101 lines
3.1 KiB
Mathematica
101 lines
3.1 KiB
Mathematica
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function [Params] = SetupParameters()
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%%--%% Parameters %%--%%
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%========= Simulation =========%
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pert = 0; % 0 = no perturbation during real-time, 1=perturbation
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%method=1; % 0 = normal dipolar potential, 1=spherical cut-off, 2=cylindrical cut-off
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% Tolerances
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Params.Etol = 5e-10;
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Params.rtol = 1e-5;
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Params.cut_off = 2e6; % sometimes the imaginary time gets a little stuck
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% even though the solution is good, this just stops it going on forever
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%========= Constants =========%
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hbar = 1.0545718e-34; % Planck constant [J.s]
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kbol = 1.38064852e-23; % Boltzmann Constant [J/K]
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mu0 = 1.25663706212e-6; % Vacuum Permeability [N/A^2] --
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muB = 9.274009994e-24; % Bohr Magneton [J/T]
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a0 = 5.2917721067e-11; % Bohr radius [m]
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m0 = 1.660539066e-27; % Atomic mass [kg]
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w0 = 2*pi*100; % Angular frequency unit [s^-1]
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mu0factor = 0.3049584233607396; % =(m0/me)*pi*alpha^2 -- me=mass of electron, alpha=fine struct. const.
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% mu0=mu0factor *hbar^2*a0/(m0*muB^2)
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%=============================%
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% Number of points in each direction
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Params.Nx = 128;
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Params.Ny = 128;
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Params.Nz = 96;
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% Dimensions (in units of l0)
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Params.Lx = 40;
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Params.Ly = 40;
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Params.Lz = 20;
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% Masses
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Params.m = 162*m0;
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l0 = sqrt(hbar/(Params.m*w0)); % Defining a harmonic oscillator length
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% Atom numbers
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% Params.ppum = 2500; % particles per micron
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% Params.N = Params.Lz*Params.ppum*l0*1e6;
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Params.N = 10^6;
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% Dipole angle
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Params.theta = pi/2; % pi/2 dipoles along x, theta=0 dipoles along z
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% Dipole lengths (units of muB)
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Params.mu = 9.93*muB;
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% Scattering lengths
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Params.as = 86*a0;
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% Trapping frequencies
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Params.wx = 2*pi*125;
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Params.wy = 2*pi*125;
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Params.wz = 2*pi*250;
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% Time step
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Params.dt = 0.0005;
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Params.mindt = 1e-6; %Minimum size for a time step using adaptive dt
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% Stochastic GPE
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Params.gamma_S = 7.5*10^(-3); % gamma for the stochastic GPE
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Params.muchem = 12.64*Params.wz/w0; % fixing the chemical potential for the stochastic GPE
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% ================ Parameters defined by those above ================ %
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% == Calculating quantum fluctuations == %
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eps_dd = Params.add/Params.as;
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if eps_dd == 0
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Q5 = 1;
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elseif eps_dd == 1
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Q5 = 3*sqrt(3)/2;
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else
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yeps = (1-eps_dd)/(3*eps_dd);
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Q5 = (3*eps_dd)^(5/2)*( (8+26*yeps+33*yeps^2)*sqrt(1+yeps) + 15*yeps^3*log((1+sqrt(1+yeps))/sqrt(yeps)) )/48;
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Q5 = real(Q5);
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end
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Params.gammaQF = 128/3*sqrt(pi*(Params.as/l0)^5)*Q5;
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% Contact interaction strength (units of l0/m)
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Params.gs = 4*pi*Params.as/l0;
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% Dipole lengths
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Params.add = mu0*Params.mu^2*Params.m/(12*pi*hbar^2);
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% DDI strength
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Params.gdd = 12*pi*Params.add/l0; %sometimes the 12 is a 4? --> depends on how Vdk (DDI) is defined
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% Trap gamma
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Params.gx=(Params.wx/w0)^2;
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Params.gy=(Params.wy/w0)^2;
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Params.gz=(Params.wz/w0)^2;
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% Loading the rest into Params
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Params.hbar = hbar; Params.kbol = kbol; Params.mu0 = mu0; Params.muB = muB; Params.a0 = a0;
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Params.w0 = w0; Params.l0 = l0;
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end
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