On the orientation of Roman towns in Italy

As is well known, several Roman sources report on the existence of a town foundation ritual, inherited from the Etruscans, which allegedly included astronomical references. However, the possible existence of astronomical orientations in the layout of Roman towns has never been tackled in a systematic way. As a first step in this direction, the orientation of virtually all Roman towns in Italy (38 cities) is studied here. Non-random orientation patterns emerge from these data, aiming at further research in this field.Comment: Archaeoastronomy/History of astronomy; 11 pages, 3 figure

Physically valid black-hole interior models

New, simple models of ``black hole interiors'', namely spherically symmetric solutions of the Einstein field equations in matter matching the Schwarzschild vacuum at spacelike hypersurfaces ``R<2M'' are constructed. The models satisfy the weak energy condition and their matter content is specified by an equation of state of the elastic type.Comment: 6 pages, TeX forma

Gravitational collapse with non-vanishing tangential stresses II: a laboratory for cosmic censorship experiments

The general exact solution describing the dynamics of anisotropic elastic spheres supported only by tangential stresses is reduced to a quadrature using Ori's mass-area coordinates. This leads to the explicit construction of the root equation governing the nature of the central singularity. Using this equation, we formulate and motivate on physical grounds a conjecture on the nature of this singularity. The conjecture covers a large sector of the space of initial data; roughly speaking, it asserts that addition of a tangential stress cannot undress a covered dust singularity. The root equation also allows us to analyze the case of self-similar spacetimes and to get some insight on the role of stresses in deciding the nature of the singularities in this case.Comment: 16 pages, Plain TeX forma

Archaeoastronomy in the Khmer heartland

The heartland of the Khmer empire is literally crowded by magnificent monuments built in the course of many centuries. These monuments include the world-famous state-temples, such as Angkor Wat, but also many other temples and huge water reservoirs. Using Google Earth data as well as GIS data and reconstructing the ancient sky with Stellarium, we investigate here on the relationships of astronomy with orientation and topography in a systematic fashion, following the methods of modern Archaeoastronomy and strictly keeping at a bay vague or esoteric proposals put forward by many authors in the past. As a result, a very clear pattern of cardinal orientation and alignment arises, connected with the temple's symbolism and the management of power by the Khmer kings. As a bonus, the comparison with the Angkor monuments allows to put forward a explanation for the anomalous orientation of the unique two peripheral state temples of Cambodia.Comment: Archaeoastronomy/History of Astronom