15,123 research outputs found
Strings and D-Branes with Boundaries
The covariant field equations of ten-dimensional super D-branes are obtained
by considering fundamental strings whose ends lie in the superworldsurface of
the D-brane. By considering in a similar fashion Dp-branes ending on
D(p+2)-branes we derive equations describing D-branes with dual potentials, as
well as the vector potentials.Comment: 12 pages, Late
The supermembrane revisited
The M2-brane is studied from the perspective of superembeddings. We review
the derivation of the M2-brane dynamics and the supergravity constraints from
the standard superembedding constraint and we discuss explicitly the induced
d=3, N=8 superconformal geometry on the worldvolume. We show that the gauged
supermembrane, for a target space with a U(1) isometry, is the standard
D2-brane in a type IIA supergravity background. In particular, the D2-brane
action, complete with the Dirac-Born-Infeld term, arises from the gauged
Wess-Zumino worldvolume 4-form via the brane action principle. The discussion
is extended to the massive D2-brane considered as a gauged supermembrane in a
massive D=11 superspace background. Type IIA supergeometry is derived using
Kaluza-Klein techniques in superspace.Comment: Latex, 46 pages, clarifying remarks and references adde
L-branes
The superembedding approach to -branes is used to study a class of
-branes which have linear multiplets on the worldvolume. We refer to these
branes as L-branes. Although linear multiplets are related to scalar multiplets
(with 4 or 8 supersymmetries) by dualising one of the scalars of the latter to
a -form field strength, in many geometrical situations it is the linear
multiplet version which arises naturally. Furthermore, in the case of 8
supersymmetries, the linear multiplet is off-shell in contrast to the scalar
multiplet. The dynamics of the L-branes are obtained by using a systematic
procedure for constructing the Green-Schwarz action from the superembedding
formalism. This action has a Dirac-Born-Infeld type structure for the -form.
In addition, a set of equations of motion is postulated directly in superspace,
and is shown to agree with the Green-Schwarz equations of motion.Comment: revised version, minor changes, references added, 22 pages, no
figures, LaTe
On the long range propagation of sound over irregular terrain
The theory of sound propagation over randomly irregular, nominally plane terrain of finite impedance is discussed. The analysis is an extension of the theory of coherent scatter originally proposed by Biot for an irregular rigid surface. It combines Biot's approach, wherein the surface irregularities are modeled by a homogeneous distribution of hemispherical bosses, with more conventional analyses in which the ground is modeled as a smooth plane of finite impedance. At sufficiently low frequencies the interaction of the surface irregularities with the nearfield of a ground-based source leads to the production of surface waves, which are effective in penetrating the ground shadow zone predicted for a smooth surface of the same impedance
On the generation of side-edge flap noise
A theory is proposed for estimating the noise generated at the side edges of part span trailing edge flaps in terms of pressure fluctuations measured just in-board of the side edge of the upper surface of the flap. Asymptotic formulae are developed in the opposite extremes of Lorentz contracted acoustic wavelength large/small compared with the chord of the flap. Interpolation between these limiting results enables the field shape and its dependence on subsonic forward flight speed to be predicted over the whole frequency range. It is shown that the mean width of the side edge gap between the flap and the undeflected portion of the airfoil has a significant influence on the intensity of the radiated sound. It is estimated that the noise generated at a single side edge of a full scale part span flap can exceed that produced along the whole of the trailing edge of the flap by 3 dB or more
Note on two-dimensional nonlinear gauge theories
A two-dimensional nonlinear gauge theory that can be proposed for
generalization to higher dimensions is derived by means of cohomological
arguments.Comment: 12 pages, LaTeX 2.
Kappa-symmetric higher derivative terms in brane actions
Using the superembedding formalism we construct supermembrane actions with
higher derivative terms which can be viewed as possible higher order terms in
effective actions. In particular, we provide the first example of an action for
an extended supersymmetric object with fully -symmetric extrinsic
curvature terms.Comment: 16 pages, Latex, References adde
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