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Question: why pdsolve fail when adding Physics:-Setup(assumingusesAssume = true)

Question:why pdsolve fail when adding Physics:-Setup(assumingusesAssume = true)

nm 11353 Maple 2025
assuming pde pdsolve differential-equations physics
May 18 2025
4

Same exact code. When adding Physics:-Setup(assumingusesAssume = true):  before, now pdsolve do not give solution.

Removing Physics:-Setup(assumingusesAssume = true): now it works.

Why? Should not solution be returned in both cases?

> 

interface(version);

`Standard Worksheet Interface, Maple 2025.0, Linux, March 24 2025 Build ID 1909157`

> 

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1872 and is the same as the version installed in this computer, created 2025, May 17, 22:58 hours Pacific Time.`

> 

SupportTools:-Version();

`The Customer Support Updates version in the MapleCloud is 17 and is the same as the version installed in this computer, created May 5, 2025, 12:37 hours Eastern Time.`

> 

restart;

Example 1. Adding Physics:-Setup(assumingusesAssume = true): makes pdsolve fail

 
> 

Physics:-Setup(assumingusesAssume = true):

> 

pde := diff(u(r, t), t) = k*diff(u(r, t), r$2):
ic  := u(r,0)=r*f(r):
bc  := u(0,t)=0,u(a,t)=a*phi(t):
sol:= pdsolve({pde, ic, bc}, u(r, t));

> 

 

> 

 

Example 2. Same code but removing Physics:-Setup(assumingusesAssume = true): makes it work

 
> 

restart;

> 

pde := diff(u(r, t), t) = k*diff(u(r, t), r$2):
ic  := u(r,0)=r*f(r):
bc  := u(0,t)=0,u(a,t)=a*phi(t):
sol:= pdsolve({pde, ic, bc}, u(r, t));

u(r, t) = Sum(2*sin(n*Pi*r/a)*exp(-k*Pi^2*n^2*t/a^2)*(Int(r*(-phi(0)+f(r))*sin(n*Pi*r/a), r = 0 .. a))/a, n = 1 .. infinity)+Int(Sum(2*sin(n*Pi*r/a)*exp(-k*Pi^2*n^2*(t-tau)/a^2)*(diff(phi(tau), tau))*a*(-1)^n/(n*Pi), n = 1 .. infinity), tau = 0 .. t)+r*phi(t)

> 

 


 

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