The problem formulated in the title is investigated. The case of nilpotent matrices of size at most 4 allows a unitary treatment. The numerical range of a nilpotent matrix M of size at most 4 is circular if and only if the traces trM M and trM M are null. The situation becomes more complicated as soon as the size is 5. The conditions under which a 5 5 nilpotent matrix has circular numerical ran...

Abstract. Let Bn be the group of upper-triangular invertible n×n matrices and Xn be the variety of strictly upper triangular n × n matrices of nilpotent order 2. Bn acts on Xn by conjugation. In this paper we describe geometry of orbits Xn/Bn in terms of link patterns. Further we apply this description to the computations of the closures of orbital varieties of nilpotent order 2 and intersectio...

In a previous work of the authors, a middle convolution operation on the category of Fuchsian differential systems was introduced. In this note we show that the middle convolution of Fuchsian systems preserves the property of global nilpotence. This leads to a globally nilpotent Fuchsian system of rank two which does not belong to the known classes of globally nilpotent rank two systems. Moreov...

A long standing open problem in the theory of hyperfinite equivalence relations asks if the orbit equivalence relation generated by a Borel action of a countable amenable group is hyperfinite. In this paper we show that this question has a positive answer when the acting group is locally nilpotent. This extends previous results obtained by Gao–Jackson for abelian groups and by Jackson–Kechris–L...

The notable exclusions from the family of automatic groups are those nilpotent groups which are not virtually abelian, and the fundamental groups of compact 3-manifolds based on the Nil or Sol geometries. Of these, the 3-manifold groups have been shown by Bridson and Gilman to lie in a family of groups defined by conditions slightly more general than those of automatic groups, that is, to have ...

Multiplier is an important key element used for arithmetic operations in digital signal processor. Power consumption in multiplier is more when compared with adders and subtractors. So reducing the power consumption of multiplier makes a digital signal processor more efficient. A Wallace tree multiplier is an efficient high speed multiplier that multiplies two integers. Here a 4*4 Wallace tree ...

High-speed parallel multipliers are one of the keys in RISCs (Reduced Instruction Set Computers), DSPs (Digital Signal Processors), and graphics accelerators and so on. Array multiplier, Booth Multiplier and Wallace Tree multipliers are some of the standard approaches used in implementation of binary multiplier which are suitable for VLSI implementation. A simple digital multiplier (henceforth ...

A nilpotent quotient algorithm for finitely presented Lie rings over Z (LIENQ) is described. The paper studies the graded and non-graded cases separately. The algorithm computes the so-called nilpotent presentation for a finitely presented, nilpotent Lie ring. A nilpotent presentation consists of generators for the abelian group and the products expressed as linear combinations for pairs formed...