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EDIT:
Let f:X->f(X)  be a polynomial function from C^n to C^p. Let r(X) be the rank of the Jacobian matrix of f in X. What is the maximal value of r(X) when X goes throught C^n ?

In other words, I'd want to obtain the maximal dimension of the components of im(f). 

How to proceed ?

Thanks in advance.

I try to sort a polynomial using the graded reverse lexicograpic order. According to the Documentation this is achieved via tdeg.
So here is what i tried:

 

with(Groebner):
sort( x+y+z, order = tdeg(x,y,z));

or

sort(x+y+z, [x,y,z], tdeg);

In both cases maple returns "x+y+z" instead of the expected "z+y+x". What am i doing wrong?

 

 

computer a Gröbner basis for <f_[1] = x^2*y - 2*y*z + 1, f_[2] = x*y^2-z^2+ 2*x,  f_[3] = y^2*z - x^2+ 5 > belong to Q[x,y,z], using ≺= <_grlex with x≺y≺z. compare your output to the Gröbner basis the Maple computers with a different order.

how to basis this...

January 17 2014 rit 200

with(Groebner):
with(LinearAlgebra):
T := lexdeg([x1,x2,x3],[e1,e2,e3]);
GB := Basis([e1+.999987406876435, e2-.999919848203811],T):

Error, (in LinearAlgebra:-Basis) invalid input: LinearAlgebra:-Basis expects its 1st argument, V, to be of type {Vector, {set(Vector), list(Vector)}} but received [e1+HFloat(0.9999874068764352), e2-HFloat(0.9999198482038109)]


with(Groebner):
with(LinearAlgebra):
T := lexdeg([x1,x2,x3,x4,x5,x6,x7,x8],[e1,e2]);
GB := Basis([e1-x4*x2^3*x5/(x3*x1^4*x6), e2-x1*x8/(x3*x7)],T):

Error, (in LinearAlgebra:-Basis) invalid input: LinearAlgebra:-Basis expects its 1st argument, V, to be of type {Vector, {set(Vector), list(Vector)}} but received [e1-x4*x2^3*x5/(x3*x1^4*x6), e2-x1*x8/(x3*x7)]

with(Groebner):
with(LinearAlgebra):
T := lexdeg([x1,x2,x3],[e1,e2,e3]);
hello1 := proc(xx,yy)
return MatrixMatrixMultiply(xx,yy);
end proc:
hello2 := proc(xx,yy)
return xx+yy- MatrixMatrixMultiply(xx,yy);
end proc:
m1 := Matrix(3, 3, {(1, 1) = -.737663975994461+0.*I, (1, 2) = -.588973463383001+0.*I, (1, 3) = .330094104689369+0.*I, (2, 1) = -.588012653178741+0.*I, (2, 2) = .320157823261769+0.*I, (2, 3) = -.742792089286083+0.*I, (3, 1) = -.331802619371428+0.*I, (3, 2) = .742030476217061+0.*I, (3, 3) = .582492741708719+0.*I});
m2 := Matrix(3, 3, {(1, 1) = -.742269137704830+0.*I, (1, 2) = -.590598631673326+0.*I, (1, 3) = .316590877121441+0.*I, (2, 1) = -.593533033362923+0.*I, (2, 2) = .360143915024171+0.*I, (2, 3) = -.719732518911068+0.*I, (3, 1) = -.311054762892221+0.*I, (3, 2) = .722142379823161+0.*I, (3, 3) = .617863510611693+0.*I});
m3 := Matrix(3, 3, {(1, 1) = -.751491355856820+0.*I, (1, 2) = -.574908634018322+0.*I, (1, 3) = .323636840615627+0.*I, (2, 1) = -.575794245520782+0.*I, (2, 2) = .332066412772496+0.*I, (2, 3) = -.747123071744916+0.*I, (3, 1) = -.322058579916187+0.*I, (3, 2) = .747804760642505+0.*I, (3, 3) = .580574121936877+0.*I});
AA := hello1(m1, m2);
BB := hello2(m1, m2);
GB := Basis([e1- AA,e2- BB],T):
NormalForm(m3, GB, T);

Two questions:

The algortihms that Groebner[Basis] uses at each step computes some "tentative" or "pseudo-basis". The "tentative" basis is not a Groebner basis but it is in the ideal generated by the original system of polynomial eq.

