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i did try but i don't know the result is not come out? also i am not sure to put equation in eq1 in pde or linear part?

restart

with(PDEtools)

with(LinearAlgebra)

NULL

with(SolveTools)

undeclare(prime)

`There is no more prime differentiation variable; all derivatives will be displayed as indexed functions`

(1)

declare(u(x, y, t))

u(x, y, t)*`will now be displayed as`*u

(2)

declare(f(x, y, t))

f(x, y, t)*`will now be displayed as`*f

(3)

pde := diff(u(x, y, t), t, y)+diff(u(x, y, t), `$`(x, 3), y)-3*(diff(u(x, y, t), x))*(diff(u(x, y, t), x, y))-3*(diff(u(x, y, t), `$`(x, 2)))*(diff(u(x, y, t), y))+alpha*(diff(u(x, y, t), x, y))+beta*(diff(u(x, y, t), `$`(x, 2)))

diff(diff(u(x, y, t), t), y)+diff(diff(diff(diff(u(x, y, t), x), x), x), y)-3*(diff(u(x, y, t), x))*(diff(diff(u(x, y, t), x), y))-3*(diff(diff(u(x, y, t), x), x))*(diff(u(x, y, t), y))+alpha*(diff(diff(u(x, y, t), x), y))+beta*(diff(diff(u(x, y, t), x), x))

(4)

pde_nonlinear, pde_linear := selectremove(proc (term) options operator, arrow; has((eval(term, u(x, y, t) = a*u(x, y, t)))/a, a) end proc, pde)

-3*(diff(u(x, y, t), x))*(diff(diff(u(x, y, t), x), y))-3*(diff(diff(u(x, y, t), x), x))*(diff(u(x, y, t), y)), diff(diff(u(x, y, t), t), y)+diff(diff(diff(diff(u(x, y, t), x), x), x), y)+alpha*(diff(diff(u(x, y, t), x), y))+beta*(diff(diff(u(x, y, t), x), x))

(5)

eq := u(x, y, t) = -2*(diff(ln(f(x, y, t)), x))

u(x, y, t) = -2*(diff(f(x, y, t), x))/f(x, y, t)

(6)

eq1 := -(1/2)*numer(normal(eval(pde_linear, eq)))

f(x, y, t)^4*(diff(diff(diff(f(x, y, t), x), x), x))*beta+f(x, y, t)^4*(diff(diff(diff(f(x, y, t), x), x), y))*alpha-f(x, y, t)^3*(diff(f(x, y, t), y))*(diff(diff(f(x, y, t), x), x))*alpha-2*f(x, y, t)^3*(diff(diff(f(x, y, t), x), y))*(diff(f(x, y, t), x))*alpha-3*f(x, y, t)^3*(diff(f(x, y, t), x))*(diff(diff(f(x, y, t), x), x))*beta+2*f(x, y, t)^2*(diff(f(x, y, t), y))*(diff(f(x, y, t), x))^2*alpha+2*f(x, y, t)^2*(diff(f(x, y, t), x))^3*beta+(diff(diff(diff(f(x, y, t), t), x), y))*f(x, y, t)^4+(diff(diff(diff(diff(diff(f(x, y, t), x), x), x), x), y))*f(x, y, t)^4-(diff(diff(f(x, y, t), t), x))*(diff(f(x, y, t), y))*f(x, y, t)^3-(diff(diff(diff(diff(f(x, y, t), x), x), x), x))*(diff(f(x, y, t), y))*f(x, y, t)^3-(diff(diff(f(x, y, t), x), y))*(diff(f(x, y, t), t))*f(x, y, t)^3-4*(diff(diff(diff(f(x, y, t), x), x), x))*(diff(diff(f(x, y, t), x), y))*f(x, y, t)^3-(diff(f(x, y, t), x))*(diff(diff(f(x, y, t), t), y))*f(x, y, t)^3-4*(diff(diff(diff(diff(f(x, y, t), x), x), x), y))*(diff(f(x, y, t), x))*f(x, y, t)^3-6*(diff(diff(f(x, y, t), x), x))*(diff(diff(diff(f(x, y, t), x), x), y))*f(x, y, t)^3+2*(diff(f(x, y, t), x))*(diff(f(x, y, t), t))*(diff(f(x, y, t), y))*f(x, y, t)^2+8*(diff(diff(diff(f(x, y, t), x), x), x))*(diff(f(x, y, t), x))*(diff(f(x, y, t), y))*f(x, y, t)^2+6*(diff(diff(f(x, y, t), x), x))^2*(diff(f(x, y, t), y))*f(x, y, t)^2+24*(diff(diff(f(x, y, t), x), x))*(diff(f(x, y, t), x))*(diff(diff(f(x, y, t), x), y))*f(x, y, t)^2+12*(diff(diff(diff(f(x, y, t), x), x), y))*(diff(f(x, y, t), x))^2*f(x, y, t)^2-36*(diff(diff(f(x, y, t), x), x))*(diff(f(x, y, t), x))^2*(diff(f(x, y, t), y))*f(x, y, t)-24*(diff(f(x, y, t), x))^3*(diff(diff(f(x, y, t), x), y))*f(x, y, t)+24*(diff(f(x, y, t), x))^4*(diff(f(x, y, t), y))

