22,572 research outputs found
Infinitesimally Nonlocal Lorentz Violation
We introduce a new Lorentz-violating modification to a scalar quantum field
theory. This interaction, while super-renormalizable by power counting, is
fundamentally different from the interactions previously considered within the
Lorentz-violating standard model extension. The Lagrange density is nonlocal,
because of the presence of a Hilbert transform term; however, this nonlocality
is also very weak. The theory has reasonable stability and causality properties
and, although the Lorentz-violating interaction possesses a single vector
index, the theory is nonetheless CPT even. As an application, we analyze the
possible effects of this new form of Lorentz violation on neutral meson
oscillations. We find that under certain circumstances, the interaction may
lead to quite peculiar sidereal modulations in the oscillation frequency.Comment: 10 page
Detection of H-alpha emission from the Magellanic Stream: evidence for an extended gaseous Galactic halo
We have detected faint, diffuse H\alpha emission of surface brightness Rayleighs, R, and R respectively,
corresponding to emission measures of 1.0 to 0.5 \cmsixpc. We have observed
several positions near the MS IV concentration, and find that the strongest
emission is on the sharp leading-edge density gradient. There is less emission
at points away from the gradient, and halfway between MS III and MS IV the
H< 0.04\alpha emission at cloud leading edges to heating of the
Stream clouds by ram pressure from ionized gas in the halo of the Galaxy. These
observations suggest that ram pressure from halo gas plays a large role in
stripping the Stream out of the Magellanic Clouds. They also suggest the
presence of a relatively large density of gas, , in the Galactic halo at kpc radius, and far above the
Galactic plane, . This implies that the Galaxy has a very large
baryonic, gaseous extent, and supports models of Lyman-$\alpha and metal-line
QSO absorption lines in which the absorption systems reside in extended
galactic halos.Comment: 15 pages, aaspp latex, + 1 table & 3 figures. Accepted in A.J. Also
available from http://www.physics.rutgers.edu/~bweiner/astro/papers
Androgen Receptor and Vasopressin Receptor (AVPR1a) Genetic Polymorphisms are not associated with Marital Status or Fertility among Ariaal Men of Northern Kenya
A growing body of scholarship implicates testosterone and vasopressin in male reproductive behavior, including in humans. Since hormones exert their effects through their respective receptors, an open question has been whether genetic polymorphisms in the androgen receptor and vasopressin 1a receptor (AVPR1a) impact human male social behavior. Here, we sought to test for associations between polymorphisms in the coding region of the androgen receptor and promoter region of AVPR1a in relation to marital status and fertility among pastoralist Ariaal men of northern Kenya. None of the three polymorphisms were related to marital status (single, monogamously married, polygynously married) or fertility (number of current living children). We discuss these null findings in light of existing data
Fully three dimensional breather solitons can be created using Feshbach resonance
We investigate the stability properties of breather solitons in a
three-dimensional Bose-Einstein Condensate with Feshbach Resonance Management
of the scattering length and con ned only by a one dimensional optical lattice.
We compare regions of stability in parameter space obtained from a fully 3D
analysis with those from a quasi two-dimensional treatment. For moderate con
nement we discover a new island of stability in the 3D case, not present in the
quasi 2D treatment. Stable solutions from this region have nontrivial dynamics
in the lattice direction, hence they describe fully 3D breather solitons. We
demonstrate these solutions in direct numerical simulations and outline a
possible way of creating robust 3D solitons in experiments in a Bose Einstein
Condensate in a one-dimensional lattice. We point other possible applications.Comment: 4 pages, 4 figures; accepted to Physical Review Letter
Superabsorption of light via quantum engineering
Almost 60 years ago Dicke introduced the term superradiance to describe a
signature quantum effect: N atoms can collectively emit light at a rate
proportional to N^2. Even for moderate N this represents a significant increase
over the prediction of classical physics, and the effect has found applications
ranging from probing exciton delocalisation in biological systems, to
developing a new class of laser, and even in astrophysics. Structures that
super-radiate must also have enhanced absorption, but the former always
dominates in natural systems. Here we show that modern quantum control
techniques can overcome this restriction. Our theory establishes that
superabsorption can be achieved and sustained in certain simple nanostructures,
by trapping the system in a highly excited state while extracting energy into a
non-radiative channel. The effect offers the prospect of a new class of quantum
nanotechnology, capable of absorbing light many times faster than is currently
possible; potential applications of this effect include light harvesting and
photon detection. An array of quantum dots or a porphyrin ring could provide an
implementation to demonstrate this effect
Genetic and environmental contributions to strabismus and phoria: Evidence from twins
AbstractThe causes of manifest (strabismus) and latent (phoria) misalignment of the visual axes are incompletely understood. We calculated genetic and environmental contributions to strabismus based upon a critical review and quantitative meta-analysis of previous strabismus twin studies (n=3418 twin pairs) and calculated contributions to phoria based upon a new twin study (n=307 twin pairs). Our results suggest that genetic liability is necessary to develop strabismus, whereas environmental factors are sufficient to cause most phorias. The different etiologies implied by this work suggest that strabismus and phoria should be carefully distinguished in epidemiological work
Multiscale Analysis of Discrete Nonlinear Evolution Equations
The method of multiscale analysis is constructed for dicrete systems of
evolution equations for which the problem is that of the far behavior of an
input boundary datum. Discrete slow space variables are introduced in a general
setting and the related finite differences are constructed. The method is
applied to a series of representative examples: the Toda lattice, the nonlinear
Klein-Gordon chain, the Takeno system and a discrete version of the
Benjamin-Bona-Mahoney equation. Among the resulting limit models we find a
discrete nonlinear Schroedinger equation (with reversed space-time), a 3-wave
resonant interaction system and a discrete modified Volterra model.Comment: published in J. Phys. A : Math. Gen. 32 (1999) 927-94
Quick actuating closure and handling system
A quick activating closure and handling system, which utilizes conical sections for locking, was developed to allow quick access to the combustor internal components of the 8 ft High Temperature Tunnel. These critical components include the existing methane spraybar, a transpiration cooled nozzle and the new liquid oxygen (LOX) injection system housed within the combustor. A substantial cost savings will be realized once the mechanism is installed since it will substantially reduce the access time and increase the time available for conducting wind tunnel tests. A need exists for more frequent inspections when the wind tunnel operates at the more severe conditions generated by using LOX in the combustor. A loads analysis and a structural (finite element) analysis were conducted to verify that the new closure system is compatible with the existing pressure shell. In addition, strain gages were placed on the pressure vessel to verify how the pressure shell reacts to transient pressure loads. A scale model of the new closure system was built to verify the operation of the conical sections in the locking mechanisms
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