1) Is this correct ? Provided this is correct, then

2) How can one retrive the last "tentative" basis?
 If I just use timelimit I can abort the computations but how can one retrive the last computation?

 

I have been struggling (reading Ore/Weyl Algebra documentation) to understand how to input a PDE system with polynomial coeff. in Weyl algebra notation so I can compute a Groebner basis for it. I would be very grateful if someone could  show, using the simple example below, which differential operators in Ore_algebra[diff_algebra] should one declare to express the system in Weyl algebra notation. The systems I'm working are more complicated but all have many dependent variables, f and g functions in this example:

pdesys:= [ x*diff( f(x,y,z),x)- z*diff( g(x,y,z),y) = 0, (x^2-y)*diff( f(x,y,z),z)- y*diff( g(x,y,z),z) = 0 ]

DoExist := proc(tau, n)

if rtable_num_elems(tau) >= n then

        return tau[n];

else

        return 0;

end if;

end proc;

 

g1 := [0, y, x];

g2 := [0, y^2-x-y, 0];

g3 := [x, x+y, 0];

g4 := [y, -y, 0];

g5 := [0, x*y+x/2+y/2, 0];

g6 := [0, x^2-x/4-y/4, 0];

 

m1 := Basis(g1, tdeg...

http://www.maplesoft.com/support/help/view.aspx?sid=2953

g1 := Vector([1, 1]);g2 := Vector([x+y, 0]);g3 := Vector([y^2+1, 0]);g4 := Vector([0, y^3+y]);g5 := Vector([0, x-y]);

i pass and tdeg(x, y, h251, h252, h253, h254, h255) to Basis

failed in Maple 15

http://www.mapleprimes.com/questions/144384-Polynomials-Not-In-The-Correct-Indeterminates

above link's comment said eliminate will NOT generate a polynomial in all cases

make me think that eliminate in above link can not return correct one.

what is the correct way to convert groebner basis of kernel into kernel?

the goal is to check kernel belong to image in Maple

restart;
with(Groebner):
K := {r-x^4,u-(x^3)*y,v-x*y^3,w-y^4};
G := Basis(K, 'tord', degrevlex(r,u,v,w));
R1 := eliminate(G, {r,u,v,w}); # eliminate is the reverse of Basis
Ga := Basis({a*G[1],a*G[2],a*G[3],a*G[4],a*G[5],a*G[6],a*G[7],a*G[8],a*G[9],a*G[10],a*G[11],a*G[12],a*G[13],a*G[14], (1-a)*K[1], (1-a)*K[2], (1-a)*K[3], (1-a)*K[4]}, 'tord', deglex(a,r,u,v,w));
Ga := remove(has, Ga, [x,y,a]);

below code is calculate basis of kernel and kernel

i guess basis of image is 

remove(has, Ga, [r,u,v,w]); if this correct, i eliminate this, i can get the image
however it include variable 'a'
is it correct? if not, how to calculate? 
my final goal is to make unexact sequence into exact sequence
restart;
with(Groebner):
g1 := x^2-w*y;
g2 := x*y-w*z;
g3 := y^2-x*z;
S13 := -y^3*w+x^3*z;
eq1:= S13 = h131*g1 + h132*g2 + h133*g3;

hsol := solve(identity(eq1, x), [h131, h132, h133]);
match(eq1,{x,y,z,w},'s');
s;
 
h131 should be x*z
h312 should be 0
h133 should be -y*w
 

3*rho1 - 2*rho2 + rho3 - rho4 = -1

4*rho1 +   rho2 - rho3        = 5

original without cost function:

with(Groebner):
K := {y1-(x1^3)*(x2^4),y2-(x2^(1+2))*(w^2),y3-(x1^(1+1))*(w^1),y4-(x2^1)*w,(y1^1000)*(y2^1)*(y3^1)*(y4^100)- x1*x2*w + 1};
G := Basis(K, plex(x1, x2, w, y1, y2, y3, y4));
Reduce((x2^(5+1))*(w^1), G, plex(x1, x2, w, y1, y2, y3, y4));

after have cost function 1000*rho1 + rho2...

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