Maths encyclopedia and lessons  
Search

Mathematics Encyclopedia and Lessons

 
     
 

Lessons

Popular
Subjects

algebra
arithmetic
calculus
equations
geometry
differential equations
trigonometry
number theory
probability theory
more
 

References

applied mathematics
mathematical games
mathematicians
more
 
 

Homogeneous (mathematics)

In mathematics, homogeneous has a variety of meanings.

  • In algebra it means an expression consisting of terms that are sums of monomials of the same total degree; or of elements of the same dimension.
  • A function f mapping a vector space V over a field F to another vector space W over F is said to be homogeneous of degree k if the equation f(a·v) = ak·f(v) holds for a in F and v in V. For a function f(x) = f(x1, ..., xn) that is homogeneous of degree k Euler's homogeneous function theorem holds:
\sum_{i=1}^n x_i \frac{\partial f}{\partial x_i} (x) = k f(x)
  • More generally, a function f is said to be homogeneous if the equation f(a v) = g(a) f(v) holds for some strictly increasing positive function g.
  • A homogeneous differential equation is usually one of the form Lf = 0, where L is a differential operator, the corresponding inhomogeneous equation being Lf = g with g a given function; the word homogeneous is also used of equations in the form Dy = f(y/x).
  • In linear algebra a homogeneous system is a one of the form Ax=0.
  • Homogeneous numbers share identical prime factors (may be repeated).
  • A homogeneous space for a Lie group G, or more general transformation group, is a space X on which G acts transitively and continuously - so equivalently a coset space G/H where H is a closed subgroup.
  • As a special case of the previous meaning, a manifold is said to be homogeneous for its homeomorphism group, or diffeomorphism group, if that group acts transitively on it; this is true for connected manifolds.
  • Given a colouring of the edges of a complete graph, the term homogeneous applies to a subset of vertices such that all edge connecting two of the subset have the same colour; and in much greater generality in Ramsey theory for colourings of k-element subsets.
01-04-2007 01:18:14
The contents of this article are licensed from Wikipedia.org
under the GNU Free Documentation License. How to see transparent copy