לוח שנה משולב

a Pseudo-Nambu-Goldstone boson (PNGB) and the resulting Higgs properties deviate from those predicted by the SM. The current Higgs and EW data favor a SM-like Higgs, requiring a hierarchy between the PNGB Higgs decay constant f and its vacuum expectation value v. The v/f hierarchy is responsible for a significant part of the fine-tuning in these models. We show that adding an independent, adjustable quartic to the Higgs potential can eliminate the v/f tuning, such that the only remaining tuning arises from radiative corrections to the Higgs mass. We demonstrate how this quartic can be obtained from extra-dimensions, revisiting the 6d origin of the little-Higgs models, this time in a warped AdS5xS1 background. We construct a 6D Composite Higgs model and also consider its deconstruction into a two-site Randall-Sundrum model. The PNGB Higgs in this model corresponds to the extra-dimensional components of a gauge field, and the quartic arises from the non-abelian gauge action in 6d. We show that this quartic is collective just like in little Higgs models, and so it is stable against quantum corrections. Our quartic scales like (R6/R), where R6 is the size of the flat circle, and R is the curvature radius of AdS. We show that a general hierarchy of (R6/R) can be naturally stabilized, and any desired quartic can be obtained.

Astronomy with gamma rays at energies above some 10 GeV has opened in the last decade a new window to the cosmos. Gamma rays allows us to take a look at the extreme places in our Universe. They are produced in Supernova remains, Black holes and active galaxies - cosmic particle accelerators, in which atomic nuclei and electrons are accelerated to vast energies.

Contrary to expectations high-energy phenomena are no exception in the cosmos, but occur in many galactic and extragalactic objects during their life cycle. There are currently over 2000 sources of GeV radiation and over 150 sources of TeV radiation. Thus the results of gamma astronomy are an important building block to the understanding of the development of the Milky Way and our Universe.

So far, gamma-ray astronomy in the TeV range, however, is performed with experiments that are only accessible to a limited circle of users.
With the Cherenkov Telescope Array CTA an international consortium of more than 1000 scientists and engineers aims for an open observatory.

Starting from the current findings of gamma-ray astronomy I will in the presentation date to look into the future to what we will be able to learn with CTA.

The Snowball Earth episodes may have affected the development of life on Earth through increasing atmospheric oxygen and spurring evolution. Considering the habitability and increase in complexity of life on other planets therefore requires thought about Snowball climate states. Using an energy balance model and global climate model, I will show that it is unlikely a tidally locked planet could experience a Snowball Earth bifurcation. Instead the planet would smoothly transition to global ice coverage. This is due to the difference in the shape of the insolation, which increases strongly toward the substellar point on a tidally locked planet. I will then change focus slightly and explain how climate oscillations between a warm state and a Snowball state can occur on a planet within the habitable zone that has a small CO2 outgassing rate. I will develop analytical relations to understand these cycles and outline scalings in variables such as the cycle period as a function of important climatic and weathering parameters. Work of this type should help us understand the context of planetary habitability and focus on appropriate targets as we seek to find the first inhabited exoplanet.

Over the past few decades, there has been steady progress in both our ability to produce biological material and in our ability to manipute matter at small length scales. These two developments merge in a fascinating area of confluence called single-molecule biophysics in which an understanding of biological matter from physical principles becomes possible. I will illustrate the development of this interdisciplinary field and show how several newly-developed techniques allow us to shed light on genomic processes such as DNA compaction, replication, and transcription.
For example, by measuring the twist and length of single DNA molecules, we are able to learn about DNA compaction into chromatin. We monitor the real-time loading of tetramers or complete histone octamers onto DNA and find, remarkably, that tetrasomes exhibit spontaneous flipping between a preferentially occupied left-handed state and a right-handed state, separated by free energy difference of 2.3 kBT (1.5 kcal/mol). The application of weak positive torque converts left-handed tetrasomes into right-handed tetrasomes, whereas nucleosomes display more gradual conformational changes. These findings reveal unexpected dynamical rearrangements of the nucleosomal structure, suggesting that chromatin can serve as a ‘‘twist reservoir,’’ offering a mechanistic explanation for the regulation of DNA supercoiling in chromatin.
By making use of high-throughput single-molecule techniques, we are able to gain new insights into the termination of DNA replication. In Escherichia coli, replisome progression beyond the termination site is prevented by Tus proteins bound to asymmetric Ter sites. Structural evidence indicates that strand separation on the blocking (non-permissive) side of Tus–Ter triggers roadblock formation, but biochemical evidence also suggests roles for protein- protein interactions. We perform DNA unzipping experiments which demonstrate that nonpermissively oriented Tus–Ter forms a tight lock in the absence of replicative proteins, whereas permissively oriented Tus–Ter allows nearly unhindered strand separation. Quantifying the lock strength reveals the existence of several intermediate lock states that are impacted by mutations in the lock domain but not by mutations in the DNA-binding domain. Lock formation is highly specific and exceeds reported in vivo efficiencies. We therefore postulate that protein-protein interactions may actually hinder, rather than promote, proper lock formation.
I will conclude by describing how such types of biophysical measurements should complement biochemical investigations in the coming few years