129 research outputs found
Nilpotency of skew braces and multipermutation solutions of the Yang-Baxter equation
We study relations between different notions of nilpotency in the context of
skew braces and applications to the structure of solutions to the Yang-Baxter
equation. In particular, we consider annihilator nilpotent skew braces, an
important class that turns out to be a brace-theoretic analog to the class of
nilpotent groups. In this vein, several well-known theorems in group theory are
proved in the more general setting of skew braces.Comment: 18 pages. Postprint versio
Factorizations of skew braces
We introduce strong left ideals of skew braces and prove that they produce non-trivial decomposition of set-theoretic solutions of the YangâBaxter equation. We study factorization of skew left braces through strong left ideals and we prove analogs of ItĂŽâs theorem in the context of skew left braces. As a corollary, we obtain applications to the retractability problem of involutive non-degenerate solutions of the YangâBaxter equation. Finally, we classify skew braces that contain no non-trivial proper characteristic ideals.Fil: Jespers, E.. Vrije Unviversiteit Brussel; BĂ©lgicaFil: Kubat, L.. Vrije Unviversiteit Brussel; BĂ©lgicaFil: Van Antwerpen, A.. Vrije Unviversiteit Brussel; BĂ©lgicaFil: Vendramin, Claudio Leandro. Institute of Mathematical Sciences at NYU Shanghai; China. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentin
On various types of nilpotency of the structure monoid and group of a set-theoretic solution of the Yang--Baxter equation
Given a finite bijective non-degenerate set-theoretic solution of the
Yang--Baxter equation we characterize when its structure monoid is
Malcev nilpotent. Applying this characterization to solutions coming from
racks, we rediscover some results obtained recently by Lebed and Mortier, and
by Lebed and Vendramin on the description of finite abelian racks and quandles.
We also investigate bijective non-degenerate multipermutation (not
necessarily finite) solutions and show, for example, that this property
is equivalent to the solution associated to the structure monoid
(respectively structure group ) being a multipermuation solution and
that is solvable of derived length not exceeding the
multipermutation level of enlarged by one, generalizing results of
Gateva-Ivanova and Cameron obtained in the involutive case. Moreover, we also
prove that if is finite and is nilpotent, then the torsion part
of the group is finite, it coincides with the commutator subgroup
of the additive structure of the skew left brace and is a
trivial left brace.Comment: 35 page
Preserving the gauge invariance of meson production currents in the presence of explicit final-state interactions
A comprehensive formalism is developed to preserve the gauge invariance of
currents describing the photo- or electroproduction of mesons off the nucleon
when the final-state interactions of mesons and nucleons is taken into account
explicitly. Replacing exchange currents by auxiliary currents, it is found that
all contributions due to explicit final-state interactions are purely
transverse and do not contain a Kroll-Ruderman-type contact current. The
relation of the present formulation to tree-level-type prescriptions is shown.Comment: 6 pages, 2 figures; published versio
Gauge-invariant theory of pion photoproduction with dressed hadrons
Based on an effective field theory of hadrons in which quantum chromodynamics
is assumed to provide the necessary bare cutoff functions, a gauge-invariant
theory of pion photoproduction with fully dressed nucleons is developed. The
formalism provides consistent dynamical descriptions of pi-N --> pi-N
scattering and Gamma-N --> pi-N production mechanisms in terms of nonlinear
integral equations for fully dressed hadrons. Defining electromagnetic currents
via the gauging of hadronic n-point Green's functions, dynamically detailed
currents for dressed nucleons are introduced. The dressed hadron currents and
the pion photoproduction current are explicitly shown to satisfy gauge
invariance in a self-consistent manner. Approximations are discussed that make
the nonlinear formalism manageable in practice and yet preserve gauge
invariance. This is achieved by recasting the gauge conditions for all
contributing interaction currents as continuity equations with ``surface''
terms for the individual particle legs coming into or going out of the hadronic
interaction region. General procedures are given that approximate any type of
(global) interaction current in a gauge-invariance preserving manner as a sum
of single-particle ``surface'' currents. It is argued that these prescriptions
carry over to other reactions, irrespective of the number or type of
contributing hadrons or hadronic systems.Comment: 33 pages, RevTeX; includes 8 postscript figures (requires psfig.sty).
This version corrects some minor errors, etc.; contains updated references.
Accepted for publication in Phys. Rev. C56 (Oct. 97
Ontwikkeling prototype residuverwijdering met VAM-Residuce : eindrapportage 1 Januari 2010- 15 Mei 2011
Voor het succesvol implementeren van een residuverwijderingsprototype in de huidige sorteerlijnen is het belangrijk dat tijdens het sorteerproces niet te veel schuim ontstaat in het sorteerwater en dat de concentratie van het gebruikte reducerend middel (VAM-Residuce) in het sorteerproces op peil gehouden kan worden. Een tweetal titratiemethodes en een schuim-onderdrukkende techniek zijn ontwikkeld om respectievelijk de concentratie VAM-Residuce te controleren en overmatige schuimvorming tijdens het sorteerproces tegen te gaan
Solution of the Bethe-Salpeter equation for pion-nucleon scattering
A relativistic description of pion-nucleon scattering based on the
four-dimensional Bethe-Salpeter equation is presented. The kernel of the
equation consists of s- and u-channel nucleon and delta pole diagrams, as well
as rho and sigma exchange in the t-channel. The Bethe-Salpeter equation is
solved by means of a Wick rotation, and good fits are obtained to the s- and
p-wave phase shifts up to 360 MeV pion laboratory energy. The coupling
constants determined by the fits are consistent with the commonly accepted
values in the literature.Comment: 34 pages, RevTeX; 7 figures. Several references added, a few typos
corrected. Accepted for publication in Physical Review
A Gauge Invariant Unitary Theory for Pion Photoproduction
A covariant, unitary and gauge invariant theory for pion photoproduction on a
single nucleon is presented. To achieve gauge invariance at the operator level
one needs to include both the and thresholds. The final
amplitude can be written in terms of a distorted wave in the final
channel provided one includes additional diagrams to the standard Born term in
which the photon is coupled to the final state pion and nucleon. These
additional diagrams are required in order to satisfy gauge invariance.Comment: 4 pages, LaTeX, 1 figure as a separate uuencoded compressed tar fil
- âŠ