122 research outputs found
Generalized metallic pseudo-Riemannian structures
We generalize the notion of metallic structure in the pseudo-Riemannian
setting, define the metallic Norden structure and study its integrability. We
construct a metallic natural connection recovering as particular case the
Ganchev and Mihova connection, which we extend to a metallic natural connection
on the generalized tangent bundle. Moreover, we construct metallic
pseudo-Riemannian structures on the tangent and cotangent bundles.Comment: 16 page
Generalized quasi-statistical structures
Given a non-degenerate -tensor field on a smooth manifold , we
consider a natural generalized complex and a generalized product structure on
the generalized tangent bundle of and we show that they are
-integrable, for an affine connection on , if and only if
is a quasi-statistical manifold. We introduce the notion of
generalized quasi-statistical structure and we prove that any quasi-statistical
structure on induces generalized quasi-statistical structures on . In this context, dual connections are considered and some of their
properties are established. The results are described in terms of
Patterson-Walker and Sasaki metrics on , horizontal lift and Sasaki
metrics on and, when the connection is flat, we define
prolongation of quasi-statistical structures on manifolds to their cotangent
and tangent bundles via generalized geometry. Moreover, Norden and Para-Norden
structures are defined on and .Comment: 28 page
Generalized metallic structures
We study the properties of a generalized metallic, a generalized product and
a generalized complex structure induced on the generalized tangent bundle of
by a metallic Riemannian structure on , providing conditions for
their integrability with respect to a suitable connection. Moreover, by using
methods of generalized geometry, we lift to metallic Riemannian
structures on the tangent and cotangent bundles of , underlying the
relations between them.Comment: 19 page
Harmonic metallic structures
The concept of harmonic metallic structure on a metallic pseudo-Riemannian
manifold is introduced. In the case of compact manifolds we prove that
harmonicity of a metallic structure , with and ,
is equivalent to . Conditions for a harmonic metallic structure to be
preserved by harmonic maps are also given. Moreover, we consider harmonic
metallic structures on the generalized tangent bundle, provide a
Weitzenb\"{o}ck formula for the dual metallic structure and express the
Hodge-Laplace operator on .Comment: 17 page
-connections in generalized geometry
We consider a family of -connections defined by a pair of generalized
dual quasi-statistical connections on the
generalized tangent bundle and determine their
curvature, Ricci curvature and scalar curvature. Moreover, we provide the
necessary and sufficient condition for to be an equiaffine
connection and we prove that if is symmetric and , then
is a conjugate Ricci-symmetric manifold. Also, we characterize the
integrability of a generalized almost product, of a generalized almost complex
and of a generalized metallic structure w.r.t. the bracket defined by the
-connection. Finally we study -connections defined by the twin
metric of a pseudo-Riemannian manifold, , with a non-degenerate
-symmetric -tensor field such that , where
is the Levi-Civita connection of .Comment: 29 page
Distance Oracles for Time-Dependent Networks
We present the first approximate distance oracle for sparse directed networks
with time-dependent arc-travel-times determined by continuous, piecewise
linear, positive functions possessing the FIFO property.
Our approach precomputes approximate distance summaries from
selected landmark vertices to all other vertices in the network. Our oracle
uses subquadratic space and time preprocessing, and provides two sublinear-time
query algorithms that deliver constant and approximate
shortest-travel-times, respectively, for arbitrary origin-destination pairs in
the network, for any constant . Our oracle is based only on
the sparsity of the network, along with two quite natural assumptions about
travel-time functions which allow the smooth transition towards asymmetric and
time-dependent distance metrics.Comment: A preliminary version appeared as Technical Report ECOMPASS-TR-025 of
EU funded research project eCOMPASS (http://www.ecompass-project.eu/). An
extended abstract also appeared in the 41st International Colloquium on
Automata, Languages, and Programming (ICALP 2014, track-A
On invariants of almost symplectic connections
We study the irreducible decomposition under Sp(2n, R) of the space of
torsion tensors of almost symplectic connections. Then a description of all
symplectic quadratic invariants of torsion-like tensors is given. When applied
to a manifold M with an almost symplectic structure, these instruments give
preliminary insight for finding a preferred linear almost symplectic connection
on M . We rediscover Ph. Tondeur's Theorem on almost symplectic connections.
Properties of torsion of the vectorial kind are deduced
On curvature tensors of Norden and metallic pseudo-Riemannian manifolds
AbstractWe study some properties of curvature tensors of Norden and, more generally, metallic pseudo-Riemannian manifolds. We introduce the notion of J-sectional and J-bisectional curvature of a metallic pseudo-Riemannian manifold (M, J, g) and study their properties.We prove that under certain assumptions, if the manifold is locally metallic, then the Riemann curvature tensor vanishes. Using a Norden structure (J, g) on M, we consider a family of metallic pseudo-Riemannian structures {Ja,b}a,b∈ℝ and show that for a ≠ 0, the J-sectional and J-bisectional curvatures of M coincide with the Ja,b-sectional and Ja,b-bisectional curvatures, respectively. We also give examples of Norden and metallic structures on ℝ2n
Effects of trinexapae-ethyl on stoloon development in potted Patriot bermudagrass
A recent technique developed for establishment of warm season turfgrasses is based on the transplant of single plug plantlets pre-rooted in the nursery. Plantlets are obtained from one-node sprigs about 2 cm long derived from stolon fragmentation. Usually, stolons must be cut several times to obtain sprigs of the right length because of overly long internodes. In the present study, potted plants of Patriot bermudagrass grown in the nursery were treated with trinexa-pac-ethyl (TE) at the rates 0.1, 0.2, 0.4 and 0.8 kg a.i. ha-1. TE application was aimed at obtaining internode shortening in order to facilitate the stolon division practice. In fact, TE-treated plants showed a decrease in the average length of internodes with respect to control at any applied rate. Nevertheless, the lowest rate applied (0.1 kg a.i. ha-1) did not assure a prolonged effect while the highest rate (0.8 kg a.i. ha-1) caused a decrease in the yield of sprigs. Therefore, our results suggest that TE may be advantageously used and at rates of 0.2-0.4 kg a.i. ha-1 to control stolon development of Patriot bermudagrass for nursery purposes
Demonstration of quantum volume 64 on a superconducting quantum computing system
We improve the quality of quantum circuits on superconducting quantum
computing systems, as measured by the quantum volume, with a combination of
dynamical decoupling, compiler optimizations, shorter two-qubit gates, and
excited state promoted readout. This result shows that the path to larger
quantum volume systems requires the simultaneous increase of coherence, control
gate fidelities, measurement fidelities, and smarter software which takes into
account hardware details, thereby demonstrating the need to continue to
co-design the software and hardware stack for the foreseeable future.Comment: Fixed typo in author list. Added references [38], [49] and [52
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