the relation between gh=0 states (wedge states) and gh=3 midpoint
duals. We find explicit and regular relations connecting the two objects. In
the case of wedge states this allows us to write down a spectral decomposition
for the gh=0 Neumann matrices, despite the fact that they are not commuting
with the matrix representation of K1. We thus trace back the origin of this
noncommutativity to be a consequence of the imaginary poles of the wedge
eigenvalues in the complex k-plane. With explicit reconstruction formulas at
hand for both gh=0 and gh=3, we can finally show how the midpoint vertex avoids
this intrinsic noncommutativity at gh=0, making everything as simple as the
zero momentum matter sector.Comment: 40 pages. v2: typos and minor corrections, presentation improved in
sect. 4.3, plots added in app. A.1, two refs added. To appear in JHE
Remark about string field for general configuration of N D-instantons
In this paper we would like to suggest matrix form of the string field for
any configuration of N D-instantons in bosonic string field theory.Comment: 17 pages, R1:corrected some typos, reference adde
Descent Relations in Cubic Superstring Field Theory
The descent relations between string field theory (SFT) vertices are
characteristic relations of the operator formulation of SFT and they provide
self-consistency of this theory. The descent relations and
in the NS fermionic string field theory in the kappa and discrete bases are
established. Different regularizations and schemes of calculations are
considered and relations between them are discussed.Comment: Replaced to JHEP styl
The Global Asthma Network rationale and methods for Phase I global surveillance: prevalence, severity, management and risk factors.
The Global Asthma Network (GAN), established in 2012, followed the International Study of Asthma and Allergies in Childhood (ISAAC). ISAAC Phase One involved over 700 000 adolescents and children from 156 centres in 56 countries; it found marked worldwide variation in symptom prevalence of asthma, rhinitis and eczema that was not explained by the current understanding of these diseases; ISAAC Phase Three involved over 1 187 496 adolescents and children (237 centres in 98 countries). It found that asthma symptom prevalence was increasing in many locations especially in low- and middle-income countries where severity was also high, and identified several environmental factors that required further investigation.GAN Phase I, described in this article, builds on the ISAAC findings by collecting further information on asthma, rhinitis and eczema prevalence, severity, diagnoses, asthma emergency room visits, hospital admissions, management and use of asthma essential medicines. The subjects will be the same age groups as ISAAC, and their parents. In this first global monitoring of asthma in children and adults since 2003, further evidence will be obtained to understand asthma, management practices and risk factors, leading to further recognition that asthma is an important non-communicable disease and to reduce its global burden
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