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Example: monte_carlo program

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The following example program is a simple demonstration of the function monte_carlo(), which was defined in the previous section. It produces animated output representing time-series data for simulated detector noise and for a simulated stochastic background having a constant frequency spectrum: $\Omega_{\rm gw}(f)=\Omega_0$ for $f_{\rm low}\le f \le f_{\rm high}$. The output from this program must be piped into xmgr. The parameters that were chosen for the example program shown below produce whitened time-series data for a stochastic background having $\Omega_{\rm gw}(f)=1.0\times 10^{-3}$ for $5\ {\rm Hz}\le f\le 5000\ {\rm Hz}$. For this particular example, the noise intrinsic to the detectors was set to zero. A sample ``snapshot'' of the animation is shown in Fig. [*].

By modifying the parameters listed at the top of the example program, one can also simulate an unwhitened stochastic background signal (Fig. [*]), and whitened and unwhitened data streams corresponding to the noise intrinsic to an initial LIGO detector (Figs. [*] and [*]). Other combinations of signal, noise, whitening, and unwhitening are of course also possible. To produce the animated output, simply enter the command:

monte_carlo | xmgr -pipe &
after compilation.

Note: The amplitude of the animated output initially builds up from zero to its nominal value over (approximately) the first 1.5 seconds. This ``turn-on'' transient is a consequence of the overlapping technique used by combine_data() to produce continuous-in-time detector output. (See the comment at the end of Section [*].)

Includes/monte_carlo.tex

Figure: Time-series data (whitened) for a stochastic background having a constant frequency spectrum: $\Omega_{\rm gw}(f)=1.0\times 10^{-3}$ for .

Figure: Time-series data (unwhitened) for a stochastic background having a constant frequency spectrum: $\Omega_{\rm gw}(f)=1.0\times 10^{-3}$ for .

Figure: Time-series data (whitened) for the noise intrinsic to an initial LIGO detector.

Figure: Time-series data (unwhitened) for the noise intrinsic to an initial LIGO detector.
\begin{figure}\begin{center}
{\epsfig{file=Figures/f2d_sb.ps,angle=-90,width=5in}}
\end{center}\end{figure}


next up previous contents
Next: Function: test_data12() Up: GRASP Routines: Stochastic background Previous: Function: monte_carlo()   Contents
Bruce Allen 2000-11-19