Статті в журналах з теми "Cauchy spinors"

AbstractLorentzian manifolds with parallel spinors are important objects of study in several branches of geometry, analysis and mathematical physics. Their Cauchy problem has recently been discussed by Baum, Leistner and Lischewski, who proved that the problem locally has a unique solution up to diffeomorphisms, provided that the intial data given on a space-like hypersurface satisfy some constraint equations. In this article we provide a method to solve these constraint equations. In particular, any curve (resp. closed curve) in the moduli space of Riemannian metrics on M with a parallel spinor gives rise to a solution of the constraint equations on $$M\times (a,b)$$ M × ( a , b ) (resp. $$M\times S^1$$ M × S 1 ).

We prove that the Cauchy problem for the Dirac–Klein–Gordon equations in two space dimensions is locally well-posed in a range of Sobolev spaces of negative index for the Dirac spinor, and an associated range of spaces of positive index for the meson field. In particular, we can go below the charge norm, that is, the L2 norm of the spinor. We hope that this can have implications for the global existence problem, since the charge is conserved. Our result relies on the null structure of the system, and bilinear space-time estimates for the homogeneous wave equation.

We prove that the Cauchy problem for the Dirac–Klein–Gordon system of equations in 1D is globally well-posed in a range of Sobolev spaces of negative index for the Dirac spinor and positive index for the scalar field. The main ingredient in the proof is the theory of "almost conservation law" and "I-method" introduced by Colliander, Keel, Staffilani, Takaoka, and Tao. Our proof also relies on the null structure in the system, and bilinear space–time estimates of Klainerman–Machedon type.

Compact description is given of algebras of poly-numbers: quaternions, bi-quaternions, double (split-complex) and dual numbers. All units of these (and exceptional) algebras are shown to be represented by direct products of 2D vectors of a local basis defined on a fundamental surface. In this math medium a series of equalities identical or similar to known formulas of physical laws is discovered. In particular, a condition of the algebras' stability with respect to transformations of the 2D-basis turns out equivalent to the spinor (Schrödinger–Pauli and Hamilton–Jacobi) equations of mechanics. It is also demonstrated that isomorphism of SO(3, 1) and SO(3, ℂ) groups leads to formulation of a quaternion relativity theory predicting all effects of special relativity but simplifying solutions of relativistic problems in non-inertial frames. Finely it is shown that the Cauchy–Riemann type equations written for functions of quaternion variable repeat vacuum Maxwell equations of electrodynamics, while a quaternion space with non-metricity comprises main relations of Yang–Mills field theory.

AbstractWe consider the Dirac equation for the classical spinor field placed in an external, time-dependent electromagnetic field of the form typical for scattering settings: $$F=F^\mathrm{ret}+F^\mathrm{in}=F^\mathrm{adv}+F^\mathrm{out}$$ F = F ret + F in = F adv + F out , where the current producing $$F^{\mathrm{ret}/\mathrm{adv}}$$ F ret / adv has past and future asymptotes homogeneous of degree $$-3$$ - 3 , and the free fields $$F^{\mathrm{in}/\mathrm{out}}$$ F in / out are radiation fields produced by currents with similar asymptotic behavior. We show the existence of the electromagnetic gauges in which the particle has ‘in’ and ‘out’ asymptotic states approaching free field states, with no long-time corrections of the free dynamics. Using a special Cauchy foliation of the spacetime, we show in this context the existence and asymptotic completeness of the wave operators. Moreover, we define a special ‘evolution picture’ in which the free evolution operator has well-defined limits for $$t\rightarrow \pm \infty $$ t → ± ∞ ; thus the scattering wave operators do not need the free evolution counteraction.

Colobomatus icopaius, sp. nov., was collected from the cephalic canal system associated with the preopercular bones of the sweetlip, Lethrinus chrysostomus Richardson, caught off Heron I. on the Great Barrier Reef. The female differs from those of all other described species in having a chitinised cephalic transverse process, a spinose oral pad, and bifid thoracic lobes, features which are suggested to function in maintaining the female in its feeding position.

