34,413 research outputs found
Generalised BPS conditions
We write down two E11 invariant conditions which at low levels reproduce the
known half BPS conditions for type II theories. These new conditions contain,
in addition to the familiar central charges, an infinite number of further
charges which are required in an underlying theory of strings and branes. We
comment on the application of this work to higher derivative string
corrections
Generalised Space-time and Gauge Transformations
We consider the generalised space-time introduced by the author in 2003 in
the context of the non-linear realisation of the semi-direct product of E11 and
its first fundamental representation. For all the fields we propose gauge
transformations which are compatible with the underlying E11 structure. A
crucial role is played by the generalised vielbein that the generalised
space-time possess. We work out the explicit form of the gauge transformations,
at low levels, in four, five and eleven dimensions.Comment: 33 page
Representations of G+++ and the role of space-time
We consider the decomposition of the adjoint and fundamental representations
of very extended Kac-Moody algebras G+++ with respect to their regular A type
subalgebra which, in the corresponding non-linear realisation, is associated
with gravity. We find that for many very extended algebras almost all the A
type representations that occur in the decomposition of the fundamental
representations also occur in the adjoint representation of G+++. In
particular, for E8+++, this applies to all its fundamental representations.
However, there are some important examples, such as An+++, where this is not
true and indeed the adjoint representation contains no generator that can be
identified with a space-time translation. We comment on the significance of
these results for how space-time can occur in the non-linear realisation based
on G+++. Finally we show that there is a correspondence between the A
representations that occur in the fundamental representation associated with
the very extended node and the adjoint representation of G+++ which is
consistent with the interpretation of the former as charges associated with
brane solutions.Comment: 45 pages, 9 figures, 9 tables, te
Duality Symmetries and G^{+++} Theories
We show that the non-linear realisations of all the very extended algebras
G^{+++}, except the B and C series which we do not consider, contain fields
corresponding to all possible duality symmetries of the on-shell degrees of
freedom of these theories. This result also holds for G_2^{+++} and we argue
that the non-linear realisation of this algebra accounts precisely for the form
fields present in the corresponding supersymmetric theory. We also find a
simple necessary condition for the roots to belong to a G^{+++} algebra.Comment: 35 pages. v2: 2 appendices added, other minor corrections. v3: tables
corrected, other minor changes, one appendix added, refs. added. Version
published in Class. Quant. Gra
Chiral Green's Functions in Superconformal Field Theory
By solving the Ward identities in a superconformal field theory we find the
unique three-point Green's functions composed of chiral superfields for N =
1,2,3,4 supersymmetry. We show that the N=1 four-point function with R-charge
equal to one is uniquely determined by the Ward identities up to the
specification of four constants. We discuss why chiral Green's functions above
three-points, with total R-charge greater than N, are not uniquely determined.Comment: 32 pages, no figures, LaTeX2e forma
Fractional Calculus as a Macroscopic Manifestation of Randomness
We generalize the method of Van Hove so as to deal with the case of
non-ordinary statistical mechanics, that being phenomena with no time-scale
separation. We show that in the case of ordinary statistical mechanics, even if
the adoption of the Van Hove method imposes randomness upon Hamiltonian
dynamics, the resulting statistical process is described using normal calculus
techniques. On the other hand, in the case where there is no time-scale
separation, this generalized version of Van Hove's method not only imposes
randomness upon the microscopic dynamics, but it also transmits randomness to
the macroscopic level. As a result, the correct description of macroscopic
dynamics has to be expressed in terms of the fractional calculus.Comment: 20 pages, 1 figur
E11 and Spheric Vacuum Solutions of Eleven- and Ten dimensional Supergravity Theories
In view of the newly conjectured Kac-Moody symmetries of supergravity
theories placed in eleven and ten dimensions, the relation between these
symmetry groups and possible compactifications are examined. In particular, we
identify the relevant group cosets that parametrise the vacuum solutions of AdS
x S type.Comment: discussion improve
Remarks on E11 approach
We consider a few topics in approach to superstring/M-theory: even
subgroups ( orbifolds) of , n=11,10,9 and their connection to
Kac-Moody algebras; subgroup of and coincidence of one of
its weights with the weight of , known to contain brane charges;
possible form of supersymmetry relation in ; decomposition of
w.r.t. the and its square root at first few levels; particle orbit
of . Possible relevance of coadjoint orbits method is
noticed, based on a self-duality form of equations of motion in .Comment: Two references adde
E_11 and M Theory
We argue that eleven dimensional supergravity can be described by a
non-linear realisation based on the group E_{11}. This requires a formulation
of eleven dimensional supergravity in which the gravitational degrees of
freedom are described by two fields which are related by duality. We show the
existence of such a description of gravity.Comment: 21 pages, some typos corrected and two references adde
Mining Missing Hyperlinks from Human Navigation Traces: A Case Study of Wikipedia
Hyperlinks are an essential feature of the World Wide Web. They are
especially important for online encyclopedias such as Wikipedia: an article can
often only be understood in the context of related articles, and hyperlinks
make it easy to explore this context. But important links are often missing,
and several methods have been proposed to alleviate this problem by learning a
linking model based on the structure of the existing links. Here we propose a
novel approach to identifying missing links in Wikipedia. We build on the fact
that the ultimate purpose of Wikipedia links is to aid navigation. Rather than
merely suggesting new links that are in tune with the structure of existing
links, our method finds missing links that would immediately enhance
Wikipedia's navigability. We leverage data sets of navigation paths collected
through a Wikipedia-based human-computation game in which users must find a
short path from a start to a target article by only clicking links encountered
along the way. We harness human navigational traces to identify a set of
candidates for missing links and then rank these candidates. Experiments show
that our procedure identifies missing links of high quality
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