17,584 research outputs found
Constraining Light Colored Particles with Event Shapes
Using recently developed techniques for computing event shapes with
Soft-Collinear Effective Theory, LEP event shape data is used to derive strong
model-independent bounds on new colored particles. In the effective field
theory computation, colored particles contribute in loops not only to the
running of alpha_s but also to the running of hard, jet and soft functions.
Moreover, the differential distribution in the effective theory explicitly
probes many energy scales, so event shapes have strong sensitivity to new
particle thresholds. Using thrust data from ALEPH and OPAL, colored adjoint
fermions (such as a gluino) below 51.0 GeV are ruled out to 95% confidence
level. This is nearly an order-of-magnitude improvement over the previous
model-independent bound of 6.3 GeV.Comment: 4 pages, 2 figure
Temporal Correlations of Local Network Losses
We introduce a continuum model describing data losses in a single node of a
packet-switched network (like the Internet) which preserves the discrete nature
of the data loss process. {\em By construction}, the model has critical
behavior with a sharp transition from exponentially small to finite losses with
increasing data arrival rate. We show that such a model exhibits strong
fluctuations in the loss rate at the critical point and non-Markovian power-law
correlations in time, in spite of the Markovian character of the data arrival
process. The continuum model allows for rather general incoming data packet
distributions and can be naturally generalized to consider the buffer server
idleness statistics
Hall effect in quasi one-dimensional organic conductors
We study the Hall effect in a system of weakly coupled Luttinger Liquid
chains, using a Memory function approach to compute the Hall constant in the
presence of umklapp scattering along the chains. In this approximation, the
Hall constant decomposes into two terms: a high-frequency term and a Memory
function term. For the case of zero umklapp scattering, where the Memory
function vanishes, the Hall constant is simply the band value, in agreement
with former results in a similar model with no dissipation along the chains.
With umklapp scattering along the chains, we find a power-law temperature
dependance of the Hall constant. We discuss the applications to quasi 1D
organic conductors at high temperatures.Comment: Proceedings of the ISCOM conference "Sixth International Symposium on
Crystalline Organic Metals, Superconductors, and Ferromagnets", Key West,
Florida, USA (Sept. 2005), to be plublished in the Journal of Low Temperature
Physic
Open ventral hernia repair with a composite ventral patch : final results of a multicenter prospective study
Background: This study assessed clinical outcomes, including safety and recurrence, from the two-year follow-up of patients who underwent open ventral primary hernia repair with the use of the Parietex (TM) Composite Ventral Patch (PCO-VP).
Methods: A prospective single-arm, multicenter study of 126 patients undergoing open ventral hernia repair for umbilical and epigastric hernias with the PCO-VP was performed.
Results: One hundred twenty-six subjects (110 with umbilical hernia and 16 with epigastric hernia) with a mean hernia diameter of 1.8cm (0.4-4.0) were treated with PCO-VP. One hundred subjects completed the two-year study. Cumulative hernia recurrence was 3.0% (3/101; 95%CI: 0.0-6.3%) within 24months. Median Numeric Rating Scale pain scores improved from 2 [0-10] at baseline to 0 [0-3] at 1 month (P<0.001) and remained low at 24months 0 [0-6] (P<0.001). 99% (102/103) of the patients were satisfied with their repair at 24months postoperative.
Conclusions: The use of PCO-VP to repair primary umbilical and epigastric defects yielded a low recurrence rate, low postoperative and chronic pain, and high satisfaction ratings, confirming that PCO-VP is effective for small ventral hernia repair in the two-year term after implantation.
Trial registration: The study was registered publically at clinicaltrials.gov (NCT01848184 registered May 7, 2013)
Stability and phase coherence of trapped 1D Bose gases
We discuss stability and phase coherence of 1D trapped Bose gases and find
that inelastic decay processes, such as 3-body recombination, are suppressed in
the strongly interacting (Tonks-Girardeau) and intermediate regimes. This is
promising for achieving these regimes with a large number of particles.
"Fermionization" of the system reduces the phase coherence length, and at T=0
the gas is fully phase coherent only deeply in the weakly interacting
(Gross-Pitaevskii) regime.Comment: published versio
On the issue of imposing boundary conditions on quantum fields
An interesting example of the deep interrelation between Physics and
Mathematics is obtained when trying to impose mathematical boundary conditions
on physical quantum fields. This procedure has recently been re-examined with
care. Comments on that and previous analysis are here provided, together with
considerations on the results of the purely mathematical zeta-function method,
in an attempt at clarifying the issue. Hadamard regularization is invoked in
order to fill the gap between the infinities appearing in the QFT renormalized
results and the finite values obtained in the literature with other procedures.Comment: 13 pages, no figure
A Multi-Wavelength Study of the Jet, Lobes and Core of the Quasar PKS 2101-490
We present a detailed study of the X-ray, optical and radio emission from the
jet, lobes and core of the quasar PKS 2101-490 as revealed by new Chandra, HST
and ATCA images. We extract the radio to X-ray spectral energy distributions
from seven regions of the 13 arcsecond jet, and model the jet X-ray emission in
terms of Doppler beamed inverse Compton scattering of the cosmic microwave
background (IC/CMB) for a jet in a state of equipartition between particle and
magnetic field energy densities. This model implies that the jet remains highly
relativistic hundreds of kpc from the nucleus, with a bulk Lorentz factor Gamma
~ 6 and magnetic field of order 30 microGauss. We detect an apparent radiative
cooling break in the synchrotron spectrum of one of the jet knots, and are able
to interpret this in terms of a standard one-zone continuous injection model,
based on jet parameters derived from the IC/CMB model. However, we note
apparent substructure in the bright optical knot in one of the HST bands. We
confront the IC/CMB model with independent estimates of the jet power, and find
that the IC/CMB model jet power is consistent with the independent estimates,
provided that the minimum electron Lorentz factor gamma_min > 50, and the knots
are significantly longer than the jet width, as implied by de-projection of the
observed knot lengths.Comment: 16 pages, 10 figures, 6 table
A density-functional approach to fermionization in the 1D Bose gas
A time-dependent Kohn-Sham scheme for 1D bosons with contact interaction is
derived based on a model of spinor fermions. This model is specifically
designed for the study of the strong interaction regime close to the Tonks gas.
It allows us to treat the transition from the strongly-interacting
Tonks-Girardeau to the weakly-interacting quasicondensate regime and provides
an intuitive picture of the extent of fermionization in the system. An
adiabatic local-density approximation is devised for the study of
time-dependent processes. This scheme is shown to yield not only accurate
ground-state properties but also overall features of the elementary excitation
spectrum, which is described exactly in the Tonks-gas limit.Comment: 15 pages, 3 figures, misprints (of published version) correcte
Random Walks in Local Dynamics of Network Losses
We suggest a model for data losses in a single node of a packet-switched
network (like the Internet) which reduces to one-dimensional discrete random
walks with unusual boundary conditions. The model shows critical behavior with
an abrupt transition from exponentially small to finite losses as the data
arrival rate increases. The critical point is characterized by strong
fluctuations of the loss rate. Although we consider the packet arrival being a
Markovian process, the loss rate exhibits non-Markovian power-law correlations
in time at the critical point.Comment: 4 pages, 2 figure
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