(7)

NULL

T := f(x, y, t) = h*a[10]+m^2+n^2+a[9]

T1 := m = t*a[3]+x*a[1]+y*a[2]+a[4]

T2 := n = t*a[7]+x*a[5]+y*a[6]+a[8]

T3 := h = a[10]*exp(t*p[3]+x*p[1]+y*p[2])

L2 := expand(subs({T1, T2, T3}, T))

f(x, y, t) = a[10]^2*exp(p[3]*t)*exp(p[1]*x)*exp(p[2]*y)+t^2*a[3]^2+2*t*x*a[1]*a[3]+2*t*y*a[2]*a[3]+x^2*a[1]^2+2*x*y*a[1]*a[2]+y^2*a[2]^2+2*t*a[3]*a[4]+2*x*a[1]*a[4]+2*y*a[2]*a[4]+a[4]^2+t^2*a[7]^2+2*t*x*a[5]*a[7]+2*t*y*a[6]*a[7]+x^2*a[5]^2+2*x*y*a[5]*a[6]+y^2*a[6]^2+2*t*a[7]*a[8]+2*x*a[5]*a[8]+2*y*a[6]*a[8]+a[8]^2+a[9]

(8)

eq9a := eval(eq1, L2)

indets(%)

{alpha, beta, t, x, y, a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], p[1], p[2], p[3], exp(p[1]*x), exp(p[2]*y), exp(p[3]*t)}

(9)

p2b := subs({exp(p[1]*x) = eX, exp(p[2]*y) = eY, exp(p[3]*t) = eT}, eq9a); indets(%)

{alpha, beta, eT, eX, eY, t, x, y, a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], p[1], p[2], p[3]}

(10)

p2c := numer(normal(p2b))

eqns := {coeffs(collect(p2c, {eT, eX, eY}, distributed), {eT, eX, eY})}; nops(%)

5

(11)

solve(eqns, {a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], p[1], p[2], p[3]})

 

NULL

Download parameters.mw

If I understand right, in the following calling an exception should be raised since the return value of the matching coercion procedure is of course not of type “set”: 

restart;
foo := (x::coerce(set, (y::rtable) -> convert(y, list))) -> x:
foo(<0>);
 = 
                              [0]

Did I miss something?

So just like the title illustrates, I found a paper authored by Gary Nicklason in 2022: Autonomous Planar Systems of Riccati Type and in the last section it mentioned about a class of Abel ODE, which belongs to AIA(Abel Inverse Abel) class. It is of First kind and the inverse of it(by swapping variables) is of second kind.

While the first kind is solvable in terms of Airy function, the inverse of it along with its equivalence class is not solvable by the existing dsolve.

I have tested it in my worksheet Nicklason_equation.mw. So is it possible to add this class into the dictionary for solvable Abel ODE, or, maybe there are some bugs within the internal procedure of dsolve, which results in failure for catching the solvable candidates?

I have a system of polynomial equations where the unknowns are real numbers. The set of solutions is infinite (positive-dimensional). How can I compute the real dimension of the solution set (i.e. of a real algebraic variety)?

As it as mentioned in arXiv:2105.10255, this can be done using the RealTriangularize function from the RegularChains package. What is best way of getting the real dimension from the regular_semi_algebraic_system object, which is returned by this function?

