ERC FUNDED PROJECTS

The interplay between two of the most important building blocks of nature, quantum mechanics and gravity, has been a great source of inspiration for theoretical physics, leading to discoveries such as the Hawking radiation of black holes and the development of string theory. In turn, the following picture emerged: physics at the most fundamental level is governed by the rules of quantum mechanics while gravity is some effective coarse-grained description of the underlying microscopic theory. Given that the microscopic degrees of freedom are non-local, standard techniques such as the renormalization group and effective field theory a priori do not apply. Nevertheless, we use effective field theories that incorporate general relativity to describe our observations. With the discovery of gravitational waves and the various ongoing and upcoming experiments that will put general relativity to the test, it has become urgent to assess the validity of the standard framework of effective field theory for describing observable quantum gravity effects. Recent developments in resolving the information loss paradox and the quantum nature of black holes concluded that effective field theory must be modified in a way that uniquely incorporates quantum gravity. The main purpose of this proposal is to describe this modification in a precise and quantitative way, ultimately connecting it to potential experimental discoveries. In order to achieve this goal, I will approach the problem using a combination of thermodynamics, hydrodynamics and quantum information theory, mostly in the context of the AdS/CFT correspondence, where a precise description of quantum gravity is available. As a by-product of identifying observational features of quantum gravity, I will also make substantial progress in several foundational problems. My broad track record and expertise, and the fact that I have already obtained promising preliminary results, makes me uniquely qualified to lead this endeavor.

2 500 000 €

Start date: 2019-09-01, End date: 2024-08-31

The study of black hole physics and string theory are leading to a novel perspective on gravity and space-time. The old frameworks are replaced by a new paradigm in which gravity is understood as an emergent phenomenon. A central role in this revolution is played by the holographic principle put forward by ‘t Hooft. It states that the microscopic information associated with the physical world can be stored on the boundary of space. From this holographic viewpoint I have recently derived the familiar laws of Newton and Einstein using only first principles. Gravity appears as an entropic force caused by changes in information associated with matter. With this ERC proposal I am aiming to build a research group that will further develop this new entropic view on gravity. The powerful string theoretic tools, such as the holographic correspondence between gauge theory and gravity, will be used to illuminate and further clarify gravity’s entropic origin. In addition, I plan to investigate the implications of the emergence of the gravitational force for the areas in which gravity plays a crucial role, in particular cosmology. For instance, the entropic viewpoint is expected to shed new light on the nature of dark energy and possibly dark matter. It may also lead to a new perspective on the other fundamental forces, since the notions of inertia and mass need to be reconsidered as well. The understanding of gravity as an emergent phenomenon will also influence and benefit from the conceptual ideas developed in condensed matter physics, such as the recently discovered connection between quantum critical electron systems and black hole horizons. The university of Amsterdam and the Netherlands provide an excellent environment for a successful completion of these goals.

2 033 983 €

Start date: 2011-04-01, End date: 2016-03-31

Holography is by now a fundamental tool in the understanding of both strongly coupled conformal field theories (CFTs) and quantum theories of gravity. While holography in Anti de Sitter (AdS) space-times is rather well understood, we currently lack a basic picture of what it means in non-AdS space-times. Considering non-AdS space-times is an essential and urgent next step in the study of quantum gravity as we seem to live in a universe with a positive cosmological constant that is approaching de Sitter (dS) in the far future. Also, the near-horizon geometries of black holes are typically described by more exotic geometries that need to be understood on their own right. I propose to address this and study the physics of holographic systems on non-AdS space-times and their connection to generalized geometric structures that naturally arise in these setups. In order do this I will use both conventional field theory techniques and new holographic tools, some of which I have developed recently. The relevance of GenGeoHol is illustrated by universal properties of black holes, e.g. their area-law entropy. These are independent of AdS, pointing towards the existence of a more general holographic principle that generalizes the usual symmetries and geometric notions. A great deal of evidence has accumulated recently indicating that this is indeed the case. The physics of extremal black holes and non relativistic systems are clear examples. GenGeoHol will impact a wide range of fields. As one moves away from AdS Einstein gravity, the dual quantum-field theories present different symmetries from that of usual relativistic systems. These systems couple naturally to generalized background geometries which are of intrinsic interest and key to a range of concepts extending from Newton-Cartan geometry in non-relativistic systems to higher-spin geometries for so-called W_N CFTs. Given my experience and track record, I am uniquely positioned to attack this problem successfully.

1 300 775 €

Start date: 2017-09-01, End date: 2023-08-31

This project focusses on realizing and studying a new hybrid ultra-cold atom-ion system for studying quantum many-body physics. It combines state-of-the-art technologies in quantum optics and quantum gases. The proposed system of cold (fermionic) atoms interacting with ion crystals has surprising analogies with natural solid state systems and molecules, with now by fermionic 6Li atoms in place of electrons and heavy 174Yb+ ions in place of ionic cores. In particular, an atomic band structure may arise with tunable atom-phonon interactions. The proposed experimental approach is inspired by advances in pioneering experiments with hybrid atom-ion systems. By using a new atom-ion combination that has the highest experimentally feasible mass ratio of 29 (Li and Yb+), heating due to the dynamical trapping potential of the ions is suppressed. This eliminates an important road block in existing hybrid atom-ion experiments towards reaching deep into the quantum regime. I will use optical micro-traps in conjunction with segmented ion traps to study the system in a regime with a small number of atoms (1-100) and ions. This offers unprecedented control over the quantum states of atoms and ions. Engineering non-classical states in the ions will allow for quantum enhanced measurements of the combined atom-ion system, with single atom and single collision resolution. State-dependence in the atom-ion interactions can be employed to engineer quantum potentials for the atoms, leading to large scale ion-atomic Schrödinger cat-type entanglement.

1 490 152 €

Start date: 2013-12-01, End date: 2018-11-30