4,268 research outputs found
Going beyond instrument interactions: towards a more comprehensive policy mix conceptualization for environmental technological change
Reaching a better understanding of the policies and politics of transitions presents a main agenda item in the emerging field of sustainability transitions. One important requirement for these transitions, such as the move towards a decarbonized energy system, is the redirection and acceleration of technological change, for which policies play a key role. Several studies of policies supporting environmental technological change have argued for the need to combine different policy instruments in so-called policy mixes. However, existing policy mix studies often fall short of reflecting the complexity and dynamics of actual policy mixes and the underlying politics of (re)designing them. In this
paper we take a first step towards a more comprehensive, interdisciplinary policy mix concept for environmental technological change based on a review of the bodies of literature on innovation studies, environmental economics and policy analysis. The concept introduces a clear terminology and consists of the three building blocks elements, processes and characteristics, which can be delineated by several dimensions. Throughout the
paper, we illustrate the concept using the example of the policy mix for fostering the transition of the German energy system to renewable power generation technologies.
We argue that the proposed concept provides an integrating analytical framework for empirical studies analyzing the impact of the policy mix on environmental technological change and sustainability transitions more broadly. Finally, we derive policy implications and suggest avenues for future research
A Measurement of Secondary Cosmic Microwave Background Anisotropies with Two Years of South Pole Telescope Observations
We present the first three-frequency South Pole Telescope (SPT) cosmic microwave background (CMB) power spectra. The band powers presented here cover angular scales 2000 < ℓ < 9400 in frequency bands centered at 95, 150, and 220 GHz. At these frequencies and angular scales, a combination of the primary CMB anisotropy, thermal and kinetic Sunyaev-Zel'dovich (SZ) effects, radio galaxies, and cosmic infrared background (CIB) contributes to the signal. We combine Planck/HFI and SPT data at 220 GHz to constrain the amplitude and shape of the CIB power spectrum and find strong evidence for nonlinear clustering. We explore the SZ results using a variety of cosmological models for the CMB and CIB anisotropies and find them to be robust with one exception: allowing for spatial correlations between the thermal SZ effect and CIB significantly degrades the SZ constraints. Neglecting this potential correlation, we find the thermal SZ power at 150 GHz and ℓ = 3000 to be 3.65 ± 0.69 μK^2, and set an upper limit on the kinetic SZ power to be less than 2.8 μK^2 at 95% confidence. When a correlation between the thermal SZ and CIB is allowed, we constrain a linear combination of thermal and kinetic SZ power: D^(tSZ)_(3000) + 0.5D^(kSZ)_(3000) = 4.60 ± 0.63 μK^2, consistent with earlier measurements. We use the measured thermal SZ power and an analytic, thermal SZ model calibrated with simulations to determine σ_8 = 0.807 ± 0.016. Modeling uncertainties involving the astrophysics of the intracluster medium rather than the statistical uncertainty in the measured band powers are the dominant source of uncertainty on σ_8. We also place an upper limit on the kinetic SZ power produced by patchy reionization; a companion paper uses these limits to constrain the reionization history of the universe
Generalised state spaces and non-locality in fault tolerant quantum computing schemes
We develop connections between generalised notions of entanglement and
quantum computational devices where the measurements available are restricted,
either because they are noisy and/or because by design they are only along
Pauli directions. By considering restricted measurements one can (by
considering the dual positive operators) construct single particle state spaces
that are different to the usual quantum state space. This leads to a modified
notion of entanglement that can be very different to the quantum version (for
example, Bell states can become separable). We use this approach to develop
alternative methods of classical simulation that have strong connections to the
study of non-local correlations: we construct noisy quantum computers that
admit operations outside the Clifford set and can generate some forms of
multiparty quantum entanglement, but are otherwise classical in that they can
be efficiently simulated classically and cannot generate non-local statistics.
Although the approach provides new regimes of noisy quantum evolution that can
be efficiently simulated classically, it does not appear to lead to significant
reductions of existing upper bounds to fault tolerance thresholds for common
noise models.Comment: V2: 18 sides, 7 figures. Corrected two erroneous claims and one
erroneous argumen
Keeping a Quantum Bit Alive by Optimized -Pulse Sequences
A general strategy to maintain the coherence of a quantum bit is proposed.
