215 research outputs found
Book review: Hannah Arendt on Educational Thinking and Practice in Dark Times: Education for a world in crisis, edited by Wayne Veck and Helen M. Gunter
Leadership legitimacy and the mobilization of capital(s): Disrupting politics and reproducing heteronormativity
The rise of populist leaders in the political sphere mounts a challenge to normative understandings of leadership. To better understand this challenge, we examine how political leaders mobilize different forms of social capital in pursuit of leadership legitimacy, providing insight into the dynamics of how leadership norms are maintained. While research has tended to focus on specific forms of capital, this article considers capital as multidimensional and strategically mobilized. The article applies a multimodal analysis to examine interactions between Donald Trump and Hillary Clinton during peak ‘Twitter Moments’ of the three 2016 presidential election debates. We theorize the paradoxical dynamics of the mobilization of multiple capitals and their intersection as a simultaneously disruptive and reproductive resource. While the mobilization of multiple capitals operates to disrupt traditional notions of who can claim legitimacy as a leader in the political field, their disruptive mobilization serves to reproduce implicit heteronormative leadership values. Hence, our theorization illuminates the resilience of implicit leadership values, and their intimate connection with heteronormativity, calling for the need to interrogate leadership legitimacy claims that promise ‘new’ approaches
Mean-field analysis of the q-voter model on networks
We present a detailed investigation of the behavior of the nonlinear q-voter
model for opinion dynamics. At the mean-field level we derive analytically, for
any value of the number q of agents involved in the elementary update, the
phase diagram, the exit probability and the consensus time at the transition
point. The mean-field formalism is extended to the case that the interaction
pattern is given by generic heterogeneous networks. We finally discuss the case
of random regular networks and compare analytical results with simulations.Comment: 20 pages, 10 figure
Quantum state transformation by dispersive and absorbing four-port devices
The recently derived input-output relations for the radiation field at a
dispersive and absorbing four-port device [T. Gruner and D.-G. Welsch, Phys.
Rev. A 54, 1661 (1996)] are used to derive the unitary transformation that
relates the output quantum state to the input quantum state, including
radiation and matter and without placing frequency restrictions. It is shown
that for each frequency the transformation can be regarded as a well-behaved
SU(4) group transformation that can be decomposed into a product of U(2) and
SU(2) group transformations. Each of them may be thought of as being realized
by a particular lossless four-port device. If for narrow-bandwidth radiation
far from the medium resonances the absorption matrix of the four-port device
can be disregarded, the well-known SU(2) group transformation for a lossless
device is recognized. Explicit formulas for the transformation of Fock-states
and coherent states are given.Comment: 24 pages, RevTe
Frequency and damping of hydrodynamic modes in a trapped Bose-condensed gas
Recently it was shown that the Landau-Khalatnikov two-fluid hydrodynamics
describes the collision-dominated region of a trapped Bose condensate
interacting with a thermal cloud. We use these equations to discuss the low
frequency hydrodynamic collective modes in a trapped Bose gas at finite
temperatures. We derive a variational expressions based on these equations for
both the frequency and damping of collective modes. A new feature is our use of
frequency-dependent transport coefficients, which produce a natural cutoff by
eliminating the collisionless low-density tail of the thermal cloud. Above the
superfluid transition, our expression for the damping in trapped inhomogeneous
gases is analogous to the result first obtained by Landau and Lifshitz for
uniform classical fluids. We also use the moment method to discuss the
crossover from the collisionless to the hydrodynamic region. Recent data for
the monopole-quadrupole mode in the hydrodynamic region of a trapped gas of
metastable He is discussed. We also present calculations for the damping of
the analogous monopole-quadrupole condensate mode in the superfluid
phase.Comment: 22 pages, 10 figures, submitted to Physical Review
Properties of pattern formation and selection processes in nonequilibrium systems with external fluctuations
We extend the phase field crystal method for nonequilibrium patterning to
stochastic systems with external source where transient dynamics is essential.
