52,812 research outputs found
An octonionic formulation of the M-theory algebra
We give an octonionic formulation of the N = 1 supersymmetry algebra in D =
11, including all brane charges. We write this in terms of a novel outer
product, which takes a pair of elements of the division algebra A and returns a
real linear operator on A. More generally, with this product comes the power to
rewrite any linear operation on R^n (n = 1,2,4,8) in terms of multiplication in
the n-dimensional division algebra A. Finally, we consider the reinterpretation
of the D = 11 supersymmetry algebra as an octonionic algebra in D = 4 and the
truncation to division subalgebras
A magic pyramid of supergravities
By formulating N = 1, 2, 4, 8, D = 3, Yang-Mills with a single Lagrangian and
single set of transformation rules, but with fields valued respectively in
R,C,H,O, it was recently shown that tensoring left and right multiplets yields
a Freudenthal-Rosenfeld-Tits magic square of D = 3 supergravities. This was
subsequently tied in with the more familiar R,C,H,O description of spacetime to
give a unified division-algebraic description of extended super Yang-Mills in D
= 3, 4, 6, 10. Here, these constructions are brought together resulting in a
magic pyramid of supergravities. The base of the pyramid in D = 3 is the known
4x4 magic square, while the higher levels are comprised of a 3x3 square in D =
4, a 2x2 square in D = 6 and Type II supergravity at the apex in D = 10. The
corresponding U-duality groups are given by a new algebraic structure, the
magic pyramid formula, which may be regarded as being defined over three
division algebras, one for spacetime and each of the left/right Yang-Mills
multiplets. We also construct a conformal magic pyramid by tensoring conformal
supermultiplets in D = 3, 4, 6. The missing entry in D = 10 is suggestive of an
exotic theory with G/H duality structure F4(4)/Sp(3) x Sp(1).Comment: 30 pages, 6 figures. Updated to match published version. References
and comments adde
Super Yang-Mills, division algebras and triality
We give a unified division algebraic description of (D=3, N=1,2,4,8), (D=4,
N=1,2,4), (D=6, N=1,2) and (D=10, N=1) super Yang-Mills theories. A given
(D=n+2, N) theory is completely specified by selecting a pair (A_n, A_{nN}) of
division algebras, A_n, A_{nN} = R, C, H, O, where the subscripts denote the
dimension of the algebras. We present a master Lagrangian, defined over
A_{nN}-valued fields, which encapsulates all cases. Each possibility is
obtained from the unique (O, O) (D=10, N=1) theory by a combination of
Cayley-Dickson halving, which amounts to dimensional reduction, and removing
points, lines and quadrangles of the Fano plane, which amounts to consistent
truncation. The so-called triality algebras associated with the division
algebras allow for a novel formula for the overall (spacetime plus internal)
symmetries of the on-shell degrees of freedom of the theories. We use imaginary
A_{nN}-valued auxiliary fields to close the non-maximal supersymmetry algebra
off-shell. The failure to close for maximally supersymmetric theories is
attributed directly to the non-associativity of the octonions.Comment: 24 pages, 2 figures. Updated to match published version. References
adde
TACAN operational description for the space shuttle orbital flight test program
The TACAN subsystems (three TACAN transponders, six antennas, a subsystem operating program, and redundancy management software in a tutorial form) are discussed and the interaction between these subsystems and the shuttle navigation system are identified. The use of TACAN during the first space transportation system (STS-1), is followed by a brief functional description of the TACAN hardware, then proceeds to cover the software units with a view to the STS-1, and ends with a discussion on the shuttle usage of the TACAN data and anticipated performance
Quantum key distribution over 122 km of standard telecom fiber
We report the first demonstration of quantum key distribution over a standard
telecom fiber exceeding 100 km in length. Through careful optimisation of the
interferometer and single photon detector, we achieve a quantum bit error ratio
of 8.9% for a 122km link, allowing a secure shared key to be formed after error
correction and privacy amplification. Key formation rates of up to 1.9 kbit/sec
are achieved depending upon fiber length. We discuss the factors limiting the
maximum fiber length in quantum cryptography
AGAPEROS: Searching for variable stars in the LMC Bar with the Pixel Method. I. Detection, astrometry and cross-identification
We extend the work developed in previous papers on microlensing with a
selection of variable stars. We use the Pixel Method to select variable stars
on a set of 2.5 x 10**6 pixel light curves in the LMC Bar presented elsewhere.
The previous treatment was done in order to optimise the detection of long
timescale variations (larger than a few days) and we further optimise our
analysis for the selection of Long Timescale and Long Period Variables
(LT&LPV). We choose to perform a selection of variable objects as comprehensive
as possible, independent of periodicity and of their position on the colour
magnitude diagram. We detail the different thresholds successively applied to
the light curves, which allow to produce a catalogue of 632 variable objects.
We present a table with the coordinate of each variable, its EROS magnitudes at
one epoch and an indicator of blending in both colours, together with a finding
chart.
A cross-correlation with various catalogues shows that 90% of those variable
objects were undetected before, thus enlarging the sample of LT&LPV previously
known in this area by a factor of 10. Due to the limitations of both the Pixel
Method and the data set, additional data -- namely a longer baseline and near
infrared photometry -- are required to further characterise these variable
stars, as will be addressed in subsequent papers.Comment: 11 pages with 10 figure
Global symmetries of Yang-Mills squared in various dimensions
Tensoring two on-shell super Yang-Mills multiplets in dimensions
yields an on-shell supergravity multiplet, possibly with additional matter
multiplets. Associating a (direct sum of) division algebra(s) with
each dimension we obtain formulae for the algebras
and of the U-duality group and its maximal
compact subgroup , respectively, in terms of the internal global symmetry
algebras of each super Yang-Mills theory. We extend our analysis to include
supergravities coupled to an arbitrary number of matter multiplets by allowing
for non-supersymmetric multiplets in the tensor product.Comment: 25 pages, 2 figures, references added, minor typos corrected, further
comments on sec. 2.4 included, updated to match version to appear in JHE
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