5,242 research outputs found
The Theoretical and Experimental Determination of the Input Impedance of a Small Loop of Electric Current Immersed in an Anisotropic Plasma
Exact expression for input impedance of small loop of electric current when loop is immersed in infinite, homogeneous, cold anisotropic plasm
A classification of the dispersion surfaces in a magneto-ionic medium and a study of the associated radiation patterns scientific report no. 2
Dispersion surface classification in magnetoionic medium and associated radiation pattern
Dyonic Membranes
We present dyonic multi-membrane solutions of the N=2 D=8 supergravity theory
that serves as the effective field theory of the -compactified type II
superstring theory. The `electric' charge is fractional for generic asymptotic
values of an axion field, as for D=4 dyons. These membrane solutions are
supersymmetric, saturate a Bogomolnyi bound, fill out orbits of an
subgroup of the type II D=8 T-duality group, and are non-singular when
considered as solutions of -compactified D=11 supergravity. On
compactification to D=4, the conjectured type II/heterotic equivalence allows
the group to be reinterpreted as the S-duality group of the
toroidally compactified heterotic string and the dyonic membranes wrapped
around homology two-cycles of as S-duals of perturbative heterotic string
states.Comment: Phyzzx. 27 pp. Additional para. added to introductio
Development and modification of a digital program for final approach to landing
The development and implementation of a dynamic digital computer simulator which may be used to evaluate aircraft performance when operating under the control and guidance of various navigation, landing, and flight control systems are discussed. The digital computer program may be used to simulate and evaluate the relationships and interactions between various factors such as the microwave landing system, avionics receivers and onboard processors, aircraft aerodynamics, aircraft automatic control systems, control surfaces, and wind and other external effects. The models used to represent aircraft aerodynamics, control system and control surfaces; weather and wind effects; and the microwave landing system are described. Example results are presented for a simulation of a Boeing 737 using two sample control systems while subjected to various atmospheric conditions and microwave landing system errors. The limitations and performance capabilities of these control systems are discussed in terms of their ability to utilize the microwave landing system signal
D=6, N=1 String Vacua and Duality
We review the structure string vacua with emphasis on the
different connections due to T-dualities and S-dualities. The topics discussed
include: Anomaly cancellation; K3 and orbifold heterotic
compactifications; T-dualities between and
heterotic vacua; non-perturbative heterotic vacua and small instantons; N=2
Type-II/Heterotic duality in D=4 ; F-theory/heterotic duality in D=6; and
heterotic/heterotic duality in six and four dimensions.Comment: 52 pages, plain Latex. To appear in the proceedings of the APCTP
Winter School on Duality, Mt. Sorak (Korea), February 199
Refinement and validation of two digital Microwave Landing System (MLS) theoretical models
Two digital microwave landing system theoretical models are considered which are generic models for the Doppler and scanning-beam frequency reference versions of the MLS. These models represent errors resulting from both system noise and discrete multipath. The data used for the validation effort were obtained from the Texas Instrument conventional scanning beam and the Hazeltine Doppler feasibility hardware versions of the MLS. Topics discussed include tape read software, time history plots, computation of power spectral density, smoothed power spectra, best-fit models, different equations for digital simulation, and discrete multipath errors
Zero Modes for the D=11 Membrane and Five-Brane
There exist extremal p-brane solutions of supergravity for
p=2~and~5. In this paper we investigate the zero modes of the membrane and the
five-brane solutions as a first step toward understanding the full quantum
theory of these objects. It is found that both solutions possess the correct
number of normalizable zero modes dictated by supersymmetry.Comment: Minor typos corrected, one reference added, agrees with published
version. 9 RevTeX pages, 1 figure include
Putting String/Fivebrane Duality to the Test
According to string/fivebrane duality, the Green-Schwarz factorization of the
spacetime anomaly polynomial into means that just
as is the anomaly polynomial of the string worldsheet so
should be the anomaly polynomial of the fivebrane worldvolume. To test
this idea we perform a fivebrane calculation of and find perfect
agreement with the string one--loop result.Comment: 14 pages, CERN TH-6614/92, CTP-TAMU 60/9
Multiple Realisations of N=1 Vacua in Six Dimensions
A while ago, examples of N=1 vacua in D=6 were constructed as orientifolds of
Type IIB string theory compactified on the K3 surface. Among the interesting
features of those models was the presence of D5-branes behaving like small
instantons, and the appearance of extra tensor multiplets. These are both
non-perturbative phenomena from the point of view of heterotic string theory.
Although the orientifold models are a natural setting in which to study these
non-perturbative Heterotic string phenomena, it is interesting and instructive
to explore how such vacua are realised in Heterotic string theory, M-theory and
F-theory, and consider the relations between them. In particular, we consider
models of M-theory compactified on K3 x S^1/Z_2 with fivebranes present on the
interval. There is a family of such models which yields the same spectra as a
subfamily of the orientifold models. By further compactifying on T^2 to four
dimensions we relate them to Heterotic string spectra. We then use
Heterotic/Type IIA duality to deduce the existence of Calabi-Yau 3-folds which
should yield the original six dimensional orientifold spectra if we use them to
compactify F-theory. Finally, we show in detail how to take a limit of such an
F-theory compactification which returns us to the Type IIB orientifold models.Comment: Uses harvmac.tex and epsf.tex, 22 pages (harvmac `b'), 1 figur
Vacuum interpolation in supergravity via super p-branes
We show that many of the recently proposed supersymmetric p-brane solutions
of d=10 and d=11 supergravity have the property that they interpolate between
Minkowski spacetime and a compactified spacetime, both being supersymmetric
supergravity vacua. Our results imply that the effective worldvolume action for
small fluctuations of the super p-brane is a supersingleton field theory for
, as has been often conjectured in the past.Comment: 8p
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