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On the Boundary Behaviour,Including Second Order Effects,of Solutions to Singular Elliptic Problems
Authors:S. Berhanu  F. Cuccu  G. Porru
Affiliation:(1) Department of Mathematics, Temple University, Philadelphia, PA 19122, USA;(2) Dipartimento di Matematica e Informatica, University of Cagliari, via Ospedale 72, 09124 Cagliari, Italy
Abstract:For γ ≥ 1 we consider the solution u = u(x) of the Dirichlet boundary value problem Δu + u γ = 0 in Ω, u = 0 on ∂Ω. For γ = 1 we find the estimate
$$
u{left( x right)} = p{left( {delta {left( x right)}} right)}{left[ {1 + A{left( x right)}{left( {log frac{1}
{{delta {left( x right)}}}} right)}^{{ -  in }} } right]},
$$
where $$
p{left( r right)} approx r{sqrt {2log {left( {1 mathord{left/
 {vphantom {1 r}} right.
 kern-nulldelimiterspace} r} right)}} }
$$ near r = 0, δ(x) denotes the distance from x to ∂Ω, 0 < < 1/2, and A(x) is a bounded function. For 1 < γ < 3 we find
$$
u{left( x right)} = {left( {frac{{gamma  + 1}}
{{{sqrt {2{left( {gamma  - 1} right)}} }}}delta {left( x right)}} right)}^{{frac{2}
{{gamma  + 1}}}} {left[ {1 + A{left( x right)}{left( {delta {left( x right)}} right)}^{{2frac{{gamma  - 1}}
{{gamma  + 1}}}} } right]}.
$$
For γ = 3 we prove that
$$
u{left( x right)} = {left( {2delta {left( x right)}} right)}^{{frac{1}
{2}}} {left[ {1 + A{left( x right)}delta {left( x right)}log frac{1}
{{delta {left( x right)}}}} right]}.
$$
Partially supported by FIRB 2001 and PRIN 2003
Keywords:elliptic problems   singular equations   boundary behaviour
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