evolvescalar(1) --- Imcat Users Guide --- section: imcattools_waves --- last changed: Thu Jul 10 HST
evolvescalar - evolve a 2-D scalar fieldSYNOPSIS
evolvescalar [-nsteps nsteps (10)] [-nframes nframes (99999)][-kstar kstar (0.3)] [-autoscale] [-dt dt (0.2)] [-lambda lambda (0.0)] [-gamma gamma (0.0)] [-u] [-gravity V0 sigma] DESCRIPTION
Evolvescalar reads from stdin a 3-D FITS file f[2][Ny][Nx] consisting of 2 planes containing the initial field d[Ny][Nx] and the initial field velocity v[Ny][Nx]. It then evolves the coupled equations dv/dt = laplacian(d) - kstar^2 d - 4 lambda d^3 - gamma v dd/dt = v With gamma = 0 these are equivalent to the Klein-Gordon equation with mass ~ kstar and a lambda phi^4 self-interaction.
With -gravity option we replace kstar by kstar (1 - V0 exp(-0.5 r**2 / sigma**2)). This simulates the effect of a fixed external gravitational potential. With non-zero damping coefficient gamma, the waves evolve as in an expanding universe with H = gamma / 3. If kstar is negative, it evolves dv/dt = laplacian(d) + kstar^2 d - 4 lambda d^3 - gamma v dd/dt = v which has a negative mass term and gives a 'w'-shaped potential. The laplacian function is computed as laplacian = d[y][x-1] + d[y][x+1] + d[y-1][x] + d[y+1][x] - 4 * d[y][x]. The evolution scheme is v += 0.5 * dv/dt * dt d += dd/dt * dt v += 0.5 * dv/dt * dt It outputs a 3-D FITS file f[nframes][Ny][Nx] containing the evolved field. OPTIONS
"-nsteps nsteps " number of steps between output frames
"-nframes nframes " total number of output frames
"-kstar kstar " Compton wave-number
"-autoscale " scale each output frame to 0-256
"-dt dt " time-step
"-lambda lambda " interaction strength
"-gamma gamma " damping rate
"-u " print man-pageSEE ALSO
AUTHOR
Nick Kaiser --- kaiser@hawaii.edu