/**
* Computes and plots correlation functions
*
* @param tauMax is the maximum time for correlation functions
*/
public void computeCorrelation(int tauMax) {
plotFrame.clearData();
double energyAccumulator = 0, magnetizationAccumulator = 0;
double energySquaredAccumulator = 0, magnetizationSquaredAccumulator = 0;
for (int t = 0; t < numberOfPoints; t++) {
energyAccumulator += energy[t];
magnetizationAccumulator += magnetization[t];
energySquaredAccumulator += energy[t] * energy[t];
magnetizationSquaredAccumulator += magnetization[t] * magnetization[t];
}
double averageEnergySquared = Math.pow(energyAccumulator / numberOfPoints, 2);
double averageMagnetizationSquared = Math.pow(magnetizationAccumulator / numberOfPoints, 2);
// compute normalization factors
double normE = (energySquaredAccumulator / numberOfPoints) - averageEnergySquared;
double normM = (magnetizationSquaredAccumulator / numberOfPoints) - averageMagnetizationSquared;
for (int tau = 1; tau <= tauMax; tau++) {
double c_MAccumulator = 0;
double c_EAccumulator = 0;
int counter = 0;
for (int t = 0; t < numberOfPoints - tau; t++) {
c_MAccumulator += magnetization[t] * magnetization[t + tau];
c_EAccumulator += energy[t] * energy[t + tau];
counter++;
}
// correlation function defined so that c(0) = 1 and c(infinity) -> 0
plotFrame.append(0, tau, ((c_MAccumulator / counter) - averageMagnetizationSquared) / normM);
plotFrame.append(1, tau, ((c_EAccumulator / counter) - averageEnergySquared) / normE);
}
plotFrame.setVisible(true);
}
/**
* Calculates the trajectory of a falling particle and plots the position as a function of time.
*/
public void calculate() {
plotFrame.setAutoclear(false); // data not cleared at beginning of each calculation
// gets initial conditions
double y0 = control.getDouble("Initial y");
double v0 = control.getDouble("Initial v");
// sets initial conditions
Particle ball = new FallingParticle(y0, v0);
// gets parameters
ball.dt = control.getDouble("dt");
while (ball.y > 0) {
ball.step();
plotFrame.append(0, ball.t, ball.y);
plotFrame.append(1, ball.t, ball.analyticPosition());
}
}
/** Calculates the wave function. */
public void calculate() {
schroedinger.xmin = control.getDouble("xmin");
schroedinger.xmax = control.getDouble("xmax");
schroedinger.stepHeight = control.getDouble("step height at x = 0");
schroedinger.numberOfPoints = control.getInt("number of points");
schroedinger.energy = control.getDouble("energy");
schroedinger.initialize();
schroedinger.solve();
frame.append(0, schroedinger.x, schroedinger.phi);
}