Effective theory
As Effective theory in science, usually in physics, refers to a theory that represents a deeper, underlying theory applied simplistic or collectively. An effective theory allows simpler calculations, as long as the microscopic properties can be averaged.
Effective theories are often the only viable method to investigate a phenomenon scientifically. It is necessary to carry out the analyzes within the limits of the effective theory; otherwise the results will be wrong.
Examples
Optics
In optics, the so-called " effective media theory" used to calculate the optical properties of non-interacting particles in a matrix system. For this, the dielectric constant of the matrix and the particulate system, and the filling factor of the particle system can be combined into an effective dielectric function. Various special cases and claims on the particle shape, particle shape distribution, etc. are taken into account by different theories such as those of DAG Bruggeman or H. Looyenga.
In the case of very small, round particles, carried by the Mie theory, the more accurate description. Describes, inter alia, the Mie scattering.
Thermodynamics
Thermodynamics is an effective theory, since it neglects the motion of individual atoms and molecules, and only average quantities such as pressure and temperature considered. She is still very successful in their description of gases.
The statistical thermodynamics is the appropriate extension of thermodynamics. With this it is possible the thermodynamic variables such as temperature and pressure, but also internal energy, entropy, etc. to be calculated from the system properties.
Fluid Mechanics
The hydrodynamics assumes that matter is made arbitrarily small particles is, and thus neglects the atomic structure of matter. Nevertheless, it is very successful, for example in the construction of aircraft.
Nuclear physics
In nuclear physics properties of the nuclei to be examined and described in core models. These models are based on the level of the core building blocks (protons and neutrons ), but neglect the fact that the same are made up of quarks.
Quantum field theory
In quantum field theory divergences can be avoided by introducing a cutoff. The cutoff is the maximum energy scale up to which one considers the theory; Particles whose mass beyond this scale are neglected. While change for the theory of the choice of a high cutoffs only the coupling constants, so it is renormalizable, limited by the selection of a low cutoff effective theories are usually not perturbatively renormalizable. How to do such as the renormalizable Glashow -Weinberg -Salam theory of the electroweak interaction for low energy in the non- renormalizable, effective Fermi theory in which a hadron and a lepton current through a vector-vector coupling the beta decay describe.
The decays of heavy hadrons are described by the effective theory of heavy quarks ( HQET for Heavy Quark Effective Theory).
Basic questions
So far the development of science in search of a fundamental theory has always been existing theories replaced by new theories in which the recent phenomena can be understood by considering smaller constituents.
Therefore, the question arises whether such a search is endless in the sense that inside every theory is a further contain - or whether there is an innermost theory that eventually ( at least theoretically) can all understand theories.
Currently the superstring theory is a promising material for such a inner theory.
Itemization
- Philosophy of Science