13,724 research outputs found
The Schr\"odinger Functional for Improved Gluon and Quark Actions
The Schr\"odinger Functional (quantum/lattice field theory with Dirichlet
boundary conditions) is a powerful tool in the non-perturbative improvement and
for the study of other aspects of lattice QCD. Here we adapt it to improved
gluon and quark actions, on isotropic as well as anisotropic lattices.
Specifically, we describe the structure of the boundary layers, obtain the
exact form of the classically improved gauge action, and outline the
modifications necessary on the quantum level. The projector structure of
Wilson-type quark actions determines which field components can be specified at
the boundaries. We derive the form of O(a) improved quark actions and describe
how the coefficients can be tuned non-perturbatively. There is one coefficient
to be tuned for an isotropic lattice, three in the anisotropic case.
Our ultimate aim is the construction of actions that allow accurate
simulations of all aspects of QCD on coarse lattices.Comment: 39 pages, LaTeX, 11 embedded eps file
QCD String Spectrum 2002
Results from a comprehensive new analysis on the excitation spectrum of the
QCD string are presented. A rapid onset of string formation is observed in the
spectrum on a length scale of 2 fm, with Dirichlet boundary conditions. The
crossover from the short distance spectrum towards string excitations and an
observed fine structure in the 1--3 fm range are related to effective string
theory. The deficiencies of the Nambu-Goto bosonic string model in describing
the observed spectrum are briefly discussed.Comment: Lattice2002(topology), 3 pages, 2 figure
Study of unstable particle through the spectral function in O(4) theory
We test application of the maximum entropy method to decompose the states
contributing to the unstable correlation function through the spectral
function in the four dimensional O(4) theory. Reliable results are
obtained for the mass and two-particle state energy using
only the correlation function. We also find that the property of the
particle is different between the unstable ()
and stable () cases.Comment: Lattice2002(spectrum), 3 page
Spectral analysis of semigroups and growth-fragmentation equations
The aim of this paper is twofold: (1) On the one hand, the paper revisits the
spectral analysis of semigroups in a general Banach space setting. It presents
some new and more general versions, and provides comprehensible proofs, of
classical results such as the spectral mapping theorem, some (quantified)
Weyl's Theorems and the Krein-Rutman Theorem. Motivated by evolution PDE
applications, the results apply to a wide and natural class of generators which
split as a dissipative part plus a more regular part, without assuming any
symmetric structure on the operators nor Hilbert structure on the space, and
give some growth estimates and spectral gap estimates for the associated
semigroup. The approach relies on some factorization and summation arguments
reminiscent of the Dyson-Phillips series in the spirit of those used in
[87,82,48,81]. (2) On the other hand, we present the semigroup spectral
analysis for three important classes of "growth-fragmentation" equations,
namely the cell division equation, the self-similar fragmentation equation and
the McKendrick-Von Foerster age structured population equation. By showing that
these models lie in the class of equations for which our general semigroup
analysis theory applies, we prove the exponential rate of convergence of the
solutions to the associated remarkable profile for a very large and natural
class of fragmentation rates. Our results generalize similar estimates obtained
in \cite{MR2114128,MR2536450} for the cell division model with (almost)
constant total fragmentation rate and in \cite{MR2832638,MR2821681} for the
self-similar fragmentation equation and the cell division equation restricted
to smooth and positive fragmentation rate and total fragmentation rate which
does not increase more rapidly than quadratically. It also improves the
convergence results without rate obtained in \cite{MR2162224,MR2114413} which
have been established under similar assumptions to those made in the present
work
Hot air ballon deceleration and recovery system Patent
Development and characteristics of hot air balloon deceleration and recovery syste
CP breaking in lattice chiral gauge theory
The CP symmetry is not manifestly implemented for the local and doubler-free
Ginsparg-Wilson operator in lattice chiral gauge theory. We precisely identify
where the effects of this CP breaking appear.Comment: 3 pages, Lattice2002(chiral
In vitro transformation of lymphoid cells by Abelson murine leukemia virus
Cell cultures prepared from fetal murine liver were infected by Abelson murine leukemia virus. After about 2 weeks, proliferating cells of lymphoid morphology appeared in some of the cultures. Addition of 2-mercaptoethanol to the initial culture medium greatly enhanced the appearance of the lymphoid cells. Immunoglobulin determinants were evident on the cells in some cultures. Continuous passage of the cells in certain cultures was possible and the passaged cells could form tumors after animal inoculation. Because Abelson murine leukemia virus is able to induce in vitro malignant transformation of lymphoid cells, it probably causes leukemia by directly affecting cellular growth control
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