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Diff — Cauchy's integral formula

Revision #1065 → #2931 · back to history

modifiedCauchy's integral formula507734b20770
FieldFrom #1065To #2931
anchors[{"section":"Theorem","snippet":"suppose the closed disk"},{"type":"math_alttext","value":"{\\displaystyle D={\\bigl \\{}z\\in \\mathbb {C} :|z-z_{0}|\\leq r{\\bigr \\}}}"},{"type":"math_alttext","value":"{\\displaystyle f(a)={\\frac {1}{2\\pi i}}\\oint _{\\gamma }{\\frac {f(z)}{z-a}}\\,dz.}"}]
noteGives ∮ (z-w)⁻¹•f z = 2πi•f w under continuity on the closed disc and differentiability on the interior, which is more general than the article's holomorphic-on-an-open-set hypothesis.Gives ∮ (z-w)⁻¹•f z = 2πi•f w under continuity on the closed disc and differentiability on the interior, more general than the article's holomorphic-on-open-set hypothesis.
modifiedAnalyticity of holomorphic functions810900af116e
FieldFrom #1065To #2931
anchors[{"section":"Theorem","snippet":"it follows that holomorphic functions are analytic"},{"type":"math_alttext","value":"{\\displaystyle {\\frac {1}{z-a}}={\\frac {1+{\\frac {a}{z}}+\\left({\\frac {a}{z}}\\right)^{2}+\\cdots }{z}},}"},{"type":"math_alttext","value":"{\\displaystyle f^{(n)}(a)={\\frac {n!}{2\\pi i}}\\oint _{\\gamma }{\\frac {f(z)}{\\left(z-a\\right)^{n+1}}}\\,dz.}"}]
labelCauchy's differentiation formula (analyticity)Analyticity of holomorphic functions
noteStates that a function differentiable on an open set in ℂ is analytic (admits a power series) on that set.A function differentiable on an open set in ℂ is analytic (admits a convergent power series expansion) on that set.
provenanceaiai-moderated
addedCauchy's differentiation formula (higher derivatives)e09a866bba07
modifiedNot every boundary function arisesd7c3253e75a7
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noteThis remark about boundary functions not all extending holomorphically has no corresponding statement in Mathlib.This informal remark about boundary functions not all extending holomorphically has no corresponding statement in Mathlib.
modifiedEvaluating a contour integralb19677ef9069
FieldFrom #1065To #2931
anchors[{"section":"Example","snippet":"the circle of radius 2"},{"type":"math_alttext","value":"{\\displaystyle g(z)={\\frac {z^{2}}{z^{2}+2z+2}},}"}]
modifiedHolomorphic implies infinitely differentiable8a254d2e5e5d
FieldFrom #1065To #2931
anchors[{"section":"Consequences","snippet":"a function that is holomorphic in an open set is in fact infinitely differentiable there"},{"type":"math_alttext","value":"{\\displaystyle f(\\zeta )={\\frac {1}{2\\pi i}}\\int _{C}{\\frac {f(z)}{z-\\zeta }}\\,dz.}"}]
noteShows a function differentiable on an open set in ℂ is ContDiffOn of any order n (including ∞), i.e. infinitely differentiable there.A function differentiable on an open set in ℂ is ContDiffOn of any order n (including ∞), i.e. infinitely differentiable there.
modifiedUniform limit of holomorphic functionse94447040f05
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noteEstablishes that a locally uniform limit of holomorphic functions on an open set is holomorphic, generalizing the uniform-limit statement.A locally uniform limit of holomorphic functions on an open set is holomorphic, generalizing the uniform-limit statement.
addedMorera's theorem8311531ea9ee
modifiedCauchy's estimate506af5d4459e
FieldFrom #1065To #2931
anchors[{"section":"Consequences","snippet":"satisfy Cauchy's estimate"},{"type":"math_alttext","value":"{\\displaystyle |a_{n}|\\leq r^{-n}\\sup _{|z|=r}|f(z)|.}"}]
modifiedLiouville's theoremd83c2c179a87
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noteProves a complex-differentiable function with bounded range is constant, stated for Banach-space-valued maps and hence more general than entire ℂ→ℂ functions.A complex-differentiable function with bounded range is constant, stated for Banach-space-valued maps and hence more general than entire ℂ→ℂ.
modifiedGauss's mean-value theoremac7c19d2a6a8
FieldFrom #1065To #2931
anchors[{"section":"Consequences","snippet":"derive Gauss's mean-value theorem"},{"type":"math_alttext","value":"{\\displaystyle f(z)={\\frac {1}{2\\pi }}\\int _{0}^{2\\pi }f(z+re^{i\\theta })\\,d\\theta .}"}]
noteStates that the circle average of a holomorphic function equals its value at the center, i.e. Gauss's mean-value property.The circle average of a holomorphic function equals its value at the center, i.e. Gauss's mean-value property.
