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In 1995 I obtained my PhD from Leiden University (Cum Laude). I have worked at the Johns Hopkins University and at Harvard University before becoming a full professor at the Kapteyn Astronomical Institute (University of Groningen). In my theoretical work I study the first stars and black holes, quantum gravity, wormholes and space-time topology, active galaxies, dark energy, formation of planets, astrobiology, the interstellar medium.

Quantum Space-Time

For my book on quantum space-time and black holes, see here (hardcopy) or see here (ebook). There is also a 1,000 Euro prize contest. To win one must resolve a remarkable coincidence between the dark energy density and the mean density of a neutron star, see here or accept that black hole number drives dark energy...

The physical idea behind my work is simple: find the individual paths that collectively weave the quantum fabric of space-time and one knows how matter must move and interact through space and time. In this, even Nature itself is uncertain in its measurements. In fact, any observer and observed can always exchange their roles, mimicking each other unremittingly! In other words, the identification of a single path, a history, is only possible through comparison with another. It thus takes one to know one, even when it comes to space-time itself. Consequently, the dynamics of quantum space-time take the form of one path inducing another: identity by mimicry. This yields a multiply connected universe with many distinct yet interacting histories.

Mathematically, one uses topology to describe the path connectivity of space-time. Below is a visual impression of travel by identification of distinct space-time locations. The red and blue ball are the same, their color simply indicates how the edges of the square are identified to form the surface of a donut in three dimensions. In four dimensions, one can do this with a solid cube to get a three-torus. A lattice is constructed by gluing many such three-tori together, so that matter is guided along many different space-time paths.

                   tori1            tori2

In 1996, see paper 1 below, I proposed a lattice of three-tori in four dimensions as the topology of Planckian space-time. Such a lattice of three-tori allows for a natural implementation of the superposition principle, through the Feynman path integral, because it imposes different paths between space-time points (two distinct paths with the same beginning and end form a loop). In fact, for any universe with a finite measuring accuracy, one must have a lattice of three-tori and therefore quantum mechanics. Furthermore, one may naturally attach wormholes (black holes) to such a lattice of three-tori, and thus include gravity. This leads to a cosmological ''constant'' term in the Einstein equation that is proportional to the number of macroscopic black holes in the universe. Paper 1 predicted that the global expansion of space-time accelerates as more and more black holes are formed through cosmic time. This is precisely what one needs in order to explain the currently popular notion of dark energy, see paper 9 below for a complete description. Paper 10 shows how black holes grow spontaneously, while paper 11 highlights how particle creation leads to a vacuum with a negative number of particles.

Combined, the papers below form the heart of my quantum space-time theory. In it, loop topology and information take central stage, and both express Nature's quantum measurement uncertainty. As a short poem: Uncertainty causes path multiplicity; matter follows and creates its own hollows.

Paper 1: read here how the number of black holes determines the cosmological ''constant''.

Paper 2: read here how space-time topology determines particle physics.

Paper 3: read here how Einstein gravity can be derived from space-time topology.

Paper 4: read here how Einstein's elevator/rocket experiment requires information.

Paper 5: read here how quantum measurement information affects general relativity.

Paper 6: read here how space-time topology causes the LHC to leak, lowering the Higgs mass.

Paper 7: read here how the connection between dark energy and black holes can be tested.

Paper 8: read here for the main points on dark energy and topological dynamics.

Paper 9: read here for everything about topological dynamics, including dark energy and inflation.

Paper 10: read here how black holes grow spontaneously, yielding a big crunch end of the universe.

Paper 11: read here how some solar mass black holes can be stimulated into rapid evaporation.