Spectral Properties of Elliptic Operators
Yu. V. Egorov, Vladimir Kondratiev · Birkhäuser Basel eBooks · 1996
Let Ω be a bounded domain in $$D\left[ \phi \right] = \int_\Omega {\sum\limits_{j = 1}^n {\left( {\frac{{\partial \phi }} {{\partial x_j }}} \right)} } ^2 dx,H\left[ \phi \right] = \int_\Omega {\phi \left( x \right)} ^2 dx$$ for real-valued functions φ from H1(Ω).