Is there a good way to include subscript(s) to a letter within a 'text' command?  Currently I do this by specifying the coordinates, letter, and font for the letter, then specify the coordinates, number and font for the subscript.  However, with this method the letter and subscript can be compressed if the viewing interval is compressed or expanded.  

Is there another way to include letters with a subscript in a text command?

is(Im(x)*x = 0);
                              true

 

Surely, Im(i)*i != 0?

i try find some part of solution of this kind of pde but i can't get results my openion is maybe this pde is wronge when i defined 

pde.mw

 Why you delete my question  most of my equation are same but demand of the questions are different, i can make a 100 account and each time i asked by one of them, and right now most of my question taged like they dublicated but they are don't ، i am not jobles and sick to post a dublicate question, You started a riot.

 Can I solve the Tolman-Oppenheimer-Volkoff equation with Maple ?  I'm having trouble with Einstein's equation with the energy tensor as the second member

How apply long wave limit for removing the constant k in such function , i need a general formula 

Limiting process from eq 12 to Bij

restart

NULL

Eq 12.

eij := ((-3*k[i]*(k[i]-k[j])*l[j]+beta)*l[i]^2-(2*(-3*k[j]*(k[i]-k[j])*l[j]*(1/2)+beta))*l[j]*l[i]+beta*l[j]^2)/((-3*k[i]*(k[i]+k[j])*l[j]+beta)*l[i]^2-(2*(3*k[j]*(k[i]+k[j])*l[j]*(1/2)+beta))*l[j]*l[i]+beta*l[j]^2)

((-3*k[i]*(k[i]-k[j])*l[j]+beta)*l[i]^2-2*(-(3/2)*k[j]*(k[i]-k[j])*l[j]+beta)*l[j]*l[i]+beta*l[j]^2)/((-3*k[i]*(k[i]+k[j])*l[j]+beta)*l[i]^2-2*((3/2)*k[j]*(k[i]+k[j])*l[j]+beta)*l[j]*l[i]+beta*l[j]^2)

(1)

eval(eij, k[j] = k[i]); series(%, k[i], 3); convert(%, polynom); eval(%, k[j] = k[i]); Bij := %

(beta*l[i]^2-2*beta*l[i]*l[j]+beta*l[j]^2)/((-6*k[i]^2*l[j]+beta)*l[i]^2-2*(3*k[i]^2*l[j]+beta)*l[j]*l[i]+beta*l[j]^2)

 

series(1+((6*l[i]^2*l[j]+6*l[i]*l[j]^2)/(beta*l[i]^2-2*beta*l[i]*l[j]+beta*l[j]^2))*k[i]^2+O(k[i]^4),k[i],4)

 

1+(6*l[i]^2*l[j]+6*l[i]*l[j]^2)*k[i]^2/(beta*l[i]^2-2*beta*l[i]*l[j]+beta*l[j]^2)

 

1+(6*l[i]^2*l[j]+6*l[i]*l[j]^2)*k[i]^2/(beta*l[i]^2-2*beta*l[i]*l[j]+beta*l[j]^2)

 

1+(6*l[i]^2*l[j]+6*l[i]*l[j]^2)*k[i]^2/(beta*l[i]^2-2*beta*l[i]*l[j]+beta*l[j]^2)

(2)

NULL

NULL

Download b12.mw

I need to find parameter a[12] any one have any vision for finding parameter  , in p2a must contain 3 exponential but we recieve 19 of them which is something i think it is trail function but trail is give me result so must be a way for finding parameter 

a[12]-pde.mw

the function is true but i want to be sure when i use pdetest must give me zero, but there must be a way for checking such function, please if your pc not strong don't click the command pdetest, i want use explore for such function but i am not sure it work or not, becuase the graph are a little bit strange  and long , i want  a way for easy plotting and visualization of such graph , can anyone help for solve this issue?

