4,494 research outputs found
Why is there no queer international theory?
Over the last decade, Queer Studies have become Global Queer Studies, generating significant insights into key international political processes. Yet, the transformation from Queer to Global Queer has left the discipline of International Relations largely unaffected, which begs the question: if Queer Studies has gone global, why has the discipline of International Relations not gone somewhat queer? Or, to put it in Martin Wight’s provocative terms, why is there no Queer International Theory? This article claims that the presumed non-existence of Queer International Theory is an effect of how the discipline of International Relations combines homologization, figuration, and gentrification to code various types of theory as failures in order to manage the conduct of international theorizing in all its forms. This means there are generalizable lessons to be drawn from how the discipline categorizes Queer International Theory out of existence to bring a specific understanding of International Relations into existence
A topological zero-one law and elementary equivalence of finitely generated groups
Let denote the space of finitely generated marked groups. We
give equivalent characterizations of closed subspaces satisfying the following zero-one law: for any sentence in
the infinitary logic , the set of all models of
in is either meager or comeager. In particular, we show
that the zero-one law holds for certain natural spaces associated to hyperbolic
groups and their generalizations. As an application, we obtain that generic
torsion-free lacunary hyperbolic groups are elementarily equivalent; the same
claim holds for lacunary hyperbolic groups without non-trivial finite normal
subgroups. Our paper has a substantial expository component. We give
streamlined proofs of some known results and survey ideas from topology, logic,
and geometric group theory relevant to our work. We also discuss some open
problems.Comment: Some typos and inaccuracies are corrected, a few minor improvement
Spatial interactions in agent-based modeling
Agent Based Modeling (ABM) has become a widespread approach to model complex
interactions. In this chapter after briefly summarizing some features of ABM
the different approaches in modeling spatial interactions are discussed.
It is stressed that agents can interact either indirectly through a shared
environment and/or directly with each other. In such an approach, higher-order
variables such as commodity prices, population dynamics or even institutions,
are not exogenously specified but instead are seen as the results of
interactions. It is highlighted in the chapter that the understanding of
patterns emerging from such spatial interaction between agents is a key problem
as much as their description through analytical or simulation means.
The chapter reviews different approaches for modeling agents' behavior,
taking into account either explicit spatial (lattice based) structures or
networks. Some emphasis is placed on recent ABM as applied to the description
of the dynamics of the geographical distribution of economic activities, - out
of equilibrium. The Eurace@Unibi Model, an agent-based macroeconomic model with
spatial structure, is used to illustrate the potential of such an approach for
spatial policy analysis.Comment: 26 pages, 5 figures, 105 references; a chapter prepared for the book
"Complexity and Geographical Economics - Topics and Tools", P. Commendatore,
S.S. Kayam and I. Kubin, Eds. (Springer, in press, 2014
Exact stabilization of entangled states in finite time by dissipative quantum circuits
Open quantum systems evolving according to discrete-time dynamics are
capable, unlike continuous-time counterparts, to converge to a stable
equilibrium in finite time with zero error. We consider dissipative quantum
circuits consisting of sequences of quantum channels subject to specified
quasi-locality constraints, and determine conditions under which stabilization
of a pure multipartite entangled state of interest may be exactly achieved in
finite time. Special emphasis is devoted to characterizing scenarios where
finite-time stabilization may be achieved robustly with respect to the order of
the applied quantum maps, as suitable for unsupervised control architectures.
