István Németi | Renyi Institute of Mathematics (original) (raw)

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On a proof of Shelah by István Németi

Journal of Philosophical Logic, 1998

Algebra universalis, 2009

Papers by István Németi

Bulletin of the Section of Logic, 1981

In this paper we try to initiate a search for an explicite and direct definition of ultraproducts... more In this paper we try to initiate a search for an explicite and direct definition of ultraproducts in categories which would share some of the attractive properties of products, coproducts, limits, and related category theoretic notions. Consider products as a motivating example. ...

In this paper we present some of our school's results in the area of building up relativity t... more In this paper we present some of our school's results in the area of building up relativity theory (RT) as a hierarchy of theories in the sense of logic. We use plain first-order logic (FOL) as in the foundation of mathematics (FOM) and we build on experience gained in FOM. The main aims of our school are the following: We

In this paper, we investigate the possibility of using closed timelike curves (CTCs) in relativis... more In this paper, we investigate the possibility of using closed timelike curves (CTCs) in relativistic hypercomputation. We introduce a wormhole based hypercomputation scenario which is free from the common worries, such as the blueshift problem. We also discuss the physical reasonability of our scenario, and why we cannot simply ignore the possibility of the existence of spacetimes containing CTCs.

The aim of this paper is to give an introduction to our axiomatic logical analysis of relativity ... more The aim of this paper is to give an introduction to our axiomatic logical analysis of relativity theories.

This is Part I of the presentation of a talk given on September 27, 2013 at the Logic and Philoso... more This is Part I of the presentation of a talk given on September 27, 2013 at the Logic and Philosophy of Mathematics seminar of ELTE University, Budapest. We present a concrete mathematical realization for the Leibnizian relationist concept of time and space, via a logical analysis of exploring time and space experimentally. We start out from ideas in James Ax’s 1978 paper entitled “The elementary foundations of spacetime”.

We prove that n-variable logics do not have the weak Beth definability property, for all n greate... more We prove that n-variable logics do not have the weak Beth definability property, for all n greater than 2. This was known for n=3 (Ildik\'o Sain and Andr\'as Simon), and for n greater than 4 (Ian Hodkinson). Neither of the previous proofs works for n=4. In this paper we settle the case of n=4, and we give a uniform, simpler proof for all n greater than 2. The case for n=2 is still open.