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Description
Albert Einstein’s Theory of Relativity predicts existence of black holes. Their gravity is so strong that everything, including light, gets captured and inevitably heads towards certain doom at singularity. Recent advancements in astronomy combined with observations of gravitational waves lead to the only possible conclusion: black holes are real. And this fact makes a serious problem, known as the “information paradox”. The relation between the two sides of a black hole resembles the relation between two sides of a mirror. But unlike a familiar mirror, a black hole looks like an extremely bumpy mirror that scrambles and distorts the reflection beyond recognition. To resolve the paradox means to figure out how to unscramble the image and what kind of a mirror would produce it. The answer rests in a combination of cosmology and holography. Holographic duality is an extremely powerful tool discovered in 1997 by Juan Maldacena. Just like famous wave-particle duality states that one object, can be described as a wave or a particle, holographic duality tells us that a black hole can be described in an alternative language that does not even include gravity. This makes many questions about black holes much simpler to deal with. When it comes to cosmology, what I mean here is the fact that the interior of a black hole resembles an evolving universe. Our universe is an expanding cosmology: it expands in all directions, while the interior of a black hole represents a crunching cosmology: it expands in some directions but contracts in others. There also exist holographic methods for cosmologies and they can be applied to crunching cosmologies. This is the essence of the proposed approach to the old problem: one can use holography for both sides of the “mirror”. In this way we should be able to learn what kind of a mirror we are dealing with here. Or, what is the fundamental structure of black holes and what is the mechanism responsible for the information paradox.
Summary of project results
Albert Einstein’s Theory of Relativity predicts the existence of black holes: extremely massive objects surrounded by incredibly strong gravitational field. Their gravity is so strong that everything, including light, gets captured and inevitably heads towards a certain doom at singularity: a point where the gravitational field becomes infinitely strong. Theoretical considerations suggest that black holes behave like no other objects in our entire Universe. In fact, black holes must necessarily break some well-established rules of either Theory of Relativity or quantum mechanics, and possibly both. Their strange and mysterious properties captivate entire generations of physicists and still remain to be uncovered. The source of the difficulty in the description of black holes is their strong gravity, which necessarily requires some sort of quantum description.
The aim of the project was to make progress in the analysis of strongly gravitating quantum objects. This includes black holes, but also cosmologies. Indeed, as our Universe expands, it evolves towards a smaller density of matter. This means that when we move back in time, the Universe used to be extremely dense and hot, very much like the interior of a black hole. Thus, the study of the early Universe requires the same tools as the study of black holes: strong quantum gravity.
In the project I used holography: a novel tool well-suited to uncover mysteries of quantum gravity and quantum cosmologies. I provided specific predictions arising from holography that should be possible to test in our Universe in the future. My theory predicts specific features that are not explained by the standard model of cosmology.
This includes already measured features such as near-scale invariance of the Cosmic Microwave Background: electromagnetic radiation filling up the entire Universe. My model also predicts a number of new features that should be measurable in 10-20 years as new satellites and telescopes are built.
Next, I applied holography to model some curious behavior of black holes. In my papers I argued that the weirdness of quantum black holes stems from the fact that in quantum gravity certain states are missing from what is naively expected. What I suggest is that the quantum system describing the black hole moves through a highly restricted space of states. From the perspective of the far away observer such restrictions resemble non-local interactions. In the literature such interactions were uncovered some time ago and deemed worrisome as they break rules of quantum mechanics and General Relativity. On a fundamental level in my approach no such rules are broken: they are simply an artifact of the incorrect description of the black hole system.
The results of the project shed new light on the nature of quantum gravity. Furthermore I provided invaluable tools in the analysis of quantum cosmologies. For example, I developed computer packages for calculations of cosmological predictions. Such tools provide invaluable support to the community and have already been used in research of other scientists. The POLS grant made it possible for me to share and collaborate with a number of physicists around the world. Furthermore, I was able to present and discuss the results of the research to the wider community at a handful of conferences and workshops.