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Electronic state of every solid is basically classified into two categories according to its electrical responses: insulator or metal. A textbook of modern solid state physics explains that shape of a Fermi surface plays a key role in most physical properties in metals. One of the well-established experimental methods to detect a Fermi surface is measurement of quantum oscillations that is a periodic response of physical quantities with respect to external magnetic fields. As insulators do not host Fermi surface, it is believed that they do not exhibit any quantum oscillations.This book presents a comprehensive review of recent observations of quantum oscillations in the Kondo insulators, SmB6 and YbB12, and discusses how the observations are demonstrated by a newly proposed mechanism where emergent charge-neutral fermions exhibit quantum oscillations instead of bare electrons. It also focuses on topological properties of Kondo insulators, and demonstrates that YbB12 hosts asurface metallic conduction owing to its non-trivial band structure. Further it presents the experiments of specific heat and thermal conductivity in YbB12 down to ultra-low temperature to discuss the possible low-energy excitations from a Fermi surface of neutral fermions. The demonstrated gapless and itinerant fermionic excitations, that is the significant contribution from charge neutral fermions, violates Wiedemann-Franz law. The discoveries point out a highly unconventional phase of quantum state¿electrically insulating but thermally metallic¿realized in the bulk of topological Kondo insulators.

Owing to the increased accuracy requirements in fields such as astrometry and geodesy the general theory of relativity must be taken into account for any mission requiring highly accurate orbit information and for practically all observation and measurement techniques. This book highlights the confluence of Applied Mathematics, Physics and Space Science as seen from Einstein's general theory of relativity and aims to bridge the gap between theoretical and applied domains. The book investigates three distinct areas of general relativity: Exact solutions of the Einstein field equations of gravitation. Dynamics of near-Earth objects and solar system bodies. Relativistic orbitography. This book is an updated and expanded version of the author¿s PhD thesis which was awarded the International Astronomical Union PhD prize in Division A: Fundamental Astronomy. Included is a new introduction aimed at graduatestudents of General Relativity and extended discussions and results on topics in post-Newtonian dynamics and general relativistic spacecraft propagation.

What are the physical mechanisms that underlie the efficient generation and transfer of energy at the nanoscale? Nature seems to know the answer to this question, having optimised the process of photosynthesis in plants over millions of years of evolution. It is conceivable that humans could mimic this process using synthetic materials, and organic semiconductors have attracted a lot of attention in this respect.Once an organic semiconductor absorbs light, bound pairs of electrons with positively charged holes, termed `excitons¿, are formed. Excitons behave as fundamental energy carriers, hence understanding the physics behind their efficient generation and transfer is critical to realising the potential of organic semiconductors for light-harvesting and other applications, such as LEDs and transistors. However, this problem is extremely challenging since excitons can interact very strongly with photons. Moreover, simultaneously with the exciton motion, organic molecules canvibrate in hundreds of possible ways, having a very strong effect on energy transfer.The description of these complex phenomena is often beyond the reach of standard quantum mechanical methods which rely on the assumption of weak interactions between excitons, photons and vibrations. In this thesis, Antonios Alvertis addresses this problem through the development and application of a variety of different theoretical methods to the description of these strong interactions, providing pedagogical explanations of the underlying physics. A comprehensive introduction to organic semiconductors is followed by a review of the background theory that is employed to approach the relevant research questions, and the theoretical results are presented in close connection with experiment, yielding valuable insights for experimentalists and theoreticians alike.