Help me

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1

I wanted to know how I can impose homogeneous Neumann boundary conditions for Lagrangre multiplier, using the HDG method for the following problem:

           @U/@t = Laplace(U); in Omegax(0,T]
           U(x,y,0) = U_0;   in Omega
             U.n = 0 ;   on @Omega
2

For homogeneous neumann bc you don’t have to do anything, for time dependent problems have a look at the iTutorials:
https://ngsolve.org/docu/latest/i-tutorials/index.html#time-dependent-and-non-linear-problems

And maybe you could give your topic a descriptive title

Best
Christopher