531 research outputs found
A note on a canonical dynamical r-matrix
It is well known that a classical dynamical -matrix can be associated with
every finite-dimensional self-dual Lie algebra \G by the definition
, where \omega\in \G and is the
holomorphic function given by for
z\in \C\setminus 2\pi i \Z^*. We present a new, direct proof of the statement
that this canonical -matrix satisfies the modified classical dynamical
Yang-Baxter equation on \G.Comment: 17 pages, LaTeX2
Conserved quantities in non-abelian monopole fields
Van Holten's covariant Hamiltonian framework is used to find conserved
quantities for an isospin-carrying particle in a non-Abelian monopole-like
field. For a Wu-Yang monopole we find the most general scalar potential such
that the combined system admits a conserved Runge-Lenz vector. It generalizes
the fine-tuned inverse-square plus Coulomb potential, found before by McIntosh
and Cisneros, and by Zwanziger, for a charged particle in the field of a Dirac
monopole. Following Feh\'er, the result is interpreted as describing motion in
the asymptotic field of a self-dual Prasad-Sommerfield monopole. In the
effective non-Abelian field for nuclear motion in a diatomic molecule due to
Moody, Shapere and Wilczek, a conserved angular momentum is constructed,
despite the non-conservation of the electric charge. No Runge-Lenz vector has
been found.Comment: 8 pages, RevTex no figures. An error corrected and a new Section
adde
Performance analysis and optimization of the JOREK code for many-core CPUs
This report investigates the performance of the JOREK code on the Intel
Knights Landing and Skylake processor architectures. The OpenMP scaling of the
matrix construction part of the code was analyzed and improved synchronization
methods were implemented. A new switch was implemented to control the number of
threads used for the linear equation solver independently from other parts of
the code. The matrix construction subroutine was vectorized, and the data
locality was also improved. These steps led to a factor of two speedup for the
matrix construction
On dynamical r-matrices obtained from Dirac reduction and their generalizations to affine Lie algebras
According to Etingof and Varchenko, the classical dynamical Yang-Baxter
equation is a guarantee for the consistency of the Poisson bracket on certain
Poisson-Lie groupoids. Here it is noticed that Dirac reductions of these
Poisson manifolds give rise to a mapping from dynamical r-matrices on a pair
\L\subset \A to those on another pair \K\subset \A, where \K\subset
\L\subset \A is a chain of Lie algebras for which \L admits a reductive
decomposition as \L=\K+\M. Several known dynamical r-matrices appear
naturally in this setting, and its application provides new r-matrices, too. In
particular, we exhibit a family of r-matrices for which the dynamical variable
lies in the grade zero subalgebra of an extended affine Lie algebra obtained
from a twisted loop algebra based on an arbitrary finite dimensional self-dual
Lie algebra.Comment: 19 pages, LaTeX, added a reference and a footnote and removed some
typo
Quantization of a relativistic particle on the SL(2,R) manifold based on Hamiltonian reduction
A quantum theory is constructed for the system of a relativistic particle
with mass m moving freely on the SL(2,R) group manifold. Applied to the
cotangent bundle of SL(2,R), the method of Hamiltonian reduction allows us to
split the reduced system into two coadjoint orbits of the group. We find that
the Hilbert space consists of states given by the discrete series of the
unitary irreducible representations of SL(2,R), and with a positive-definite,
discrete spectrum.Comment: 12 pages, INS-Rep.-104
Hamiltonian reductions of free particles under polar actions of compact Lie groups
Classical and quantum Hamiltonian reductions of free geodesic systems of
complete Riemannian manifolds are investigated. The reduced systems are
described under the assumption that the underlying compact symmetry group acts
in a polar manner in the sense that there exist regularly embedded, closed,
connected submanifolds meeting all orbits orthogonally in the configuration
space. Hyperpolar actions on Lie groups and on symmetric spaces lead to
families of integrable systems of spin Calogero-Sutherland type.Comment: 15 pages, minor correction and updated references in v
Extended matrix Gelfand-Dickey hierarchies: reduction to classical Lie algebras
The Drinfeld-Sokolov reduction method has been used to associate with
extensions of the matrix r-KdV system. Reductions of these systems to the fixed
point sets of involutive Poisson maps, implementing reduction of to
classical Lie algebras of type , are here presented. Modifications
corresponding, in the first place to factorisation of the Lax operator, and
then to Wakimoto realisations of the current algebra components of the
factorisation, are also described.Comment: plain TeX, 12 page
The impact of physiologically relevant temperatures on physical properties of thylakoid membranes:a molecular dynamics study
Thylakoid membranes are energy-converting membranes with a unique lipid composition. Though the membranes are primarily composed of proteins, their photosynthetic function is strongly influenced by the lipid constituents. Here we characterize, with molecular dynamics (MD) simulations, lipid bilayers with compositions representative of plant thylakoid membranes. We determine, in a wide range of temperatures, the physical parameters of the model membranes which are relevant for the photosynthetic function. We found a marked impact of temperature on membrane permeability due to a combination of increased compressibility and curvature of the membrane at elevated temperatures. With increasing temperatures, we observed increasingly smeared transmembrane density profiles of the membrane forming lipid headgroups predicting increased membrane flexibility. The diffusion coefficient of the lipids increased with temperature without apparent specificity for lipid species. Instead of a comprehensive experimental dataset in the relevant temperature range, we quantitatively compared and validated our MD results with MD simulations on a dipalmitoylphosphatidylcholine model system.</p
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