18,570 research outputs found
Naturality of Heegaard Floer invariants under positive rational contact surgery
For a nullhomologous Legendrian knot in a closed contact 3-manifold Y we
consider a contact structure obtained by positive rational contact surgery. We
prove that in this situation the Heegaard Floer contact invariant of Y is
mapped by a surgery cobordism to the contact invariant of the result of contact
surgery. In addition we characterize the spin-c structure on the cobordism that
induces the relevant map. As a consequence we determine necessary and
sufficient conditions for the nonvanishing of the contact invariant after
rational surgery when Y is the standard 3-sphere, generalizing previous results
of Lisca-Stipsicz and Golla. In fact our methods allow direct calculation of
the contact invariant in terms of the rational surgery mapping cone of
Ozsv\'ath and Szab\'o. The proof involves a construction called reducible open
book surgery, which reduces in special cases to the capping-off construction
studied by Baldwin.Comment: Extended the main results from surgery coefficients that are at least
1 to all positive surgery coefficients. This version to appear in Journal of
Differential Geometr
On the Heegaard Floer homology of a surface times a circle
We make a detailed study of the Heegaard Floer homology of the product of a
closed surface Sigma_g of genus g with S^1. We determine HF^+ for this
3-manifold completely for the spin^c structure having trivial first Chern
class, which for g>2 was previously unknown. We show that in this case
HF^\infty is closely related to the cohomology of the total space of a certain
circle bundle over the Jacobian torus of Sigma_g, and furthermore that HF^+ of
a surface times a circle with integral coefficients contains nontrivial
2-torsion whenever g>2. This is the first example known to the authors of
torsion in Heegaard Floer homology with integral coefficients. Our methods also
give new information on the action of H_1 of a surface times the circle on HF^+
of the same with spin^c-structures with nonzero first Chern class.Comment: Minor corrections and expositional improvements at referee's
suggestion. This version to appear in Advances in Mathematics. 32 pages, 5
figure
Distribution, Abundance, and Biological Characteristics of Groundfish off the Coast of Washington, Oregon, and California, 1977-1986
We compare results of bottom trawl surveys off Washington, Oregon, and California in 1977, 1980, 1983, and 1986 to discern trends in population abundance, distribution, and
biology. Catch per unit of effort, area-swept biomass estimates, and age and length compositions for 12 commercially important west coast groundfishes are presented to illustrate trends over the lO-year period. We discuss the precision, accuracy, and statistical significance of observed trends in abundance estimates. The influence of water temperature on the distribution of groundfishes is also briefly examined. Abundance estimates of canary rockfish, Sebastes pinniger, and yellowtail rockfish, S. Jlavidus, declined during the study
period; greater declines were observed in Pacific ocean perch, S. alutus, lingcod, Ophiodon elongatus, and arrowtooth flounder, Atheresthes stomias. Biomass estimates of Pacific hake, Merluccius productus, and English, rex, and Dover soles (Pleuronectes vetulus, Errex zachirus,
and Microstomus pacificus) increased, while bocaccio, S. paucispinis, and chilipepper, S. goodei, were stable. Sablefish, Anoplopoma fimbria, biomass estimates increased markedly from 1977 to 1980 and declined moderately thereafter. Precision was lowest for rockfishes, lingcod, and sablefish; it was highest for flatfishes because they were uniformly distributed. The accuracy of survey estimates could be gauged only for yellowtail and canary rockfish and sablefish. All fishery-based analyses produced much larger estimates of abundance than bottom trawl surveys-indicative of the true catchability of survey trawls. Population trends from all analyses compared well except in canary rockfish, the species that presents the
greatest challenge to obtaining reasonable precision and one that casts doubts on the usefulness of bottom trawl surveys for estimating its abundance. (PDF file contains 78 pages.
Comparison of Leafhopper Species Complexes in the Ground Cover of Sprayed and Unsprayed Peach Orchards in Michigan (Homoptera: Cicadellldae)
Two Michigan peach orchards were sampled for leafhoppers using a fixed-area ground sampling device attached to a D-vac®. Absolute abundance estimates indicated that routine tree insecticide applications greatly depressed leafhopper populations. This, and the fact that no resident, known vectors of the X-disease pathogen were detected, suggests that increasing insecticide applications to check the spread of the disease through vector control would be ineffective
Toxic Power: What the Toxics Release Inventory Tells Us About Power Plant Pollution
Examines nationwide and state electric utility data to show the quantity and nature of toxic pollutants reported by power plants, and describes the potential health damage they can cause. Suggests ways for reducing toxic power plant pollution
Signatures of multiple stellar populations in unresolved extragalactic globular/ young massive star clusters
We present an investigation of potential signatures of the formation of
multiple stellar populations in recently formed extragalactic star clusters.
All of the Galactic globular clusters for which good samples of individual
stellar abundances are available show evidence for multiple populations. This
appears to require that multiple episodes of star formation and light element
enrichment are the norm in the history of a globular cluster. We show that
there are detectable observational signatures of multiple formation events in
the unresolved spectra of massive, young extragalactic star clusters. We
present the results of a pilot program to search for one of the cleanest
signatures that we identify - the combined presence of emission lines from a
very recently formed population and absorption lines from a somewhat older
population. A possible example of such a system is identified in the Antennae
galaxies. This source's spectrum shows evidence of two stellar populations with
ages of 8 Myr and 80 Myr. Further investigation shows that these populations
are in fact physically separated, but only by a projected distance of 59 pc. We
show that the clusters are consistent with being bound and discuss the
possibility that their coalescence could result in a single globular cluster
hosting multiple stellar populations. While not the prototypical system
proposed by most theories of the formation of multiple populations in clusters,
the detection of this system in a small sample is both encouraging and
interesting. Our investigation suggests that expanded surveys of massive young
star clusters should detect more clusters with such signatures.Comment: 11 pages, 7 figures: accepted for publication in Ap
Wage determination and wage inequality inside a Russian firm in late transition: Evidence from personnel data – 1997 to 2002.
personnel economics, Russia, transition;wage determination;
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