Timed automata are finite automata extended with clocks that can be reset and tested on the transitions. Clocks hence measure the delay between actions of the automaton. Timed automata are widely used to model real-time systems and for model-checking real-time specifications. The state-space of a timed automaton is infinite (and even not countable). To overcome this problem, verification algorithms use a finite abstraction of the executions of the automaton. The efficiency of the verification algorithms heavily rely on the coarseness of the abstraction. These last years, we have proposed several optimizations of the abstractions and the underlying algorithms. The goals of this thesis are:

- to develop new abstractions that dynamically use the informations collected by verification algorithms,
- to study which are the properties preserved by these abstractions,
- the combination to verification techniques for distributed systems.

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