13,111 research outputs found
Magnetic phenomena at and near nu =1/2 and 1/4: theory, experiment and interpretation
I show that the hamiltonian theory of Composite Fermions (CF) is capable of
yielding a unified description in fair agreement with recent experiments on
polarization P and relaxation rate 1/T_1 in quantum Hall states at filling nu =
p/(2ps+1), at and near nu = 1/2 and 1/4, at zero and nonzero temperatures. I
show how rotational invariance and two dimensionality can make the underlying
interacting theory behave like a free one in a limited context.Comment: Latex 4 pages, 2 figure
Optical, near-IR and -ray observations of SN 2015J and its host galaxy
SN 2015J was discovered on April 27th 2015 and is classified as a type IIn
supernova. At first, it appeared to be an orphan SN candidate, i.e. without any
clear identification of its host galaxy. Here, we present the analysis of the
observations carried out {by the VLT 8-m class telescope with the FORS2 camera
in the R band and the Magellan telescope (6.5 m) equipped with the IMACS
Short-Camera (V and I filters) and the FourStar camera (Ks filter)}. We show
that SN 2015J resides in what appears to be a very compact galaxy establishing
a relation between the SN event and its natural host. We also present and
discuss archival and new -ray data centred on SN 2015J. At the time of the
supernova explosion, Swift/XRT observations were made and a weak X-ray source
was detected at the location of SN 2015J. Almost one year later, the same
source was unambiguously identified during serendipitous observations by
Swift/XRT and -Newton, clearly showing an enhancement of the 0.3-10 keV
band flux by a factor with respect to the initial state. Swift/XRT
observations show that the source is still active in the -rays at a level of
counts s. The unabsorbed X-ray luminosity derived from the
{\it XMM}-Newton slew and SWIFT observations, erg
s, places SN 2015J among the brightest young supernovae in X-rays.Comment: The Astrophysical Journal, Volume 850, Number
Gravitational wave bursts from cosmic (super)strings: Quantitative analysis and constraints
We discuss data analysis techniques that can be used in the search for
gravitational wave bursts from cosmic strings. When data from multiple
interferometers are available, we describe consistency checks that can be used
to greatly reduce the false alarm rates. We construct an expression for the
rate of bursts for arbitrary cosmic string loop distributions and apply it to
simple known solutions. The cosmology is solved exactly and includes the
effects of a late-time acceleration. We find substantially lower burst rates
than previous estimates suggest and explain the disagreement. Initial LIGO is
unlikely to detect field theoretic cosmic strings with the usual loop sizes,
though it may detect cosmic superstrings as well as cosmic strings and
superstrings with non-standard loop sizes (which may be more realistic). In the
absence of a detection, we show how to set upper limits based on the loudest
event. Using Initial LIGO sensitivity curves, we show that these upper limits
may result in interesting constraints on the parameter space of theories that
lead to the production of cosmic strings.Comment: Replaced with version accepted for publication in PR
Kondo Lattice without Nozieres Exhaustion Effect
We discuss the properties of layered Anderson/Kondo lattices with metallic
electrons confined in 2D xy planes and local spins in insulating layers forming
chains in z direction. Each spin in this model possesses its own 2D Kondo
cloud, so that the Nozieres' exhaustion problem does not occur. The excitation
spectrum of the model is gapless both in charge and spin sectors. The
disordered phases and possible experimental realizations of the model are
briefly discussed.Comment: 4 pages, 3 figure
The X-ray Properties of the Nearby Star-Forming Galaxy IC 342: The XMM-Newton View
We present the X-ray properties of IC342 using XMM-Newton. Thirty-five
sources are detected coincident with the disk of IC342 (more than tripling the
number known), of which ~31 are likely to be intrinsic to IC342. This
population shows a range of spectral properties and has an X-ray luminosity
function slope and infrared luminosity comparable to that of starburst galaxies
such as M82 and the Antennae, while its relative lack of extended X-ray
emission is similar to the properties of quiescent spirals. We do detect
long-term variability between this observation and the 1991 ROSAT and 1993/2000
ASCA observations for five sources. Notably, the second most luminous source
IC342 X-2 is is found to be in its the lowest luminosity state observed for X-2
to date, although the slope of the spectrum is intermediate between the
previously observed low/hard and high/soft states. IC342 X-1, on the other
hand, is found to be in an identical state to that observed in 2000 with ASCA.
