266 research outputs found
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
The triviality bound on the Higgs mass; its value and what it means
Older lattice work exploring the Higgs mass triviality bound is briefly
reviewed. It indicates that a strongly interacting scalar sector in the minimal
standard model cannot exist; on the other hand low energy QCD phenomenology
might be interpreted as an indication that it could. We attack this puzzle
using the expansion and discover a simple criterion for selecting a
lattice action that is more likely to produce a heavy Higgs particle. Depending
on the precise form of the limitation put on the cutoff effects, our large
calculations, when combined with old numerical data, suggest that the Higgs
mass bound might be around 750 , which is higher than the
previously obtained. Preliminary numerical work indicates that an increase of
at least 19\% takes place at on the lattice when the old simple
action is replaced with a new action (still containing only nearest neighbor
interactions) if one uses the lattice spacing as the physical cutoff for both
actions. It appears that, while a QCD like theory could produce , a meaningful ``minimal elementary Higgs'' theory cannot have M_H/ F~
\gtapprox 3. Still, even at 750 , the Higgs particle is so wide (GeV), that one cannot argue any more that the scalar sector is weakly
coupled.Comment: 8 pages. Latex file with 4 ps figures included. Preprint RU-92-22,
SCRI-92-11
Domain wall fermions and applications
Domain wall fermions provide a complimentary alternative to traditional
lattice fermion approaches. By introducing an extra dimension, the amount of
chiral symmetry present in the lattice theory can be controlled in a linear
way. This results in improved chiral properties as well as robust topological
zero modes. A brief introduction on the subject and a discussion of chiral
properties and applications, such as zero and finite temperature QCD, N = 1
super Yang-Mills, and four-fermion theories, is presented.Comment: Contribution to Lattice 2000 (Plenary), LaTeX, 12 pages, 15 eps
figure
The staggered domain wall fermion method
A different lattice fermion method is introduced. Staggered domain wall
fermions are defined in 2n+1 dimensions and describe 2^n flavors of light
lattice fermions with exact U(1) x U(1) chiral symmetry in 2n dimensions. As
the size of the extra dimension becomes large, 2^n chiral flavors with the same
chiral charge are expected to be localized on each boundary and the full
SU(2^n) x SU(2^n) flavor chiral symmetry is expected to be recovered. SDWF give
a different perspective into the inherent flavor mixing of lattice fermions and
by design present an advantage for numerical simulations of lattice QCD
thermodynamics. The chiral and topological index properties of the SDWF Dirac
operator are investigated. And, there is a surprise ending...Comment: revtex4, 7 figures, minor revisions, 2 references adde
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
Solomonoff Induction Violates Nicod's Criterion
Nicod's criterion states that observing a black raven is evidence for the
hypothesis H that all ravens are black. We show that Solomonoff induction does
not satisfy Nicod's criterion: there are time steps in which observing black
ravens decreases the belief in H. Moreover, while observing any computable
infinite string compatible with H, the belief in H decreases infinitely often
when using the unnormalized Solomonoff prior, but only finitely often when
using the normalized Solomonoff prior. We argue that the fault is not with
Solomonoff induction; instead we should reject Nicod's criterion.Comment: ALT 201
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