The specimens of the pteromalid wasps (Hymenoptera: Chalcidoidea, Ptero-malidae) were caught using Malaise traps and sweeping net in Kerman province of Iran during March 2016 to August 2017. The genus Coelopisthia Förster, 1856 and the species: C. areolata Askew, 1980, Homoporus apharetus (Walker, 1839), Norbanus brevicornis Szelenyi, 1974, Pachyneuron gibbiscuta Thomson, 1878, and Sphegigaster pedunculiventris (Spinola, 1808) are recorded for the first time from Iran. The diagnostic characteristics and illustrations are given for the newly recorded species.

Abstract A new species, Skrjabinopsolus nudidorsalis sp. nov. is described from the sterlet Acipenser ruthenus, caught in the River Volga basin (Russia). This species differs from previously described congeners by the absence of vitelline follicles on the dorsal side of the body. The complete 18S rRNA and partial 28S rRNA gene sequences obtained for S. nudidorsalis are the first molecular data for the family Deropristidae. The results of phylogenetic analysis indicate that Deropristidae is sister to the Monorchiidae + Lissorchiidae group. The results of the phylogenetic study contradict the current taxonomic hypothesis that Deropristidae belongs to the superfamily Lepocreadioidea and allow inclusion of this family in Monorchioidea. The morphological similarity of deropristids to other monorchioids is recognizable from the presence of a bipartite internal seminal vesicle, spinous cirrus and a voluminous, armed metraterm.

Three new species of myxosporeans are described from the gall bladders of Lophius piscatorius L. and L. budegassa Spinola. Ceratomyxa lophii n. sp. was found in 14 of 42 L. piscatorius from two locations to the northwest of Scotland in March 2000. Alataspora budegassai n. sp. was found in all eight specimens of L. budegassa caught off Algarve in the south of Portugal in June and August 2000. Pseudalataspora lophii n. sp. was found in 21 of 48 L. piscatorius from six locations to the west and northwest of Scotland in March 2000, March 2004 and October 2004. Ceratomyxa lophii n. sp. is one of only a few species of the genus having unequal spore valves, but differs from all the other species in spore dimensions and in the form of the plasmodium. The dimensions of the spore of Alataspora budegassai n. sp. are very similar to those of A. africana Shulman, Kovaleva & Dubina, 1979, described from a species of perciform fish caught off West Africa, but are markedly different from those of any of the other 15 described species of Alataspora. Pseudalataspora lophii n. sp. differs from the other 11 species of Pseudalataspora described to date in the dimensions of the spore and other features.