Assuming X-1 is in an anomalous very high (VH) state, then either (1) X-1 has
remained in this state between 2000 and 2002, and is therefore the longest
duration VH-state binary ever observed, or (2) it was simply caught in a VH
state by chance in both the 2000 ASCA and 2002 XMM-Newton observations. We have
also confirmed the ROSAT HRI result that the nucleus of IC342 is made up of
both point-like and extended emission. The relative fluxes of the two spectral
components suggest that the nucleus is complex, with a soft extended component
contributing approximately half of the total luminosity. (Abridged)Comment: AJ in press (December 2003), 9 pages, 7 figures, 2 tables,
emulateapj.cls use
Strength, rate of force development, power and reactive strength in adult male athletic populations post anterior cruciate ligament reconstruction - a systematic review and meta-analysis
Background
Residual deficits in athletic performance are common despite rehabilitation guidelines following anterior cruciate ligament reconstruction including criterion-based progressions to protect healing structures, ensure safe restoration of fundamental physical capacities, and guide appropriate return to sports activities. A synthesis of the available literature is warranted to examine the physical readiness to re-perform of athletic populations in the later stages of rehabilitation in comparison to healthy controls.
Objectives
To determine the level of strength, power, rate of force development, and reactive strength in adult males who are more than six months following anterior cruciate ligament reconstruction.
Methods
A systematic review of the literature was undertaken using the Medline, CINAHL and SPORTDiscus databases and the PRISMA (Preferred Reporting Items for Systematic
Reviews and Meta-Analyses) guidelines. Studies including males only and assessed strength, power, rate of force development and reactive strength comparing performance to healthy controls were included. A meta-analysis was also performed to compute standardized mean differences (SMD ± 95% confidence intervals), calculated using Hedge’s g, and examine the effect of ACLR on these fundamental physical capacities.
Results
2023 articles were identified, of which 14 articles with similar level of evidence and methodological quality met the inclusion criteria. The most commonly investigated and impaired physical capacity was quadriceps (g= -0.89, 95% CI [-1.33,-0.44]) and hamstring strength (g= -0.44, 95% CI [-0.78,-0.10]). Only one study investigated rate of force development and none measuring reactive strength met our eligibility criteria.
Conclusions
Pooled data showed moderate evidence indicating large and small negative deficits on knee peak extension and flexion, respectively, in male adults at more than 6 months post anteriorcruciate ligament reconstruction. The magnitude of these differences are influenced by graft type and can be mitigated by targeted rehabilitation programs. Insufficient evidence is available in male adults following anterior cruciate ligament reconstruction to examine rate of force development and reactive strength
Relationships between physical capacities and biomechanical variables during movement tasks in athletic populations following anterior cruciate ligament reconstruction
Background
Anterior cruciate ligament (ACL) reconstruction has a detrimental impact on athletic performance. Despite rehabilitation guidelines and criterion-based progressions to ensure safe restoration of fundamental physical capacities and maladaptive movement strategies, residual deficits in maximal strength, rate of force development (RFD), power and reactive strength are commonly reported. These combined with associated compensatory inter and intra-limb strategies increase the risk of re-injury.
Objective
The aim of this article is to examine the relationships between fundamental physical capacities and biomechanical variables during dynamic movement tasks.
Design
Narrative review
Results
The available data suggests that quadriceps strength and rate of torque development, explain a moderate portion of the variance in aberrant kinetic and kinematic strategies commonly detected in ACL reconstructed cohorts at who are during the later stages of rehabilitation and RTS
Conclusion
The available data suggests that quadriceps strength and rate of torque development, explain a moderate portion of the variance in aberrant kinetic and kinematic strategies commonly detected in ACL reconstructed cohorts at who are in the later stages of rehabilitation and RT
The X-ray Luminosity Function of "The Antennae" Galaxies (NGC4038/39) and the Nature of Ultra-Luminous X-ray Sources
We derive the X-ray luminosity function (XLF) of the X-ray source population
detected in the Chandra observation of NGC4038/39 (the Antennae).
We explicitly include photon counting and spectral parameter uncertainties in
our calculations. The cumulative XLF is well represented by a flat power law
(), similar to those describing the XLFs of other star-forming
systems (e.g. M82, the disk of M81), but different from those of early type
galaxies. This result associates the X-ray source population in the Antennae
with young High Mass X-ray Binaries. In comparison with less actively
star-forming galaxies, the XLF of the Antennae has a highly significant excess
of sources with luminosities above 10^{39} erg\s (Ultra Luminous Sources;
ULXs). We discuss the nature of these sources, based on the XLF and on their
general spectral properties, as well as their optical counterparts discussed in
Paper III. We conclude that the majority of the ULXs cannot be intermediate
mass black-holes (M > 10-1000 \msun) binaries, unless they are linked to the
remnants of massive Population III stars (the Madau & Rees model). Instead,
their spatial and multiwavelength properties can be well explained by beamed
emission as a consequence of supercritical accretion.
Binaries with a neutron star or moderate mass black-hole (up to 20\msun), and
B2 to A type star companions would be consistent with our data. In the beaming
scenario, the XLF should exibit caracteristic breaks that will be visible in
future deeper observations of the Antennae.Comment: 15 pages, submitted to Ap
- …