4,695 research outputs found
Changes in methanogenic populations residing in the rumen of dairy cows in response to a sainfoin (Onobrychis viciifolia Scop.) based diet
Baryonic Operators for Lattice Simulations
The construction of baryonic operators for determining the N* excitation
spectrum is discussed. The operators are designed with one eye towards
maximizing overlaps with the low-lying states of interest, and the other eye
towards minimizing the number of sources needed in computing the required quark
propagators. Issues related to spin identification are outlined. Although we
focus on tri-quark baryon operators, the construction method is applicable to
both mesons and penta-quark operators.Comment: 3 pages, poster presented at Lattice2003(spectrum), Tsukuba, Japan,
July 15-19, 200
Adjoint bi-continuous semigroups and semigroups on the space of measures
For a given bi-continuous semigroup T on a Banach space X we define its
adjoint on an appropriate closed subspace X^o of the norm dual X'. Under some
abstract conditions this adjoint semigroup is again bi-continuous with respect
to the weak topology (X^o,X). An application is the following: For K a Polish
space we consider operator semigroups on the space C(K) of bounded, continuous
functions (endowed with the compact-open topology) and on the space M(K) of
bounded Baire measures (endowed with the weak*-topology). We show that
bi-continuous semigroups on M(K) are precisely those that are adjoints of a
bi-continuous semigroups on C(K). We also prove that the class of bi-continuous
semigroups on C(K) with respect to the compact-open topology coincides with the
class of equicontinuous semigroups with respect to the strict topology. In
general, if K is not Polish space this is not the case
Signal at subleading order in lattice HQET
We discuss the correlators in lattice HQET that are needed to go beyond the
static theory. Based on our implementation in the Schr\"odinger functional we
focus on their signal-to-noise ratios and check that a reasonable statistical
precision can be reached in quantities like and .Comment: 3 pages, Lattice2004(heavy), v2: corrected definition of X^{kin/spin
The Divertor Tokamak Test facility proposal: Physical requirements and reference design
The main goal of the Divertor Tokamak Test facility (DTT) is to explore alternative power exhaust solutions for DEMO. The principal objective is to mitigate the risk of a difficult extrapolation to fusion reactor of the conventional divertor based on detached conditions under test on ITER. The task includes several issues, as: (i) demonstrating a heat exhaust system capable of withstanding the large load of DEMO in case of inadequate radiated power fraction; (ii) closing the gaps in the exhaust area that cannot be addressed by present devices; (iii) demonstrating how the possible implemented solutions (e.g., advanced divertor configurations or liquid metals) can be integrated in a DEMO device. In view of these goals, the basic physical DTT parameters have been selected according to the following guidelines: (i) edge conditions as close as possible to DEMO in terms of dimensionless parameters; (ii) flexibility to test a wide set of divertor concepts and techniques; (iii) compatibility with bulk plasma performance; (iv) an upper bound of 500 M€ for the investment costs. © 2017 The Author
Effectiveness of the Chebyshev Approximation in Magnetic Field Line Tracking
The tracking of magnetic field lines can be very expensive, in terms of computational burden, when the field sources are numerous and have complex geometries, especially when accuracy is a priority, because an evaluation of the field is required in many situations. In some important applications, the computational cost can be significantly reduced by using a suitable approximation of the field in the integrated regions. This paper shows how Chebyshev polynomials are well-suited for field interpolation in magnetic field-line tracking, then discusses the conditions in which they are most appropriate, and quantifies the effectiveness of parallel computing in the approximation procedures
Baryon operators and spectroscopy in lattice QCD
The construction of the operators and correlators required to determine the
excited baryon spectrum is presented, with the aim of exploring the spatial and
spin structure of the states while minimizing the number of propagator
inversions. The method used to construct operators that transform irreducibly
under the symmetries of the lattice is detailed, and the properties of example
operators are studied using domain-wall fermion valence propagators computed on
MILC asqtad dynamical lattices.Comment: 7 pages, 2 figures, to appear in Proceedings of Workshop on Lattice
Hadron Physics 2003, Cairns, Australia, July 22 - July 30, 200
A New Way to Set the Energy Scale in Lattice Gauge Theories and its Application to the Static Force and in SU(2) Yang--Mills Theory
We introduce a hadronic scale through the force between static
quarks at intermediate distances . The definition amounts
to ~fm in phenomenological potential models. Since is
well defined and can be calculated accurately in a Monte Carlo simulation, it
is an ideal quantity to set the scale. In SU(2) pure gauge theory, we use new
data (and to set the scale) to extrapolate to the continuum limit
for distances ~fm to ~fm. Through we determine the energy
scale in the recently calculated running coupling, which used the recursive
finite size technique to reach large energy scales. Also in this case, the
lattice data can be extrapolated to the continuum limit. The use of one loop
Symanzik improvement is seen to reduce the lattice spacing dependence
significantly.
Warning: The preprint is not completely fresh, but maybe you haven't seen
it...Comment: accepted in Nucl. Phys. B, 18 pages postscript-file with all figure
Developement of real time diagnostics and feedback algorithms for JET in view of the next step
Real time control of many plasma parameters will be an essential aspect in
the development of reliable high performance operation of Next Step Tokamaks.
The main prerequisites for any feedback scheme are the precise real-time
determination of the quantities to be controlled, requiring top quality and
highly reliable diagnostics, and the availability of robust control algorithms.
A new set of real time diagnostics was recently implemented on JET to prove the
feasibility of determining, with high accuracy and time resolution, the most
important plasma quantities. With regard to feedback algorithms, new
model–based controllers were developed to allow a more robust control of
several plasma parameters. Both diagnostics and algorithms were successfully
used in several experiments, ranging from H-mode plasmas to configuration with
ITBs. Since elaboration of computationally heavy measurements is often
required, significant attention was devoted to non-algorithmic methods like
Digital or Cellular Neural/Nonlinear Networks. The real time hardware and
software adopted architectures are also described with particular attention to
their relevance to ITER.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
Bounds on the Wilson Dirac Operator
New exact upper and lower bounds are derived on the spectrum of the square of
the hermitian Wilson Dirac operator. It is hoped that the derivations and the
results will be of help in the search for ways to reduce the cost of
simulations using the overlap Dirac operator. The bounds also apply to the
Wilson Dirac operator in odd dimensions and are therefore relevant to domain
wall fermions as well.Comment: 16 pages, TeX, 3 eps figures, small corrections and improvement
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