1,161 research outputs found
Kant's philosophy of the aesthetic and the philosophy of praxis
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2012 Association for Economic and Social Analysis.This essay seeks to reconstruct the terms for a more productive engagement with Kant than is typical within contemporary academic cultural Marxism, which sees him as the cornerstone of a bourgeois model of the aesthetic. The essay argues that, in the Critique of Judgment, the aesthetic stands in as a substitute for the missing realm of human praxis. This argument is developed in relation to Kant's concept of reflective judgment that is in turn related to a methodological shift toward inductive and analogical procedures that help Kant overcome the dualisms of the first two Critiques. This reassessment of Kant's aesthetic is further clarified by comparing it with and offering a critique of Terry Eagleton's assessment of the Kantian aesthetic as synonymous with ideology
Convergence and Energy Landscape for Cheeger Cut Clustering
This paper provides both theoretical and algorithmic results for the l 1-relaxation of the Cheeger cut problem. The l2- relaxation, known as spectral clustering, only loosely relates to the Cheeger cut; however, it is convex and leads to a simple optimization problem. The l1-relaxation, in contrast, is non-convex but is provably equivalent to the original problem. The l1-relaxation therefore trades convexity for exactness, yielding improved clustering results at the cost of a more challenging optimization. The first challenge is understanding convergence of algorithms. This paper provides the first complete proof of convergence for algorithms that minimize the l1-relaxation. The second challenge entails comprehending the l1-energy landscape, i.e. the set of possible points to which an algorithm might converge. We show that l 1-algorithms can get trapped in local minima that are not globally optimal and we provide a classification theorem to interpret these local minima. This classification gives meaning to these suboptimal solutions and helps to explain, in terms of graph structure, when the l1-relaxation provides the solution of the original Cheeger cut problem
Ultrahigh and persistent optical depths of caesium in Kagom\'e-type hollow-core photonic crystal fibres
Alkali-filled hollow-core fibres are a promising medium for investigating
light-matter interactions, especially at the single-photon level, due to the
tight confinement of light and high optical depths achievable by light-induced
atomic desorption. However, until now these large optical depths could only be
generated for seconds at most once per day, severely limiting the practicality
of the technology. Here we report the generation of highest observed transient
( for up to a minute) and highest observed persistent ( for
hours) optical depths of alkali vapours in a light-guiding geometry to date,
using a caesium-filled Kagom\'e-type hollow-core photonic crystal fibre. Our
results pave the way to light-matter interaction experiments in confined
geometries requiring long operation times and large atomic number densities,
such as generation of single-photon-level nonlinearities and development of
single photon quantum memories.Comment: Author Accepted versio
Theory of noise suppression in {\Lambda}-type quantum memories by means of a cavity
Quantum memories, capable of storing single photons or other quantum states
of light, to be retrieved on-demand, offer a route to large-scale quantum
information processing with light. A promising class of memories is based on
far-off-resonant Raman absorption in ensembles of -type atoms. However
at room temperature these systems exhibit unwanted four-wave mixing, which is
prohibitive for applications at the single-photon level. Here we show how this
noise can be suppressed by placing the storage medium inside a moderate-finesse
optical cavity, thereby removing the main roadblock hindering this approach to
quantum memory.Comment: 10 pages, 3 figures. This paper provides the theoretical background
to our recent experimental demonstration of noise suppression in a
cavity-enhanced Raman-type memory ( arXiv:1510.04625 ). See also the related
paper arXiv:1511.05448, which describes numerical modelling of an atom-filled
cavity. Comments welcom
High-speed noise-free optical quantum memory
Quantum networks promise to revolutionise computing, simulation, and
communication. Light is the ideal information carrier for quantum networks, as
its properties are not degraded by noise in ambient conditions, and it can
support large bandwidths enabling fast operations and a large information
capacity. Quantum memories, devices that store, manipulate, and release on
demand quantum light, have been identified as critical components of photonic
quantum networks, because they facilitate scalability. However, any noise
introduced by the memory can render the device classical by destroying the
quantum character of the light. Here we introduce an intrinsically noise-free
memory protocol based on two-photon off-resonant cascaded absorption (ORCA). We
consequently demonstrate for the first time successful storage of GHz-bandwidth
heralded single photons in a warm atomic vapour with no added noise; confirmed
by the unaltered photon statistics upon recall. Our ORCA memory platform meets
the stringent noise-requirements for quantum memories whilst offering technical
simplicity and high-speed operation, and therefore is immediately applicable to
low-latency quantum networks
Titan's Atomic and Molecular Nitrogen Tori
Shematovich et al. (2003) recently showed plasma induced sputtering in
Titan's atmosphere is a source of neutral nitrogen in Saturn's magnetosphere
comparable to the photo-dissociation source. These sources form a toroidal
nitrogen cloud roughly centered at Titan's orbital radius but gravitationally
bound to Saturn. Once ionized, these particles contribute to Saturn's plasma.
When Titan is inside Saturn's magnetopause, newly formed ions can diffuse
inward becoming inner magnetospheric energetic nitrogen where they can sputter
and be implanted into icy satellite surfaces. Our 3-D simulation produces the
first consistent Titan generated N and N2 neutral clouds; solar UV radiation
and magnetospheric plasma subject these particles to dissociation and
ionization. The cloud morphologies and associated nitrogen plasma source rates
are predicted in anticipation of Cassini data. Since the amount of molecular
nitrogen ejected from Titan by photo-dissociation is small, molecular nitrogen
ions detection by Cassini will be an indicator of atmospheric sputtering.Comment: Accepted for Publication in Geophysical Research Letter
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