The paper by Jean-Pierre Demailly discusses the computation of effective bounds for the degree of embeddings of algebraic varieties in projective space, focusing on the problem of determining explicit integers \( m_0 \) such that \( mL \) is very ample for \( m \geq m_0 \) when \( L \) is a positive or ample line bundle on a projective manifold \( X \). The author highlights the importance of adjoint line bundles \( 2(K_X + mL) \) and presents a combination of powerful analytic methods to derive such bounds, including the theory of positive currents and plurisubharmonic functions, \( L^2 \) estimates for \( \overline{\partial} \), the Nadel vanishing theorem, the Aubin-Calabi-Yau theorem, and holomorphic Morse inequalities.
The paper also covers fundamental concepts in hermitian differential geometry, such as connections, curvature tensors, and singular hermitian metrics. It introduces the notions of positivity and ampleness for holomorphic vector bundles, and provides examples and definitions related to these concepts. The Bochner technique and vanishing theorems are discussed, along with Hörmander's \( L^2 \) estimates and their applications in existence theorems. The concept of multiplier ideal sheaves is introduced, and the Nadel vanishing theorem is presented, which generalizes the Kawamata-Viehweg vanishing theorem.
The paper concludes with numerical criteria for very ample line bundles, including a recent technique due to Siu that uses Nadel's vanishing theorem and the Riemann-Roch formula. It also presents strong Morse inequalities and their algebraic versions, leading to effective versions of the big Matsusaka theorem and other results on the very ampleness of line bundles.The paper by Jean-Pierre Demailly discusses the computation of effective bounds for the degree of embeddings of algebraic varieties in projective space, focusing on the problem of determining explicit integers \( m_0 \) such that \( mL \) is very ample for \( m \geq m_0 \) when \( L \) is a positive or ample line bundle on a projective manifold \( X \). The author highlights the importance of adjoint line bundles \( 2(K_X + mL) \) and presents a combination of powerful analytic methods to derive such bounds, including the theory of positive currents and plurisubharmonic functions, \( L^2 \) estimates for \( \overline{\partial} \), the Nadel vanishing theorem, the Aubin-Calabi-Yau theorem, and holomorphic Morse inequalities.
The paper also covers fundamental concepts in hermitian differential geometry, such as connections, curvature tensors, and singular hermitian metrics. It introduces the notions of positivity and ampleness for holomorphic vector bundles, and provides examples and definitions related to these concepts. The Bochner technique and vanishing theorems are discussed, along with Hörmander's \( L^2 \) estimates and their applications in existence theorems. The concept of multiplier ideal sheaves is introduced, and the Nadel vanishing theorem is presented, which generalizes the Kawamata-Viehweg vanishing theorem.
The paper concludes with numerical criteria for very ample line bundles, including a recent technique due to Siu that uses Nadel's vanishing theorem and the Riemann-Roch formula. It also presents strong Morse inequalities and their algebraic versions, leading to effective versions of the big Matsusaka theorem and other results on the very ampleness of line bundles.