Encyclopedias, with their Pretensions to Comprehensive or Universal knowledge, are by their very nature audacious undertakings. That such exercises in intellectual hubris sometimes fail is not surprising; it is more astonishing how well some of them accomplish their goal. As evidenced by the volumes published to date, the Encyclopaedia Iranica is clearly another such success in the making. One way to appreciate its achievement is to take stock of its place within the encyclopedic tradition by examining the story of its inception and preparation, its vision and purpose, and its general features and strengths as an encyclopedia.

We consider the equation Δu = Vu in the half-space ${\open R}_ + ^d $, d ⩾ 2 where V has certain periodicity properties. In particular, we show that such equations cannot have non-trivial superexponentially decaying solutions. As an application this leads to a new proof for the absolute continuity of the spectrum of particular periodic Schrödinger operators. The equation Δu = Vu is studied as part of a broader class of elliptic evolution equations.

The heat transfer properties of the organic molecular crystal α-RDX were studied using three phonon scattering based thermal conductivity models. It was found that the widely used Peierls-Boltzmann model for thermal transport in crystalline materials breaks down for α-RDX. We show this breakdown is due to a large degree of anharmonicity that leads to a dominance of diffusive-like carriers. Despite being developed for disordered systems, the Allen-Feldman theory for thermal conductivity actually gives the best description of thermal transport. This is likely because diffusive carriers contribute to over 95% of the thermal conductivity in α-RDX. The dominance of diffusive carriers is larger than previously observed in other fully ordered crystalline systems. These results indicate that van der Waals bonded organic crystalline solids conduct heat in a manner more akin to amorphous materials than simple atomic crystals.

We develop a spectral theory for the equation (∇ + ieA) × u = ±mu on Minkowski 3-space (one time variable and two space variables); here, A is a real vector potential and the vector product is defined with respect to the Minkowski metric. This equation was formulated by Elton and Vassiliev, who conjectured that it should have properties similar to those of the two-dimensional Dirac equation. Our equation contains a large parameter c (speed of light), and this motivates the study of the asymptotic behaviour of its spectrum as c → +∞. We show that the essential spectrum of our equation is the same as that of Dirac (theorem 3.1), whereas the discrete spectrum agrees with Dirac to a relative accuracy δλ/mc2 ~ O(c−4) (theorem 3.3). In other words, we show that our equation has the same accuracy as the two-dimensional Pauli equation, its advantage over Pauli being relativistic invariance.

In the year 352/963, according to independent evidence and the author's own testimony, the Samanid ruler Manṣūr b. Nūḥ sent an order via his major-domo and closest confidant, al-Fā'iq al-Khāṣṣa, to his minister Abū 'Alī Bal'amī, commissioning the latter to prepare a translation into court Persian of the famous historical annals written in Arabic by Muḥammad b. Jarīr al-Ṭabarī. Bal'amī completed this task, producing a book whose popularity in many ways eclipsed that of the original text throughout the Persian-speaking world and beyond (being translated into various Turkish dialects and even, ironically enough, back into Arabic). Unfortunately, exploitation of this source by modern scholars has been hindered both by its identification as a “translation” of Ṭabarī's work and by the lack of a suitable edition of the Persian text. This article attempts to explore these problems and the extent to which they have been rectified by recent studies and editions of this important work.

A recent burst of interest in revisionist interpretations of early Islamic and especially Abbasid history may be attributed in large measure to the availability of a number of fresh source materials, one of the most important of which is an anonymous history of the Abbasid family. A number of problems surrounding this work are still far from being satisfactorily resolved, including the questions of its title, the date of its composition, the identity of its author, and its historical and historiographical value.