منابع مشابه
Type Checking with Universes
Various formulations of constructive type theories have been proposed to serve as the basis for machine-assisted proof and as a theoretical basis for studying programming languages. Many of these calculi include a cumulative hierarchy of \universes," each a type of types closed under a collection of type-forming operations. Universes are of interest for a variety of reasons, some philosophical ...
متن کاملOn Universes in Type Theory
The notion of a universe of types was introduced into constructive type theory by Martin-Löf (1975). According to the propositions-as-types principle inherent in type theory, the notion plays two rôles. The first is as a collection of sets or types closed under certain type constructions. The second is as a set of constructively given infinitary formulas. In this paper we discuss the notion of ...
متن کاملBlack holes in Gödel-type universes with a cosmological constant
We discuss supersymmetric black holes embedded in a Gödel-type universe with cosmological constant in five dimensions. The spacetime is a fibration over a four-dimensional Kähler base manifold, and generically has closed timelike curves. Asymptotically the space approaches a deformation of AdS5, which suggests that the appearance of closed timelike curves should have an interpretation in some d...
متن کاملBianchi Type V Universes with Bulk Viscosity in General Relativity
Bianchi type V bulk viscous fluid cosmological models are investigated. Using a generation technique (Camci et al., 2001), it is shown that the Einstein’s field equations are solvable for any arbitrary cosmic scale function. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density. Solutions for particular forms of cosmic scale functions are also obtaine...
متن کاملGödel-type Universes and the Landau problem
We point out a close relation between a family of Gödel-type solutions of 3+1 General Relativity and the Landau problem in S2,R2 and H2; in particular, the classical geodesics correspond to Larmor orbits in the Landau problem. We discuss the extent of this relation, by analyzing the solutions of the Klein-Gordon equation in these backgrounds. Guided by the analogy with the Landau problem, we sp...
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ژورنال
عنوان ژورنال: Theoretical Computer Science
سال: 1991
ISSN: 0304-3975
DOI: 10.1016/0304-3975(90)90108-t