MY RESEARCH INTEREST STRETCHES BETWEEN BLACK HOLE PHYSICS, QUANTUM GRAVITY, STRING THEORY, QUANTUM INFORMATION THEORY, TOPOLOGICAL FIELD THEORY AND COSMOLOGY. HERE IS THE TEXT OF A PUBLIC LECTURE I GAVE IN HOLLAND AND MOSCOW IN 2011, WITH A HISTORICAL PERSPECTIVE ON SOME OF THE QUESTIONS THAT I'M TRYING TO ANSWER.

IN THE PAST FEW YEARS, I HAVE BEEN INTERESTED IN THE QUESTION OF HOW BLACK HOLES ABSORB, STORE AND RELEASE QUANTUM INFORMATION. THIS QUESTION IS KNOWN AS THE BLACK HOLE INFORMATION PARADOX, AND GAVE THE IMPETUS FOR IMPORTANT DISCOVERIES SUCH AS THE PHENOMENON OF HAWKING RADIATION AND THE HOLOGRAPHIC PRINCIPLE.

A CENTRAL ELEMENT IN THE PARADOX IS THE NOTION OF VACUUM ENTANGLEMENT. THE VACUUM IS FILLED WITH VIRTUAL PARTICLE PAIRS, THAT ARE CREATED OUT OF NOTHING DUE TO QUANTUM FLUCTUATIONS OF EMPTY SPACE. THESE VACUUM PAIRS ARE VERY SHORT-LIVED, AND QUICKLY DISAPPEAR AGAIN. NEAR A BLACK HOLE HORIZON, HOWEVER, THINGS ARE DIFFERENT: ONE OF THE PARTICLES CAN FALL INTO THE BLACK HOLE, WHILE THE OTHER STAYS OUTSIDE. THE OUTSIDE PARTICLE CAN ESCAPE AND BE DETECTED AS HAWKING RADIATION. THE STATE OF THE OUTSIDE PARTICLE IS CORRELATED WITH THE STATE OF THE PARTICLE THAT DISAPPEARED IN THE BLACK HOLE. THIS CORRELATION IS CALLED VACUUM ENTANGLEMENT.