It was shown that at short time scales the system manifests pattern selection
processes. These processes are studied by means of the structure function
dynamics analysis. Nonequilibrium pattern-forming transitions are analyzed by
means of numerical simulations.Comment: 15 poages, 8 figure
Ecological Invasion, Roughened Fronts, and a Competitor's Extreme Advance: Integrating Stochastic Spatial-Growth Models
Both community ecology and conservation biology seek further understanding of
factors governing the advance of an invasive species. We model biological
invasion as an individual-based, stochastic process on a two-dimensional
landscape. An ecologically superior invader and a resident species compete for
space preemptively. Our general model includes the basic contact process and a
variant of the Eden model as special cases. We employ the concept of a
"roughened" front to quantify effects of discreteness and stochasticity on
invasion; we emphasize the probability distribution of the front-runner's
relative position. That is, we analyze the location of the most advanced
invader as the extreme deviation about the front's mean position. We find that
a class of models with different assumptions about neighborhood interactions
exhibit universal characteristics. That is, key features of the invasion
dynamics span a class of models, independently of locally detailed demographic
rules. Our results integrate theories of invasive spatial growth and generate
novel hypotheses linking habitat or landscape size (length of the invading
front) to invasion velocity, and to the relative position of the most advanced
invader.Comment: The original publication is available at
www.springerlink.com/content/8528v8563r7u2742
Coarse-Grained Finite-Temperature Theory for the Condensate in Optical Lattices
In this work, we derive a coarse-grained finite-temperature theory for a Bose
condensate in a one-dimensional optical lattice, in addition to a confining
harmonic trap potential. We start from a two-particle irreducible (2PI)
effective action on the Schwinger-Keldysh closed-time contour path. In
principle, this action involves all information of equilibrium and
non-equilibrium properties of the condensate and noncondensate atoms. By
assuming an ansatz for the variational function, i.e., the condensate order
parameter in an effective action, we derive a coarse-grained effective action,
which describes the dynamics on the length scale much longer than a lattice
constant. Using the variational principle, coarse-grained equations of motion
for the condensate variables are obtained. These equations include a
dissipative term due to collisions between condensate and noncondensate atoms,
as well as noncondensate mean-field. To illustrate the usefulness of our
formalism, we discuss a Landau instability of the condensate in optical
lattices by using the coarse-grained generalized Gross-Pitaevskii
hydrodynamics. We found that the collisional damping rate due to collisions
between the condensate and noncondensate atoms changes sign when the condensate
velocity exceeds a renormalized sound velocity, leading to a Landau instability
consistent with the Landau criterion. Our results in this work give an insight
into the microscopic origin of the Landau instability.Comment: 38 pages, 2 figures. Submitted to Journal of Low Temperature Physic
Non-Equilibrium Statistical Physics of Currents in Queuing Networks
We consider a stable open queuing network as a steady non-equilibrium system
of interacting particles. The network is completely specified by its underlying
graphical structure, type of interaction at each node, and the Markovian
transition rates between nodes. For such systems, we ask the question ``What is
the most likely way for large currents to accumulate over time in a network
?'', where time is large compared to the system correlation time scale. We
identify two interesting regimes. In the first regime, in which the
accumulation of currents over time exceeds the expected value by a small to
moderate amount (moderate large deviation), we find that the large-deviation
distribution of currents is universal (independent of the interaction details),
and there is no long-time and averaged over time accumulation of particles
(condensation) at any nodes. In the second regime, in which the accumulation of
currents over time exceeds the expected value by a large amount (severe large
deviation), we find that the large-deviation current distribution is sensitive
to interaction details, and there is a long-time accumulation of particles
(condensation) at some nodes. The transition between the two regimes can be
described as a dynamical second order phase transition. We illustrate these
ideas using the simple, yet non-trivial, example of a single node with
feedback.Comment: 26 pages, 5 figure
Selective quantum evolution of a qubit state due to continuous measurement
We consider a two-level quantum system (qubit) which is continuously measured
by a detector. The information provided by the detector is taken into account
to describe the evolution during a particular realization of measurement
process. We discuss the Bayesian formalism for such ``selective'' evolution of
an individual qubit and apply it to several solid-state setups. In particular,
we show how to suppress the qubit decoherence using continuous measurement and
the feedback loop.Comment: 15 pages (including 9 figures
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