hi Gennaro,
create a group on ticket, and then right click on the technician and choose Insert > Summary > Distinct Count and insert this (using the Summary location) at the group level.
now go into your Report > Selection Formula > Group and use that summary you just created.
DistinctCount ({your technician field name}, {your ticket field name}) = 1
please note that group selection is not a filter...so your report will still bring back all records. if you need to create a filter (due to performance issues with the report) then let us know...this will involve writing a Command object though instead of using tables and will require a new report usually.
cheers,
jamie