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Search Results: 1 - 10 of 654107 matches for " A. J. Mountain "
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Invariant tensors and Casimir operators for simple compact Lie groups
A. J. Mountain
Physics , 1998, DOI: 10.1063/1.532552
Abstract: The Casimir operators of a Lie algebra are in one-to-one correspondence with the symmetric invariant tensors of the algebra. There is an infinite family of Casimir operators whose members are expressible in terms of a number of primitive Casimirs equal to the rank of the underlying group. A systematic derivation is presented of a complete set of identities expressing non-primitive symmetric tensors in terms of primitive tensors. Several examples are given including an application to an exceptional Lie algebra.
Construction of supercharges for the one-dimensional supersymmetric nonlinear sigma model
A. J. Macfarlane,A. J. Mountain
Physics , 1997, DOI: 10.1088/1126-6708/1999/06/005
Abstract: This paper addresses an issue essential to the study of hidden supersymmetries (meaning here ones that do not close on the Hamiltonian) for one-dimensional non-linear supersymmetric sigma models. The issue relates to ambiguities, due to partial integrations in superspace, both in the actual definition of these supersymmetries and in the Noether definition of the associated supercharges. The unique consistent forms of both these definitions have to be determined simultaneously by a process that adjusts the former definitions so that the associated supercharges do indeed correctly generate them with the aid of the canonical formalism. The paper explains and illustrates these matters and gives some new results.
Commuting charges and symmetric spaces
J. M. Evans,A. J. Mountain
Physics , 2000, DOI: 10.1016/S0370-2693(00)00566-9
Abstract: Every classical sigma-model with target space a compact symmetric space $G/H$ (with $G$ classical) is shown to possess infinitely many local, commuting, conserved charges which can be written in closed form. The spins of these charges run over a characteristic set of values, playing the role of exponents of $G/H$, and repeating modulo an integer $h$ which plays the role of a Coxeter number.
Two monopoles of one type and one of another
Conor Houghton,Patrick Irwin,A. J. Mountain
Physics , 1999, DOI: 10.1088/1126-6708/1999/04/029
Abstract: The metric on the moduli space of charge (2,1) SU(3) Bogomolny-Prasad-Sommerfield monopoles is calculated and investigated. The hyperKahler quotient construction is used to provide an alternative derivation of the metric. Various properties of the metric are derived using the hyperKahler quotient construction and the correspondence between BPS monopoles and rational maps. Several interesting limits of the metric are also considered.
Invariant tensors for simple groups
J. A. de Azcarraga,A. J. Macfarlane,A. J. Mountain,J. C. Perez Bueno
Physics , 1997, DOI: 10.1016/S0550-3213(97)00609-3
Abstract: The forms of the invariant primitive tensors for the simple Lie algebras A_l, B_l, C_l and D_l are investigated. A new family of symmetric invariant tensors is introduced using the non-trivial cocycles for the Lie algebra cohomology. For the A_l algebra it is explicitly shown that the generic forms of these tensors become zero except for the l primitive ones and that they give rise to the l primitive Casimir operators. Some recurrence and duality relations are given for the Lie algebra cocycles. Tables for the 3- and 5-cocycles for su(3) and su(4) are also provided. Finally, new relations involving the d and f su(n) tensors are given.
Local conserved charges in principal chiral models
J. M. Evans,M. Hassan,N. J. MacKay,A. J. Mountain
Physics , 1999, DOI: 10.1016/S0550-3213(99)00489-7
Abstract: Local conserved charges in principal chiral models in 1+1 dimensions are investigated. There is a classically conserved local charge for each totally symmetric invariant tensor of the underlying group. These local charges are shown to be in involution with the non-local Yangian charges. The Poisson bracket algebra of the local charges is then studied. For each classical algebra, an infinite set of local charges with spins equal to the exponents modulo the Coxeter number is constructed, and it is shown that these commute with one another. Brief comments are made on the evidence for, and implications of, survival of these charges in the quantum theory.
Conserved Charges and Supersymmetry in Principal Chiral Models
J. M. Evans,M. Hassan,N. J. MacKay,A. J. Mountain
Physics , 1997,
Abstract: We report on investigations of local (and non-local) charges in bosonic and supersymmetric principal chiral models in 1+1 dimensions. In the bosonic PCM there is a classically conserved local charge for each symmetric invariant tensor of the underlying group. These all commute with the non-local Yangian charges. The algebra of the local charges amongst themselves is rather more subtle. We give a universal formula for infinite sets of mutually commuting local charges with spins equal to the exponents of the underlying classical algebra modulo its Coxeter number. Many of these results extend to the supersymmetric PCM, but with local conserved charges associated with antisymmetric invariants in the Lie algebra. We comment briefly on the quantum conservation of local charges in both the bosonic and super PCMs.
Conserved charges and supersymmetry in principal chiral and WZW models
J. M. Evans,M. Hassan,N. J. MacKay,A. J. Mountain
Physics , 2000, DOI: 10.1016/S0550-3213(00)00257-1
Abstract: Conserved and commuting charges are investigated in both bosonic and supersymmetric classical chiral models, with and without Wess-Zumino terms. In the bosonic theories, there are conserved currents based on symmetric invariant tensors of the underlying algebra, and the construction of infinitely many commuting charges, with spins equal to the exponents of the algebra modulo its Coxeter number, can be carried out irrespective of the coefficient of the Wess-Zumino term. In the supersymmetric models, a different pattern of conserved quantities emerges, based on antisymmetric invariant tensors. The current algebra is much more complicated than in the bosonic case, and it is analysed in some detail. Two families of commuting charges can be constructed, each with finitely many members whose spins are exactly the exponents of the algebra (with no repetition modulo the Coxeter number). The conserved quantities in the bosonic and supersymmetric theories are only indirectly related, except for the special case of the WZW model and its supersymmetric extension.
Development of a Hybrid Photo-Diode and its Front-End Electronics for the BTEV Experiment
R. J. Mountain,for the BTeV Collaboration
Physics , 2002, DOI: 10.1016/S0168-9002(03)00271-7
Abstract: This paper describes the development of a 163-channel Hybrid Photo-Diode (HPD) to be used in the RICH Detector for the BTEV Experiment. This is a joint development project with DEP, Netherlands. It also reports on the development of associated front-end readout electronics based on the va_btev ASIC, undertaken with IDEAS, Norway. Results from bench tests of the first prototypes are presented.
Advanced Technology Large-Aperture Space Telescope (ATLAST): Characterizing Habitable Worlds
M. Postman,W. Traub,J. Krist,K. Stapelfeldt,R. Brown,W. Oegerle,A. Lo,M. Clampin,R. Soummer,J. Wiseman,M. Mountain
Physics , 2009,
Abstract: The Advanced Technology Large Aperture Space Telescope (ATLAST) is a set of mission concepts for the next generation UV-Optical-Near Infrared space telescope with an aperture size of 8 to 16 meters. ATLAST, using an internal coronagraph or an external occulter, can characterize the atmosphere and surface of an Earth-sized exoplanet in the Habitable Zone of long-lived stars at distances up to ~45 pc, including its rotation rate, climate, and habitability. ATLAST will also allow us to glean information on the nature of the dominant surface features, changes in cloud cover and climate, and, potentially, seasonal variations in surface vegetation. ATLAST will be able to visit up to 200 stars in 5 years, at least three times each, depending on the technique used for starlight suppression and the telescope aperture. More frequent visits can be made for interesting systems.
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