6,297 research outputs found
Ixodes brunneus (Acari: Ixodidae) from Two Bird Hosts: A New Michigan Tick
The tick Ixodes brunneus Koch (Acari: Ixodidae) is reported for the first time in Michigan from two bird hosts at two locations in the lower peninsula. All stages of this tick exclusively feed on birds, and are primarily known from the southern U.S., although abundant records occur from northern states. The role of this species as a vector of pathogens is discussed
Trions in a periodic potential
The group-theoretical classification of trion states is presented. It is
based on considerations of products of irreducible representations of the 2D
translation group. For a given BvK period N degeneracy of obtained states is
N^2. Trions consist of two identical particles so the symmetrization of states
with respect to particles transposition is considered. Completely antisymmetric
states can be constructed by introducing antisymmetric spin functions. Two
symmetry adapted bases are considered. The third possibility is postponed for
the further investigations.Comment: revtex, 5 p., sub. to Physica
Quantum Gravitational Bremsstrahlung, Massless versus Massive Gravity
The massive spin-2 quantum gauge theory previously developed is applied to
calculate gravitational bremsstrahlung. It is shown that this theory is unique
and free from defects. In particular, there is no strong coupling if the
graviton mass becomes small. The cross sections go over smoothly into the ones
of the massless theory in the limit of vanishing graviton mass. The massless
cross sections are calculated for the full tensor theory.Comment: 13 pages, 1 figur
The WARPS Survey. VIII. Evolution of the Galaxy Cluster X-ray Luminosity Function
We present measurements of the galaxy cluster X-ray Luminosity Function (XLF)
from the Wide Angle ROSAT Pointed Survey (WARPS) and quantify its evolution.
WARPS is a serendipitous survey of the central region of ROSAT pointed
observations and was carried out in two phases (WARPS-I and WARPS-II). The
results here are based on a final sample of 124 clusters, complete above a flux
limit of 6.5 10E-15 erg/s/cm2, with members out to redshift z ~ 1.05, and a sky
coverage of 70.9 deg2. We find significant evidence for negative evolution of
the XLF, which complements the majority of X-ray cluster surveys. To quantify
the suggested evolution, we perform a maximum likelihood analysis and conclude
that the evolution is driven by a decreasing number density of high luminosity
clusters with redshift, while the bulk of the cluster population remains nearly
unchanged out to redshift z ~ 1.1, as expected in a low density Universe. The
results are found to be insensitive to a variety of sources of systematic
uncertainty that affect the measurement of the XLF and determination of the
survey selection function. We perform a Bayesian analysis of the XLF to fully
account for uncertainties in the local XLF on the measured evolution, and find
that the detected evolution remains significant at the 95% level. We observe a
significant excess of clusters in the WARPS at 0.1 < z < 0.3 and LX ~ 2 10E42
erg/s compared with the reference low-redshift XLF, or our Bayesian fit to the
WARPS data. We find that the excess cannot be explained by sample variance, or
Eddington bias, and is unlikely to be due to problems with the survey selection
function.Comment: 13 pages, 12 figures, accepted for publication in MNRA
Relating on-shell and off-shell formalism in perturbative quantum field theory
In the on-shell formalism (mostly used in perturbative quantum field theory)
the entries of the time ordered product T are on-shell fields (i.e. the basic
fields satisfy the free field equations). With that, (multi)linearity of T is
incompatible with the Action Ward identity. This can be circumvented by using
the off-shell formalism in which the entries of T are off-shell fields. To
relate on- and off-shell formalism correctly, a map sigma from on-shell fields
to off-shell fields was introduced axiomatically by Duetsch and Fredenhagen. In
that paper it was shown that, in the case of one real scalar field in N=4
dimensional Minkowski space, these axioms have a unique solution. However, this
solution was given there only recursively. We solve this recurrence relation
and give a fully explicit expression for sigma in the cases of the scalar,
Dirac and gauge fields for arbitrary values of the dimension N.Comment: The case of gauge fields was added. 16 page
The Interaction of Quantum Gravity with Matter
The interaction of (linearized) gravitation with matter is studied in the
causal approach up to the second order of perturbation theory. We consider the
generic case and prove that gravitation is universal in the sense that the
existence of the interaction with gravitation does not put new constraints on
the Lagrangian for lower spin fields. We use the formalism of quantum off-shell
fields which makes our computation more straightforward and simpler.Comment: 25 page
Studies of uncontrolled air traffic patterns, phase 1
