922 research outputs found
Proof of vanishing cohomology at the tachyon vacuum
We prove Sen's third conjecture that there are no on-shell perturbative
excitations of the tachyon vacuum in open bosonic string field theory. The
proof relies on the existence of a special state A, which, when acted on by the
BRST operator at the tachyon vacuum, gives the identity. While this state was
found numerically in Feynman-Siegel gauge, here we give a simple analytic
expression.Comment: 19 pages, 4 figures; v2: references adde
Female teat size is a reliable indicator of annual breeding success in European badgers: Genetic validation
Assessing which females have bred successfully is a central requirement in many ecological field studies,
providing an estimate of the effective female population size. Researchers have applied teat measurements
previously to assess whether females, in a variety of mammalian species, have bred; however, this
technique has not been validated genetically. Furthermore, several analytical techniques are available to
classify individuals, but their misclassification rates have not been compared. We used 22 microsatellite
loci to assign maternity, with 95% confidence, within a high-density population of European badgers Meles
meles, as plural and subterranean breeding means that maternity cannot be inferred from behavioural
observations. The teat lengths and diameters of 136 females, measured May–July 1994–2005, from social
groups in which all offspring were assigned a mother, were reliable indicators of recent breeding success.
A Generalised Linear Mixed Model (GLMM) classified both breeding and non-breeding females with
lower error rates than discriminant analyses and crude teat-size criteria. The GLMM model logit probability
=
−20 + 1.8 month + 1.6 mean teat length + 1.0 mean teat diameter can be applied quickly in the field
to assess the probability with which a female badger should be assigned maternity. This is a low-cost
measure which, after validation, could be used in other badger or mammalian populations to assess the
breeding success of females. This may be a particularly useful welfare tool for veterinary practitioners,
especially during badger culls
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
Level Truncated Tachyon Potential in Various Gauges
New gauge fixing condition with single gauge parameter proposed by the
authors is applied to the level truncated analysis of tachyon condensation in
cubic open string field theory. It is found that the only one real non-trivial
extremum persists to appear in the well-defined region of the gauge parameter,
while the other solutions are turned out to be gauge-artifacts. Contrary to the
previously known pathology in the Feynman-Siegel gauge, tachyon potential is
remarkably smooth enough around Landau-type gauge.Comment: 13 pages, 5 figures. For associated movie files, see
http://hep1.c.u-tokyo.ac.jp/~kato/sft
Self-Reported Truck Traffic on the Street of Residence and Symptoms of Asthma and Allergic Disease: A Global Relationship in ISAAC Phase 3
BACKGROUND: Associations between traffic pollution on the street of residence and a range of respiratory and allergic outcomes in children have been reported in developed countries, but little is known about such associations in developing countries. METHODS: The third phase of the International Study of Asthma and Allergies in Childhood (ISAAC) was carried out in 13- to 14-year-old and 6- to 7-year-old children across the world. A question about frequency of truck traffic on the street of residence was included in an additional questionnaire. We investigated the association between self-reported truck traffic on the street of residence and symptoms of asthma, rhinoconjunctivitis, and eczema with logistic regression. Adjustments were made for sex, region of the world, language, gross national income, and 10 other subject-specific covariates. RESULTS: Frequency of truck traffic on the street of residence was positively associated with the prevalence of symptoms of asthma, rhinoconjunctivitis, and eczema with an exposure-response relationship. Odds ratios (95% confidence intervals) for "current wheeze" and "almost the whole day" versus "never" truck traffic were 1.35 (1.23-1.49) for 13- to 14-year-olds and 1.35 (1.22-1.48) for 6- to 7-year-olds. CONCLUSIONS: Higher exposure to self-reported truck traffic on the street of residence is associated with increased reports of symptoms of asthma, rhinitis, and eczema in many locations in the world. These findings require further investigation in view of increasing exposure of the world's children to traffic
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
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
Solving Open String Field Theory with Special Projectors
Schnabl recently found an analytic expression for the string field tachyon
condensate using a gauge condition adapted to the conformal frame of the sliver
projector. We propose that this construction is more general. The sliver is an
example of a special projector, a projector such that the Virasoro operator
\L_0 and its BPZ adjoint \L*_0 obey the algebra [\L_0, \L*_0] = s (\L_0 +
\L*_0), with s a positive real constant. All special projectors provide abelian
subalgebras of string fields, closed under both the *-product and the action of
\L_0. This structure guarantees exact solvability of a ghost number zero string
field equation. We recast this infinite recursive set of equations as an
ordinary differential equation that is easily solved. The classification of
special projectors is reduced to a version of the Riemann-Hilbert problem, with
piecewise constant data on the boundary of a disk.Comment: 64 pages, 6 figure
Why are biotic iron pools uniform across high- and low-iron pelagic ecosystems?
Dissolved iron supply is pivotal in setting global phytoplankton productivity and pelagic ecosystem structure. However, most studies of the role of iron have focussed on carbon biogeochemistry within pelagic ecosystems, with less effort to quantify the iron biogeochemical cycle. Here we compare mixed-layer biotic iron inventories from a low-iron (~0.06nmol L-1) subantarctic (FeCycle study) and a seasonally high-iron (~0.6nmol L-1) subtropical (FeCycle II study) site. Both studies were quasi-Lagrangian, and had multi-day occupation, common sampling protocols, and indirect estimates of biotic iron (from a limited range of available published biovolume/carbon/iron quotas). Biotic iron pools were comparable (~100±30pmol L-1) for low- and high-iron waters, despite a tenfold difference in dissolved iron concentrations. Consistency in biotic iron inventories (~80±24pmol L-1, largely estimated using a limited range of available quotas) was also conspicuous for three Southern Ocean polar sites. Insights into the extent to which uniformity in biotic iron inventories was driven by the need to apply common iron quotas obtained from laboratory cultures were provided from FeCycle II. The observed twofold to threefold range of iron quotas during the evolution of FeCycle II subtropical bloom was much less than reported from laboratory monocultures. Furthermore, the iron recycling efficiency varied by fourfold during FeCycle II, increasing as stocks of new iron were depleted, suggesting that quotas and iron recycling efficiencies together set biotic iron pools. Hence, site-specific differences in iron recycling efficiencies (which provide 20-50% and 90% of total iron supply in high- and low-iron waters, respectively) help offset the differences in new iron inputs between low- and high-iron sites. Future parameterization of iron in biogeochemical models must focus on the drivers of biotic iron inventories, including the differing iron requirements of the resident biota, and the subsequent fate (retention/export/recycling) of the biotic iron
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
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