<p>En el presente estudio se colectaron cuatro parasitoides de <em>Dasiops inedulis </em>Steyskal (Diptera: Lonchaeidae), i.e., uno de tipo larva-pupa identificado como <em>Utetes anastrephae </em>(Viereck) (Hymenoptera: Braconidae), y tres parasitoides de pupas identificados como <em>Pachycrepoideus vindemmiae </em>Rondani, <em>Spalangia </em>sp. (Hymenoptera: Pteromalidae) y <em>Aganaspis </em>sp. (Hymenoptera: Figitidae). En el campo se observaron daños ocasionados por una larva de Chrysopidae (Neuroptera) sobre pupas centinelas de<em>D. inedulis</em>. Se realizaron experimentos con un cebo tóxico de origen natural a base de <em>Saccharopolyspora spinosa </em>en los municipios de Palmira y Toro, en el departamento del Valle del Cauca, destacándose como una nueva alternativa para el control de <em>D. inedulis </em>en maracuyá amarillo, ya que en las dos localidades mantuvo los niveles de daño por debajo del manejo convencional del agricultor y el testigo absoluto. Se provee una lista de enemigos naturales de <em>D. inedulis </em>tomada mediante muestreos de botones florales de maracuyá, uso de pupas centinelas, e información en la literatura científica. Para el control de la mosca del botón floral del maracuyá, <em>D. inedulis</em>, se propone una estrategia de manejo integrado de plagas que le permitirán al productor mantener las poblaciones de <em>D. inedulis </em>reguladas con diferentes herramientas, i.e., enemigos naturales que se pueden incorporar en diferentes etapas de la fenología de <em>D. inedulis</em>, uso de cebos tóxicos de baja toxicidad, recolección de botones con síntomas de daño, y monitoreo con el uso de trampas McPhail cebadas con proteína hidrolizada, interviniendo en diferentes estados de desarrollo, cortando ciclos y disminuyendo así futuras generaciones del insecto. </p><p> </p><p><strong>Integrated pest management as a strategy to control the passionfruit flower-bud fly, <em>Dasiops inedulis</em>Steyskal (Diptera: Lonchaeidae)</strong></p><span> Four parasitoids of the passion fruit flower bud fly, </span><em>Dasiops inedulis </em><span>Steyskal (Diptera: Lonchaeidae) were collected in the present study, i.e., a larva-pupa type parasitoid, </span><em>Utetes anastrephae </em><span>(Viereck) (Hymenoptera: Braconidae), and three pupal parasitoids, namely </span><em>Pachycrepoideus vindemmiae</em><span>Rondani, </span><em>Spalangia </em><span>sp. (Hymenoptera: Pteromalidae) and</span><em>Aganaspis </em><span>sp. (Hymenoptera: Figitidae). In the field we observed a species of Chrysopidae (Neuroptera) larva feeding on the sentinel pupae of </span><em>D. inedulis</em><span>. We conducted experiments in the municipalities of Palmira and Toro, in the State of Valle del Cauca, Colombia, on the efficiency of a toxic bait made from the bacteria </span><em>Saccharopolyspora spinosa</em><span>, standing out as a new alternative for controlling </span><em>D. inedulis</em><span>on yellow passion fruit. This toxic bait maintained the injury levels below the conventional management used by the farmers and the control plots in both study areas. A list of natural enemies of </span><em>D. inedulis </em><span>was compiled by inspecting passion fruit flower buds, using sentinel pupae, and information taken from the literature. For the control of </span><em>D. inedulis</em><span>, an integrated pest management strategy is proposed that will allow the farmer to maintain </span><em>D. inedulis </em><span>populations under control with different management tools, i.e., natural enemies which can be incorporated at different stages of development of </span><em>D. inedulis</em><span>, low toxicity baits, recollection of flower buds with symptoms of damage, monitoring with McPhail traps baited with protein hydrolysate, thus intervening at different stages the development of the lonchaeid fly pest, breaking its life cycle and thus decreasing their populations in future generations.</span>

Real estate investment trusts (REITs) have recently made headlines in major media outlets and have caught the attention of lawmakers and analysts because they erode the corporate tax base. REITs are not subject to the entity-level tax that typically applies to corporations. To avoid being taxed on real estate income, some corporations spin off real estate into REITs. After a REIT spinoff, such corporations rent the real estate from the REIT and continue to use it in their operations. Thus, a mere change in corporate form removes taxable income from the corporation (i.e., erodes the corporate tax base) and eliminates the entity-level tax on income from the spun-off real estate. This erosion of the corporate tax base concerns lawmakers (who have proposed prohibiting tax-free REIT spinoffs), some economists, and the media. Another concern is that the IRS has extended REIT classification to entities that hold nontraditional real estate, such as telecommunications infrastructure, billboards, oil and gas pipeline systems, timber, casinos, prisons, and data centers. The extension of REIT taxation to nontraditional real estate may not erode the corporate tax base because the assets may come from noncorporate entities. Thus, the tax-revenue effect of REIT taxation extends beyond REIT spinoffs and the erosion of the corporate tax base. Nonetheless, intuition suggests that more REIT spinoffs, the expansion of REIT taxation, and the growth of the REIT industry must erode the corporate tax base and significantly reduce government tax revenue. This Article challenges that intuition and presents two counterintuitive findings. First, it shows that REIT spinoffs can actually increase tax revenue even though they erode the corporate tax base. Second, it reveals that loss of tax revenue from REIT taxation primarily results from REITs forming from partnerships, not from REIT spinoffs. The Article concludes by recommending how these findings should influence discussions of REIT reform.