3,837 research outputs found
Nonlinear Faraday Rotation and Superposition-State Detection in Cold Atoms
We report on the first observation of nonlinear Faraday rotation with cold
atoms at a temperature of ~100 uK. The observed nonlinear rotation of the light
polarization plane is up to 0.1 rad over the 1 mm size atomic cloud in
approximately 10 mG magnetic field. The nonlinearity of rotation results from
long-lived coherence of ground-state Zeeman sublevels created by a
near-resonant light. The method allows for creation, detection and control of
atomic superposition states. It also allows applications for precision
magnetometry with high spatial and temporal resolution.Comment: 5 pages, 6 figure
Testing for variation in Leptasterias spp. prey preference across different populations and microhabitats
Sea star wasting disease (SSWD) has affected many asteroid populations on the Pacific Northwest coast in recent years. Because sea stars are keystone predators, the absence of them can severely alter the structure of intertidal communities. As populations diminish, it is important to understand what the preferred prey of sea stars is and how prey preference may affect distribution and abundance of sea stars. This laboratory study examined the prey preference of Leptasterias populations from Friday Harbor, Washington, Humboldt County, California, and Pigeon Point, California. The purpose of the study was to 1) determine if sea stars have a preferred prey type, 2) determine if there is a difference in prey preference across different populations, and 3) determine if there is a difference in prey preference between sea stars of different microhabitats (i.e. in pools or attached to rocks within the intertidal). To assess this, multiple binary choice trials were conducted in which sea stars were offered different prey types of equal accessibility. Preference was determined by calculating the average position of sea stars in an experimental tank. Preliminary observations suggest that there is a difference in prey preference between stars of different populations and microhabitats, however statistical analyses are needed at this time. Future studies are necessary that include larger sample sizes, a more controlled laboratory environment, and field-based experiments and observations
Noncovariant gauge fixing in the quantum Dirac field theory of atoms and molecules
Starting from the Weyl gauge formulation of quantum electrodynamics (QED),
the formalism of quantum-mechanical gauge fixing is extended using techniques
from nonrelativistic QED. This involves expressing the redundant gauge degrees
of freedom through an arbitrary functional of the gauge-invariant transverse
degrees of freedom. Particular choices of functional can be made to yield the
Coulomb gauge and Poincar\'{e} gauge representations. The Hamiltonian we derive
therefore serves as a good starting point for the description of atoms and
molecules by means of a relativistic Dirac field. We discuss important
implications for the ontology of noncovariant canonical QED due to the gauge
freedom that remains present in our formulation.Comment: 8 pages, 0 figure
Lattice study of ChPT beyond QCD
We describe initial results by the Lattice Strong Dynamics (LSD)
collaboration of a study into the variation of chiral properties of chiral
properties of SU(3) Yang-Mills gauge theory as the number of massless flavors
changes from to , with a focus on the use of chiral
perturbation theory.Comment: 9 pages, 3 figures. Presented at the 6th International Workshop on
Chiral Dynamics, University of Bern, Switzerland, July 6-10 200
Toward TeV Conformality
We study the chiral condensate for an SU(3) gauge theory
with massless Dirac fermions in the fundamental representation when
is increased from 2 to 6. For , our lattice simulations of , where is the Nambu-Goldstone-boson decay constant, agree with
the measured QCD value. For , this ratio shows significant
enhancement, presaging an even larger enhancement anticipated as
increases further, toward the critical value for transition from confinement to
infrared conformality.Comment: 4 pages, 4 figures. v2: revised version for PR
Using Synchronization for Prediction of High-Dimensional Chaotic Dynamics
We experimentally observe the nonlinear dynamics of an optoelectronic
time-delayed feedback loop designed for chaotic communication using commercial
fiber optic links, and we simulate the system using delay differential
equations. We show that synchronization of a numerical model to experimental
measurements provides a new way to assimilate data and forecast the future of
this time-delayed high-dimensional system. For this system, which has a
feedback time delay of 22 ns, we show that one can predict the time series for
up to several delay periods, when the dynamics is about 15 dimensional.Comment: 10 pages, 4 figure
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