Time periodic forcing in the form of coherent radiation is a standard tool for the coherent control of small quantum systems like single atoms. In the last years, periodic driving has more and more also been considered as a means for the coherent manipulation of many-body systems. In particular, experiments with atomic quantum gases in optical lattices subjected to driving in the lower kilohertz regime have attracted a lot of attention [see, e.g., RMP 89, 011004 (2017)]. Milestones include, i.a., the observation of dynamic localization, the coherent control of quantum phase transitions, and the realization of artificial gauge fields and topological band structures for
charge-neutral atoms. It is the fact that atomic quantum gases are very well isolated from their environment and highly controllable in a time-dependent fashion that allowed for these recent advances. I will give an introduction to the concept of Floquet engineering, which underlies these experiments, present various examples like the realization of quantum-Hall physics and the coherent control of interactions, and discuss also challenges related to interaction-induced heating.
I will discuss the thermal and non-thermal way of dark matter production. In a thermal way, dark matter produces via the usual freeze-out mechanism and this type of dark matter is called Weekly Interacting Massive Particle (WIMP). To explain WIMP DM, SM is extended with additional particles and one of them becomes a suitable DM candidate. WIMP type DM signatures will also be discussed for this setup, mainly direct detection (DD), indirect detection and collider search. In another half, I will talk about DM production via the freeze-in mechanism. This type of DM is called non-thermal because it never achieves thermal equilibrium with cosmic soup due to its very feeble interactions (also called FIMP DM). This type of scenario is well motivated because we have not detected any signal so far in the DD experiments, hence the DM interaction may lie in the feeble regime. In explaining this, I consider the (\mu-\tau) abelian extension of the SM and naturally, a fermionic DM candidate comes out when we try to address the neutrino mass via one loop diagram mediated by the inert doublet.
There are many ways to study life, and one that is particularly appealing to physicists is regarding it as self-organized 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 begin to put together simple systems - from basic ingredients that we fully understand - that would exhibit the kind of active behaviour we find in living systems. I will address the question of stability of a living system made of active components and propose a fundamentally new mechanism in which a competition between chemical signalling and cell division can determine the homeostatic conditions at the systemic level.
In recent years, the synergy between ALMA and HST has allowed to detect and characterize galaxies at redshift >6, near the end of the Epoch of Reionization. However, many questions remain open: What is the structure of these objects? How dusty are they? Are they the sources of reionization? We present results from state-of-the-art simulation of a high-redshift galaxy ("Althaea"), augmented with multi-wavelength radiative transfer. Our analysis focuses on dust content in direct comparison with observations.
The harsh and detrimental Martian surface conditions are generally associated with the radiation environment that is dominated by highly cytotoxic UV radiation. UV radiation both directly affects living organisms through modifications of the genetic code as well as indirectly through peroxidation of proteins and membrane lipids by reactive oxygen species (ROS) formation including H2O2 that are cytotoxic. I will introduce an alternative mechanism that equally results in ROS formation and can account for direct and indirect cell death: ABRASION BY SALTATION.
Magnetic skyrmions are the smallest non-trivial entities in magnetism with great potential for data storage applications. These chiral and topological quasi-particles furthermore exhibit fascinating static and dynamical properties that render them the ideal candidates to study new physics in high spin-orbit coupling materials. In this talk, I will first give a general introduction to the field of skyrmionics and the fundamental properties of skyrmions that derive from their energetics. I will then discuss various ways of creating and stabilizing room-temperature skyrmions experimentally, as well as how we can move them and observe their topological dynamics via high resolution time-resolved x-ray imaging. I will conclude with perspectives of future research in this field and related areas.