6,385 research outputs found
On the construction of variant supergravities in D=11, D=10
We construct with a geometric procedure the supersymmetry transformation laws
and Lagrangian for all the ``variant'' D=11 and D=10 Type IIA supergravities.
We identify into our classification the D=11 and D=10 Type IIA ``variant''
theories first introduced by Hull performing T-duality transformation on both
spacelike and timelike circles. We find in addition a set of D=10 Type IIA
``variant'' supergravities that can not be obtained trivially from eleven
dimensions compactifying on a circle.Comment: 21 pages, Late
Complexified sigma model and duality
We show that the equations of motion associated with a complexified
sigma-model action do not admit manifest dual SO(n,n) symmetry. In the process
we discover new type of numbers which we called `complexoids' in order to
emphasize their close relation with both complex numbers and matroids. It turns
out that the complexoids allow to consider the analogue of the complexified
sigma-model action but with (1+1)-worldsheet metric, instead of
Euclidean-worldsheet metric. Our observations can be useful for further
developments of complexified quantum mechanics.Comment: 15 pages, Latex, improved versio
Time-like T-duality algebra
When compactifying M- or type II string-theories on tori of indefinite
space-time signature, their low energy theories involve sigma models on
E_{n(n)}/H_n, where H_n is a not necessarily compact subgroup of E_{n(n)} whose
complexification is identical to the complexification of the maximal compact
subgroup of E_{n(n)}. We discuss how to compute the group H_n. For finite
dimensional E_{n(n)}, a formula derived from the theory of real forms of E_n
algebra's gives the possible groups immediately. A few groups that have not
appeared in the literature are found. For n=9,10,11 we compute and describe the
relevant real forms of E_n and H_n. A given H_n can correspond to multiple
signatures for the compact torus. We compute the groups H_n for all
compactifications of M-, M*-, and M'-theories, and type II-, II*- and
II'-theories on tori of arbitrary signature, and collect them in tables that
outline the dualities between them. In an appendix we list cosets G/H, with G
split and H a subgroup of G, that are relevant to timelike toroidal
compactifications and oxidation of theories with enhanced symmetries.Comment: LaTeX, 37 pages, 1 eps-figure, uses JHEP.cls; v2. corrected typo's in
tables 16 and 17, minor changes to tex
U-duality as General Coordinate Transformations, and Spacetime Geometry
We show that the full global symmetry groups of all the D-dimensional maximal
supergravities can be described in terms of the closure of the internal general
coordinate transformations of the toroidal compactifications of D=11
supergravity and of type IIB supergravity, with type IIA/IIB T-duality
providing an intertwining between the two pictures. At the quantum level, the
part of the U-duality group that corresponds to the surviving discretised
internal general coordinate transformations in a given picture leaves the
internal torus invariant, while the part that is not described by internal
general coordinate transformations can have the effect of altering the size or
shape of the internal torus. For example, M-theory compactified on a large
torus T^n can be related by duality to a compactification on a small torus, if
and only if n\ge 3. We also discuss related issues in the toroidal
compactification of the self-dual string to D=4. An appendix includes the
complete results for the toroidal reduction of the bosonic sector of type IIB
supergravity to arbitrary dimensions D\ge3.Comment: Latex, 28 page
Harmonic superpositions of non-extremal p-branes
The plot of allowed p and D values for p-brane solitons in D-dimensional
supergravity is the same whether the solitons are extremal or non-extremal. One
of the useful tools for relating different points on the plot is vertical
dimensional reduction, which is possible if periodic arrays of p-brane solitons
can be constructed. This is straightforward for extremal p-branes, since the
no-force condition allows arbitrary multi-centre solutions to be constructed in
terms of a general harmonic function on the transverse space. This has also
been shown to be possible in the special case of non-extremal black holes in
D=4 arrayed along an axis. In this paper, we extend previous results to include
multi-scalar black holes, and dyonic black holes. We also consider their
oxidation to higher dimensions, and we discuss general procedures for
constructing the solutions, and studying their symmetries.Comment: Latex, 23 page
Generalized Geometry and M theory
We reformulate the Hamiltonian form of bosonic eleven dimensional
supergravity in terms of an object that unifies the three-form and the metric.
For the case of four spatial dimensions, the duality group is manifest and the
metric and C-field are on an equal footing even though no dimensional reduction
is required for our results to hold. One may also describe our results using
the generalized geometry that emerges from membrane duality. The relationship
between the twisted Courant algebra and the gauge symmetries of eleven
dimensional supergravity are described in detail.Comment: 29 pages of Latex, v2 References added, typos fixed, v3 corrected
kinetic term and references adde
Stiffness and energy losses in cylindrically symmetric superconductor levitating systems
Stiffness and hysteretic energy losses are calculated for a magnetically
levitating system composed of a type-II superconductor and a permanent magnet
when a small vibration is produced in the system. We consider a cylindrically
symmetric configuration with only vertical movements and calculate the current
profiles under the assumption of the critical state model. The calculations,
based on magnetic energy minimization, take into account the demagnetization
fields inside the superconductor and the actual shape of the applied field. The
dependence of stiffness and hysteretic energy losses upon the different
important parameters of the system such as the superconductor aspect ratio, the
relative size of the superconductor-permanent magnet, and the critical current
of the superconductor are all systematically studied. Finally, in view of the
results, we provide some trends on how a system such as the one studied here
could be designed in order to optimize both the stiffness and the hysteretic
losses.Comment: 8 pages; 8 figure
Symmetries in M-theory: Monsters, Inc
We will review the algebras which have been conjectured as symmetries in
M-theory. The Borcherds algebras, which are the most general Lie algebras under
control, seem natural candidates.Comment: 6 pages, talk given by PHL at Cargese 200
A black hole hologram in de Sitter space
In this paper we show that the entropy of de Sitter space with a black hole
in arbitrary dimension can be understood using a modified Cardy-Verlinde
entropy formula. We also comment on the observer dependence of the de Sitter
entropy.Comment: 13 pages. Final version accepted for publication in JHEP. Added
references and improved presentatio
Chiral Reductions in the Salam-Sezgin Model
Reductions from six to four spacetime dimensions are considered for a class
of supergravity models based on the six-dimensional Salam-Sezgin model, which
is a chiral theory with a gauged U(1) R-symmetry and a positive scalar-field
potential. Reduction on a sphere and monopole background of such models
naturally yields four-dimensional theories without a cosmological constant. The
question of chirality preservation in such a reduction has been a topic of
debate. In this article, it is shown that the possibilities of dimensional
reduction bifurcate into two separate consistent dimensional-reduction schemes.
One of these retains the massless SU(2) vector gauge triplet arising from the
sphere's isometries, but it produces a non-chiral four-dimensional theory. The
other consistent scheme sets to zero the SU(2) gauge fields, but retains the
gauged U(1) from six dimensions and preserves chirality although the U(1) is
spontaneously broken. Extensions of the Salam-Sezgin model to include larger
gauge symmetries produce genuinely chiral models with unbroken gauge
symmetries.Comment: 37 page
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