 sol.mw

i don't know how apply conversation language to matlab in righ hand side  don't show up to do conversation language for short is come up but for this not 

restart

K := (2*(k[1]*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1])+((p[1]-p[2])^2*alpha-(k[1]-k[2])^2)*(k[1]+k[2])*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2])/((p[1]-p[2])^2*alpha-(k[1]+k[2])^2)+k[2]*exp((3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2])+((p[2]-p[3])^2*alpha-(k[2]-k[3])^2)*(k[2]+k[3])*exp((3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/((p[2]-p[3])^2*alpha-(k[2]+k[3])^2)+((p[1]-p[2])^2*alpha-(k[1]-k[2])^2)*((p[1]-p[3])^2*alpha-(k[1]-k[3])^2)*((p[2]-p[3])^2*alpha-(k[2]-k[3])^2)*(k[1]+k[2]+k[3])*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/(((p[1]-p[2])^2*alpha-(k[1]+k[2])^2)*((p[1]-p[3])^2*alpha-(k[1]+k[3])^2)*((p[2]-p[3])^2*alpha-(k[2]+k[3])^2))+((p[1]-p[3])^2*alpha-(k[1]-k[3])^2)*(k[1]+k[3])*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/((p[1]-p[3])^2*alpha-(k[1]+k[3])^2)+k[3]*exp((3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])))/(1+exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1])+((p[1]-p[2])^2*alpha-(k[1]-k[2])^2)*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2])/((p[1]-p[2])^2*alpha-(k[1]+k[2])^2)+exp((3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2])+((p[2]-p[3])^2*alpha-(k[2]-k[3])^2)*exp((3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/((p[2]-p[3])^2*alpha-(k[2]+k[3])^2)+((p[1]-p[2])^2*alpha-(k[1]-k[2])^2)*((p[1]-p[3])^2*alpha-(k[1]-k[3])^2)*((p[2]-p[3])^2*alpha-(k[2]-k[3])^2)*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/(((p[1]-p[2])^2*alpha-(k[1]+k[2])^2)*((p[1]-p[3])^2*alpha-(k[1]+k[3])^2)*((p[2]-p[3])^2*alpha-(k[2]+k[3])^2))+((p[1]-p[3])^2*alpha-(k[1]-k[3])^2)*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/((p[1]-p[3])^2*alpha-(k[1]+k[3])^2)+exp((3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3]))

2*(k[1]*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1])+((p[1]-p[2])^2*alpha-(k[1]-k[2])^2)*(k[1]+k[2])*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2])/((p[1]-p[2])^2*alpha-(k[1]+k[2])^2)+k[2]*exp((3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2])+((p[2]-p[3])^2*alpha-(k[2]-k[3])^2)*(k[2]+k[3])*exp((3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/((p[2]-p[3])^2*alpha-(k[2]+k[3])^2)+((p[1]-p[2])^2*alpha-(k[1]-k[2])^2)*((p[1]-p[3])^2*alpha-(k[1]-k[3])^2)*((p[2]-p[3])^2*alpha-(k[2]-k[3])^2)*(k[1]+k[2]+k[3])*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/(((p[1]-p[2])^2*alpha-(k[1]+k[2])^2)*((p[1]-p[3])^2*alpha-(k[1]+k[3])^2)*((p[2]-p[3])^2*alpha-(k[2]+k[3])^2))+((p[1]-p[3])^2*alpha-(k[1]-k[3])^2)*(k[1]+k[3])*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/((p[1]-p[3])^2*alpha-(k[1]+k[3])^2)+k[3]*exp((3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3]))/(1+exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1])+((p[1]-p[2])^2*alpha-(k[1]-k[2])^2)*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2])/((p[1]-p[2])^2*alpha-(k[1]+k[2])^2)+exp((3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2])+((p[2]-p[3])^2*alpha-(k[2]-k[3])^2)*exp((3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/((p[2]-p[3])^2*alpha-(k[2]+k[3])^2)+((p[1]-p[2])^2*alpha-(k[1]-k[2])^2)*((p[1]-p[3])^2*alpha-(k[1]-k[3])^2)*((p[2]-p[3])^2*alpha-(k[2]-k[3])^2)*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[2]*t*alpha*p[2]^2+(1/4)*t*k[2]^3+k[2]*p[2]*y+k[2]*x+k[2]*z+eta[2]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/(((p[1]-p[2])^2*alpha-(k[1]+k[2])^2)*((p[1]-p[3])^2*alpha-(k[1]+k[3])^2)*((p[2]-p[3])^2*alpha-(k[2]+k[3])^2))+((p[1]-p[3])^2*alpha-(k[1]-k[3])^2)*exp((3/4)*k[1]*t*alpha*p[1]^2+(1/4)*t*k[1]^3+k[1]*p[1]*y+k[1]*x+k[1]*z+eta[1]+(3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3])/((p[1]-p[3])^2*alpha-(k[1]+k[3])^2)+exp((3/4)*k[3]*t*alpha*p[3]^2+(1/4)*t*k[3]^3+k[3]*p[3]*y+k[3]*x+k[3]*z+eta[3]))