The general aviation air traffic flow patterns at uncontrolled airports are investigated and analyzed and traffic pattern concepts are developed to minimize the midair collision hazard in uncontrolled airspace. An analytical approach to evaluate midair collision hazard probability as a function of traffic densities is established which is basically independent of path structure. Two methods of generating space-time interrelationships between terminal area aircraft are presented; one is a deterministic model to generate pseudorandom aircraft tracks, the other is a statistical model in preliminary form. Some hazard measures are presented for selected traffic densities. It is concluded that the probability of encountering a hazard should be minimized independently of any other considerations and that the number of encounters involving visible-avoidable aircraft should be maximized at the expense of encounters in other categories
HST/Acs Weak-Lensing and Chandra X-Ray Studies of the High-Redshift Cluster MS 1054-0321
We present Hubble Space Telescope/Advanced Camera for Surveys (ACS)
weak-lensing and Chandra X-ray analyses of MS 1054-0321 at z=0.83, the most
distant and X-ray luminous cluster in the Einstein Extended Medium-Sensitivity
Survey (EMSS). The high-resolution mass reconstruction through ACS weak-lensing
reveals the complicated dark matter substructure in unprecedented detail,
characterized by the three dominant mass clumps with the four or more minor
satellite groups within the current ACS field. The direct comparison of the
mass map with the Chandra X-ray image shows that the eastern weak-lensing
substructure is not present in the X-ray image and, more interestingly, the two
X-ray peaks are displaced away from the hypothesized merging direction with
respect to the corresponding central and western mass clumps, possibly because
of ram pressure. In addition, as observed in our previous weak-lensing study of
another high-redshift cluster CL 0152-1357 at z=0.84, the two dark matter
clumps of MS 1054-0321 seem to be offset from the galaxy counterparts. We
examine the significance of these offsets and discuss a possible scenario,
wherein the dark matter clumps might be moving ahead of the cluster galaxies.
The non-parametric weak-lensing mass modeling gives a projected mass of M(r<1
Mpc)=(1.02+-0.15)x 10^{15} solar mass, where the uncertainty reflects both the
statistical error and the cosmic shear effects. Our temperature measurement of
T=8.9_{-0.8}^{+1.0} keV utilizing the newest available low-energy quantum
efficiency degradation prescription for the Chandra instrument, together with
the isothermal beta description of the cluster (r_c=16"+-15" and
beta=0.78+-0.08), yields a projected mass of M(r<1 Mpc)=(1.2+-0.2) x 10^{15}
solar mass, consistent with the weak-lensing result.Comment: Accepted for publication in apj. Full-resolution version can be
downloaded from http://acs.pha.jhu.edu/~mkjee/ms1054.pd
Quantum Black Hole in the Generalized Uncertainty Principle Framework
In this paper we study the effects of the Generalized Uncertainty Principle
(GUP) on canonical quantum gravity of black holes. Through the use of modified
partition function that involves the effects of the GUP, we obtain the
thermodynamical properties of the Schwarzschild black hole. We also calculate
the Hawking temperature and entropy for the modification of the Schwarzschild
black hole in the presence of the GUP.Comment: 11 pages, no figures, to appear in Physical Review
Physical instrumental vetoes for gravitational-wave burst triggers
We present a robust strategy to \emph{veto} certain classes of instrumental
glitches that appear at the output of interferometric gravitational-wave (GW)
detectors.This veto method is `physical' in the sense that, in order to veto a
burst trigger, we make use of our knowledge of the coupling of different
detector subsystems to the main detector output. The main idea behind this
method is that the noise in an instrumental channel X can be \emph{transferred}
to the detector output (channel H) using the \emph{transfer function} from X to
H, provided the noise coupling is \emph{linear} and the transfer function is
\emph{unique}. If a non-stationarity in channel H is causally related to one in
channel X, the two have to be consistent with the transfer function. We
formulate two methods for testing the consistency between the burst triggers in
channel X and channel H. One method makes use of the \emph{null-stream}
constructed from channel H and the \emph{transferred} channel X, and the second
involves cross-correlating the two. We demonstrate the efficiency of the veto
by `injecting' instrumental glitches in the hardware of the GEO 600 detector.
The \emph{veto safety} is demonstrated by performing GW-like hardware
injections. We also show an example application of this method using 5 days of
data from the fifth science run of GEO 600. The method is found to have very
high veto efficiency with a very low accidental veto rate.Comment: Minor changes, To appear in Phys. Rev.
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