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排序方式: 共有133条查询结果,搜索用时 15 毫秒
51.
Brett Milburn 《Differential Geometry and its Applications》2011,29(5):615-641
The aim of this paper is to study generalized complex geometry (Hitchin, 2002) [6] and Dirac geometry (Courant, 1990) [3], (Courant and Weinstein, 1988) [4] on homogeneous spaces. We offer a characterization of equivariant Dirac structures on homogeneous spaces, which is then used to construct new examples of generalized complex structures. We consider Riemannian symmetric spaces, quotients of compact groups by closed connected subgroups of maximal rank, and nilpotent orbits in sln(R). For each of these cases, we completely classify equivariant Dirac structures. Additionally, we consider equivariant Dirac structures on semisimple orbits in a semisimple Lie algebra. Here equivariant Dirac structures can be described in terms of root systems or by certain data involving parabolic subalgebras. 相似文献
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54.
Development of a new lectron-recoil ion/photon coincidence setup for investigating some of the electron induced collision processes, such as electron bremsstrahlung, electron backscattering,
innershell excitation and multiple ionization of target atoms/molecules in bombardment of electrons having energies from 2.0
keV to 30.0 keV with solid and gaseous targets is described. The new features include the use of a compact multipurpose scattering
chamber, a time-of-flight spectrometer for detection of multiply charged target ions, a 45°-parallel plate electrostatic analyzer
for measuring energy and angle of the ejected electrons, a room temperature high resolution Si-PIN photo diode X-ray detector
for counting the collisionally induced photons, a coincidence data acquisition system consisting of a 200 MHz Pentium based
8K-multichannel analyzer and a standard network of a fast/slow coincidence electronics. In particular, the details of design,
fabrication and assembly of indigenous components employed in the setup are presented. Selected experiments planned with the
setup are mentioned and briefly discussed. A report on performance, optimization, efficiency, time resolution etc. of the
time-of-flight (TOF) spectrometer and that of the 45°-parallel plate electrostatic analyzer (PPEA) is presented. Test spectra
of electron-recoil ion coincidences, energy distribution of ejected electrons and characteristic plus non-characteristic X-ray
spectrum are illustrated to exhibit the satisfactory performance of the developed setup. 相似文献
55.
Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Copty NK Cremaldi LM Darling C Denisenko K Devmal S Fernandez A Fox GF Gagnon P Göbel C Gounder K Halling AM Herrera G Hurvits G James C Kasper PA Kwan S Langs DC Leslie J Lundberg B Magnin J Massafferri A MayTal-Beck S Meadows B de Mello Neto JR Mihalcea D Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV 《Physical review letters》2002,89(12):121801
We study the Dalitz plot of the decay D(+)-->K(-)pi(+)pi(+) with a sample of 15090 events from Fermilab experiment E791. Modeling the decay amplitude as the coherent sum of known Kpi resonances and a uniform nonresonant term, we do not obtain an acceptable fit. If we allow the mass and width of the K(*)(0)(1430) to float, we obtain values consistent with those from PDG but the chi(2) per degree of freedom of the fit is still unsatisfactory. A good fit is found when we allow for the presence of an additional scalar resonance, with mass 797+/-19+/-43 MeV/c(2) and width 410+/-43+/-87 MeV/c(2). The mass and width of the K(*)(0)(1430) become 1459+/-7+/-5 MeV/c(2) and 175+/-12+/-12 MeV/c(2), respectively. Our results provide new information on the scalar sector in hadron spectroscopy. 相似文献
56.
Hariprakash Sharma B Sethi P Banerjee Ranjana Goswami RK Bhandari Jahan Singh 《Pramana》2001,57(1):171-174
Recent experimental data on 125I has revealed several interesting structural features. These include the observation of a three quasiparticle band, prolate
and oblate deformed bands, signature inversion in the yrast positive-parity band and identification of the unfavoured πh
11/2 band showing very large signature splitting. In the present work, particle-rotor-model calculations have been performed for
the πh
11/2 band, using an axially symmetric deformed Nilsson potential. The calculations reproduce the experimental results well and
predict a moderate prolate quadrupole deformation of about 0.2 for the band. 相似文献
57.
Alves GA Amato S Anjos JC Appel JA Astorga J Bernard T Bracker SB Cremaldi LM Darling CL Dixon RL Errede D Gay C Green DR Jedicke R Karchin PE Kwan S Lueking LJ de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Passmore D Rafatian A dos Reis AC Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wallace A Wu Z 《Physical review letters》1994,72(6):812-815
58.
We investigate the quantum dynamics of a periodically kicked nonlinear spin system which exhibits regular and chaotic dynamics in the classical regime. The quantum behaviour is characterised by the evolving eigenvalue distributions for the angular momentum components and the features, including recurrences in the quantum means and the presence of quantum tunneling, are discussed. We employ the evolution operator eigenvalue distribution to prove that coherent quantum tunneling occurs between the fixed points in the regular regions of phase space. Continual quantum measurement is included in the model: the classical dynamics are unchanged but a destruction of coherences occurs in the quantum system. Recurrences in the means are destroyed and quantum tunneling is suppressed by measurement, a manifestation of the quantum Zeno effect. 相似文献
59.
60.
I. Last M. Baer M. J. Konopnicki P. D. Drummond J. H. Eberly A. E. Kaplan P. Meystre J. Bergou S. Varró F. T. Hioe J. Benjamin R. D. Levine O. S. Roosmalen F. Tachello J. S. Zmuidzinas D. F. Walls G. Strini F. Casagrande L. A. Lugiato G. J. Milburn H. P. Yuen 《Applied physics. B, Lasers and optics》1982,28(2-3):102-111