Ginzburg-Landau-Schrodinger equation: Difference between revisions

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The '''Ginsberg-Landau-Schrodinger''' equation is
The '''Ginzburg-Landau-Schrodinger''' equation is


<center><math>i u^\epsilon_t + \Delta u^\epsilon = \frac{1}{\epsilon^2} (|u^\epsilon|^2 - 1)u^\epsilon.</math></center>
<center><math>i u^\epsilon_t + \Delta u^\epsilon = \frac{1}{\epsilon^2} (|u^\epsilon|^2 - 1)u^\epsilon.</math></center>


The main focus of study for this equation is the formation of vortices and their dynamics in the limit <math>\epsilon \to 0</math>.
The main focus of study for this equation is the formation of vortices and their dynamics in the limit <math>\epsilon \to 0</math>.
The [http://en.wikipedia.org/wiki/Ginzburg-Landau_theory Ginzburg-Landau theory] is briefly surveyed on [http://en.wikipedia.org Wikipedia].
==Perturbative Approach==
The limit <math>\epsilon\to 0</math> can be treated with the same methods given in [[Perturbation theory]]. To see this we note that an exact solution can be written as
<math> u^\epsilon = \sqrt{n_0}e^{-i(n_0-1)\frac{t}{\epsilon^2}} </math>
<math>n_0</math> being a real constant. Then, if we rescale time as <math>\tau=t/\epsilon^2</math> and take the solution series
<math> u^\epsilon = u_0+\epsilon^2 u_1+\epsilon^4 u_2+\ldots </math>
one has the non trivial set of equations
<math>i\dot u_0=u_0(|u_0|^2-1)</math>
<math>i\dot u_1+\Delta u_0=u_1(|u_0|^2-1)+(u_1^*u_0+u_0^*u_1)u_0</math>
<math>i\dot u_2+\Delta u_1=u_2(|u_0|^2-1)+(u_1^*u_0+u_0^*u_1)u_1+(|u_1|^2+u_2^*u_0+u_0^*u_2)u_0</math>
<math>\ldots</math>.
where dot means derivation with respect to <math>\tau</math>. The leading order solution is easily written down as
<math>u_0 = \sqrt{n_0(x)}e^{-i[n_0(x)-1]\tau} </math>.
With this expression we can write down the next order correction as
<math>u_1 = \phi(x,\tau)e^{-i[2n_0(x)-1]\tau}</math>
<math>i\dot\phi=n_0(x)\phi^*e^{-i[2n_0(x)-1]\tau}-(\Delta u_0)e^{-i[2n_0(x)-1]\tau}</math>
<math>-i\dot\phi^*=n_0(x)\phi e^{i[2n_0(x)-1]\tau}-(\Delta u_0^*)e^{i[2n_0(x)-1]\tau}</math>.
This set is easy to solve. The most important point to notice is the limit surface <math>n_0(x)=1/2</math> that denotes a change into the stability of the solution of GL equation. It should also be pointed out the appearence at this order of secular terms going like <math>\tau</math>
and <math>\tau^2</math>. These terms can be treated with several known techniques.


[[Category:Schrodinger]]
[[Category:Schrodinger]]
[[Category:Equations]]
[[Category:Equations]]

Latest revision as of 07:45, 2 October 2007


The Ginzburg-Landau-Schrodinger equation is

The main focus of study for this equation is the formation of vortices and their dynamics in the limit .

The Ginzburg-Landau theory is briefly surveyed on Wikipedia.

Perturbative Approach

The limit can be treated with the same methods given in Perturbation theory. To see this we note that an exact solution can be written as

being a real constant. Then, if we rescale time as and take the solution series

one has the non trivial set of equations

.

where dot means derivation with respect to . The leading order solution is easily written down as

.

With this expression we can write down the next order correction as

.

This set is easy to solve. The most important point to notice is the limit surface that denotes a change into the stability of the solution of GL equation. It should also be pointed out the appearence at this order of secular terms going like and . These terms can be treated with several known techniques.