13,001 research outputs found
Classification of supersymmetric backgrounds of string theory
We review the recent progress made towards the classification of
supersymmetric solutions in ten and eleven dimensions with emphasis on those of
IIB supergravity. In particular, the spinorial geometry method is outlined and
adapted to nearly maximally supersymmetric backgrounds. We then demonstrate its
effectiveness by classifying the maximally supersymmetric IIB G-backgrounds and
by showing that N=31 IIB solutions do not exist.Comment: 8 pages, contribution to the proceedings of the RTN project
`Constituents, Fundamental Forces and Symmetries of the Universe' conference
in Napoli, October 9 - 13, 200
Supersymmetric geometries of IIA supergravity I
IIA supergravity backgrounds preserving one supersymmetry locally admit four
types of Killing spinors distinguished by the orbits of on the
space of spinors. We solve the Killing spinor equations of IIA supergravity
with and without cosmological constant for Killing spinors representing two of
these orbits, with isotropy groups and .
In both cases, we identify the geometry of spacetime and express the fluxes in
terms of the geometry. We find that the geometric constraints of backgrounds
with a invariant Killing spinor are identical to
those found for heterotic backgrounds preserving one supersymmetry.Comment: 21 page
GAMMA: A Mathematica package for performing gamma-matrix algebra and Fierz transformations in arbitrary dimensions
We have developed a Mathematica package capable of performing gamma-matrix
algebra in arbitrary (integer) dimensions. As an application we can compute
Fierz transformations.Comment: 12 pages, LaTeX, v2: some clarifications added, updated package
availabl
A modern control approach to the design of the SPS control system
The structural dynamics of the solar power satellite were considered. The requirements on the vibration of the microwave antenna and the possibility of thermal induced vibration and severe structural-thermal interactions were considered. The possibility of using an active control system and modern control methods to mitigate structural problems is discussed
Invariant Killing spinors in 11D and type II supergravities
We present all isotropy groups and associated groups, up to discrete
identifications of the component connected to the identity, of spinors of
eleven-dimensional and type II supergravities. The groups are products
of a Spin group and an R-symmetry group of a suitable lower dimensional
supergravity theory. Using the case of SU(4)-invariant spinors as a paradigm,
we demonstrate that the groups, and so the R-symmetry groups of
lower-dimensional supergravity theories arising from compactifications, have
disconnected components. These lead to discrete symmetry groups reminiscent of
R-parity. We examine the role of disconnected components of the groups
in the choice of Killing spinor representatives and in the context of
compactifications.Comment: 22 pages, typos correcte
The supersymmetric solutions and extensions of ungauged matter-coupled N=1,d=4 supergravity
We find the most general supersymmetric solutions of ungauged N=1,d=4
supergravity coupled to an arbitrary number of vector and chiral
supermultiplets, which turn out to be essentially pp-waves and strings. We also
introduce magnetic 1-forms and their supersymmetry transformations and 2-forms
associated to the isometries of the scalar manifold and their supersymmetry
transformations. Only the latter can couple to BPS objects (strings), in
agreement with our results.Comment: Some misprints and citations correcte
Monotone-light factorisation systems and torsion theories
Given a torsion theory (Y,X) in an abelian category C, the reflector I from C
to the torsion-free subcategory X induces a reflective factorisation system (E,
M) on C. It was shown by A. Carboni, G.M. Kelly, G. Janelidze and R. Par\'e
that (E, M) induces a monotone-light factorisation system (E',M*) by
simultaneously stabilising E and localising M, whenever the torsion theory is
hereditary and any object in C is a quotient of an object in X. We extend this
result to arbitrary normal categories, and improve it also in the abelian case,
where the heredity assumption on the torsion theory turns out to be redundant.
Several new examples of torsion theories where this result applies are then
considered in the categories of abelian groups, groups, topological groups,
commutative rings, and crossed modules.Comment: 12 page
Non-Commutative Open (p,q)-String Theories
In this paper we make an SL(2,Z)-covariant generalisation of the
noncommutative theories, NCYM and NCOS on the D3-brane, and NCOS on the
D5-brane in type IIB. Usually, the noncommutative theories are obtained by
studying perturbative F-string theory, and the parameters governing the
noncommutative theories are given by the open string data. The S-duality of
NCYM and NCOS on the D3-brane has been seen by dualising the background,
keeping the F-string under study fixed. We give an SL(2,Z)-covariant
generalisation of the open string data relevant when one instead studies
perturbative (p,q)-string theory. The S-duality of NCYM and NCOS on the
D3-brane is reproduced by instead keeping the background fixed and studying
different (p,q)-string theories. We also obtain new noncommutative open
(p,q)-string theories on the D3-brane and the D5-brane which are S-dual to
ordinary NCOS. The theories are studied using the supergravity duals of the
D3-brane and the D5-brane, corresponding to a probe brane in the relevant
background.Comment: AMSLaTeX. 23 pages. Minor clarifications added. To be published in
JHE
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