2,359 research outputs found
Borcherds symmetries in M-theory
It is well known but rather mysterious that root spaces of the Lie
groups appear in the second integral cohomology of regular, complex, compact,
del Pezzo surfaces. The corresponding groups act on the scalar fields (0-forms)
of toroidal compactifications of M theory. Their Borel subgroups are actually
subgroups of supergroups of finite dimension over the Grassmann algebra of
differential forms on spacetime that have been shown to preserve the
self-duality equation obeyed by all bosonic form-fields of the theory. We show
here that the corresponding duality superalgebras are nothing but Borcherds
superalgebras truncated by the above choice of Grassmann coefficients. The full
Borcherds' root lattices are the second integral cohomology of the del Pezzo
surfaces. Our choice of simple roots uses the anti-canonical form and its known
orthogonal complement. Another result is the determination of del Pezzo
surfaces associated to other string and field theory models. Dimensional
reduction on corresponds to blow-up of points in general position
with respect to each other. All theories of the Magic triangle that reduce to
the sigma model in three dimensions correspond to singular del Pezzo
surfaces with (normal) singularity at a point. The case of type I and
heterotic theories if one drops their gauge sector corresponds to non-normal
(singular along a curve) del Pezzo's. We comment on previous encounters with
Borcherds algebras at the end of the paper.Comment: 30 pages. Besides expository improvements, we exclude by hand real
fermionic simple roots when they would naively aris
Comportamento produtivo de quatorze genĂłtipos de manga rosa na microrregiĂŁo homogĂȘnea de Teresina, PI.
O objetivo foi avaliar o desempenho produtivo de 14 genótipos de manga rosa nas condiçÔes agro-ecológicas da microrregião geogråfica de Teresina, PI
Comportamento produtivo de dezessete cultivares de mangueira nas condiçÔes agro-ecológicas da microrregião geogråfica de Teresina, PI.
Este trabalho teve como objetivo avaliar o desempenho produtivo de 17 cultivares de manga nas condiçÔes agro-ecolĂłgicas da microrregiĂŁo homogĂȘnea de Teresina, PI
Hunting for the New Symmetries in Calabi-Yau Jungles
It was proposed that the Calabi-Yau geometry can be intrinsically connected
with some new symmetries, some new algebras. In order to do this it has been
analyzed the graphs constructed from K3-fibre CY_d (d \geq 3) reflexive
polyhedra. The graphs can be naturally get in the frames of Universal
Calabi-Yau algebra (UCYA) and may be decode by universal way with changing of
some restrictions on the generalized Cartan matrices associated with the Dynkin
diagrams that characterize affine Kac-Moody algebras. We propose that these new
Berger graphs can be directly connected with the generalizations of Lie and
Kac-Moody algebras.Comment: 29 pages, 15 figure
SobrevivĂȘncia e desenvolvimento de mudas enxertadas de genĂłtipos de bacurizeiro.
O objetivo deste trabalho foi avaliar a taxa de sobrevivĂȘncia e o desenvolvimento de mudas enxertadas de 16 genĂłtipos de bacurizeiro
MĂ©todos de enxertia na sobrevivĂȘncia e desenvolvimento de mudas de trĂȘs genĂłtipos de chichĂĄ.
