214 research outputs found
On Casimir's Ghost
We define on the universal enveloping superalgebra of osp(1|2n) a nonstandard
adjoint action, endowing it with a module structure. This allows, in
particular, to construct a bosonic operator which anticommutes with all the
fermionic generators and which appears to be the square root of a certain
Casimir operator.Comment: LaTeX2e, 13 pages,also available at
http://lapphp0.in2p3.fr/preplapp/psth/ENSLAPP587.ps.gz ; one sentence removed
and a note added. Not a major revisio
Remote Data Acquisition for SPS 352 MHz Superconducting Cavities
The SPS Machine is equipped with four SuperConducting (SC) Cavities. These are used to accelerate the beams during the electron and positron cycles of LEP. During the last two years the control system for these cavities has been upgraded to the LEP standard environment but, as the diagnostic capabilities were not sufficient to ensure their reliable operation, it was decided to build a Data Acquisition system based on commercial products. The present system is based on National Instrument PXI (an extension to CompactPCI for instrumentation) with 166 MHz Pentium running Windows NT and Labview5.1. In order to meet the user requirements, in terms of portability and speed, a client/server approach has been used. The Server can acquire 16 signals at a rate of 1 ms during the whole SPS supercycle. The Client is composed of a virtual oscilloscope interface (one or four channels) with on-line signal and timing selections and automatic data and user setting storage capabilities. The Client can run on the two platforms used at CERN (PC and HP/UX)
Super Yangian Y(osp(1|2)) and the Universal R-matrix of its Quantum Double
We present the Drinfel'd realisation of the super Yangian Y(osp(1|2)),
including the explicit expression for the coproduct. We show in particular that
it is necessary to introduce supplementary Serre relations. The construction of
its quantum double is carried out. This allows us to give the universal
R-matrix of DY(osp(1|2)).Comment: Latex2e, 21 page
Classical and Quantum sl(1|2) Superalgebras, Casimir Operators and Quantum Chain Hamiltonians
We examine the two parameter deformed superalgebra and use
the results in the construction of quantum chain Hamiltonians. This study is
done both in the framework of the Serre presentation and in the -matrix
scheme of Faddeev, Reshetikhin and Takhtajan (FRT). We show that there exists
an infinite number of Casimir operators, indexed by integers in the
undeformed case and by in the deformed case, which obey quadratic
relations. The construction of the dual superalgebra of functions on
is also given and higher tensor product representations are
discussed. Finally, we construct quantum chain Hamiltonians based on the
Casimir operators. In the deformed case we find two Hamiltonians which describe
deformed models.Comment: 27 pages, LaTeX, one reference moved and one formula adde
On the Quasi-Hopf structure of deformed double Yangians
We construct universal twists connecting the centrally extended double
Yangian DY(sl(2))_c with deformed double Yangians DY_r(sl(2))_c, thereby
establishing the quasi-Hopf structures of the latter.Comment: 11 page
Sugawara and vertex operator constructions for deformed Virasoro algebras
From the defining exchange relations of the A_{q,p}(gl_{N}) elliptic quantum
algebra, we construct subalgebras which can be characterized as q-deformed W_N
algebras. The consistency conditions relating the parameters p,q,N and the
central charge c are shown to be related to the singularity structure of the
functional coefficients defining the exchange relations of specific vertex
operators representations of A_{q,p}({gl_{N}) available when N=2.Comment: 23 page
Control of total voltage in the large distributed RF system of LEP
The LEP RF system is made up of a large number of independent RF units situated around the ring near the interaction points. These have different available RF voltages depending on their type and they may be inactive or unable to provide full voltage for certain periods. The original RF voltage control system was based on local RF unit voltage function generators pre-loaded with individual tables for energy ramping. This was replaced this year by a more flexible global RF voltage control system. A central controller in the main control room has direct access to the units over the LEP TDM system via multiplexers and local serial links. It continuously checks the state of all the units and adjusts their voltages to maintain the desired total voltage under all conditions. This voltage is distributed among the individual units to reduce the adverse effects of RF voltage asymmetry around the machine as far as possible. The central controller is a VME system with 68040 CPU and real time multitasking operating system. Event driven communication handlers allow fast reliable concurrent data communication with the remote units. The RF unit low level RF G64 equipment controllers use a VME 68030 CPU to achieve the necessary response time and reliability
Integrable XYZ Model with Staggered Anisotropy Parameter
We apply to the XYZ model the technique of construction of integrable models
with staggered parameters, presented recently for the XXZ case. The solution of
modified Yang-Baxter equations is found and the corresponding integrable
zig-zag ladder Hamiltonian is calculated. The result is coinciding with the XXZ
case in the appropriate limit.Comment: 8 pages ; epic packag
Duality and Representations for New Exotic Bialgebras
We find the exotic matrix bialgebras which correspond to the two
non-triangular nonsingular 4x4 R-matrices in the classification of Hietarinta,
namely, R_{S0,3} and R_{S1,4}. We find two new exotic bialgebras S03 and S14
which are not deformations of the of the classical algebras of functions on
GL(2) or GL(1|1). With this we finalize the classification of the matrix
bialgebras which unital associative algebras generated by four elements. We
also find the corresponding dual bialgebras of these new exotic bialgebras and
study their representation theory in detail. We also discuss in detail a
special case of R_{S1,4} in which the corresponding algebra turns out to be a
special case of the two-parameter quantum group deformation GL_{p,q}(2).Comment: 33 pages, LaTeX2e, using packages: cite,amsfonts,amsmath,subeqn;
reference updated; v3: corrections in subsection 3.
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