Conjugation of Complex Functions in Partial Differential Equations

[L0r3n20]

I'm in truble with a partial differential equation. Actually it is a system of PDE but It would be useful to solve at least one of them.
The most easy one is this one

<br /> 2 \bar{\xi}\left(\bar{s},\bar{t},\bar{u}\right) - 2 \xi\left(s,t,u\right) + \left(s-\bar{s}\right)\left(\bar{\partial}_\bar{s} \bar{\xi} + \partial_s \xi \right) = 0<br />

This equation can be simplified to

<br /> 2 A^*\left(z^*\right) - 2 A\left(z\right) + \left(z-z^*\right)\left(\bar{\partial}_{z^*}A^*+\partial_{z}A\right)= 0<br />

I further developed my computation using A(z) = u(x,y) + i v(x,y) with u,v \in \mathbb{R}
finding (I used Cauchy-Riemann equations)
v(x,y) = y^2 f(x+y)
Here is where I get stucked since I cannot find a suitable form of "f(x+y)" in order to obtain "u" and satisfy Cauchy-Riemann equations...
Any ideas?

 

[jackmell]

I'm in truble with a partial differential equation. Actually it is a system of PDE but It would be useful to solve at least one of them.
The most easy one is this one

<br /> 2 \bar{\xi}\left(\bar{s},\bar{t},\bar{u}\right) - 2 \xi\left(s,t,u\right) + \left(s-\bar{s}\right)\left(\bar{\partial}_\bar{s} \bar{\xi} + \partial_s \xi \right) = 0<br />

This equation can be simplified to

<br /> 2 A^*\left(z^*\right) - 2 A\left(z\right) + \left(z-z^*\right)\left(\bar{\partial}_{z^*}A^*+\partial_{z}A\right)= 0<br />

Any ideas?

Consider the expression:

<br /> \bar{\partial}_{z^*}A^*

I assume that means:

\overline{\frac{\partial \bar{f}}{\partial\bar{s}}}

but we know that:

\frac{\partial \overline{f}}{\partial \overline{s}}=\overline{\frac{\partial f}{\partial s}}

which means you have:

2\overline{A}(\overline{z})-2A(z)+2(z-\overline{z})\frac{\partial A}{\partial z}=0

 

[L0r3n20]

I'm afraid I use the wrong notation or maybe I didn't understand at all! =)
with
\bar{\partial}_{\bar{s}} \xi^*
I mean the derivate of xi* wrt the complex conjugate of s (i.e. \bar{s}). I use the bar over the partial derivative to point out that the derivate is made over \bar{s} and not s. Sorry about this misleading notation! :)

 

[jackmell]

I'm afraid I use the wrong notation or maybe I didn't understand at all! =)
with
\bar{\partial}_{\bar{s}} \xi^*
I mean the derivate of xi* wrt the complex conjugate of s (i.e. \bar{s}). I use the bar over the partial derivative to point out that the derivate is made over \bar{s} and not s. Sorry about this misleading notation! :)

Ok, that's confussing. Tell you what, how about we just do it my way:

2\overline{A}(\overline{z})-2A(z)+2(z-\overline{z})\frac{d A}{d z}=0

Can we even solve that one? The conjugate variables really hit me with a surprise though and I'm not use to working with DEs like that. I mean what do you do with something like that? Is it even well-posed? Suppose nobody could help us and we had to do something with it, a thesis or something? What do we do? Suppose we could first look at:

\frac{dy}{dz}+\overline{y}(\overline{z})=0

Can we even do that one? Does it even make sense? Looks like another whole-semester type problem to me.

 

[L0r3n20]

I have to admit I'm confused too...
My problem, I mean in its original formulation, require to find the holomorphic Killing vector of a given Kahler manifold. In order to do that I found I have to solve that equation (and many more to be honest...).
Now I wondering if by \bar{A}(\bar{z})
they actually mean \left(A(z)\right)^*
In that case I can set A = u(x,y)+iv(x,y) \qquad \bar{A} = u(x,y)-iv(x,y)
For which I found this solution
<br /> u(x,y) = \frac{1}{2} C_1 \left(x^2-y^2\right)+C_2 x + C_3 \qquad <br /> v(x,y) = C_1 xy + C_2 y<br />
Which is a bit tempting since it satisfy also Cauchy Riemann equations..

 

[jackmell]

Now I wondering if by \bar{A}(\bar{z})
they actually mean \left(A(z)\right)^*

I think that means the conjugate of A at the conjugate of z. So if:

A(z)=iz

A(\overline{z})=i\overline{z}

\overline{A(\overline{z})}=-iz

Not sure though ok?

 

[L0r3n20]

Bulletin from the front. :)

As I supposed they intended just the conjugation of the entire function not of both function and variables... So I solved, thank you anyway!