modifiedCauchy–Pompeiu formula5f119651b900
FieldFrom #1065To #2931
anchors[{"section":"Smooth functions","snippet":"is a complex-valued C 1 function on the closure of"},{"type":"math_alttext","value":"{\\displaystyle f(\\zeta )={\\frac {1}{2\\pi i}}\\int _{\\partial D}{\\frac {f(z)\\,dz}{z-\\zeta }}-{\\frac {1}{\\pi }}\\iint _{D}{\\frac {\\partial f}{\\partial {\\bar {z}}}}(z){\\frac {dx\\wedge dy}{z-\\zeta }}.}"}]
modifiedSolution of inhomogeneous Cauchy–Riemann equationsb998b3fd832c
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anchors[{"section":"Smooth functions","snippet":"to solve the inhomogeneous Cauchy–Riemann equations in"},{"type":"math_alttext","value":"{\\displaystyle d\\mu ={\\frac {1}{2\\pi i}}\\varphi \\,dz\\wedge d{\\bar {z}}}"},{"type":"math_alttext","value":"{\\displaystyle {\\frac {\\partial f}{\\partial {\\bar {z}}}}=\\varphi (z,{\\bar {z}}).}"}]
modifiedCauchy kernel is a fundamental solution7a6cad57a75b
FieldFrom #1065To #2931
anchors[{"section":"Smooth functions","snippet":"the Cauchy kernel is a fundamental solution of the Cauchy–Riemann equations"},{"type":"math_alttext","value":"{\\displaystyle k(z)=\\operatorname {p.v.} {\\frac {1}{z}}}"},{"type":"math_alttext","value":"{\\displaystyle f(\\zeta )={\\frac {1}{2\\pi i}}\\iint {\\frac {\\partial f}{\\partial {\\bar {z}}}}{\\frac {dz\\wedge d{\\bar {z}}}{z-\\zeta }},}"}]
modifiedDistributional derivative of characteristic functionbaeba3e8ce74
FieldFrom #1065To #2931
anchors[{"section":"Smooth functions","snippet":"the formula for the distributional derivative of the characteristic function"},{"type":"math_alttext","value":"{\\displaystyle {\\frac {\\partial \\chi _{X}}{\\partial {\\bar {z}}}}={\\frac {i}{2}}\\oint _{\\partial X}\\,dz,}"}]
modifiedCauchy formula on polydiscs8ea27145fd3d
FieldFrom #1065To #2931
anchors[{"section":"Several variables","snippet":"the Cauchy integral formula can be generalized to polydiscs"},{"type":"math_alttext","value":"{\\displaystyle D=\\prod _{j=1}^{n}D_{j}.}"}]
modifiedGreen's function of the derivative operator2e3aabb26cd8
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anchors[{"section":"In real algebras","snippet":"This particular derivative operator has a Green's function"},{"type":"math_alttext","value":"{\\displaystyle G\\left(\\mathbf {r} ,\\mathbf {r} '\\right)={\\frac {1}{S_{n}}}{\\frac {\\mathbf {r} -\\mathbf {r} '}{\\left|\\mathbf {r} -\\mathbf {r} '\\right|^{n}}}}"},{"type":"math_alttext","value":"{\\displaystyle \\nabla G\\left(\\mathbf {r} ,\\mathbf {r} '\\right)=\\delta \\left(\\mathbf {r} -\\mathbf {r} '\\right).}"}]
modifiedMonogenic functionf994357f2ad5
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anchors[{"section":"In real algebras","snippet":"is called a monogenic function"},{"type":"math_alttext","value":"{\\displaystyle \\oint _{\\partial V'}G\\left(\\mathbf {r} ,\\mathbf {r} '\\right)\\;d\\mathbf {S} '\\;f\\left(\\mathbf {r} '\\right)=\\int _{V}\\left[\\nabla 'G\\left(\\mathbf {r} ,\\mathbf {r} '\\right)\\right]f\\left(\\mathbf {r} '\\right)=-\\int _{V}\\delta \\left(\\mathbf {r} -\\mathbf {r} '\\right)f\\left(\\mathbf {r} '\\right)\\;d\\mathbf {V} =-i_{n}f(\\mathbf {r} )}"},{"type":"math_alttext","value":"{\\displaystyle f(\\mathbf {r} )=-{\\frac {1}{i_{n}}}\\oint _{\\partial V}G\\left(\\mathbf {r} ,\\mathbf {r} '\\right)\\;d\\mathbf {S} \\;f\\left(\\mathbf {r} '\\right)=-{\\frac {1}{i_{n}}}\\oint _{\\partial V}{\\frac {\\mathbf {r} -\\mathbf {r} '}{S_{n}\\left|\\mathbf {r} -\\mathbf {r} '\\right|^{n}}}\\;d\\mathbf {S} \\;f\\left(\\mathbf {r} '\\right)}"}]