We consider discrete spin models on arbitrary planar graphs and lattices with frustrated interactions. We first analyze the Ising model with frustrated plaquettes. We use an algebraic approach to derive the result that an Ising model with some of its plaquettes frustrated has a dual model which is an Ising model with an external field ipi/2 applied to the dual sites centered at frustrated plaqu...

In an effort to understand the glass transition, the dynamics of a nonrandomly frustrated spin model has been analyzed. The phenomenology of the spin model is similar to that of a supercooled liquid undergoing the glass transition. The slow dynamics can be associated with the presence of extended stringlike structures which demarcate regions of fast spin flips. An entropy-vanishing transition, ...

2014 The energy spectrum of a tight-binding honeycomb lattice in the presence of a uniform magnetic field is analysed. The graph of the spectrum over a wide range of rational reduced flux 03A6/03A60 through elementary hexagonal cells is plotted. The energy spectrum is found to have recursive properties similar to those discussed previously on the square and triangular lattices. New features of ...

In spite of the prevalence of frustration in everyday life, very few neuroimaging studies were focused on this emotional state. In the current study we aimed to examine effects of frustration on brain activity while performing a well-learned task in participants with low and high tolerance for arousal. Prior to the functional magnetic resonance imaging session, the subjects underwent 2 weeks of...

Highly dispersed molybdenum oxide supported on mesoporous silica SBA-15 has been prepared by anion exchange resulting in a series of catalysts with changing Mo densities (0.2-2.5 Mo atoms nm(-2) ). X-ray absorption, UV/Vis, Raman, and IR spectroscopy indicate that doubly anchored tetrahedral dioxo MoO4 units are the major surface species at all loadings. Higher reducibility at loadings close to...

Artificial spin ice, made up of planar nanostructured arrays of simple ferromagnetic bars, is a playground for rich physics associated with the spin alignment of the bars and spin texture associated with the magnetic frustration at the bar vertices. The phase diagram is exotic, showing magnetic monopole-like defects and liquid and solid phases of spins arranged in loop states with predicted chi...

The structural, magnetic, and dielectric properties of Pb3Mn7O15 have been investigated using highquality single crystals. Pb3Mn7O15 adopts a pseudohexagonal orthorhombic structure, with partially filled Kagomé layers connected by ribbons of edge-sharing MnO6 octahedra and intercalated Pb cations. There are 9 inequivalent sites in the structure for the Mn ions, which exist both as Mn and Mn. Pb...

A three-dimensional elemental carbon kagome lattice, made of only fourfold-coordinated carbon atoms, is proposed based on first-principles calculations. Despite the existence of 60° bond angles in the triangle rings, widely perceived to be energetically unfavorable, the carbon kagome lattice is found to display exceptional stability comparable to that of C(60). The system allows us to study the...

Dimer models have long been a fruitful playground for understanding topological physics. We introduce a new class of dimer models -termed Majorana-dimer models -where the dimers represent pairs of Majorana modes, to capture the physics of strongly interacting Majoranas. We find that the simplest examples of such systems realize an intriguing, intrinsically fermionic phase of matter that can be ...

Security is not an isolated good, but just one component of a complicated economy. That imposes limitations on how effective it can be. The interactions of human society and human nature suggest that security will continue being applied as an afterthought. We will have to put up with the equivalent of bailing wire and chewing gum, and to live on the edge of intolerable frustration. However, tha...