applied physics Applied physics is the application of physics to solve scientific or engineering problems. It is usually considered a bridge or a connection between physics and engineering. "Applied" is distinguished from "pure" by a subtle combination of fac ...

, the concept of controlling self-organized criticality refers to the control of processes by which a self-organized system dissipates

energy Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and l ...

. The objective of the control is to reduce the probability of occurrence of and size of energy dissipation bursts, often called ''avalanches'', of self-organized systems. Dissipation of energy in a self-organized critical system into a lower energy state can be costly for society, since it depends on avalanches of all sizes usually following a kind of

power law In statistics, a power law is a Function (mathematics), functional relationship between two quantities, where a Relative change and difference, relative change in one quantity results in a relative change in the other quantity proportional to the ...

distribution and large avalanches can be damaging and disruptive.

Schemes

Several strategies have been proposed to deal with the issue of controlling self-organized criticality: #''The design of controlled avalanches.'' Daniel O. Cajueiro and Roberto F. S. Andrade show that if well-formulated small and medium avalanches are exogenously triggered in the system, the energy of the system is released in a way that large avalanches are rarer. #'' The modification of the degree of interdependence of the network where the avalanche spreads.'' Charles D. Brummitt, Raissa M. D'Souza and E. A. Leicht show that the dynamics of self-organized critical systems on complex networks depend on connectivity of the complex network. They find that while some connectivity is beneficial (since it suppresses the largest cascades in the system), too much connectivity gives space for the development of very large cascades and increases the size of capacity of the system. #'' The modification of the deposition process of the self-organized system.'' Pierre-Andre Noel, Charles D. Brummitt and Raissa M. D'Souza show that it is possible to control the self-organized system by modifying the natural deposition process of the self-organized system adjusting the place where the avalanche starts. #'' Dynamically modifying the local thresholds of cascading failures.'' In a model of an electric transmission network, Heiko Hoffmann and David W. Payton demonstrated that either randomly upgrading lines (sort of like preventive maintenance) or upgrading broken lines to a random breakage threshold suppresses self-organized criticality. Apparently, these strategies undermine the self-organization of large critical clusters. Here, a critical cluster is a collection of transmission lines that are near the failure threshold and that collapse entirely if triggered.

Applications

There are several events that arise in nature or society and that these ideas of control may help to avoid: #

Flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

caused by systems of dams and reservoirs or interconnected valleys. # Snow avalanches that take place in snow hills. # Forest fires in areas susceptible to a lightning bolt or a match lighting. # Cascades of load shedding that take place in power grids (a type of

power outage A power outage, also called a blackout, a power failure, a power blackout, a power loss, a power cut, or a power out is the complete loss of the electrical power network supply to an end user. There are many causes of power failures in an el ...

). The OPA model is used to study different techniques for criticality control. #

Cascading failure A cascading failure is a failure in a system of interconnection, interconnected parts in which the failure of one or few parts leads to the failure of other parts, growing progressively as a result of positive feedback. This can occur when a singl ...

in the internet switching fabric. # Ischemic cascades, a series of biochemical reactions releasing toxins during moments of inadequate blood supply. #

Systemic risk In finance, systemic risk is the risk of collapse of an entire financial system or entire market, as opposed to the risk associated with any one individual entity, group or component of a system, that can be contained therein without harming the ...

in financial systems. # Excursions in nuclear energy systems. #

Earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

s and

induced seismicity Induced seismicity is typically earthquakes and tremors that are caused by human activity that alters the stresses and strains on Earth's crust. Most induced seismicity is of a low magnitude. A few sites regularly have larger quakes, such as The ...

. The failure cascades in electrical transmission and financial sectors occur because economic forces that push for efficiency cause these systems to operate near a critical point, where avalanches of indeterminate size become possible. Financial investments that are vulnerable to this kind of failure may exhibit a

Taleb distribution In economics and finance, a Taleb distribution is the statistical profile of an investment which normally provides a payoff of small positive returns, while carrying a small but significant risk of catastrophic losses. The term was coined by jou ...

References

{{reflist Applied and interdisciplinary physics Control theory Chaos theory Self-organization Critical phenomena

Schemes

Applications

See also

References