The Transient High-Energy Sky and Early Universe Surveyor (THESEUS)

International audienceThe Transient High-Energy Sky and Early Universe Surveyor (THESEUS) is a missionconcept developed in the last years by a large European consortium and currentlyunder study by ESA as one of the three candidates for next M5 mission (launch in2032). As detailed in Amati et al. 2017 [1] and Stratta et al. 2017 [2], THESEUSaims at exploiting high-redshift GRBs for getting unique clues to the earlyUniverse and, being an unprecedentedly powerful machine for the detection,accurate location (from ~arcmin to ~arcsec) and redshift determination of alltypes of GRBs (long, short, ~high-z, under-luminous, ultra-long) and many otherclasses of transient sources and phenomena, at providing a substantialcontribution to multi-messenger time-domain astrophysics. Under these respects,THESEUS will show a beautiful synergy with the large observing facilities of thefuture, like E-ELT, TMT, SKA, CTA, ATHENA, in the electromagnetic domain, aswell as with next-generation gravitational-waves and neutrino detectors, thusenhancing importantly their scientific return