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Functional analysis

Normed, Banach and Hilbert spaces, bounded operators, the Hahn–Banach, open mapping, closed graph and uniform boundedness theorems, weak topologies, and the spectral theorem for compact self-adjoint operators.

math.analysis.functional-analysis

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عدد المتطلبات السابقة الإلزامية (حتى الأساس): 42

ستتعلّم

  • Prove the Riesz representation theorem for Hilbert spaces and work with orthonormal bases.
  • State and apply the Hahn–Banach, open mapping and uniform boundedness theorems.
  • Prove the spectral theorem for compact self-adjoint operators.

تعريف

  • A Banach space is a complete normed vector space; a Hilbert space is a complete inner product space.
  • A linear operator T between normed spaces is bounded if ‖Tx‖ ≤ C‖x‖ for some constant C and all x.
  • A bounded operator is compact if it maps bounded sets to sets with compact closure.

مبرهنة

  • Riesz: every bounded linear functional on a Hilbert space H has the form x ↦ ⟨x, y⟩ for a unique y ∈ H.
  • Uniform boundedness principle.
  • Spectral theorem: a compact self-adjoint operator on a Hilbert space has an orthonormal basis of eigenvectors for the closure of its range, and its non-zero eigenvalues can only accumulate at 0.
  • The closed unit ball of an infinite-dimensional normed space is not compact in the norm topology.

مفاهيم خاطئة شائعة

  • Assuming every linear map between normed spaces is continuous.
  • Thinking all norms on an infinite-dimensional vector space are equivalent.

يقود إلى

اكتشافات اختيارية

مسارات التعلّم

قراءات إضافية

  • Haim Brezis, Functional Analysis, Sobolev Spaces and Partial Differential Equations (2011)
  • Michael Reed and Barry Simon, Methods of Modern Mathematical Physics I: Functional Analysis (1972)