The analytical result is derived rigorously including all memory and
back-action effects. It is based on an optimized -pulse sequence for
dynamic decoupling extending the Carr-Purcell-Meiboom-Gill (CPMG) cycle. The
optimized sequence is very efficient, in particular for strong couplings to the
environment.Comment: 4 pages, 2 figures; revised version with additional references for
better context, more stringent discussio
Raman spectroscopy on mechanically exfoliated pristine graphene ribbons
We present Raman spectroscopy measurements of non-etched graphene
nanoribbons, with widths ranging from 15 to 160 nm, where the D-line intensity
is strongly dependent on the polarization direction of the incident light. The
extracted edge disorder correlation length is approximately one order of
magnitude larger than on previously reported graphene ribbons fabricated by
reactive ion etching techniques. This suggests a more regular crystallographic
orientation of the non-etched graphene ribbons here presented. We further
report on the ribbons width dependence of the line-width and frequency of the
long-wavelength optical phonon mode (G-line) and the 2D-line of the studied
graphene ribbons
Stability of graph communities across time scales
The complexity of biological, social and engineering networks makes it
desirable to find natural partitions into communities that can act as
simplified descriptions and provide insight into the structure and function of
the overall system. Although community detection methods abound, there is a
lack of consensus on how to quantify and rank the quality of partitions. We
show here that the quality of a partition can be measured in terms of its
stability, defined in terms of the clustered autocovariance of a Markov process
taking place on the graph. Because the stability has an intrinsic dependence on
time scales of the graph, it allows us to compare and rank partitions at each
time and also to establish the time spans over which partitions are optimal.
Hence the Markov time acts effectively as an intrinsic resolution parameter
that establishes a hierarchy of increasingly coarser clusterings. Within our
framework we can then provide a unifying view of several standard partitioning
measures: modularity and normalized cut size can be interpreted as one-step
time measures, whereas Fiedler's spectral clustering emerges at long times. We
apply our method to characterize the relevance and persistence of partitions
over time for constructive and real networks, including hierarchical graphs and
social networks. We also obtain reduced descriptions for atomic level protein
structures over different time scales.Comment: submitted; updated bibliography from v
Flux Qubits and Readout Device with Two Independent Flux Lines
We report measurements on two superconducting flux qubits coupled to a
readout Superconducting QUantum Interference Device (SQUID). Two on-chip flux
bias lines allow independent flux control of any two of the three elements, as
illustrated by a two-dimensional qubit flux map. The application of microwaves
yields a frequency-flux dispersion curve for 1- and 2-photon driving of the
single-qubit excited state, and coherent manipulation of the single-qubit state
results in Rabi oscillations and Ramsey fringes. This architecture should be
scalable to many qubits and SQUIDs on a single chip.Comment: 5 pages, 4 figures, higher quality figures available upon request.
Submitted to PR
How Massless Neutrinos Affect the Cosmic Microwave Background Damping Tail
We explore the physical origin and robustness of constraints on the energy
density in relativistic species prior to and during recombination, often
expressed as constraints on an effective number of neutrino species, Neff.
Constraints from current data combination of Wilkinson Microwave Anisotropy
Probe (WMAP) and South Pole Telescope (SPT) are almost entirely due to the
impact of the neutrinos on the expansion rate, and how those changes to the
expansion rate alter the ratio of the photon diffusion scale to the sound
horizon scale at recombination. We demonstrate that very little of the
constraining power comes from the early Integrated Sachs-Wolfe (ISW) effect,
and also provide a first determination of the amplitude of the early ISW
effect. Varying the fraction of baryonic mass in Helium, Yp, also changes the
ratio of damping to sound-horizon scales. We discuss the physical effects that
prevent the resulting near-degeneracy between Neff and Yp from being a complete
one. Examining light element abundance measurements, we see no significant
evidence for evolution of Neff and the baryon-to-photon ratio from the epoch of
big bang nucleosynthesis to decoupling. Finally, we consider measurements of
the distance-redshift relation at low to intermediate redshifts and their
implications for the value of Neff.Comment: 11 pages. Replaced version extends our discussion of origin of
constraints and updates for current data, submitted to PR
Impact of Many-Body Effects on Landau Levels in Graphene
We present magneto-Raman spectroscopy measurements on suspended graphene to
investigate the charge carrier density-dependent electron-electron interaction
in the presence of Landau levels. Utilizing gate-tunable magneto-phonon
resonances, we extract the charge carrier density dependence of the Landau
level transition energies and the associated effective Fermi velocity
. In contrast to the logarithmic divergence of at
zero magnetic field, we find a piecewise linear scaling of as a
function of charge carrier density, due to a magnetic field-induced suppression
of the long-range Coulomb interaction. We quantitatively confirm our
experimental findings by performing tight-binding calculations on the level of
the Hartree-Fock approximation, which also allow us to estimate an excitonic
binding energy of 6 meV contained in the experimentally extracted
Landau level transitions energies.Comment: 10 pages, 6 figure
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