9,539 research outputs found
Ozonation of cooling tower waters
Continuous ozone injection into water circulating between a cooling tower and heat exchanger with heavy scale deposits inhibits formation of further deposits, promotes flaking of existing deposits, inhibits chemical corrosion and controls algae and bacteria
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
The Schwinger SU(3) construction - I: Multiplicity problem and relation to induced representations
The Schwinger oscillator operator representation of SU(3) is analysed with
particular reference to the problem of multiplicity of irreducible
representations. It is shown that with the use of an unitary
representation commuting with the SU(3) representation, the infinity of
occurrences of each SU(3) irreducible representation can be handled in complete
detail. A natural `generating representation' for SU(3), containing each
irreducible representation exactly once, is identified within a subspace of the
Schwinger construction; and this is shown to be equivalent to an induced
representation of SU(3).Comment: Latex, 25 page
Low-degree multi-spectral p-mode fitting
We combine unresolved-Sun velocity and intensity observations at multiple wavelengths from the Helioseismic and Magnetic Imager and Atmospheric Imaging Array onboard the Solar Dynamics Observatory to investigate the possibility of multi-spectral mode-frequency estimation at low spherical harmonic degree. We test a simple multi-spectral algorithm using a common line width and frequency for each mode and a separate amplitude, background and asymmetry parameter, and compare the results with those from fits to the individual spectra. The preliminary results suggest that this approach may provide a more stable fit than using the observables separately
The cohomology of superspace, pure spinors and invariant integrals
The superform construction of supersymmetric invariants, which consists of
integrating the top component of a closed superform over spacetime, is
reviewed. The cohomological methods necessary for the analysis of closed
superforms are discussed and some further theoretical developments presented.
The method is applied to higher-order corrections in heterotic string theory up
to \a'^3. Some partial results on and are also given.Comment: 24 pages. Minor changes; added reference
Spinorial cohomology and maximally supersymmetric theories
Fields in supersymmetric gauge theories may be seen as elements in a
spinorial cohomology. We elaborate on this subject, specialising to maximally
supersymmetric theories, where the superspace Bianchi identities, after
suitable conventional constraints are imposed, put the theories on shell. In
these cases, the spinorial cohomologies describe in a unified manner gauge
transformations, fields and possible deformations of the models, e.g.
string-related corrections in an alpha' expansion. Explicit cohomologies are
calculated for super-Yang-Mills theory in D=10, for the N=(2,0) tensor
multiplet in D=6 and for supergravity in D=11, in the latter case from the
point of view of both the super-vielbein and the super-3-form potential. The
techniques may shed light on some questions concerning the alpha'-corrected
effective theories, and result in better understanding of the role of the
3-form in D=11 supergravity.Comment: 23 pp, plain tex. v2: Minor changes, references adde
BPS Solitons in M5-Brane Worldvolume Theory with Constant Three-Form Field
We study BPS solutions for a self-dual string and a neutral string in
M5-brane worldvolume theory with constant three-form field. We further
generalize such solitons to superpose with a calibrated surface. We also study
a traveling wave on a calibrated surface in the constant three-form field
background.Comment: 12 pages, LaTeX, minor correction, added referenc
11D supergravity at
We compute certain spinorial cohomology groups controlling possible
supersymmetric deformations of eleven-dimensional supergravity up to order
in the Planck length. At and the spinorial
cohomology groups are trivial and therefore the theory cannot be deformed
supersymmetrically. At the corresponding spinorial cohomology
group is generated by a nontrivial element. On an eleven-dimensional manifold
such that , this element corresponds to a supersymmetric
deformation of the theory, which can only be redefined away at the cost of
shifting the quantization condition of the four-form field strength.Comment: 10 pages, 1 figure. v2: references adde
Super-Yang-Mills and M5-branes
We uplift 5-dimensional super-Yang-Mills theory to a 6-dimensional gauge
theory with the help of a space-like constant vector , whose norm
determines the Yang-Mills coupling constant. After the localization of
the 6D gauge theory acquires Lorentzian invariance as well as scale invariance.
We discuss KK states, instantons and the flux quantization. The 6D theory
admits extended solutions like 1/2 BPS `strings' and monopoles.Comment: 15 pages; minor changes, to appear in JHE
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