239 research outputs found
Domain Walls on the Brane
We show that all branes admit worldvolume domain wall solutions. We find one
class of solutions for which the tension of the brane changes discontinuously
along the domain wall. These solutions are not supersymmetric. We argue that
there is another class of domain wall solutions which is supersymmetric. A
particular case concerns supersymmetric domain wall solutions on IIB D-5- and
NS-5-branes.Comment: 18 pages, Tex, uses phyzz
A Brane Teaser
In this note we study the puzzle posed by two M5-branes intersecting on a
string (or equivalently, a single M5-brane wrapping a holomorphic four-cycle in
C^4). It has been known for a while that this system is different from all
other configurations built using self-intersecting M-branes; in particular the
corresponding supergravity solution exhibits various curious features which
have remained unexplained. We propose that the resolution to these puzzles lies
in the existence of a non-zero two-form on the M5-brane world-volume.Comment: 21 pages. References adde
M2-branes wrapped on holomorphic curves
The generalised calibration for a wrapped membrane is gauge equivalent to the
supergravity three-form under which the membrane is electrically charged. Given
the relevant calibration, one can go a long way towards constructing the
supergravity solution for the wrapped brane. Applications of this method have
been restricted since generalised calibrations have not yet been completely
classified in spacetimes with non-vanishing flux. In this paper, we take a
first step towards such a classification by studying membranes wrapping
holomorphic curves. Supersymmetry preservation imposes a constraint on the
Hermitean metric in the embedding space and it is found that this can be
expressed as a restriction on possible generalised calibrations. Allowed
calibrations in a particular spacetime are simply those which satisfy the
constraint equation relevant to that background; in particular, we see that the
previously considered Kahler calibrations are just a subclass of possible
solutions.Comment: Discussion clarified, typos corrected, references updated. Results
remain unchanged. 12 page
That's a wrap!
Calibration technology provides us with a fast and elegant way to find the
supergravity solutions for BPS wrapped M-branes. Its true potential had however
remained untapped due to the absence of a classification of calibrations in
spacetimes with non-trivial flux. The applications of this method were thus
limited in practise to M-branes wrapping Kahler calibrated cycles. In this
paper, we catagorize a type of generalised calibrations which exist in
supergravity backgrounds and contain Kahler calibrations as a sub-class. This
broadens the arena of brane configurations whose supergravity solutions are
accessible through the calibration 'short-cut' method.Comment: 19 pages, typos correcte
D-brane Solitons in Supersymmetric Sigma-Models
Massive D=4 N=2 supersymmetric sigma models typically admit domain wall
(Q-kink) solutions and string (Q-lump) solutions, both preserving 1/2
supersymmetry. We exhibit a new static 1/4 supersymmetric `kink-lump' solution
in which a string ends on a wall, and show that it has an effective realization
as a BIon of the D=4 super DBI-action. It is also shown to have a
time-dependent Q-kink-lump generalization which reduces to the Q-lump in a
limit corresponding to infinite BI magnetic field. All these 1/4 supersymmetric
sigma-model solitons are shown to be realized in M-theory as calibrated, or
`Q-calibrated', M5-branes in an M-monopole background.Comment: 16 pages, 3 figures, Late
The holonomy of the supercovariant connection and Killing spinors
We show that the holonomy of the supercovariant connection for M-theory
backgrounds with Killing spinors reduces to a subgroup of SL(32-N,\bR)\st
(\oplus^N \bR^{32-N}). We use this to give the necessary and sufficient
conditions for a background to admit Killing spinors. We show that there is
no topological obstruction for the existence of up to 22 Killing spinors in
eleven-dimensional spacetime. We investigate the symmetry superalgebras of
supersymmetric backgrounds and find that their structure constants are
determined by an antisymmetric matrix. The Lie subalgebra of bosonic generators
is related to a real form of a symplectic group. We show that there is a
one-one correspondence between certain bases of the Cartan subalgebra of
sl(32, \bR) and supersymmetric planar probe M-brane configurations. A
supersymmetric probe configuration can involve up to 31 linearly independent
planar branes and preserves one supersymmetry. The space of supersymmetric
planar probe M-brane configurations is preserved by an SO(32,\bR) subgroup of
SL(32, \bR).Comment: 27 pages, a key reference was added. v3: minor change
1.2dB/cm gain in an erbium:lutecium co-doped Al/P silica fibre
We report a peak gain of 1.2dB/cm at 1535nm in an Erbium:Lutecium codoped Al/P/Si fibre fabricated using a standard MCVD and solution doping technique. This is the highest gain per unit length yet reported in an erbium doped fiber amplifier. The incorporation of lutetium into the glass is shown to reduce the erbium ion clustering within the fiber
Branes on Generalized Calibrated Submanifolds
We extend previous results on generalized calibrations to describe
supersymmetric branes in supergravity backgrounds with diverse fields turned
on, and provide several new classes of examples. As an important application,
we show that supersymmetric D-branes in compactifications with field strength
fluxes, and on SU(3)-structure spaces, wrap generalized calibrated
submanifolds, defined by simple conditions in terms of the underlying globally
defined, but non-closed, 2- and 3-forms. We provide examples where the
geometric moduli of D-branes (for instance D7-branes in 3-form flux
configurations) are lifted by the generalized calibration condition. In
addition, we describe supersymmetric D6-branes on generalized calibrated
3-submanifolds of half-flat manifolds, which provide the mirror of B-type
D-branes in IIB CY compactifications with 3-form fluxes. Supersymmetric sets of
such D-branes carrying no homology charges are mirror to supersymmetric sets of
D-branes which are homologically non-trivial, but trivial in K-theory. As an
additional application, we describe models with chiral gauge sectors, realized
in terms of generalized calibrated brane box configurations of NS- and
D5-branes, which are supersymmetric but carry no charges, so that no
orientifold planes are required in the compactification.Comment: 40 pages, 3 figures, references adde
Multiple Intersections of D-branes and M-branes
We give a classification of all multiple intersections of D-branes in ten
dimensions and M-branes in eleven dimensions that corresponds to threshold BPS
bound states. The residual supersymmetry of these composite branes is
determined. By dimensional reduction composite p-branes in lower dimensions can
be constructed. We emphasize in dimensions D greater or equal than two, those
solutions which involve a single scalar and depend on a single harmonic
function. For these extremal branes we obtain the strength of the coupling
between the scalar and the gauge field. In particular we give a D-brane and
M-brane interpretation of extreme p-branes in two, three and four dimensions.Comment: 28 pages, LaTeX, 4 figures, corrections in table 1 and figure
BPS preons and the AdS-M-algebra
We present here the AdS generalization of BPS preons, which were introduced
as the hypothetical constituents of M-theory preserving all but one
supersymmetries. Our construction, suggested by the relation of `lower
dimensional preons' with higher spin theories, can be considered as a
deformation of the M-algebraic description of the single supersymmetry broken
by a preon, and provides another reason to identify the AdS generalization of
the M-algebra, which we call the AdS-M-algebra, with osp(1|32).Comment: Plain latex, no figures, 19 pages minor corrections, one ref. added,
as published in JHEP 04 (2008) 06
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