7,289 research outputs found
Bound-state/elementary-particle duality in the Higgs sector and the case for an excited 'Higgs' within the standard model
Though being weakly interacting, QED can support bound states. In principle,
this can be expected for the weak interactions in the Higgs sector as well. In
fact, it has been argued long ago that there should be a duality between bound
states and the elementary particles in this sector, at least in leading order
in an expansion in the Higgs condensate. Whether this remains true beyond the
leading order is investigated using lattice simulations, and support is found.
This provides a natural interpretation of peaks in cross sections as bound
states. Unambiguously, this would imply the existence of (possibly very broad)
resonances of Higgs and W and Z bound states within the standard model.Comment: 15 pages, 3 figures v2: added appendix with technical details, some
minor improvement
Prediction of disease progression, treatment response and dropout in chronic obstructive pulmonary disease (COPD).
Drug development in chronic obstructive pulmonary disease (COPD) has been characterised by unacceptably high failure rates. In addition to the poor sensitivity in forced expiratory volume in one second (FEV1), numerous causes are known to contribute to this phenomenon, which can be clustered into drug-, disease- and design-related factors. Here we present a model-based approach to describe disease progression, treatment response and dropout in clinical trials with COPD patients
Keplerian discs around post-AGB stars: a common phenomenon?
Aims: We aim at showing that the broad-band SED characteristics of our sample
of post-AGB stars are best interpreted, assuming the circumstellar dust is
stored in Keplerian rotating passive discs.
Methods: We present a homogeneous and systematic study of the Spectral Energy
Distributions (SEDs) of a sample of 51 post-AGB objects. The selection criteria
to define the whole sample were tuned to cover the broad-band characteristics
of known binary post-AGB stars. The whole sample includes 20 dusty RV Tauri
stars from the General Catalogue of Variable Stars (GCVS). We supplemented our
own Geneva optical photometry with literature data to cover a broad range of
fluxes from the UV to the far-IR.
Results: All the SEDs display very similar characteristics: a large IR excess
with a dust excess starting near the sublimation temperature, irrespective of
the effective temperature of the central star. Moreover, when available, the
long wavelength fluxes show a black-body slope indicative of the presence of a
component of large mm sized grains.
Conclusions: We argue that in all systems, gravitationally bound dusty discs
are present. The discs must be puffed-up to cover a large opening angle for the
central star and we argue that the discs have some similarity with the passive
discs detected around young stellar objects. We interpret the presence of a
disc to be a signature for binarity of the central object, but this will need
confirmation by long-term monitoring of the radial velocities. We argue that
dusty RV Tauri stars are those binaries which happen to be in the Population II
instability strip.Comment: 29 pages, 5 figures, accepted for publication in A&
Statistically-secure ORAM with Overhead
We demonstrate a simple, statistically secure, ORAM with computational
overhead ; previous ORAM protocols achieve only
computational security (under computational assumptions) or require
overheard. An additional benefit of our ORAM is its
conceptual simplicity, which makes it easy to implement in both software and
(commercially available) hardware.
