computing killing vectors
The following system of 15 first order PDEs eq1=0,..,eqF=0 computes all Killing vectors of a certain 5-dimensional space. It is a system for the 5 functions X1,..,X5 of the 5 variables f, chi, phi, v, u. It is slightly complicated through the fact that also a constant `a' is to be determined such that solutions exist. eq1 := X1 - df(X1,f)*f; eq2 := df(X2,f) - u*df(X4,f) + v*df(X5,f) + df(X1,chi); eq3 := 4*df(X3,f)*f**2 + df(X1,phi); eq4 := u*df(X2,f) - df(X4,f)*u**2 + 2*df(X4,f)*exp(-2*a*phi)*f + u*v*df(X5,f) - df(X1,v); eq5 := v*df(X2,f) - u*v*df(X4,f) + df(X5,f)*v**2 - 2*df(X5,f)*exp(2*a*phi)*f + df(X1,u); eq6 := f*df(X2,chi) - f*u*df(X4,chi) + f*v*df(X5,chi) - X1; eq7 := 4*df(X3,chi)*f**2 + df(X2,phi) - u*df(X4,phi) + v*df(X5,phi); eq8 := f*u*df(X2,chi) - f*df(X4,chi)*u**2 + 2*f**2*df(X4,chi)*exp(-2*a*phi) + f*u*v*df(X5,chi) - 2*X1*u + X5*f - f*df(X2,v) + f*u*df(X4,v) - f*v*df(X5,v); eq9 := f*v*df(X2,chi) - f*u*v*df(X4,chi) + f*df(X5,chi)*v**2 - 2*f**2*df(X5,chi)*exp(2*a*phi) - 2*X1*v + X4*f + f*df(X2,u) - f*u*df(X4,u) + f*v*df(X5,u); eqA := df(X3,phi); eqB := u*df(X2,phi) - df(X4,phi)*u**2 + 2*df(X4,phi)*exp(-2*a*phi)*f + u*v*df(X5,phi) - 4*df(X3,v)*f**2; eqC := v*df(X2,phi) - u*v*df(X4,phi) + df(X5,phi)*v**2 - 2*df(X5,phi)*exp(2*a*phi)*f + 4*df(X3,u)*f**2; eqD := -f*u*df(X2,v) + f*df(X4,v)*u**2 - 2*f**2*df(X4,v)*exp(-2*a*phi) + f*u*X5 - f*u*v*df(X5,v) + X1*f*exp(-2*a*phi) - X1*u**2 + 2*X3*exp(-2*a*phi)*a*f^2; eqE := f*v*df(X2,v) - f*u*X4 - f*u*v*df(X4,v) + f*df(X5,v)*v**2 - f*v*X5 - 2*f**2*exp(2*a*phi)*df(X5,v) + 2*X1*u*v - f*u*df(X2,u) + f*df(X4,u)*u**2 - 2*f**2*exp(-2*a*phi)*df(X4,u) - f*u*v*df(X5,u); eqF := -f*v*df(X2,u) - f*v*X4 + f*u*v*df(X4,u) - f*df(X5,u)*v**2 + 2*f**2*df(X5,u)*exp(2*a*phi) - X1*exp(2*a*phi)*f + X1*v**2 + 2*X3*a*f**2*exp(2*a*phi); The system is solved by CRACK on a 3GHz AMD64 PC under Linux in less than 5 sec but the user who posted that problem to me claims that he tried different software for computing differential Groebner Bases which gave different number of solutions which would make it interesting to run this system for comparison with rif and diffalg.Thanks to Thomas Wolf (twolf@brocku.ca).