Colloquia Archive 2015

I discuss the current status of particle physics, and aim to answer questions such as Where are we now? What is special about the Higgs boson? What questions remain to be answered? How are we going to answer them?

The relative importance of determinism and contingency in biological evolution is the subject of a long-standing debate. In the words of Stephen J. Gould, if we could replay the tape of life on earth, would the outcome at all resemble the present biosphere? Recent work in the more modest arena ...

There are many ways to study life, and one that is particularly appealing to physicists is regarding it as self-organised active soft matter that is away from equilibrium ``just the right way''. In this Colloquium, I will discuss this notion, and provide a number of examples of how we can ...

The evidence that our galaxy is a barred galaxy will be summarised. The bar's impact on local kinematics and on the flow of the ISM are significant lines of evidence. Hydrodynamical simulations will be used to examine critically the conjecture that gas streamlines approximate closed orbits. It turns out ...

The Detection of gravitational waves is eagely expected as one of the most important scientific discoveries of the next decade. A worldwide effort is now working actively to pursue this goal both at an experimental level, by building ever sensitive detectors, and at a theoretical level, by improving the modelling ...

I will review how the interplay between theory and experiment has written a success story in particle physics over the last decades. Then I will discuss recent developments which have lead to what is sometimes called a "revolution" with regard to precision calculations in perturbative quantum field theory. The second ...

The way galaxies form and evolve is a major open question in cosmology. Rapid progress is made based on observations and simulations of galaxies during the peak of their assembly and star-formation activity, in the first few billion years of cosmic evolution. The emerging picture highlights the formation of galaxies ...

Ring polymers represent one of the last major theoretical challenges facing polymer physics. The essential difficulty lies in the non- local nature of the topological constraint associated with polymers of fixed topology, such as rings (unknots), that cannot cross one-another. We perform molecular dynamics and Monte Carlo simulations of ring ...

Hawking has discovered more than 40 years ago that black holes (BH's) evaporate. Ever since, ideas about how they evaporate have been a source of constant interest and controversy. In Hawking's model, the process of BH evaporation respects the Einstein equivalence principle but it is not unitary. Page ...

The Higgs boson mass miraculously turns out to have a value which has been expected form vacuum stability up to the Planck scale. This opens the possibility that the Higgs boson not only provides masses to all SM particles, but very likely also supplied a huge dark energy which inflated ...

When Osborne Reynolds documented his observations on the transition to turbulence in pressure driven pipe flow in 1883, he noticed that the turbulence remained localized to regions that extended over the full cross section but did not cover the entire length of the pipe. In recent years similar phenomena have ...

The theory of quantum entanglement is revolutionizing the field of quantum many body physics. One of the most relevant developments in this direction has been the introduction of quantum tensor networks, which provide a natural framework for describing the entanglement structure in ground states of strongly correlated systems. I will ...

Flocking - the collective motion of large numbers of organisms or other self- propelled entities - exhibits a number of strange and baffling phenomena. The most baffling is that it exists at all in two dimensions: a long-known theorem of statistical mechanics called the Mermin-Wagner theorem implies that it would be impossible ...

We discuss a unified picture where both inflation and a present dynamical dark energy arise from the same scalar field. The history of the Universe describes a crossover from a „past fixed point" where all particles are massless, to a „future fixed point" where exact scale invariance is spontaneously broken ...

Models of systems biology, climate change, ecosystems, and macroeconomics have parameters that are hard or impossible to measure directly. If we fit these unknown parameters, fiddling with them until they agree with past experiments, how much can we trust their predictions? We have found that predictions can be made despite ...

The inflationary scenario has become the paradigm of early universe cosmology. However, inflation is not the only early universe model which can explain the current cosmological data. I will discuss some alternative

Many natural systems are far from thermodynamic equilibrium and keep on exchanging matter, energy or information with their surroundings. These exchanges produce currents, or fluxes, that break time-reversal invariance. Such systems lie beyond the realm of traditional thermodynamics and the principles of equilibrium statistical mechanics do not apply to them ...

Topology is emerging as an important new tool for understanding our world. Computational homology, for example, has become standard for analyzing the connectivity of large-dimensional data sets. Here I present another approach, which is more dynamical in nature. The trajectories of 'particles,' whether oceanic floats or people, can be regarded ...

Statistical properties of the observed fluctuations of temperature and polarisation anisotropies of the cosmic microwave background are remarkably consistent with the basic predictions of cosmic inflation driven by a single energy component. The observed fluctuations are Gaussian and adiabatic, and the strength of fluctuations weakly depends on spatial scales. The ...

Reaction-diffusion dynamics endows cells with the capacity for accurate positioning, control of length, and timing of processes. Protein systems in cells employ different types of spatio-temporal patterns to ensure precise cell division and guide intracellular processes. The length of biopolymers is regulated by the interplay between polymerization kinetics and patterns ...

In this talk I will review at an introductory level recent developments pointing to symmetry concepts beyond (maximal) supersymmetry that may not only be relevant for the unification of particle interactions, but also to a better understanding of cosmological singularities in General Relativity. A key role in these considerations is ...