2,879 research outputs found
Non-collinear magnetoconductance of a quantum dot
We study theoretically the linear conductance of a quantum dot connected to
ferromagnetic leads. The dot level is split due to a non-collinear magnetic
field or intrinsic magnetization. The system is studied in the non-interacting
approximation, where an exact solution is given, and, furthermore, with Coulomb
correlations in the weak tunneling limit. For the non-interacting case, we find
an anti-resonance for a particular direction of the applied field,
non-collinear to the parallel magnetization directions of the leads. The
anti-resonance is destroyed by the correlations, giving rise to an interaction
induced enhancement of the conductance. The angular dependence of the
conductance is thus distinctly different for the interacting and
non-interacting cases when the magnetizations of the leads are parallel.
However, for anti-parallel lead magnetizations the interactions do not alter
the angle dependence significantly.Comment: 7 pages, 7 figure
Morphing Planar Graph Drawings Optimally
We provide an algorithm for computing a planar morph between any two planar
straight-line drawings of any -vertex plane graph in morphing steps,
thus improving upon the previously best known upper bound. Further, we
prove that our algorithm is optimal, that is, we show that there exist two
planar straight-line drawings and of an -vertex plane
graph such that any planar morph between and requires
morphing steps
From paradox to pattern shift: Conceptualising liminal hotspots and their affective dynamics
This article introduces the concept of liminal hotspots as a specifically psychosocial and sociopsychological type of wicked problem, best addressed in a process-theoretical framework. A liminal hotspot is defined as an occasion characterised by the experience of being trapped in the interstitial dimension between different forms-of-process. The paper has two main aims. First, to articulate a nexus of concepts associated with liminal hotspots that together provide general analytic purchase on a wide range of problems concerning âtroubledâ becoming. Second, to provide concrete illustrations through examples drawn from the health domain. In the conclusion, we briefly indicate the sense in which liminal hotspots are part of broader and deeper historical processes associated with changing modes for the management and navigation of liminality
Boxicity and separation dimension
A family of permutations of the vertices of a hypergraph is
called 'pairwise suitable' for if, for every pair of disjoint edges in ,
there exists a permutation in in which all the vertices in one
edge precede those in the other. The cardinality of a smallest such family of
permutations for is called the 'separation dimension' of and is denoted
by . Equivalently, is the smallest natural number so that
the vertices of can be embedded in such that any two
disjoint edges of can be separated by a hyperplane normal to one of the
axes. We show that the separation dimension of a hypergraph is equal to the
'boxicity' of the line graph of . This connection helps us in borrowing
results and techniques from the extensive literature on boxicity to study the
concept of separation dimension.Comment: This is the full version of a paper by the same name submitted to
WG-2014. Some results proved in this paper are also present in
arXiv:1212.6756. arXiv admin note: substantial text overlap with
arXiv:1212.675
Convex drawings of graphs with non-convex boundary
Abstract. In this paper, we study a new problem of finding a convex drawing of graphs with a non-convex boundary. It is proved that every triconnected plane graph whose boundary is fixed with a star-shaped polygon admits a drawing in which every inner facial cycle is drawn as a convex polygon. Such a drawing, called an inner-convex drawing, can be obtained in linear time.
On vertex coloring without monochromatic triangles
We study a certain relaxation of the classic vertex coloring problem, namely,
a coloring of vertices of undirected, simple graphs, such that there are no
monochromatic triangles. We give the first classification of the problem in
terms of classic and parametrized algorithms. Several computational complexity
results are also presented, which improve on the previous results found in the
literature. We propose the new structural parameter for undirected, simple
graphs -- the triangle-free chromatic number . We bound by
other known structural parameters. We also present two classes of graphs with
interesting coloring properties, that play pivotal role in proving useful
observation about our problem. We give/ask several conjectures/questions
throughout this paper to encourage new research in the area of graph coloring.Comment: Extended abstrac
Effect of V2O5 on NickelâZinc Ferrite Formation
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70856/2/JCPSA6-23-11-2205-1.pd
Voting procedures and parliamentary representation in the European Parliament
Parliamentary representation is a fluid concept. Yet, while the behaviour of elected representatives during roll call votes has been widely analysed, we know little about how parliamentarians act when their individual voting choices are not made public. This paper explores the relationship between voting procedures and the likelihood that Members of the European Parliament prioritise the interests of their EP party group versus the interests of their national party. Using an original survey, I find that MEPs are more likely to prioritise the interests of their national party over those of their EP party group when voting by show of hands or electronically, as opposed to by roll call. Moreover, this voting procedure effect is particularly salient among MEPs elected from 2004/07 accession countries
Contact Representations of Graphs in 3D
We study contact representations of graphs in which vertices are represented
by axis-aligned polyhedra in 3D and edges are realized by non-zero area common
boundaries between corresponding polyhedra. We show that for every 3-connected
planar graph, there exists a simultaneous representation of the graph and its
dual with 3D boxes. We give a linear-time algorithm for constructing such a
representation. This result extends the existing primal-dual contact
representations of planar graphs in 2D using circles and triangles. While
contact graphs in 2D directly correspond to planar graphs, we next study
representations of non-planar graphs in 3D. In particular we consider
representations of optimal 1-planar graphs. A graph is 1-planar if there exists
a drawing in the plane where each edge is crossed at most once, and an optimal
n-vertex 1-planar graph has the maximum (4n - 8) number of edges. We describe a
linear-time algorithm for representing optimal 1-planar graphs without
separating 4-cycles with 3D boxes. However, not every optimal 1-planar graph
admits a representation with boxes. Hence, we consider contact representations
with the next simplest axis-aligned 3D object, L-shaped polyhedra. We provide a
quadratic-time algorithm for representing optimal 1-planar graph with L-shaped
polyhedra
Non-Convex Representations of Graphs
We show that every plane graph admits a planar straight-line drawing in which all faces with more than three vertices are non-convex polygon
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