2,042 research outputs found
Undoubled Chiral Fermions on a Lattice
We analyze the dynamics of an chiral theory on the
lattice with a strong multifermion coupling. It is shown that no spontaneous
symmetry breaking occurs; the ``spectator'' fermion is a free mode;
doublers are decoupled as massive Dirac fermions consistently with the chiral
symmetries. In 1+1 dimension, we show that the right-handed three-fermion state
disappears at the threshold and an undoubled left-handed chiral fermion remains
in the continuum limit.Comment: Talk presented at LATTICE96 (chiral gauge), Late
Getting Around the Nielsen-Ninomiya Theorem, towards the Rome Approach
The ``no-go'' theorem of Nielsen and Ninomiya has been the most tenacious
obstacle against the construction of a chiral gauge theory with reasonable low
energy spectrum, couplings and anomaly. In this paper we construct a model
which supplements the usual (bilinear in the Fermi fields) lagrangian with
quadrilinear fermionic terms. We show that in a certain region of the parameter
space the difficulties of the ``no-go'' theorem may be overcome, and a
``renormalized'' perturbative strategy can be carried out, akin to the one
followed in the Rome Approach (RA), whose counterterms are forced to be gauge
invariant.Comment: LaTex 12 pages, the version to appear in Phys. Lett.
Mass Relation Between Top and Bottom Quarks
In the framework of the recently proposed electroweak theory on a Planck
lattice, we are able to solve approximately the lattice Dyson equation for the
fermion self-energy functions, and obtain the ratio between the masses of the
and quarks in terms of the electroweak coupling constants. The
predicted top mass agrees with recent determinations from electroweak
observables.Comment: To appear in Phys. Lett. B, 8 pages + 3 figure
Nuclear halo and the coherent nuclear interaction
The unusual structure of Li11, the first halo nucleus found, is analyzed by
the Preparata model of nuclear structure. By applying Coherent Nucleus Theory,
we obtain an interaction potential for the halo-neutrons that rightly
reproduces the fundamental state of the system.Comment: 9 pages Submitted to International Journal of Modern Physics E
(IJMPE
A possible scaling region of chiral fermions on a lattice
We present the details of analyzing an chiral theory
with multifermion couplings on a lattice. An existence of a possible scaling
region in the phase space of multifermion couplings for defining the continuum
limit of chiral fermions is advocated. In this scaling region, no spontaneous
symmetry breaking occurs; the ``spectator'' fermion is a free mode
and decoupled; doublers are decoupled as massive Dirac fermions consistently
with the chiral symmetry, whereas the normal mode of
is plausibly speculated to be chiral in the continuum limit. This
is not in agreement with the general belief of the definite failure of theories
so constructed.Comment: 32 pages, Latex and 5 figures, to appear in Nucl. Phys.
A Probabilistic Analysis of the Power of Arithmetic Filters
The assumption of real-number arithmetic, which is at the basis of
conventional geometric algorithms, has been seriously challenged in recent
years, since digital computers do not exhibit such capability.
A geometric predicate usually consists of evaluating the sign of some
algebraic expression. In most cases, rounded computations yield a reliable
result, but sometimes rounded arithmetic introduces errors which may invalidate
the algorithms. The rounded arithmetic may produce an incorrect result only if
the exact absolute value of the algebraic expression is smaller than some
(small) varepsilon, which represents the largest error that may arise in the
evaluation of the expression. The threshold varepsilon depends on the structure
of the expression and on the adopted computer arithmetic, assuming that the
input operands are error-free.
A pair (arithmetic engine,threshold) is an "arithmetic filter". In this paper
we develop a general technique for assessing the efficacy of an arithmetic
filter. The analysis consists of evaluating both the threshold and the
probability of failure of the filter.
To exemplify the approach, under the assumption that the input points be
chosen randomly in a unit ball or unit cube with uniform density, we analyze
the two important predicates "which-side" and "insphere". We show that the
probability that the absolute values of the corresponding determinants be no
larger than some positive value V, with emphasis on small V, is Theta(V) for
the which-side predicate, while for the insphere predicate it is Theta(V^(2/3))
in dimension 1, O(sqrt(V)) in dimension 2, and O(sqrt(V) ln(1/V)) in higher
dimensions. Constants are small, and are given in the paper.Comment: 22 pages 7 figures Results for in sphere test inproved in
cs.CG/990702
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