251 research outputs found
Extreme sea levels at different global warming levels
The Paris agreement focused global climate mitigation policy on limiting global warming to 1.5 or 2 °C above pre-industrial levels. Consequently, projections of hazards and risk are increasingly framed in terms of global warming levels rather than emission scenarios. Here, we use a multimethod approach to describe changes in extreme sea levels driven by changes in mean sea level associated with a wide range of global warming levels, from 1.5 to 5 °C, and for a large number of locations, providing uniform coverage over most of the world’s coastlines. We estimate that by 2100 ~50% of the 7,000+ locations considered will experience the present-day 100-yr extreme-sea-level event at least once a year, even under 1.5 °C of warming, and often well before the end of the century. The tropics appear more sensitive than the Northern high latitudes, where some locations do not see this frequency change even for the highest global warming levels
Rare events and breakdown of simple scaling in the Abelian sandpile
Due to intermittency and conservation, the Abelian sandpile in 2D obeys
multifractal, rather than finite size scaling. In the thermodynamic limit, a
vanishingly small fraction of large avalanches dominates the statistics and a
constant gap scaling is recovered in higher moments of the toppling
distribution. Thus, rare events shape most of the scaling pattern and preserve
a meaning for effective exponents, which can be determined on the basis of
numerical and exact results.Comment: RevTex, 4 Pages, 2 Figure
From waves to avalanches: two different mechanisms of sandpile dynamics
Time series resulting from wave decomposition show the existence of different
correlation patterns for avalanche dynamics. For the d=2 Bak-Tang-Wiesenfeld
model, long range correlations determine a modification of the wave size
distribution under coarse graining in time, and multifractal scaling for
avalanches. In the Manna model, the distribution of avalanches coincides with
that of waves, which are uncorrelated and obey finite size scaling, a result
expected also for the d=3 Bak et al. model.Comment: 5 pages, 4 figure
Branching Processes and Evolution at the Ends of a Food Chain
In a critically self--organized model of punctuated equilibrium, boundaries
determine peculiar scaling of the size distribution of evolutionary avalanches.
This is derived by an inhomogeneous generalization of standard branching
processes, extending previous mean field descriptions and yielding
together with , as distribution exponent of avalanches starting from
species at the ends of a food chain. For the nearest neighbor chain one obtains
numerically , and for the
first return times of activity, again distinct from bulk exponents.Comment: REVTex file, 12 pages, 2 figures in eps-files uuencoded, psfig.st
Stochastic processes and conformal invariance
We discuss a one-dimensional model of a fluctuating interface with a dynamic
exponent . The events that occur are adsorption, which is local, and
desorption which is non-local and may take place over regions of the order of
the system size. In the thermodynamic limit, the time dependence of the system
is given by characters of the conformal field theory of percolation. This
implies in a rigorous way a connection between CFT and stochastic processes.
The finite-size scaling behavior of the average height, interface width and
other observables are obtained. The avalanches produced during desorption are
analyzed and we show that the probability distribution of the avalanche sizes
obeys finite-size scaling with new critical exponents.Comment: 4 pages, 6 figures, revtex4. v2: change of title and minor
correction
Field theory of absorbing phase transitions with a non-diffusive conserved field
We investigate the critical behavior of a reaction-diffusion system
exhibiting a continuous absorbing-state phase transition. The
reaction-diffusion system strictly conserves the total density of particles,
represented as a non-diffusive conserved field, and allows an infinite number
of absorbing configurations. Numerical results show that it belongs to a wide
universality class that also includes stochastic sandpile models. We derive
microscopically the field theory representing this universality class.Comment: 13 pages, 1 eps figure, RevTex styl
Scenarios in IPCC assessments: lessons from AR6 and opportunities for AR7
Scenarios have been an important integrating element in the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) in the understanding of possible climate outcomes, impacts and risks, and mitigation futures. Integration supports a consistent, coherent assessment, new insights and the opportunity to address policy-relevant questions that would not be possible otherwise, for example, which impacts are unavoidable, which are reversible, what is a consistent remaining carbon budget to keep temperatures below a level and what would be a consistent route of action to achieve that goal. The AR6 builds on community frameworks that are developed to support a coherent use of scenarios across the assessment, yet their use in the assessment and the related timelines presented coordination challenges. From lessons within each Working Group (WG) assessment and the cross-WG experience, we present insights into the role of scenarios in future assessments, including the enhanced integration of impacts into scenarios, near-term information and community coordination efforts. Recommendations and opportunities are discussed for how scenarios can support strengthened consistency and policy relevance in the next IPCC assessment cycle
Critical behavior of a one-dimensional fixed-energy stochastic sandpile
We study a one-dimensional fixed-energy version (that is, with no input or
loss of particles), of Manna's stochastic sandpile model. The system has a
continuous transition to an absorbing state at a critical value of
the particle density. Critical exponents are obtained from extensive
simulations, which treat both stationary and transient properties. In contrast
with other one-dimensional sandpiles, the model appears to exhibit finite-size
scaling, though anomalies exist in the scaling of relaxation times and in the
approach to the stationary state. The latter appear to depend strongly on the
nature of the initial configuration. The critical exponents differ from those
expected at a linear interface depinning transition in a medium with point
disorder, and from those of directed percolation.Comment: 15 pages, 11 figure
Demagnetization via Nucleation of the Nonequilibrium Metastable Phase in a Model of Disorder
We study both analytically and numerically metastability and nucleation in a
two-dimensional nonequilibrium Ising ferromagnet. Canonical equilibrium is
dynamically impeded by a weak random perturbation which models homogeneous
disorder of undetermined source. We present a simple theoretical description,
in perfect agreement with Monte Carlo simulations, assuming that the decay of
the nonequilibrium metastable state is due, as in equilibrium, to the
competition between the surface and the bulk. This suggests one to accept a
nonequilibrium "free-energy" at a mesoscopic/cluster level, and it ensues a
nonequilibrium "surface tension" with some peculiar low-T behavior. We
illustrate the occurrence of intriguing nonequilibrium phenomena, including:
(i) Noise-enhanced stabilization of nonequilibrium metastable states; (ii)
reentrance of the limit of metastability under strong nonequilibrium
conditions; and (iii) resonant propagation of domain walls. The cooperative
behavior of our system may also be understood in terms of a Langevin equation
with additive and multiplicative noises. We also studied metastability in the
case of open boundaries as it may correspond to a magnetic nanoparticle. We
then observe burst-like relaxation at low T, triggered by the additional
surface randomness, with scale-free avalanches which closely resemble the type
of relaxation reported for many complex systems. We show that this results from
the superposition of many demagnetization events, each with a well- defined
scale which is determined by the curvature of the domain wall at which it
originates. This is an example of (apparent) scale invariance in a
nonequilibrium setting which is not to be associated with any familiar kind of
criticality.Comment: 26 pages, 22 figure
Smart cities, social media platforms and security: online content regulation as a site of controversy and conflict
Abstract Smart, technologically managed city-regions are one of the main characteristics of the contemporary world. Since the attack to the Charlie Hebdo offices, city-regions and social media digital technologies have increasingly been changing the definition of 'territory of security' and 'security governance'. What are the characteristics of the security architecture created by the interaction of smart city-regions and digital technologies? Drawing from Actor-Network theory and Science and Technology Studies, we provide an empirical account of the shape of this new territory, by presenting a study of the controversy concerning security and social media in UK, the role of cities in this changed security space, and how social sciences can help better understand and respond to the opportunities and threats of smart cities
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