ThmDex – An index of mathematical definitions, results, and conjectures.
Result R5304 on D1719: Expectation
Complex-linearity of real expectation
Formulation 0
Let $P = (\Omega, \mathcal{F}, \mathbb{P})$ be a D1159: Probability space such that
(i) $X, Y : \Omega \to \mathbb{R}$ are each a D3161: Random real number on $P$
(ii) \begin{equation} \mathbb{E} |X|, \mathbb{E} |Y| < \infty \end{equation}
(iii) $\alpha, \beta \in \mathbb{C}$ are each a D1207: Complex number
Then \begin{equation} \mathbb{E}(\alpha X + \beta Y) = \alpha \mathbb{E} X + \beta \mathbb{E} Y \end{equation}
Formulation 1
Let $X, Y \in \text{Random}(\Omega \to \mathbb{R})$ each be a D3161: Random real number such that
(i) \begin{equation} \mathbb{E} |X|, \mathbb{E} |Y| < \infty \end{equation}
Let $\alpha, \beta \in \mathbb{C}$ each be a D1207: Complex number.
Then \begin{equation} \mathbb{E}(\alpha X + \beta Y) = \alpha \mathbb{E} X + \beta \mathbb{E} Y \end{equation}
Proofs
Proof 0
Let $P = (\Omega, \mathcal{F}, \mathbb{P})$ be a D1159: Probability space such that
(i) $X, Y : \Omega \to \mathbb{R}$ are each a D3161: Random real number on $P$
(ii) \begin{equation} \mathbb{E} |X|, \mathbb{E} |Y| < \infty \end{equation}
(iii) $\alpha, \beta \in \mathbb{C}$ are each a D1207: Complex number
This result is a particular case of R1817: Complex-linearity of complex expectation. $\square$