<p>This paper presents a synthesis of the theories of portfolio-generating functions and option pricing. The theory of portfolio generation is extended to measure the value of portfolios generated by strictly positive <InlineEquation ID="IEq1"> <EquationSource Format="MATHML"><math> <msup> <mi>C</mi> <mrow> <mn>2</mn> <mo>,</mo> <mn>1</mn> </mrow> </msup> </math></EquationSource> <EquationSource Format="TEX">$C^{2,1}$</EquationSource> </InlineEquation>-functions of asset prices and time directly, rather than with respect to a numéraire portfolio. If a portfolio-generating function satisfies a specific partial differential equation, then the value of the portfolio generated by that function replicates the value of the function. This differential equation is a general form of the Black–Scholes equation. Similar results apply to contingent claim functions, which are portfolio-generating functions that are homogeneous of degree&#xa0;1. With the addition of a riskless asset, an inhomogeneous portfolio-generating function <InlineEquation ID="IEq2"> <EquationSource Format="MATHML"><math> <mi>V</mi> <mo>:</mo> <msubsup> <mi mathvariant="double-struck">R</mi> <mrow> <mo>+</mo> <mo>+</mo> </mrow> <mi>n</mi> </msubsup> <mo>×</mo> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mi>T</mi> <mo stretchy="false">]</mo> <mo stretchy="false">→</mo> <msub> <mi mathvariant="double-struck">R</mi> <mrow> <mo>+</mo> <mo>+</mo> </mrow> </msub> </math></EquationSource> <EquationSource Format="TEX">${V}\colon {\mathbb{R}}_{++}^{n}\times [0,T]\to {\mathbb{R}}_{++}$</EquationSource> </InlineEquation> can be extended to an equivalent contingent claim function <InlineEquation ID="IEq3"> <EquationSource Format="MATHML"><math> <mover accent="true"> <mi>V</mi> <mo>ˆ</mo> </mover> <mo>:</mo> <msub> <mi mathvariant="double-struck">R</mi> <mrow> <mo>+</mo> <mo>+</mo> </mrow> </msub> <mo>×</mo> <msubsup> <mi mathvariant="double-struck">R</mi> <mrow> <mo>+</mo> <mo>+</mo> </mrow> <mi>n</mi> </msubsup> <mo>×</mo> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mi>T</mi> <mo stretchy="false">]</mo> <mo stretchy="false">→</mo> <msub> <mi mathvariant="double-struck">R</mi> <mrow> <mo>+</mo> <mo>+</mo> </mrow> </msub> </math></EquationSource> <EquationSource Format="TEX">${{\widehat{V}}}\colon {\mathbb{R}}_{++}\times {\mathbb{R}}_{++}^{n} \times [0,T]\to {\mathbb{R}}_{++}$</EquationSource> </InlineEquation> that generates the same portfolio and is replicable if and only if <InlineEquation ID="IEq4"> <EquationSource Format="MATHML"><math> <mi>V</mi> </math></EquationSource> <EquationSource Format="TEX">${V}$</EquationSource> </InlineEquation> is replicable. Several examples are presented.</p>

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Portfolios generated by contingent claim functions, with applications to option pricing

  • Ricardo T. Fernholz,
  • Robert Fernholz

摘要

This paper presents a synthesis of the theories of portfolio-generating functions and option pricing. The theory of portfolio generation is extended to measure the value of portfolios generated by strictly positive C 2 , 1 $C^{2,1}$ -functions of asset prices and time directly, rather than with respect to a numéraire portfolio. If a portfolio-generating function satisfies a specific partial differential equation, then the value of the portfolio generated by that function replicates the value of the function. This differential equation is a general form of the Black–Scholes equation. Similar results apply to contingent claim functions, which are portfolio-generating functions that are homogeneous of degree 1. With the addition of a riskless asset, an inhomogeneous portfolio-generating function V : R + + n × [ 0 , T ] R + + ${V}\colon {\mathbb{R}}_{++}^{n}\times [0,T]\to {\mathbb{R}}_{++}$ can be extended to an equivalent contingent claim function V ˆ : R + + × R + + n × [ 0 , T ] R + + ${{\widehat{V}}}\colon {\mathbb{R}}_{++}\times {\mathbb{R}}_{++}^{n} \times [0,T]\to {\mathbb{R}}_{++}$ that generates the same portfolio and is replicable if and only if V ${V}$ is replicable. Several examples are presented.