We show that if a decomposition of the physical Hilbert space into virtual
subsystems is found, which is compatible with the locality constraint and
relative to which the target state factorizes, then robust stabilization may be
achieved by independently cooling each component. We further show that if the
same condition holds for a scalable class of pure states, a continuous-time
quasi-local Markov semigroup ensuring rapid mixing can be obtained. Somewhat
surprisingly, we find that the commutativity of the canonical parent
Hamiltonian one may associate to the target state does not directly relate to
its finite-time stabilizability properties, although in all cases where we can
guarantee robust stabilization, a (possibly non-canonical) commuting parent
Hamiltonian may be found. Beside graph states, quantum states amenable to
finite-time robust stabilization include a class of universal resource states
displaying two-dimensional symmetry-protected topological order, along with
tensor network states obtained by generalizing a construction due to Bravyi and
Vyalyi. Extensions to representative classes of mixed graph-product and thermal
states are also discussed.Comment: 20 + 9 pages, 9 figure
General fixed points of quasi-local frustration-free quantum semigroups: from invariance to stabilization
We investigate under which conditions a mixed state on a finite-dimensional
multipartite quantum system may be the unique, globally stable fixed point of
frustration-free semigroup dynamics subject to specified quasi-locality
constraints. Our central result is a linear-algebraic necessary and sufficient
condition for a generic (full-rank) target state to be frustration-free
quasi-locally stabilizable, along with an explicit procedure for constructing
Markovian dynamics that achieve stabilization. If the target state is not
full-rank, we establish sufficiency under an additional condition, which is
naturally motivated by consistency with pure-state stabilization results yet
provably not necessary in general. Several applications are discussed, of
relevance to both dissipative quantum engineering and information processing,
and non-equilibrium quantum statistical mechanics. In particular, we show that
a large class of graph product states (including arbitrary thermal graph
states) as well as Gibbs states of commuting Hamiltonians are frustration-free
stabilizable relative to natural quasi-locality constraints. Likewise, we
provide explicit examples of non-commuting Gibbs states and non-trivially
entangled mixed states that are stabilizable despite the lack of an underlying
commuting structure, albeit scalability to arbitrary system size remains in
this case an open question.Comment: 44 pages, main results are improved, several proofs are more
streamlined, application section is refine
Selective Categories and Linear Canonical Relations
A construction of Wehrheim and Woodward circumvents the problem that
compositions of smooth canonical relations are not always smooth, building a
category suitable for functorial quantization. To apply their construction to
more examples, we introduce a notion of highly selective category, in which
only certain morphisms and certain pairs of these morphisms are "good". We then
apply this notion to the category of linear canonical
relations and the result of our version of the WW
construction, identifying the morphisms in the latter with pairs
consisting of a linear canonical relation and a nonnegative integer. We put a
topology on this category of indexed linear canonical relations for which
composition is continuous, unlike the composition in itself.
Subsequent papers will consider this category from the viewpoint of derived
geometry and will concern quantum counterparts
Hierarchical Economic Agents and their Interactions
We present a new type of spin market model, populated by hierarchical agents,
represented as configurations of sites and arcs in an evolving network. We
describe two analytic techniques for investigating the asymptotic behavior of
this model: one based on the spectral theory of Markov chains and another
exploiting contingent submartingales to construct a deterministic cellular
automaton that approximates the stochastic dynamics. Our study of this system
documents a phase transition between a sub-critical and a super-critical regime
based on the values of a coupling constant that modulates the tradeoff between
local majority and global minority forces. In conclusion, we offer a
speculative socioeconomic interpretation of the resulting distributional
properties of the system.Comment: 38 pages, 13 figures, presented at the 2013 WEHIA conference; to
appear in Journal of Economic Interaction and Coordination, to appear in
Journal of Economic Interaction and Coordinatio
Cell shape analysis of random tessellations based on Minkowski tensors
To which degree are shape indices of individual cells of a tessellation
characteristic for the stochastic process that generates them? Within the
context of stochastic geometry and the physics of disordered materials, this
corresponds to the question of relationships between different stochastic
models. In the context of image analysis of synthetic and biological materials,
this question is central to the problem of inferring information about
formation processes from spatial measurements of resulting random structures.
We address this question by a theory-based simulation study of shape indices
derived from Minkowski tensors for a variety of tessellation models. We focus
on the relationship between two indices: an isoperimetric ratio of the
empirical averages of cell volume and area and the cell elongation quantified
by eigenvalue ratios of interfacial Minkowski tensors. Simulation data for
these quantities, as well as for distributions thereof and for correlations of
cell shape and volume, are presented for Voronoi mosaics of the Poisson point
process, determinantal and permanental point processes, and Gibbs hard-core and
random sequential absorption processes as well as for Laguerre tessellations of
polydisperse spheres and STIT- and Poisson hyperplane tessellations. These data
are complemented by mechanically stable crystalline sphere and disordered
ellipsoid packings and area-minimising foam models. We find that shape indices
of individual cells are not sufficient to unambiguously identify the generating
process even amongst this limited set of processes. However, we identify
significant differences of the shape indices between many of these tessellation
models. Given a realization of a tessellation, these shape indices can narrow
the choice of possible generating processes, providing a powerful tool which
can be further strengthened by density-resolved volume-shape correlations.Comment: Chapter of the forthcoming book "Tensor Valuations and their
Applications in Stochastic Geometry and Imaging" in Lecture Notes in
Mathematics edited by Markus Kiderlen and Eva B. Vedel Jense
- …