Time consistency of dynamic risk measures in markets with transaction costs

Set-valued dynamic risk measures are defined on <inline-formula id="ILM0001"> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="rquf_a_781668_o_ilm0001.gif"/> </inline-formula> with <inline-formula id="ILM0002"> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="rquf_a_781668_o_ilm0002.gif"/> </inline-formula> and with an image space in the power set of <inline-formula id="ILM0003"> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="rquf_a_781668_o_ilm0003.gif"/> </inline-formula>. Primal and dual representations of dynamic risk measures are deduced. Definitions of different time consistency properties in the set-valued framework are given. It is shown that the recursive form for multivariate risk measures as well as an additive property for the acceptance sets is equivalent to a stronger time consistency property called multi-portfolio time consistency.