804 research outputs found
The Nambu--Jona-Lasinio Model of QCD on the Lattice
In an effort to investigate some of the low energy properties of QCD, in
particular those related to chiral symmetry breaking, as well as to obtain
insights on the behavior of an interacting theory of fermions on the lattice,
the two flavor Nambu--Jona-Lasinio model with chiral
symmetry is studied on the four--dimensional hypercubic lattice using large
techniques and numerical simulations. Naive and Wilson fermions are considered
and transparent results are obtained regarding the following: the scalar and
pseudoscalar spectrum, the approach to the continuum and chiral limits, the
size of the corrections, and the effects of the zero momentum fermionic
modes on finite lattices. Also, some interesting observations are made by
viewing the model as an embedding theory of the Higgs sector. Note: The full ps
file of this preprint is also available via anonymous ftp to ftp.scri.fsu.edu.
To get the ps file, ftp to this address and use for username "anonymous" and
for password your name. The file is in the directory pub/vranas (to go to that
directory type: cd pub/vranas) and is called NJL.ps (to get it type: get
NJL.ps)Comment: 10 pages, LaTex file. FSU-SCRI-93-12
Regularization dependence of the Higgs mass triviality bound
We calculate the triviality bound on the Higgs mass in scalar field theory
models whose global symmetry group has been replaced by and has been taken to infinity.
Limits on observable cutoff effects at four percent in several regularized
models with tunable couplings in the bare action yield triviality bounds
displaying a large degree of universality. Extrapolating from to
we conservatively estimate that a Higgs particle with mass up to
and width up to is realizable without large cutoff
effects, indicating that strong scalar self interactions in the standard model
are not ruled out. We also present preliminary numerical results of the
physical case for the lattice that are in agreement with the large
expectations. Note: The full ps file is also available via anonymous ftp to
ftp.scri.fsu.edu. To get the ps file, ftp to this address and use for username
"anonymous" and for password your name. The file is in the directory pub/vranas
(to go to that directory type: cd pub/vranas) and is called lat92_proc.ps (to
get it type: get lat92_proc.ps)Comment: 5 pages with 5 ps figures included. LaTex file. Contribution to the
LAT92 proceedings. Preprint, FSU-SCRI-92-150, RU-92-4
The finite temperature QCD phase transition with domain wall fermions
Results from the Columbia lattice group study of the QCD finite temperature
phase transition with dynamical domain wall fermions on
lattices are presented. These results include an investigation of the U(1)
axial symmetry breaking above but close to the transition, the use of zero
temperature calculations that set the scale at the transition and preliminary
measurements close to the transition.Comment: LATTICE99(hightemp), LaTeX, 3 pages, 3 eps figure
Interacting staggered domain wall fermions
The behavior of staggered domain wall fermions in the presence of gauge
fields is presented. In particular, their response to gauge fields with
nontrivial topology is discussed.Comment: Lattice2002(Chiral) proceedings, LaTeX, 3 pages 2 eps figure
On the Perturbation of the Three-Dimensional Stokes Flow of Micropolar Fluids by a Constant Uniform Magnetic Field in a Circular Cylinder
Modern engineering technology involves the micropolar magnetohydrodynamic flow of magnetic fluids. Here, we consider a colloidal suspension of non-conductive ferromagnetic material, which consists of small spherical particles that behave as rigid magnetic dipoles, in a carrier liquid of approximately zero conductivity and low-Reynolds number properties. The interaction of a 3D constant uniform magnetic field with the three-dimensional steady creeping motion (Stokes flow) of a viscous incompressible micropolar fluid in a circular cylinder is investigated, where the magnetization of the ferrofluid has been taken into account and the magnetic Stokes partial differential equations have been presented. Our goal is to apply the proper boundary conditions, so as to obtain the flow fields in a closed analytical form via the potential representation theory, and to study several characteristics of the flow. In view of this aim, we make use of an improved new complete and unique differential representation of magnetic Stokes flow, valid for non-axisymmetric geometries, which provides the velocity and total pressure fields in terms of easy-to-find potentials. We use these results to simulate the creeping flow of a magnetic fluid inside a circular duct and to obtain the flow fields associated with this kind of flow
Calm Multi-Baryon Operators
Outstanding problems in nuclear physics require input and guidance from
lattice QCD calculations of few baryons systems. However, these calculations
suffer from an exponentially bad signal-to-noise problem which has prevented a
controlled extrapolation to the physical point. The variational method has been
applied very successfully to two-meson systems, allowing for the extraction of
the two-meson states very early in Euclidean time through the use of improved
single hadron operators. The sheer numerical cost of using the same techniques
in two-baryon systems has been prohibitive. We present an alternate strategy
which offers some of the same advantages as the variational method while being
significantly less numerically expensive. We first use the Matrix Prony method
to form an optimal linear combination of single baryon interpolating fields
generated from the same source and different sink interpolators. Very early in
Euclidean time this linear combination is numerically free of excited state
contamination, so we coin it a calm baryon. This calm baryon operator is then
used in the construction of the two-baryon correlation functions.
To test this method, we perform calculations on the WM/JLab iso-clover gauge
configurations at the SU(3) flavor symmetric point with m{\pi} 800 MeV
--- the same configurations we have previously used for the calculation of
two-nucleon correlation functions. We observe the calm baryon removes the
excited state contamination from the two-nucleon correlation function to as
early a time as the single-nucleon is improved, provided non-local (displaced
nucleon) sources are used. For the local two-nucleon correlation function
(where both nucleons are created from the same space-time location) there is
still improvement, but there is significant excited state contamination in the
region the single calm baryon displays no excited state contamination.Comment: 8 pages, 3 figures, proceedings for LATTICE 201
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