1,729 research outputs found
Eco-aesthetic dimensions: Herbert Marcuse, ecollogy and art
In his last book, The Aesthetic Dimension (1978), Marcuse argued that a concern for aesthetics is justified when political change is unlikely. But the relation between aesthetics and politics is oblique: “Art cannot change the world, but it can contribute to changing the consciousness … of the men and women who could change the world.” (p. 33). Marcuse also linked his critique of capitalism to environmentalism in the early 1970s: “the violation of the Earth is a vital aspect of the counterrevolution.” (Ecology and Revolution, in The New Left and the 1960s, Collected Papers 3, 2005, p. 173). This article revisits Marcuse’s ideas on aesthetics and ecology, and reviews two recent art projects which engage their audiences in ecological issues: The Jetty Project (2014) by Wolfgang Weileder—which used recycled material and community participation to construct a temporary monument within a wider conservation project on the Tyne, N-E England—and Fracking Futures by HeHe (Helen Evans and Heiko Hansen)—which turned the interior of the gallery at FACT, Liverpool, into what appeared to be a fracking site. The aim is not to evaluate the projects, nor to test the efficacy of Marcuse’s ideas, more to ask again whether art has a role in a shift of attitude which might contribute to dealing with the political and economic causes of climate change
On the attenuation coefficient of monomode periodic waveguides
It is widely accepted that, on ensemble average, the transmission T of guided
modes decays exponentially with the waveguide length L due to small
imperfections, leading to the important figure of merit defined as the
attenuation-rate coefficient alpha = -/L. In this letter, we evidence
that the exponential-damping law is not valid in general for periodic monomode
waveguides, especially as the group velocity decreases. This result that
contradicts common beliefs and experimental practices aiming at measuring alpha
is supported by a theoretical study of light transport in the limit of very
small imperfections, and by numerical results obtained for two waveguide
geometries that offer contrasted damping behaviours
Unified theory for Goos-H\"{a}nchen and Imbert-Fedorov effects
A unified theory is advanced to describe both the lateral Goos-H\"{a}nchen
(GH) effect and the transverse Imbert-Fedorov (IF) effect, through representing
the vector angular spectrum of a 3-dimensional light beam in terms of a 2-form
angular spectrum consisting of its 2 orthogonal polarized components. From this
theory, the quantization characteristics of the GH and IF displacements are
obtained, and the Artmann formula for the GH displacement is derived. It is
found that the eigenstates of the GH displacement are the 2 orthogonal linear
polarizations in this 2-form representation, and the eigenstates of the IF
displacement are the 2 orthogonal circular polarizations. The theoretical
predictions are found to be in agreement with recent experimental results.Comment: 15 pages, 3 figure
Comparison of Quantum and Classical Local-field Effects on Two-Level Atoms in a Dielectric
The macroscopic quantum theory of the electromagnetic field in a dielectric
medium interacting with a dense collection of embedded two-level atoms fails to
reproduce a result that is obtained from an application of the classical
Lorentz local-field condition. Specifically, macroscopic quantum
electrodynamics predicts that the Lorentz redshift of the resonance frequency
of the atoms will be enhanced by a factor of the refractive index n of the host
medium. However, an enhancement factor of (n*n+2)/3 is derived using the
Bloembergen procedure in which the classical Lorentz local-field condition is
applied to the optical Bloch equations. Both derivations are short and
uncomplicated and are based on well-established physical theories, yet lead to
contradictory results. Microscopic quantum electrodynamics confirms the
classical local-field-based results. Then the application of macroscopic
quantum electrodynamic theory to embedded atoms is proved false by a specific
example in which both the correspondence principle and microscopic theory of
quantum electrodynamics are violated.Comment: Published version with rewritten abstract and introductio
Coherent Control of Ultra-High Frequency Acoustic Resonances in Photonic Crystal Fibers
Ultra-high frequency acoustic resonances (2 GHz) trapped within the
glass core (1 m diameter) of a photonic crystal fiber are
selectively excited through electrostriction using laser pulses of duration 100
ps and energy 500 pJ. Using precisely timed sequences of such driving pulses,
we achieve coherent control of the acoustic resonances by constructive or
destructive interference, demonstrating both enhancement and suppression of the
vibrations. A sequence of 27 resonantly-timed pulses provides a 100-fold
increase in the amplitude of the vibrational mode. The results are explained
and interpreted using a semi-analytical theory, and supported by precise
numerical simulations of the complex light-matter interaction.Comment: 4 pages, 3 figures, 3 avi movies (external link) - accepted in PR
Analysis of Optical Pulse Propagation with ABCD Matrices
We review and extend the analogies between Gaussian pulse propagation and
Gaussian beam diffraction. In addition to the well-known parallels between
pulse dispersion in optical fiber and CW beam diffraction in free space, we
review temporal lenses as a way to describe nonlinearities in the propagation
equations, and then introduce further concepts that permit the description of
pulse evolution in more complicated systems. These include the temporal
equivalent of a spherical dielectric interface, which is used by way of example
to derive design parameters used in a recent dispersion-mapped soliton
transmission experiment. Our formalism offers a quick, concise and powerful
approach to analyzing a variety of linear and nonlinear pulse propagation
phenomena in optical fibers.Comment: 10 pages, 2 figures, submitted to PRE (01/01
Eigenvector Expansion and Petermann Factor for Ohmically Damped Oscillators
Correlation functions in ohmically damped
systems such as coupled harmonic oscillators or optical resonators can be
expressed as a single sum over modes (which are not power-orthogonal), with
each term multiplied by the Petermann factor (PF) , leading to "excess
noise" when . It is shown that is common rather than
exceptional, that can be large even for weak damping, and that the PF
appears in other processes as well: for example, a time-independent
perturbation \sim\ep leads to a frequency shift \sim \ep C_j. The
coalescence of () eigenvectors gives rise to a critical point, which
exhibits "giant excess noise" (). At critical points, the
divergent parts of contributions to cancel, while time-independent
perturbations lead to non-analytic shifts \sim \ep^{1/J}.Comment: REVTeX4, 14 pages, 4 figures. v2: final, 20 single-col. pages, 2
figures. Streamlined with emphasis on physics over formalism; rewrote Section
V E so that it refers to time-dependent (instead of non-equilibrium) effect
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