International contacts of János Baranyai Decsi

2 János Kollár

Real Face of János Bolyai Tamás Dénes

I n Vol. 56, No. 11, of Notices, I saw a fascinating article with the title: Changing Faces—The Mistaken Portrait of Legendre. The author, Peter Duren, writes with understandable bewilderment: “It seems incredible that such egregious error could have gone undetected for somany years.” This encouraged me to publish, in the same journal, the story—no less fascinating—of the real face of János Bol...

ePassport: Securing International Contacts with Contactless Chips

Electronic passports (ePassports) have known a wide and fast deployment all around the world since the International Civil Aviation Organization published their specifications in 2004. Based on an integrated circuit, ePassports are significantly more secure than their predecessors. Forging an ePassport is definitely thwarted by the use of cryptographic means. In spite of their undeniable benefi...

János Kollár and Sándor J Kovács

1. INTRODUCTION A recurring difficulty in the Minimal Model Program (MMP) is that while log terminal sin-gularities are quite well behaved (for instance, they are rational), log canonical singularities are much more complicated; they need not even be Cohen-Macaulay. The aim of this paper is to prove that, as conjectured in [Kol92, 1.13], log canonical singularities are Du Bois. The concept of D...

Colloquia Mathematica Societatis János Bolyai

1 . Our investigations might be suggested by a sort of optimalization problem which could be described vividly in practical terms as follows : suppose we are given a network of routes on which there are critical points endangered by fire. We want to place fire stations at an appropriate number of points from which any endangered point can be reached within a given time interval in case of emerg...