My question concerns Proposition 3.14 (series with positive terms) of Olav Kallenberg's 'Foundations of Modern Probability'. He states:
Let $\xi_1,\xi_2 ...$ be independent $\mathbb{R}_+$-valued random variables. Then $\sum_n\xi_n<\infty$ a.s. iff $\sum_n E[\xi_n \wedge 1]<\infty$
I am confused by the $\wedge$ symbol. Unfortunately, he does not define it in his book and I am not an expert in probability theory. So, does someone know how $E[\xi_n \wedge 1]$ is defined?
Questions concerning the statement of Proposition 3.14 were posed in
Criteria for a.s. convergence of series of independent positive random variables. and
Convergence of expected value series.
but they seem to contradict each other and do not solve my confusion.
Thank you very much for your help!