Degenerate Nonlinear Diffusion Equations by Angelo Favini, Gabriela Marinoschi

By Angelo Favini, Gabriela Marinoschi

The objective of those notes is to incorporate in a uniform presentation sort a number of issues regarding the speculation of degenerate nonlinear diffusion equations, taken care of within the mathematical framework of evolution equations with multivalued m-accretive operators in Hilbert areas. the issues quandary nonlinear parabolic equations concerning circumstances of degeneracy. extra accurately, one case is because of the vanishing of the time by-product coefficient and the opposite is equipped by means of the vanishing of the diffusion coefficient on subsets of confident degree of the domain.
From the mathematical viewpoint the implications offered in those notes may be regarded as basic leads to the idea of degenerate nonlinear diffusion equations. even though, this paintings doesn't search to offer an exhaustive learn of degenerate diffusion equations, yet fairly to stress a few rigorous and effective strategies for imminent a variety of difficulties related to degenerate nonlinear diffusion equations, akin to well-posedness, periodic suggestions, asymptotic behaviour, discretization schemes, coefficient identity, and to introduce correct fixing equipment for every of them.

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1 Well-Posedness for the Cauchy Problem with Fast Diffusion 33 Taking into account the choice of z(t, x) we have j(y)dxdt + Br (t0 ,x0 ) ≤ j(y)dxdt B r (t0 ,x0 ) j(w)dxdt + Br (t0 ,x0 ) j(y)dxdt B r (t0 ,x0 ) + Br (t0 ,x0 ) ζ(y − w)dxdt + B r (t0 ,x0 ) ζ(y − y)dxdt from where it remains Br (t0 ,x0 ) j(y)dxdt ≤ j(w)dxdt + Br (t0 ,x0 ) Br (t0 ,x0 ) ζ(y − w)dxdt. We recall the following definition. Let l be a Lebesgue measurable function on a set S and let z0 ∈ S. The point z0 is called a Lebesgue point for l if lim r→0 1 meas(Br (z0 )) Br (z0 ) l(x)dx = l(z0 ).

95). For simplicity, here we denoted tr(ψ) still by ψ. 69), ζ = lim βε∗ (yε ). e. on Qu . 99) where ∂(uy) is the derivative in the sense of distributions. 69). e. 69). The common boundary ∂Ω0 of the domains Ωu and Ω0 is regular. e. 1 Well-Posedness for the Cauchy Problem with Fast Diffusion 37 ζ(t) on any line L0 ⊂ Ω crossing the boundary ∂Ω0 belongs to V, so that it is continuous across L0 . e. t ∈ (0, T ). e. e. e. 102) in Qu . 27). e. on Q. 99)). 26). e. on Q. 100). Now, let f ∈ L2 (0, T ; V ) and θ0 ∈ L2 (Ω).

For simplicity we present a more formal ∂β ∗ (y ) computation. 40) by ε∂t ε and integrate over (0, t) × Ω. We get t Ω 0 uε βε (yε ) t = 0 Ω dyε dτ 2 dxdτ + a(x)K(yε ) · ∇ 1 2 t 0 d ∇βε∗ (yε (τ )) dτ dβε∗ (yε (τ )) dτ 2 dτ t dxdτ + f 0 Ω dβε∗ (yε ) dxdτ. 1 Well-Posedness for the Cauchy Problem with Fast Diffusion 23 After the integration with respect to τ in the second term on the left-hand side, we obtain t Ω 0 = Ω 1 ∗ β (yε (t)) 2 ε dxdτ + a(x)K(yε (t)) · ∇βε∗ (yε (t))dx − t − 2 dyε dτ uε βε (yε ) a(x) Ω 0 + Ω 2 V 1 ∗ β (yε (0)) 2 ε − 2 V a(x)K(yε (0)) · ∇βε∗ (yε (0))dx Ω ∂K(yε ) · ∇βε∗ (yε (τ ))dxdτ ∂τ f (t)βε∗ (yε (t))dx − Ω f (0)βε∗ (yε (0))dx − t ∂f ∗ β (yε )dxdτ.

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