modals requiring past tense

[Peter Arkadiev]

Dear colleagues,

on behalf of my colleague Natasha Korotkova from UCLA I would like to ask you whether you know about cases when epistemic modal expressions (auxiliaries, affixes, particles etc.) require that the epistemically evaluated proposition be always located in the past?
I mean the following. In English, both (a) and (b) are possible:

(a) John must be dancing now.  (proposition in the present)
(b) John must have danced yesterday. (proposition in the past)

The questions is whether there are modal expressions in the languages of the world which are specialized for contexts like (b) and don't occur in contexts like (a)?

Thank you very much in advance!

Peter

-- 
Peter Arkadiev, PhD
Institute of Slavic Studies
Russian Academy of Sciences 
Leninsky prospekt 32-A 119334 Moscow
peterarkadiev at yandex.ru
http://www.inslav.ru/index.php?option=com_content&view=article&id=279