The rotational energy of a Kerr black hole is often invoked as the free energy source that powers compact astrophysical systems. An important question concerning the energy extraction mechanism is whether a Kerr black hole can communicate stresses to a distant load via a surrounding, force-free magnetosphere, and whether such structures are stable. In this paper we address this question. We fir...

Canonical quantization of local field theories in classical black hole spacetimes with a single horizon leads to a particle number density with a thermal distribution in equilibrium at the Hawking temperature. A complete treatment including non-local quantum gravity effects has shown however that the full " thermal vacuum " of the theory is the false vacuum. In this work, we find the true vacuu...

As a rst approximation, a metal can be modelled as an electron gas. A non-interacting electron gas has a continuous spectrum of electron-hole pair excitations. At each wavevector ~ Q with j~ Qj less than the maximum Fermi surface spanning vector (2kF ) there is a continuous set of electron-hole pair states, with a maximum energy but no gap (the minimum energy is zero.) Once the Coulomb interact...

The electron and hole relaxation in the (7, 0) zigzag carbon nanotube is simulated in time domain using a surface-hopping Kohn-Sham density functional theory. Following a photoexcitation between the second van Hove singularities, the electrons and holes decay to the Fermi level on characteristic subpicosecond time scales. Surprisingly, despite a lower density of states, the electrons relax fast...

We propose a model for a spatially modulated collective state of supercon-ducting cuprates in which the electronic properties vary locally in space. In this model the regions of higher hole density (called stripes) are described as Luttinger liquids and the regions of lower density (antiferromagnetic ladders) as an interacting bosonic gas of d x 2 −y 2 hole pairs. We show that the transition to...

Doping evolution of the Fermi surface topology of Na(x)CoO(2) is studied systematically. Both local density approximation (LDA) and local spin density approximation (LSDA) predict a large Fermi surface as well as small hole pockets for doping levels x approximately 0.5. In contrast, the hole pockets are completely absent for all doping levels within LSDA+U. More importantly, we find no violatio...

Patterning of biomolecules on graphene layers could provide new avenues to modulate their electrical properties for novel electronic devices. Single-stranded deoxyribonucleic acids (ssDNAs) are found to act as negative-potential gating agents that increase the hole density in single-layer graphene. Current-voltage measurements of the hybrid ssDNA/graphene system indicate a shift in the Dirac po...

Control over the doping density in copper sulfide nanocrystals is of great importance and determines its use in optoelectronic applications such as NIR optical switches and photovoltaic devices. Here, we demonstrate that we can reversibly control the hole carrier density (varying from >1022 cm-3 to intrinsic) in copper sulfide nanocrystals by electrochemical methods. We can control the type of ...