Integrated Calendar

In recent decades, various temperature proxies have been developed and further established in the scientific community, at both low and high accuracy, however, not every method can be applied without restriction to all minerals or rocks. Evaporitic rocks, for example, are abundant chemical sediments at the Earth's surface that are deposited from supersaturated brines in marine, terrestrial, and lacustrine environments. Halite is the most abundant rock-forming mineral in this group, which during crystal formation entraps tiny water droplets (fluid inclusions, FIs) that store the chemical composition of the parent brine at a specific pressure-temperature dependent density. Such FIs are therefore excellent records of the original physicochemical conditions of the source brine.
Brillouin spectroscopy (BS) is a novel laser-based technique that uses density fluctuations in FIs to directly measure entrapment temperatures and thus the initial brine temperature during crystal growth. In this seminar, the BS method will be introduced and two application cases will be presented using salt layers from the Dead Sea which were deposited during two interglacial periods. In addition to the basic principles, both the recommended sampling strategy and pitfalls along with associated limitations will be presented.
The conclusion will be that the salt layers commonly deposited in the Dead Sea basin consist of two types that formed preferentially in summer (coarse-grained crystals) and winter (fine-grained crystals), which is mainly controlled by the degree of salt saturation of the lake water. Furthermore, it will be shown how (1) lake bottom temperatures have fluctuated seasonally (summer/winter), and that (2) paleo temperature trends can be reconstructed for an entire halite layer that was deposited during holomictic periods in the Dead Sea basin. This method is particularly promising for evaporites that formed near the surface if the material has not been affected by external processes such as tectonic burial/uplift, erosion, or mineral replacement.

A prominent goal of present-day condensed-matter physics is the design of electronic devices with ever faster switching times. As an example I will present the optically induced spin transfer between magnetic sublattices, the so-called OISTR effect, which allows the switching of magnetic textures on the scale of a femto-second or less. This effect was first predicted with real-time TDDFT and later confirmed in many experiments. To create from this effect a real-world device on has to face the problem of decoherence, i.e. the phenomenon that quantum systems tend to lose their quantumness due to interactions with the environment. For electrons, the principal source of decoherence is the non-adiabatic interaction with nuclear degrees of freedom, i.e. with an “environment” that cannot be removed. In fact, the paradigm of electronic-structure theory where electrons move in the static Coulomb potential of clamped nuclei, while useful in the ground state, is an idealization hardly ever satisfied in dynamical processes. Non-adiabaticity, i.e. effects of the coupled motion of electrons and nuclei beyond the Born-Oppenheimer approximation are found everywhere. In this lecture, the exact factorization will be presented as a universal approach to understand and, ultimately, control non-adiabatic effects, in particular decoherence, from an ab-initio perspective.

The general synchronization problem asks to recover states of objects from their corrupted relative measurements. When the states are represented by group elements (e.g. 3-D rotations or permutations) this problem is known as group synchronization. In several applications, the algebraic structure of the states is more complicated, for example, the states can be represented by partial permutations. The synchronization problem has many applications, in particular, to structure-from-motion (SfM), where one needs to estimate the 3D structure of a scene from a set of its projected 2D images. I will first describe a general framework for group synchronization, the Cycle-Edge Message Passing (CEMP), and then explain its generalization to non groups, by exemplifying the case of partial permutation synchronization. I will emphasize mathematical difficulties, review some mathematical guarantees for the proposed methods and also demonstrate an application. This is a joint work with Shaohan Li and Yunpeng Shi.

Mantle fluids are the primary carriers of key volatile elements that make the Earth’s long-term planetary habitability possible. The interaction of such volatile-rich fluids with the mantle rocks, especially the sub-cratonic lithospheric mantle leads to alteration of the mantle as well as its melting. High-density fluids encased inside diamonds are the best natural representation of mantle fluid compositions, suggesting their compositions are saline, silicic or carbonatitic. However, the origin and role in the mantle as well as their role in altering the mantle are still unclear.
In my research, we approach these questions by experimentally simulating the interaction of volatile-rich fluids with mantle rocks at known pressure and temperature relevant to the mantle. Examining different mixtures of volatiles (H2O and CO2) and mantle rocks (peridotite and eclogite), we attempt to understand the origin of each type of fluid found in diamonds as well as study the effect of such interaction on the mantle chemistry and mineralogy.
Compiling many experimental studies reveals that fluids ranging from silicic to low-Mg carbonatitic are formed in systems of eclogite+H2O+CO2, the more CO2 in the system, the more carbonatitic the fluid is. Fluids ranging from low-Mg carbonatitic to high-Mg carbonatitic in nature are the results of the formation of fluids in the peridotite-H2O-CO2 system. The more CO2 in the system, the more high-Mg carbonatitic the fluid composition is. These results suggest that the various fluids found in the mantle result from changes in the bulk composition of the mantle rocks.
The mantle rocks are significantly affected during percolation of such fluids through them. For example, experimentally interacting silicic fluid with peridotite demonstrated the formation of various metasomatic peridotites as a function of pressure and temperature, composing of amphibole and mica. The mineral assemblages, chemistry, and P-T conditions in the experiments are similar to those found in metasomatic xenoliths from Kimberly, South Africa, and surrounding localities.