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
 
 

Riccati equation

In mathematics, a Riccati equation is any ordinary differential equation that has the form

y' = q_0(x) + q_1(x) \, y + q_2(x) \, y^2

It is named after Count Jacopo Francesco Riccati (1676-1754).

The Riccati equation is not amenable to elementary techniques in solving differential equations, except as follows. If one can find any solution y1, the general solution is obtained as

y = y1 + u

Substituting

y1 + u

in the Riccati equation yields

y_1' + u' = q_0 + q_1 \cdot (y_1 + u) + q_2 \cdot (y_1 + u)^2,

and since

y_1' = q_0 + q_1 \, y_1 + q_2 \, y_1^2
u' = q_1 \, u + 2 \, q_2 \, y_1 \, u + q_2 \, u^2

or

u' - (q_1 + 2 \, q_2 \, y_1) \, u = q_2 \, u^2,

which is a Bernoulli equation . Unfortunately, one finds y1 by guessing. The substitution that is needed to solve this Bernoulli equation is

z = u^{1-2} = \frac{1}{u}

Substituting

y = y_1 + \frac{1}{z}

directly into the Riccati equation yields the linear equation

z' + (q_1 + 2 \, q_2 \, y_1) \, z = -q_2

The general solution to the Riccati equation is then given by

y = y_1 + \frac{1}{z}

where z is the general solution to the aforementioned linear equation.

External link

Bibliography

  • A. D. Polyanin and V. F. Zaitsev, Handbook of Exact Solutions for Ordinary Differential Equations, 2nd Edition, Chapman & Hall/CRC Press, Boca Raton, 2003.
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