6,990 research outputs found
The Algebra of Non-Local Charges in Non-Linear Sigma Models
We obtain the exact Dirac algebra obeyed by the conserved non-local charges
in bosonic non-linear sigma models. Part of the computation is specialized for
a symmetry group . As it turns out the algebra corresponds to a cubic
deformation of the Kac-Moody algebra. The non-linear terms are computed in
closed form. In each Dirac bracket we only find highest order terms (as
explained in the paper), defining a saturated algebra. We generalize the
results for the presence of a Wess-Zumino term. The algebra is very similar to
the previous one, containing now a calculable correction of order one unit
lower.Comment: 27 pages + figures available via ftp, Plain TeX, IFUSP/P-106
Scalar field perturbations of the Schwarzschild black hole in the G\"{o}del Universe
We investigate the scalar field perturbations of the 4+1-dimensional
Schwarzschild black hole immersed in a G\"{o}del Universe, described by the
Gimon-Hashimoto solution.This may model the influence of the possible rotation
of the Universe upon the radiative processes near a black hole. In the regime
when the scale parameter of the G\"{o}del background is small, the
oscillation frequency is linearly decreasing with , while the damping time
is increasing. The quasinormal modes are damping, implying stability of the
Schwarzschild-G\"{o}del space-time against scalar field perturbations. The
approximate analytical formula for large multipole numbers is found.Comment: 13 pages, 4 figures, 1 table, misprints corrected, to be published in
Phys.Rev.
Non-critical superstrings: a comparison between continuum and discrete approaches
We review the relation between the matrix model and Liouville approaches to
two-dimensional gravity as elaborated by Moore, Seiberg and Staudacher. Then,
based on the supersymmetric Liouville formulation and the discrete eigenvalue
model proposed by Alvarez-Gaum\'e, Itoyama, Ma\~nes and Zadra, we extend the
previous relation to the supersymmetric case. The minisuperspace approximation
for the supersymmetric case is formulated, and the corresponding wave equation
is found.Comment: 25 pages, plain tex, prep CERN-TH-7161/9
Current Algebra of Super WZNW Models
We derive the current algebra of supersymmetric principal chiral models with
a Wess-Zumino term. At the critical point one obtains two commuting super
Kac-Moody algebra as expected, but in general there are intertwining fields
connecting both right and left sectors, analogously to the bosonic case.
Moreover, in the present supersymmetric extension we have a quadratic algebra,
rather than an affine Lie algebra, due to the mixing between bosonic and
fermionic fields since the purely fermionic sector displays a Lie algebra as
well.Comment: 13 page
Integrable models: from dynamical solutions to string theory
We review the status of integrable models from the point of view of their
dynamics and integrability conditions. Some integrable models are discussed in
detail. We comment on the use it is made of them in string theory. We also
discuss the Bethe Ansatz solution of the SO(6) symmetric Hamiltonian with SO(6)
boundary.
This work is especially prepared for the seventieth anniversaries of
Andr\'{e} Swieca (in memoriam) and Roland K\"{o}berle.Comment: 24 pages, to appear in Brazilian Journal of Physic
Integrability of the Wess_Zumino-Witten model as a non-ultralocal theory
We consider the 2--dimensional Wess--Zumino--Witten (WZW) model in the
canonical formalism introduced in a previous paper by two of us. Using an
-- matrix approach to non--ultralocal field theories we find the Poisson
algebra of monodromy matrices and of conserved quantities with a new,
non--dynamical, matrix.Comment: Revised version. 3 references added. 13 pages, latex, no figure
NASA refan program status
The objective of the refan program is to demonstrate the technical feasibility of substantially reducing the noise levels of existing JT8D powered aircraft. The program consists of the design, manufacturing and testing of the refan engines and modified nacelles and airplanes. Experimental testing was completed for the refan engine both at sea level and at altitude conditions. Ground testing for the B727 side- and center-engine installations and flight testing of the DC-9 with refan engines and acoustic nacelles were performed. Preliminary results presented show that substantial noise reductions were achieved
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