Our construction is based on recent ORAM constructions due to Shi, Chan,
Stefanov, and Li (Asiacrypt 2011) and Stefanov and Shi (ArXiv 2012), but with
some crucial modifications in the algorithm that simplifies the ORAM and enable
our analysis. A central component in our analysis is reducing the analysis of
our algorithm to a "supermarket" problem; of independent interest (and of
importance to our analysis,) we provide an upper bound on the rate of "upset"
customers in the "supermarket" problem
Waves attractors in rotating fluids: a paradigm for ill-posed Cauchy problems
In the limit of low viscosity, we show that the amplitude of the modes of
oscillation of a rotating fluid, namely inertial modes, concentrate along an
attractor formed by a periodic orbit of characteristics of the underlying
hyperbolic Poincar\'e equation. The dynamics of characteristics is used to
elaborate a scenario for the asymptotic behaviour of the eigenmodes and
eigenspectrum in the physically relevant r\'egime of very low viscosities which
are out of reach numerically. This problem offers a canonical ill-posed Cauchy
problem which has applications in other fields.Comment: 4 pages, 5 fi
The Mrs1 Splicing Factor Binds the bI3 Group I Intron at Each of Two Tetraloop-Receptor Motifs
Most large ribozymes require protein cofactors in order to function efficiently. The yeast mitochondrial bI3 group I intron requires two proteins for efficient splicing, Mrs1 and the bI3 maturase. Mrs1 has evolved from DNA junction resolvases to function as an RNA cofactor for at least two group I introns; however, the RNA binding site and the mechanism by which Mrs1 facilitates splicing were unknown. Here we use high-throughput RNA structure analysis to show that Mrs1 binds a ubiquitous RNA tertiary structure motif, the GNRA tetraloop-receptor interaction, at two sites in the bI3 RNA. Mrs1 also interacts at similar tetraloop-receptor elements, as well as other structures, in the self-folding Azoarcus group I intron and in the RNase P enzyme. Thus, Mrs1 recognizes general features found in the tetraloop-receptor motif. Identification of the two Mrs1 binding sites now makes it possible to create a model of the complete six-component bI3 ribonucleoprotein. All protein cofactors bind at the periphery of the RNA such that every long-range RNA tertiary interaction is stabilized by protein binding, involving either Mrs1 or the bI3 maturase. This work emphasizes the strong evolutionary pressure to bolster RNA tertiary structure with RNA-binding interactions as seen in the ribosome, spliceosome, and other large RNA machines
Electromagnetic radiative corrections in parity-violating electron-proton scattering
QED radiative corrections have been calculated for leptonic and hadronic
variables in parity-violating elastic ep scattering. For the first time, the
calculation of the asymmetry in the elastic radiative tail is performed without
the peaking-approximation assumption in hadronic variables configuration. A
comparison with the PV-A4 data validates our approach. This method has been
also used to evaluate the radiative corrections to the parity-violating
asymmetry measured in the G0 experiment. The results obtained are here
presented.Comment: 12 pages, 11 figure
Measurement of the Transverse Beam Spin Asymmetry in Elastic Electron Proton Scattering and the Inelastic Contribution to the Imaginary Part of the Two-Photon Exchange Amplitude
We report on a measurement of the asymmetry in the scattering of transversely
polarized electrons off unpolarized protons, A, at two Q values of
\qsquaredaveragedlow (GeV/c) and \qsquaredaveragedhighII (GeV/c) and a
scattering angle of . The measured transverse
asymmetries are A(Q = \qsquaredaveragedlow (GeV/c)) =
(\experimentalasymmetry alulowcorr \statisticalerrorlow
\combinedsyspolerrorlowalucor) 10 and
A(Q = \qsquaredaveragedhighII (GeV/c)) = (\experimentalasymme
tryaluhighcorr \statisticalerrorhigh
\combinedsyspolerrorhighalucor) 10. The first
errors denotes the statistical error and the second the systematic
uncertainties. A arises from the imaginary part of the two-photon
exchange amplitude and is zero in the one-photon exchange approximation. From
comparison with theoretical estimates of A we conclude that
N-intermediate states give a substantial contribution to the imaginary
part of the two-photon amplitude. The contribution from the ground state proton
to the imaginary part of the two-photon exchange can be neglected. There is no
obvious reason why this should be different for the real part of the two-photon
amplitude, which enters into the radiative corrections for the Rosenbluth
separation measurements of the electric form factor of the proton.Comment: 4 figures, submitted to PRL on Oct.
Evidence for Strange Quark Contributions to the Nucleon's Form Factors at = 0.108 (GeV/c)
We report on a measurement of the parity violating asymmetry in the elastic
scattering of polarized electrons off unpolarized protons with the A4 apparatus
at MAMI in Mainz at a four momentum transfer value of = \Qsquare
(GeV/c) and at a forward electron scattering angle of 30. The measured asymmetry is = (\Aphys
\Deltastat \Deltasyst) 10. The
expectation from the Standard Model assuming no strangeness contribution to the
vector current is A = (\Azero \DeltaAzero) 10. We
have improved the statistical accuracy by a factor of 3 as compared to our
previous measurements at a higher . We have extracted the strangeness
contribution to the electromagnetic form factors from our data to be +
\FakGMs = \GEsGMs \DeltaGEsGMs at = \Qsquare (GeV/c).
As in our previous measurement at higher momentum transfer for + 0.230
, we again find the value for + \FakGMs to be positive,
this time at an improved significance level of 2 .Comment: 4 pages, 3 figure
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