6,008 research outputs found
Probing the Light Pseudoscalar Window
Very light pseudoscalars can arise from the symmetry-breaking sector in many
extensions of the Standard Model. If their mass is below 200 MeV, they can be
long-lived and have interesting phenomenology. We discuss the experimental
constraints on several models with light pseudoscalars, including one in which
the pseudoscalar is naturally fermiophobic. Taking into account the stringent
bounds from rare K and B decays, we find allowed parameter space in each model
that may be accessible in direct production experiments. In particular, we
study the photoproduction of light pseudoscalars at Jefferson Lab and conclude
that a beam dump experiment could explore some of the allowed parameter space
of these models.Comment: 22 pages, 4 figure
Static interactions and stability of matter in Rindler space
Dynamical issues associated with quantum fields in Rindler space are
addressed in a study of the interaction between two sources at rest generated
by the exchange of scalar particles, photons and gravitons. These static
interaction energies in Rindler space are shown to be scale invariant, complex
quantities. The imaginary part will be seen to have its quantum mechanical
origin in the presence of an infinity of zero modes in uniformly accelerated
frames which in turn are related to the radiation observed in inertial frames.
The impact of a uniform acceleration on the stability of matter and the
properties of particles is discussed and estimates are presented of the
instability of hydrogen atoms when approaching the horizon.Comment: 28 pages, 4 figure
Paramagnetic anisotropic magnetoresistance in thin films of SrRuO3
SrRuO3 is an itinerant ferromagnet and in its thin film form when grown on
miscut SrTiO3 it has Tc of ~ 150 K and strong uniaxial anisotropy. We measured
both the Hall effect and the magnetoresistance (MR) of the films as a function
of the angle between the applied field and the normal to the films at
temperatures above Tc. We extracted the extraordinary Hall effect that is
proportional to the perpendicular component of the magnetization and thus the
MR for each angle of the applied field could be correlated with the magnitude
and orientation of the induced magnetization. We successfully fit the MR data
with a second order magnetization expansion, which indicates large anisotropic
MR in the paramagnetic state. The extremum values of resistivity are not
obtained for currents parallel or perpendicular to the magnetization, probably
due to the crystal symmetry.Comment: 3 pages, 3 figure
Conservative 3+1 General Relativistic Variable Eddington Tensor Radiation Transport Equations
We present conservative 3+1 general relativistic variable Eddington tensor
radiation transport equations, including greater elaboration of the momentum
space divergence (that is, the energy derivative term) than in previous work.
These equations are intended for use in simulations involving numerical
relativity, particularly in the absence of spherical symmetry. The independent
variables are the lab frame coordinate basis spacetime position coordinates and
the particle energy measured in the comoving frame. With an eye towards
astrophysical applications---such as core-collapse supernovae and compact
object mergers---in which the fluid includes nuclei and/or nuclear matter at
finite temperature, and in which the transported particles are neutrinos, we
pay special attention to the consistency of four-momentum and lepton number
exchange between neutrinos and the fluid, showing the term-by-term
cancellations that must occur for this consistency to be achieved.Comment: Version accepted by Phys. Rev.
Remote sensing and hydrologic models for performance assessment in Sirsa Irrigation Circle, India
Irrigation management / Irrigation systems / Irrigation canals / Performance evaluation / Remote sensing / GIS / Models / Irrigated farming / Hydrology / Satellite surveys / Irrigation scheduling / Evapotranspiration / India
Monte Carlo Renormalization of the 3-D Ising model: Analyticity and Convergence
We review the assumptions on which the Monte Carlo renormalization technique
is based, in particular the analyticity of the block spin transformations. On
this basis, we select an optimized Kadanoff blocking rule in combination with
the simulation of a d=3 Ising model with reduced corrections to scaling. This
is achieved by including interactions with second and third neighbors. As a
consequence of the improved analyticity properties, this Monte Carlo
renormalization method yields a fast convergence and a high accuracy. The
results for the critical exponents are y_H=2.481(1) and y_T=1.585(3).Comment: RevTeX, 4 PostScript file
<i>Brevundimonas halotolerans</i> sp. nov., <i>Brevundimonas poindexterae</i> sp. nov. and <i>Brevundimonas staleyi</i> sp. nov., prosthecate bacteria from aquatic habitats
Eight strains of Gram-negative, bacteroid-shaped, prosthecate bacteria, isolated from brackish water (MCS24T, MCS17 and MCS35), the marine environment (CM260, CM272 and CM282) and activated sludge (FWC40T and FWC43T), were characterized using a polyphasic approach. Analysis of 16S rRNA gene sequences determined that all strains were affiliated to the alphaproteobacterial genus Brevundimonas, forming three distinct phyletic lineages within the genus. The strains grew best with 5–30 g NaCl l-1 at 20–30 °C. DNA G+C contents for strains MCS24T, FWC40T and FWC43T were between 65 and 67 mol%, in accordance with values reported previously for other species of the genus. Moreover, chemotaxonomic data and physiological and biochemical tests allowed the phenotypic differentiation of three novel species within the genus Brevundimonas, for which the names Brevundimonas halotolerans sp. nov. (type strain MCS24T =LMG 25346T =CCUG 58273T), Brevundimonas poindexterae sp. nov. (type strain FWC40T =LMG 25261T =CCUG 57883T) and Brevundimonas staleyi sp. nov. (type strain FWC43T =LMG 25262T =CCUG 57884T) are proposed
eXamine: a Cytoscape app for exploring annotated modules in networks
Background. Biological networks have growing importance for the
interpretation of high-throughput "omics" data. Statistical and combinatorial
methods allow to obtain mechanistic insights through the extraction of smaller
subnetwork modules. Further enrichment analyses provide set-based annotations
of these modules.
Results. We present eXamine, a set-oriented visual analysis approach for
annotated modules that displays set membership as contours on top of a
node-link layout. Our approach extends upon Self Organizing Maps to
simultaneously lay out nodes, links, and set contours.
Conclusions. We implemented eXamine as a freely available Cytoscape app.
Using eXamine we study a module that is activated by the virally-encoded
G-protein coupled receptor US28 and formulate a novel hypothesis about its
functioning
Investigation of the Domain Wall Fermion Approach to Chiral Gauge Theories on the Lattice
We investigate a recent proposal to construct chiral gauge theories on the
lattice using domain wall fermions. We restrict ourselves to the finite volume
case, in which two domain walls are present, with modes of opposite chirality
on each of them. We couple the chiral fermions on only one of the domain walls
to a gauge field. In order to preserve gauge invariance, we have to add a
scalar field, which gives rise to additional light mirror fermion and scalar
modes. We argue that in an anomaly free model these extra modes would decouple
if our model possesses a so-called strong coupling symmetric phase. However,
our numerical results indicate that such a phase most probably does not exist.
---- Note: 9 Postscript figures are appended as uuencoded compressed tar file.Comment: 27p. Latex; UCSD/PTH 93-28, Wash. U. HEP/93-6
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