O objetivo deste trabalho foi avaliar o efeito de diferentes mĂ©todos de enxertia na taxa de sobrevivĂȘncia e desenvolvimento de trĂȘs genĂłtipos de chichazeiro
Intersexuality and the Cricket Frog Decline: Historic and Geographic Trends
Exposure to anthropogenic endocrine disruptors has been listed as one of several potential causes of amphibian declines in recent years. We examined gonads of 814 cricket frogs (Acris crepitans) collected in Illinois and deposited in museum collections to elucidate relationships between the decline of this species in Illinois and the spatial and temporal distribution of individuals with intersex gonads. Compared with the preorganochlorine era studied (1852â1929), the percentage of intersex cricket frogs increased during the period of industrial growth and initial uses of polychlorinated biphenyls (PCBs) (1930â1945), was highest during the greatest manufacture and use of p,p-dichlorodiphenyltrichloroethane (DDT) and PCBs (1946â1959), began declining with the increase in public concern and environmental regulations that reduced and then prevented sales of DDT in the United States (1960â1979), and continued to decline through the period of gradual reductions in environmental residues of organochlorine pesticides and PCBs in the midwestern United States (1980â2001). The proportion of intersex individuals among those frogs was highest in the heavily industrialized and urbanized northeastern portion of Illinois, intermediate in the intensively farmed central and northwestern areas, and lowest in the less intensively managed and ecologically more diverse southern part of the state. Records of deposits of cricket frog specimens into museum collections indicate a marked reduction in numbers from northeastern Illinois in recent decades. These findings are consistent with the hypothesis that endocrine disruption contributed to the decline of cricket frogs in Illinois
HAT-P-56b: An inflated massive Hot Jupiter transiting a bright F star followed up with K2 Campaign 0 observations
We report the discovery of HAT-P-56b by the HATNet survey, an inflated hot
Jupiter transiting a bright F type star in Field 0 of NASA's K2 mission. We
combine ground-based discovery and follow-up light curves with high precision
photometry from K2, as well as ground-based radial velocities from TRES on the
FLWO 1.5m telescope to determine the physical properties of this system.
HAT-P-56b has a mass of , radius of , and transits its host
star on a near-grazing orbit with a period of 2.7908 d. The radius of HAT-P-56b
is among the largest known for a planet with . The host star has a
V-band magnitude of 10.9, mass of 1.30 , and radius of 1.43 .
The periodogram of the K2 light curve suggests the star is a Dor
variable. HAT-P-56b is an example of a ground-based discovery of a transiting
planet, where space-based observations greatly improve the confidence in the
confirmation of its planetary nature, and also improve the accuracy of the
planetary parameters.Comment: 13 pages, 11 figures, accepted by A
A semi-Lagrangian view of ozone production tendency in North American outflow in the summers of 2009 and 2010
The Pico Mountain Observatory, located at 2225 m a.s.l. in the Azores Islands, was established in 2001 to observe long-range transport from North America to the central North Atlantic. In previous research conducted at the observatory, ozone enhancement (\u3e 55 ppbv) in North American outflows was observed, and efficient ozone production in these outflows was postulated. This study is focused on determining the causes for high d[O3] / d[CO] values (~1 ppbv ppbvâ1) observed in the summers of 2009 and 2010. The folded retroplume technique, developed by Owen and Honrath (2009), was applied to combine upwind FLEXPART transport pathways with GEOS-Chem chemical fields. The folded result provides a semi-Lagrangian view of polluted North American outflow in terms of physical properties and chemical processes, including production/loss rate of ozone and NOx produced by lightning and thermal decomposition of peroxy acetyl nitrate (PAN). Two transport events from North America were identified for detailed analysis. High d[O3] / d[CO] was observed in both events, but due to differing transport mechanisms, ozone production tendency differed between the two. A layer of net ozone production was found at 2 km a.s.l. over the Azores in the first event plume, apparently driven by PAN decomposition during subsidence of air mass in the AzoresâBermuda High. In the second event, net ozone loss occurred during transport in the lower free troposphere, yet observed d[O3] / d[CO] was high. We estimate that in both events, CO loss through oxidation contributed significantly to d[O3] / d[CO] enhancement. Thus, it is not appropriate to use CO as a passive tracer of pollution in these events. In general, use of d[O3] / d[CO] as an indicator of net ozone production/loss may be invalid for any situation in which oxidants are elevated. Based on our analysis, use of d[O3] / d[CO] to diagnose ozone enhancement without verifying the assumption of negligible CO loss is not advisable
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