15,273 research outputs found
Ionization of atoms by few-cycle EUV laser pulses: carrier-envelope phase dependence of the intra-pulse interference effects
We have investigated the ionization of the H atom by intense few-cycle laser
pulses, in particular the intra-pulse interference effects, and their
dependence on the carrier-envelope phase (CEP) of the laser pulse. In the final
momentum distribution of the continuum electrons the imprint of two types of
intra-pulse interference effects can be observed, namely the temporal and
spatial interference. During the spatial interference electronic wave packets
emitted at the same time, but following different paths interfere leading to an
interference pattern measurable in the electron spectra. This can be also
interpreted as the interference between a direct and a scattered wave, and the
spatial interference pattern as the holographic mapping (HM) of the target.
This HM pattern is strongly influenced by the carrier-envelope phase through
the shape of the laser pulse. Here, we have studied how the shape of the HM
pattern is modified by the CEP, and we have found an optimal CEP for the
observation of HM
Investigation of the composition of the Luna 16 lunar sample
The concentrations of aluminum, manganese, sodium, chromium, iron, cobalt, and 12 rare earth elements were determined by neutron activation analysis using slow neutrons. Oxygen and silicon were determined using a fast neutron generator. Mossbauer spectroscopy was used to investigate iron compounds in Luna 16 regolith samples from the upper part of the core
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
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
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
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