(1)
 

NULL

Download convert-to-matlab.mw

I have plotted a 3D figure by maple 2023. but all numbers and units on axes are seen a black boxes. How can fix this problem?

Dear Maple Community,

I come to you with a question about the reduced involutive form (rif) package. Namely, I decided to try the classic example from the "LONG GUIDE TO THE STANDARD FORM PACKAGE", which dates back to 1993. Here is the link to the complete documentation:

https://wayback.cecm.sfu.ca/~wittkopf/files/standard_manual.txt

So, the example is the following:

2.1 SIMPLE EXAMPLES

EXAMPLE A

Consider the system of nonlinear PDEs:       

y Zxxx - x Zxyy  =  Zyy - y Zy

                        2     2    2
2 y x Zxxx Zxyy + x Zxxx + x y Zxyy  =  0

                  2    2
y Zxyy - x W + 2 x  y Z  =  0

                 2    2
Zyy - y Zy  + 2 x  y W  =  x W

where the dependent variables W and Z are functions of the
independent variables x and y, and Zxxx denotes the third partial
derivative of Z with respect to x etc.

After making computations back in 1993 with Maple V, they obtain the following involutive form:

In our original notation the (considerably) simplified system is:
                                            2
  Zxxx = 0, Zxy = 0, Zyy = y Zy, W = 2 x y Z

So, I tried the same system of PDEs in the modern Maple and the modern rifsimp() command. You can find the result below:

demo_question.mw

The problem is that nowadays [Maple 2022.1] , I get only the trivial solution: z = 0 and w = 0.

Could someone clarify, please, where the truth is and what am I doing wrong?

Thanks a lot in advance for any help and clarification!

Best regards,

Dr. Denys D.
 

restart:

with(DETools):

PDE1 := y*diff(z(x,y), x$3) - x*diff(z(x,y),x,y$2) = diff(z(x,y),y$2) - y*diff(z(x,y), y);

y*(diff(diff(diff(z(x, y), x), x), x))-x*(diff(diff(diff(z(x, y), x), y), y)) = diff(diff(z(x, y), y), y)-y*(diff(z(x, y), y))

(1)

PDE2 := 2*x*y*diff(z(x,y),x$3)*diff(z(x,y),x,y$2) + x*(diff(z(x,y),x$3))^2 + x*y^2*(diff(z(x,y),x,y$2))^2 = 0;

2*x*y*(diff(diff(diff(z(x, y), x), x), x))*(diff(diff(diff(z(x, y), x), y), y))+x*(diff(diff(diff(z(x, y), x), x), x))^2+x*y^2*(diff(diff(diff(z(x, y), x), y), y))^2 = 0

(2)

PDE3 := y*diff(z(x,y),x,y$2) - x*w(x,y) + 2*x^2*y*z(x,y)^2 = 0;

y*(diff(diff(diff(z(x, y), x), y), y))-x*w(x, y)+2*x^2*y*z(x, y)^2 = 0

(3)

PDE4 := diff(z(x,y), y$2) - y*diff(z(x,y),y) + 2*x^2*y*w(x,y)^2 = x*w(x,y);

diff(diff(z(x, y), y), y)-y*(diff(z(x, y), y))+2*x^2*y*w(x, y)^2 = x*w(x, y)

(4)

sys := [PDE1, PDE2, PDE3, PDE4]:

rif := rifsimp(sys, [[w], [z]], indep = [x,y]);

table( [( Case ) = [[z(x, y)*(8*z(x, y)^2*y^2*x^2-1) = 0, diff(z(x, y), x), "false split"]], ( Solved ) = [w(x, y) = 0, z(x, y) = 0] ] )

(5)
 

 

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