60 research outputs found
The STAR MAPS-based PiXeL detector
The PiXeL detector (PXL) for the Heavy Flavor Tracker (HFT) of the STAR
experiment at RHIC is the first application of the state-of-the-art thin
Monolithic Active Pixel Sensors (MAPS) technology in a collider environment.
Custom built pixel sensors, their readout electronics and the detector
mechanical structure are described in detail. Selected detector design aspects
and production steps are presented. The detector operations during the three
years of data taking (2014-2016) and the overall performance exceeding the
design specifications are discussed in the conclusive sections of this paper
Bicrossed products for finite groups
We investigate one question regarding bicrossed products of finite groups
which we believe has the potential of being approachable for other classes of
algebraic objects (algebras, Hopf algebras). The problem is to classify the
groups that can be written as bicrossed products between groups of fixed
isomorphism types. The groups obtained as bicrossed products of two finite
cyclic groups, one being of prime order, are described.Comment: Final version: to appear in Algebras and Representation Theor
Extending structures I: the level of groups
Let be a group and a set such that . We shall describe
and classify up to an isomorphism of groups that stabilizes the set of all
group structures that can be defined on such that is a subgroup of .
A general product, which we call the unified product, is constructed such that
both the crossed product and the bicrossed product of two groups are special
cases of it. It is associated to and to a system called a group extending
structure and we denote it by . There exists a group structure on
containing as a subgroup if and only if there exists an isomorphism of
groups , for some group extending structure
. All such
group structures on are classified up to an isomorphism of groups that
stabilizes by a cohomological type set . A Schreier type theorem is proved and an explicit example is given: it
classifies up to an isomorphism that stabilizes all groups that contain
as a subgroup of index 2.Comment: 17 pages; to appear in Algebras and Representation Theor
Presentations: from Kac-Moody groups to profinite and back
We go back and forth between, on the one hand, presentations of arithmetic
and Kac-Moody groups and, on the other hand, presentations of profinite groups,
deducing along the way new results on both
Schreier type theorems for bicrossed products
We prove that the bicrossed product of two groups is a quotient of the
pushout of two semidirect products. A matched pair of groups is deformed using a combinatorial datum consisting of
an automorphism of , a permutation of the set and a
transition map in order to obtain a new matched pair such that there exist an -invariant
isomorphism of groups . Moreover, if we fix the group and the automorphism
\sigma \in \Aut(H) then any -invariant isomorphism between two
arbitrary bicrossed product of groups is obtained in a unique way by the above
deformation method. As applications two Schreier type classification theorems
for bicrossed product of groups are given.Comment: 21 pages, final version to appear in Central European J. Mat
On the growth of generating sets for direct powers of semigroups
For a semigroup S its d-sequence is d(S) = (d1, d2, d3, . . .), where di is the smallest number of elements needed to generate the ith direct power of S. In this paper we present a number of facts concerning the type of growth d(S) can have when S is an infinite semigroup, comparing them with the corresponding known facts for infinite groups, and also for finite groups and semigroups.PostprintPeer reviewe
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