10,092 research outputs found
The quantum integrable system
The quantum integrable system is a 3D system with rational potential
related to the non-crystallographic root system . It is shown that the
gauge-rotated Hamiltonian as well as one of the integrals, when written
in terms of the invariants of the Coxeter group , is in algebraic form: it
has polynomial coefficients in front of derivatives. The Hamiltonian has
infinitely-many finite-dimensional invariant subspaces in polynomials, they
form the infinite flag with the characteristic vector \vec \al\ =\ (1,2,3).
One among possible integrals is found (of the second order) as well as its
algebraic form. A hidden algebra of the Hamiltonian is determined. It is
an infinite-dimensional, finitely-generated algebra of differential operators
possessing finite-dimensional representations characterized by a generalized
Gauss decomposition property. A quasi-exactly-solvable integrable
generalization of the model is obtained. A discrete integrable model on the
uniform lattice in a space of -invariants "polynomially"-isospectral to
the quantum model is defined.Comment: 32 pages, 3 figure
Hadron spectroscopy and static quark potential in full QCD: A comparison of improved actions on the CP-PACS
We present first results from a full QCD calculation on the CP-PACS,
comparing various actions at and --0.9. We use the plaquette and a renormalization group improved action for
the gluons, and the Wilson and the SW-Clover action for quarks. We find that
significant improvements in the hadron spectrum results from improving the
quarks, while the gluon improvement is required for a rotationally invariant
static potential. An ongoing effort towards exploring the chiral limit in full
QCD is described.Comment: 6 pages, based on talks presented by R. Burkhalter and T. Kaneko at
Lattice97, Edinburg
Shuttle orbiter Ku-band radar/communications system design evaluation: High gain antenna/widebeam horn
The physical characteristics of the high gain antenna reflector and feed elements are described. Deficiencies in the sum feed are discussed, and lack of atmospheric venting is posed as a potential problem area. The measured RF performance of the high gain antenna is examined and the high sidelobe levels measured are related to the physical characteristics of the antenna. An examination of the attributes of the feed which might be influenced by temperature extremes shows that the antenna should be insensitive to temperature variations. Because the feed support bipod structure is considered a significant contributor to the high sidelobe levels measured in the azimuth plane, pod relocation, material changes, and shaping are suggested as improvements. Alternate feed designs are presented to further improve system performance. The widebeam horn and potential temperature effects due to the polarizer are discussed as well as in the effects of linear polarization on TDRS acquisition, and the effects of circular polarization on radar sidelobe avoidance. The radar detection probability is analyzed as a function of scan overlap and target range
The Internal Control System of Russian Corporations
corporate form, organizational behavior, institutional complementarity, stock ownership, corporate governance, separation of ownership and management, ownership structure, corporate performance, managerial turnover, Russia
Full QCD simulation on CP-PACS
A status report is made of an on-going full QCD study on the CP-PACS aiming
at a comparative analysis of the effects of improving gauge and quark actions
on hadronic quantities and static quark potential. Simulations are made for
four action combinations, the plaquette or an RG-improved action for gluons and
the Wilson or SW-clover action for quarks, at -1.3GeV and
-0.9. Results demonstrate clearly that the clover
term markedly reduces discretization errors for hadron spectrum, while adding
six-link terms to the plaquette action leads to much better rotational symmetry
in the potential. These results extend experience with quenched simulations to
full QCD.Comment: Talk presented by K. Kanaya at the International Workshop on
``LATTICE QCD ON PARALLEL COMPUTERS'', 10-15 March 1997, Center for
Computational Physics, University of Tsukub
Thermodynamics with Dynamical Clover Fermions
We investigate the finite temperature behavior of nonperturbatively improved
clover fermions on lattices with temporal extent N_t=4 and 6. Unfortunately in
the gauge coupling range, where the clover coefficient has been determined
nonperturbatively, the finite temperature crossover/transition occurs at heavy
pseudoscalar masses and large pseudoscalar to vector meson mass ratios.
However, on an N_t=6 lattice the thermal crossover for the improved fermions is
much smoother than for unimproved Wilson fermions and no strange metastable
behavior is observed.Comment: 8 pages, LaTeX, 5 postscript figure
Preliminary Centaur Systems Analysis
The Centaur is stored in the Orbiter payload bay on the Centaur Integrated Support System (CISS). The CISS not only cradles the Centaur prior to deployment but also provides any signal conditioning required to make the Centaur/Orbiter hardwire interfaces compatible. In addition, the CISS provides other Centaur functions such as controlling all the avionics safety features and providing all the helium supplies for tank pressurizations. Problems associated with a Centaur design concept using a transponder and two switchable antennas are defined. Solutions to these problems are presented
Phase structure of lattice QCD for general number of flavors
We investigate the phase structure of lattice QCD for the general number of
flavors in the parameter space of gauge coupling constant and quark mass,
employing the one-plaquette gauge action and the standard Wilson quark action.
Performing a series of simulations for the number of flavors --360 with
degenerate-mass quarks, we find that when there is a line of a bulk
first order phase transition between the confined phase and a deconfined phase
at a finite current quark mass in the strong coupling region and the
intermediate coupling region. The massless quark line exists only in the
deconfined phase. Based on these numerical results in the strong coupling limit
and in the intermediate coupling region, we propose the following phase
structure, depending on the number of flavors whose masses are less than
which is the physical scale characterizing the phase transition in
the weak coupling region: When , there is only a trivial IR fixed
point and therefore the theory in the continuum limit is free. On the other
hand, when , there is a non-trivial IR fixed point and
therefore the theory is non-trivial with anomalous dimensions, however, without
quark confinement. Theories which satisfy both quark confinement and
spontaneous chiral symmetry breaking in the continuum limit exist only for .Comment: RevTeX, 20 pages, 43 PS figure
Non-perturbative determination of anisotropy coefficients in lattice gauge theories
We propose a new non-perturbative method to compute derivatives of gauge
coupling constants with respect to anisotropic lattice spacings (anisotropy
coefficients), which are required in an evaluation of thermodynamic quantities
from numerical simulations on the lattice. Our method is based on a precise
measurement of the finite temperature deconfining transition curve in the
lattice coupling parameter space extended to anisotropic lattices by applying
the spectral density method. We test the method for the cases of SU(2) and
SU(3) gauge theories at the deconfining transition point on lattices with the
lattice size in the time direction -- 6. In both cases, there is a
clear discrepancy between our results and perturbative values. A longstanding
problem, when one uses the perturbative anisotropy coefficients, is a
non-vanishing pressure gap at the deconfining transition point in the SU(3)
gauge theory. Using our non-perturbative anisotropy coefficients, we find that
this problem is completely resolved: we obtain and
on and 6 lattices, respectively.Comment: 24pages,7figures,5table
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