146 research outputs found
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 Induced Quark Masses in Topologically-Nontrivial Background
In the domain-wall formulation of chiral fermion, the finite separation
between domain-walls () induces an effective quark mass ()
which complicates the chiral limit. In this work, we study the size of the
effective mass as the function of and the domain-wall height by
calculating the smallest eigenvalue of the hermitian domain-wall Dirac operator
in the topologically-nontrivial background fields. We find that, just like in
the free case, decreases exponentially in with a rate
depending on . However, quantum fluctuations amplify the wall effects
significantly. Our numerical result is consistent with a previous study of the
effective mass from the Gell-Mann-Oakes-Renner relation.Comment: 10 pages, an appendix and minor changes adde
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
Adjoint Wilson Line in SU(2) Lattice Gauge Theory
The behavior of the adjoint Wilson line in finite-temperature, ,
lattice gauge theory is discussed. The expectation value of the line and the
associated excess free energy reveal the response of the finite-temperature
gauge field to the presence of an adjoint source. The value of the adjoint line
at the critical point of the deconfining phase transition is highlighted. This
is not calculable in weak or strong coupling. It receives contributions from
all scales and is nonanalytic at the critical point. We determine the general
form of the free energy. It includes a linearly divergent term that is
perturbative in the bare coupling and a finite, nonperturbative piece. We use a
simple flux tube model to estimate the value of the nonperturbative piece. This
provides the normalization needed to estimate the behavior of the line as one
moves along the critical curve into the weak coupling region.Comment: 21 pages, no figures, Latex/Revtex 3, UCD-93-1
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
High Energy Physics from High Performance Computing
We discuss Quantum Chromodynamics calculations using the lattice regulator.
The theory of the strong force is a cornerstone of the Standard Model of
particle physics. We present USQCD collaboration results obtained on Argonne
National Lab's Intrepid supercomputer that deepen our understanding of these
fundamental theories of Nature and provide critical support to frontier
particle physics experiments and phenomenology.Comment: Proceedings of invited plenary talk given at SciDAC 2009, San Diego,
June 14-18, 2009, on behalf of the USQCD collaboratio
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