8,843 research outputs found
A Scalar Wigner Theory for Polarized Light in Nonlinear Kerr Media
A scalar Wigner distribution function for describing polarized light is
proposed in analogy with the treatment of spin variables in quantum kinetic
theory. The formalism is applied to the propagation of circularly polarized
light in nonlinear Kerr media and an extended phase space evolution equation is
derived along with invariant quantities. We further consider modulation
instability as well as the extension to partially coherent fields.Comment: 6 page
Higgs Pain? Take a Preon!
The Higgs mechanism is the favourite cure for the main problem with
electroweak unification, namely how to reconcile a gauge theory with the need
for massive gauge bosons. This problem does not exist in preon models for quark
and lepton substructure with composite and s, which, consequently,
also avoid all other theoretical complications and paradoxes with the Higgs
mechanism. We present a new, minimal preon model, which explains the family
structure, and predicts several new, heavy quarks, leptons and vector bosons.
Our preons obey a phenomenological supersymmetry, but without so-called squarks
and sleptons, since this SUSY is effective only on the composite scale.Comment: The preon contents of some quarks and leptons have been changed in
order to achieve a more consistent scheme. A few new comments have been
added. 13 pages, LaTeX, no figures. To be published in Proc. of the Meeting
on 'The Fundamental Structure of Matter' and 'Tests of the Electroweak
Symmetry Breaking', Ouranoupolis, Greece, May 199
Preon Trinity
We present a new minimal model for the substructure of all known quarks,
leptons and weak gauge bosons, based on only three fundamental and stable
spin-1/2 preons. As a consequence, we predict three new quarks, three new
leptons, and six new vector bosons. One of the new quarks has charge .
The model explains the apparent conservation of three lepton numbers, as well
as the so-called Cabibbo-mixing of the and quarks, and predicts
electromagnetic decays or oscillations between the neutrinos
() and (). Other neutrino oscillations, as well
as rarer quark mixings and CP violation can come about due to a small
quantum-mechanical mixing of two of the preons in the quark and lepton wave
functions.Comment: 5 pages, Latex, no figure
The Pfaffian quantum Hall state made simple--multiple vacua and domain walls on a thin torus
We analyze the Moore-Read Pfaffian state on a thin torus. The known six-fold
degeneracy is realized by two inequivalent crystalline states with a four- and
two-fold degeneracy respectively. The fundamental quasihole and quasiparticle
excitations are domain walls between these vacua, and simple counting arguments
give a Hilbert space of dimension for holes and particles
at fixed positions and assign each a charge . This generalizes the
known properties of the hole excitations in the Pfaffian state as deduced using
conformal field theory techniques. Numerical calculations using a model
hamiltonian and a small number of particles supports the presence of a stable
phase with degenerate vacua and quarter charged domain walls also away from the
thin torus limit. A spin chain hamiltonian encodes the degenerate vacua and the
various domain walls.Comment: 4 pages, 1 figure. Published, minor change
Microscopic theory of the quantum Hall hierarchy
We solve the quantum Hall problem exactly in a limit and show that the ground
states can be organized in a fractal pattern consistent with the
Haldane-Halperin hierarchy, and with the global phase diagram. We present wave
functions for a large family of states, including those of Laughlin and Jain
and also for states recently observed by Pan {\it et. al.}, and show that they
coincide with the exact ones in the solvable limit. We submit that they
establish an adiabatic continuation of our exact results to the experimentally
accessible regime, thus providing a unified approach to the hierarchy states.Comment: 4 pages, 2 figures. Publishe
Moths sense but do not learn flower odors with their proboscis during flower investigation
Insect pollinators, such as the tobacco hawkmoth Manduca sexta, are known for locating flowers and learning floral odors by using their antennae. A recent study revealed, however, that the tobacco hawkmoth additionally possesses olfactory sensilla at the tip of its proboscis. Here, we asked whether this second ânoseâ of the hawkmoth is involved in odor learning, similar to the antennae. We first show that M. sexta foraging efficiency at Nicotiana attenuata flowers increases with experience. This raises the question whether olfactory learning with the proboscis plays a role during flower handling. By rewarding the moths at an artificial flower, we show that, although moths learn an odor easily when they perceive it with their antennae, experiencing the odor just with the proboscis is not sufficient for odor learning. Furthermore, experiencing the odor with the antennae during training does not affect the behavior of the moths when they later detect the learned odor with the proboscis only. Therefore, there seems to be no cross-talk between the antennae and proboscis, and information learnt by the antennae cannot be retrieved by the proboscis
Does export dependency hurt economic development? Empirical evidence from Singapore
A rapid export growth in East Asia was once identified as a source of the sustainable economic development that the region enjoyed. However, the current global recession has turned exports from an economic virtue to a vice. There is a growing awareness that a heavy reliance on exports has caused a serious economic downturn in the region. The present paper chooses Singapore as a case study to examine the relationship between the origin of the East Asian Miracle (i.e. export dependency) and the economic growth. For this purpose, the study employs a causality test developed by Toda and Yamamoto. The empirical findings indicate that despite a negative long-run relationship between export dependency and economic growth, Singapore's heavy reliance on exports does not seem to have produced negative effects on the nation's economic growth. This is because the increase in export dependency was an effect, and not a cause, of the country's output expansion.
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