Quasilinear: Difference between revisions

From DispersiveWiki
Jump to navigationJump to search
No edit summary
 
m (typo, QNLW link)
 
(2 intermediate revisions by one other user not shown)
Line 1: Line 1:
A ''quasilinear equation'' is an equation of the form
{{stub}}
 
A '''quasilinear equation''' is an equation of the form
<center><math>F( u, Du, \ldots, D^k u ) = 0</math></center>
<center><math>F( u, Du, \ldots, D^k u ) = 0</math></center>
which is linear (and nontrivial) in the top order terms <math>D^k u</math>.  Thus a quasilinear equation takes the schematic form
which is linear (and nontrivial) in the top order terms <math>D^k u</math>.  Thus a quasilinear equation takes the schematic form
Line 6: Line 8:
one can place such equations in the slightly simpler form
one can place such equations in the slightly simpler form
<center><math>F( v) D^k v = G( v, Dv, \ldots, D^{k-1} v )</math></center>
<center><math>F( v) D^k v = G( v, Dv, \ldots, D^{k-1} v )</math></center>
thoug hthis trick comes at the cost of lowering the regularity of the fields.
though this trick comes at the cost of lowering the regularity of the fields.
 
Quasilinear equations are more nonlinear than [[semilinear]] ones, but less nonlinear than [[fully nonlinear]] equations.


Quasilinear equations are more nonlinear than ''semilinear'' ones, but less nonlinear than [[fully nonlinear]] equations.
==See also==
[[QNLW|Quasilinear nonlinear wave (QNLW)]]


[[Category:Concept]]
[[Category:Concept]]

Latest revision as of 15:35, 12 December 2007


A quasilinear equation is an equation of the form

which is linear (and nontrivial) in the top order terms . Thus a quasilinear equation takes the schematic form

By differentiating this equation up to times and working with the system of fields , one can place such equations in the slightly simpler form

though this trick comes at the cost of lowering the regularity of the fields.

Quasilinear equations are more nonlinear than semilinear ones, but less nonlinear than fully nonlinear equations.

See also

Quasilinear nonlinear wave (QNLW)