1,032 research outputs found
A Double Sigma Model for Double Field Theory
We define a sigma model with doubled target space and calculate its
background field equations. These coincide with generalised metric equation of
motion of double field theory, thus the double field theory is the effective
field theory for the sigma model.Comment: 26 pages, v1: 37 pages, v2: references added, v3: updated to match
published version - background and detail of calculations substantially
condensed, motivation expanded, refs added, results unchange
The Complexity of Routing with Few Collisions
We study the computational complexity of routing multiple objects through a
network in such a way that only few collisions occur: Given a graph with
two distinct terminal vertices and two positive integers and , the
question is whether one can connect the terminals by at least routes (e.g.
paths) such that at most edges are time-wise shared among them. We study
three types of routes: traverse each vertex at most once (paths), each edge at
most once (trails), or no such restrictions (walks). We prove that for paths
and trails the problem is NP-complete on undirected and directed graphs even if
is constant or the maximum vertex degree in the input graph is constant.
For walks, however, it is solvable in polynomial time on undirected graphs for
arbitrary and on directed graphs if is constant. We additionally study
for all route types a variant of the problem where the maximum length of a
route is restricted by some given upper bound. We prove that this
length-restricted variant has the same complexity classification with respect
to paths and trails, but for walks it becomes NP-complete on undirected graphs
On the Riemann Tensor in Double Field Theory
Double field theory provides T-duality covariant generalized tensors that are
natural extensions of the scalar and Ricci curvatures of Riemannian geometry.
We search for a similar extension of the Riemann curvature tensor by developing
a geometry based on the generalized metric and the dilaton. We find a duality
covariant Riemann tensor whose contractions give the Ricci and scalar
curvatures, but that is not fully determined in terms of the physical fields.
This suggests that \alpha' corrections to the effective action require \alpha'
corrections to T-duality transformations and/or generalized diffeomorphisms.
Further evidence to this effect is found by an additional computation that
shows that there is no T-duality invariant four-derivative object built from
the generalized metric and the dilaton that reduces to the square of the
Riemann tensor.Comment: 36 pages, v2: minor changes, ref. added, v3: appendix on frame
formalism added, version to appear in JHE
Boundary Conditions for Interacting Membranes
We investigate supersymmetric boundary conditions in both the Bagger-Lambert
and the ABJM theories of interacting membranes. We find boundary conditions
associated to the fivebrane, the ninebrane and the M-theory wave. For the ABJM
theory we are able to understand the enhancement of supersymmetry to produce
the (4,4) supersymmetry of the self-dual string. We also include supersymmetric
boundary conditions on the gauge fields that cancel the classical gauge anomaly
of the Chern-Simons terms.Comment: 36 pages, latex, v2 minor typos correcte
Entropy of the self-dual string soliton
We compute the entropy and the corresponding central charge of the self-dual
string soliton in the supergravity regime using the blackfold description of
the fully localized M2-M5 intersection.Comment: 15 pages, 1 figure, harvma
The Conformal Anomaly of M5-Branes
We show that the conformal anomaly for N M5-branes grows like . The
method we employ relates Coulomb branch interactions in six dimensions to
interactions in four dimensions using supersymmetry. This leads to a relation
between the six-dimensional conformal anomaly and the conformal anomaly of N=4
Yang-Mills. Along the way, we determine the structure of the four derivative
interactions for the toroidally compactified (2,0) theory, while encountering
interesting novelties in the structure of the six derivative interactions.Comment: 38 pages, LaTeX; references adde
Differential geometry with a projection: Application to double field theory
In recent development of double field theory, as for the description of the
massless sector of closed strings, the spacetime dimension is formally doubled,
i.e. from D to D+D, and the T-duality is realized manifestly as a global O(D,D)
rotation. In this paper, we conceive a differential geometry characterized by a
O(D,D) symmetric projection, as the underlying mathematical structure of double
field theory. We introduce a differential operator compatible with the
projection, which, contracted with the projection, can be covariantized and may
replace the ordinary derivatives in the generalized Lie derivative that
generates the gauge symmetry of double field theory. We construct various gauge
covariant tensors which include a scalar and a tensor carrying two O(D,D)
vector indices.Comment: 1+22 pages, No figure; a previous result on 4-index tensor removed,
presentation improve
Scleroderma, Stress and CAM Utilization
Scleroderma is an autoimmune disease influenced by interplay among genetic and environmental factors, of which one is stress. Complementary and alternative medicine (CAM) is frequently used to treat stress and those diseases in which stress has been implicated. Results are presented from a survey of patients with scleroderma. Respondents were a convenient sample of those attending a national conference in Las Vegas in 2002. Findings implicate stress in the onset, continuation and exacerbation of scleroderma. The implication is that CAM providers may be filling an important patient need in their provision of services that identify and treat stress and its related disorders
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