about a closed path
21Nonholonomic system — A nonholonomic system in physics and mathematics is a system whose state depends on the path taken to achieve it. Such a system is described by a set of parameters subject to differential constraints, such that when the system evolves along a… …
22Action (physics) — In physics, the action is a particular quantity in a physical system that can be used to describe its operation. Action is an alternative to differential equations. The action is not necessarily the same for different types of systems.The action… …
23Glossary of fuel cell terms — The Glossary of fuel cell terms lists the definitions of many terms used within the fuel cell industry. The terms in this glossary may be used by fuel cell industry associations, in education material and fuel cell codes and standards to name but …
24relativity — /rel euh tiv i tee/, n. 1. the state or fact of being relative. 2. Physics. a theory, formulated essentially by Albert Einstein, that all motion must be defined relative to a frame of reference and that space and time are relative, rather than… …
25Torus — Not to be confused with Taurus (disambiguation). This article is about the surface and mathematical concept of a torus. For other uses, see Torus (disambiguation). A torus As the distance to th …
26Out(Fn) — In mathematics, Out(Fn) is the outer automorphism group of a free group on n generators. These groups play an important role in geometric group theory. Contents 1 Outer space 1.1 Definition 1.2 Connection to length fun …
27Kosterlitz–Thouless transition — The Kosterlitz–Thouless transition, or Berezinsky–Kosterlitz–Thouless transition, is a special transition seen in the XY model for interacting spin systems in 2 spatial dimensions.The XY model is a 2 Dimensional vector spin model that possesses… …
28Complex analysis — Plot of the function f(x)=(x2 1)(x 2 i)2/(x2 + 2 + 2i). The hue represents the function argument, while the brightness represents the magnitude. Complex analysis, traditionally known as the theory of functions of a complex variable, is the branch …
29Lorentz force — This article is about the equation governing the electromagnetic force. For a qualitative overview of the electromagnetic force, see Electromagnetism. For magnetic force of one magnet on another, see force between magnets. Electromagnetism …
30List of streets and roads in Hong Kong — Here is a partial list of expressways, tunnels, bridges, roads, avenues, streets, crescents, squares and bazaars in Hong Kong.Routes Hong Kong s Transport Department is responsible for maintenance and control of highways and roadways. In 2004, a… …
