67 citations · 528 across the 47 of their papers we have counts for
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Cohomological analysis of the Epstein-Glaser renormalization
Nikolay M. Nikolov
A cohomological analysis of the renormalization freedom is performed in the Epstein-Glaser scheme on a flat Euclidean space. We study the deviation from commutativity between the r…
Pole structure and biharmonic fields in conformal QFT in four dimensions
N. M. Nikolov, K. -H. Rehren, I. Todorov
Imposing Huygens' Principle in a 4D Wightman QFT puts strong constraints on its algebraic and analytic structure. These are best understood in terms of ``biharmonic fields'', whose…
Generation of polycyclic groups
Martin Kassabov, Nikolay Nikolov
In this note we give an alternative proof of a theorem of Linnell and Warhurst that the number of generators d(G) of a polycyclic group G is at most d(\hat G), where d(\hat G) is t…
Infinite dimensional Lie algebras in 4D conformal quantum field theory
B. Bakalov, N. M. Nikolov, K. -H. Rehren +1
The concept of global conformal invariance (GCI) opens the way of applying algebraic techniques, developed in the context of 2-dimensional chiral conformal field theory, to a highe…
Harmonic bilocal fields generated by globally conformal invariant scalar fields
Nikolay M. Nikolov, Karl-Henning Rehren, Ivan Todorov
The twist two contribution in the operator product expansion of phi_1(x_1) phi_2(x_2) for a pair of globally conformal invariant, scalar fields of equal scaling dimension d in four…
Product decompositions of quasirandom groups and a Jordan type theorem
Nikolay Nikolov, László Pyber
We first note that a result of Gowers on product-free sets in groups has an unexpected consequence: If k is the minimal degree of a representation of the finite group G, then for e…
The rank gradient from a combinatorial viewpoint
Miklos Abert, Andrei Jaikin-Zapirain, Nikolay Nikolov
This paper investigates the asymptotic behaviour of the minimal number of generators of finite index subgroups in residually finite groups. We analyze three natural classes of grou…
Rank gradient, cost of groups and the rank versus Heegaard genus problem
Miklos Abert, Nikolay Nikolov
We study the growth of the rank of subgroups of finite index in residually finite groups, by relating it to the notion of cost. As a by-product, we show that the `Rank vs. Heegaard…