67,787 research outputs found
Monodromy of the SL_2 Hitchin fibration
We calculate the monodromy action on the mod 2 cohomology for SL(2,C) Hitchin
systems and give an application of our results in terms of the moduli space of
semistable SL(2,R) Higgs bundles.Comment: 17 pages, 3 figures. v2: Version to appear in IJ
Bounds on Scalar Leptoquarks from Z Physics
We analyse the constraints on scalar leptoquarks coming from radiative
corrections to physics. We perform a global fitting to the LEP data
including the contributions of the most general effective Lagrangian for scalar
leptoquarks, which exhibits the gauge invariance. We
show that the bounds on leptoquarks that couple to the top quark are much
stronger than the ones obtained from low energy experiments.Comment: RevTeX 3.0, 26 pages, 4 postscript figures included as uufil
Quantum mechanical analysis of the elastic propagation of electrons in the Au/Si system: application to Ballistic Electron Emission Microscopy
We present a Green's function approach based on a LCAO scheme to compute the
elastic propagation of electrons injected from a STM tip into a metallic film.
The obtained 2D current distribution in real and reciprocal space furnish a
good representation of the elastic component of Ballistic Electron Emission
Microscopy (BEEM) currents. Since this component accurately approximates the
total current in the near threshold region, this procedure allows --in contrast
to prior analyses-- to take into account effects of the metal band structure in
the modeling of these experiments. The Au band structure, and in particular its
gaps appearing in the [111] and [100] directions provides a good explanation
for the previously irreconcilable results of nanometric resolution and
similarity of BEEM spectra on both Au/Si(111) and Au/Si(100).Comment: 12 pages, 9 postscript figures, revte
The potential link between corporate innovations and corporate competitiveness:Evidence from IT firms in the UK
Purpose: The purpose of this paper is to provide a thorough empirical investigation of the potential link between corporate innovations and corporate competitiveness in the context of the UK IT industry. Design/methodology/approach: This research uses a panel of 216 UK IT firms for the period from 2000 to 2016. The sample data for this study were extracted from the Worldscope, extracted from the Datastream database from Thomson Reuters. For the analysis of the data, the generalised method of moments model is applied. Findings: The results of this study provide empirical evidence that there exists a strong, positive link between corporate innovations and corporate competitiveness. Such evidence further reinforces the common view in the current literature of strategic management that because of the nature of their business, firms in the IT industry need to enhance their innovative capacities on a continual basis because of their critical role on these firms’ success and survival. Also, it is found that when the proxies for corporate innovations are lagged by two periods, their impact on corporate competitiveness becomes relatively more significant. However, when they are further lagged, i.e. by three periods, such an impact turns out to be relatively less pronounced. Research limitations/implications: The data gathered for this paper was restricted to IT-oriented firms in the UK. Using a secondary database (Datastream), the paper considered the period of 2000-2016. Originality/value: The research makes a significant contribution to the current debate on the relationship between information technology, innovation and performance, referred to in the literature as the productivity paradox, by studying the problem in the IT industry. It supports organisations from the sector in their efforts to deal with the dynamic nature of technological innovations and of the context where they operate. Methodologically, the way the study has measured the concepts of innovation and performance and the lessons learned from their analysis has also brought value to the research
Daily Stress Recognition from Mobile Phone Data, Weather Conditions and Individual Traits
Research has proven that stress reduces quality of life and causes many
diseases. For this reason, several researchers devised stress detection systems
based on physiological parameters. However, these systems require that
obtrusive sensors are continuously carried by the user. In our paper, we
propose an alternative approach providing evidence that daily stress can be
reliably recognized based on behavioral metrics, derived from the user's mobile
phone activity and from additional indicators, such as the weather conditions
(data pertaining to transitory properties of the environment) and the
personality traits (data concerning permanent dispositions of individuals). Our
multifactorial statistical model, which is person-independent, obtains the
accuracy score of 72.28% for a 2-class daily stress recognition problem. The
model is efficient to implement for most of multimedia applications due to
highly reduced low-dimensional feature space (32d). Moreover, we identify and
discuss the indicators which have strong predictive power.Comment: ACM Multimedia 2014, November 3-7, 2014, Orlando, Florida, US
Signals for New Spin-1 Resonances in Electroweak Gauge Boson Pair Production at the LHC
The mechanism of electroweak symmetry breaking (EWSB) will be directly
scrutinized soon at the CERN Large Hadron Collider (LHC). We analyze the LHC
potential to look for new vector bosons associated with the EWSB sector. We
present a possible model independent approach to search for these new spin--1
resonances. We show that the analyses of the processes pp --> l^+ l^- Emiss_T,
l^\pm j j Emiss_T, l^\pm l^+ l^- Emiss_T, and l^+ l^- j j (with l=e or \mu and
j=jet) have a large reach at the LHC and can lead to the discovery or exclusion
of many EWSB scenarios such as Higgsless models.Comment: 10 pages, 11 figure
New insights on the dense molecular gas in NGC253 as traced by HCN and HCO+
We have imaged the central ~1kpc of the circumnuclear starburst disk in the
galaxy NGC253 in the HCN(1-0), HCO+(1-0), and CO(1-0) transitions at 60pc
resolution using the Owens Valley Radio Observatory Millimeter-Wavelength Array
(OVRO). We have also obtained Atacama Pathfinder Experiment (APEX) observations
of the HCN(4-3) and the HCO+(4-3) lines of the starburst disk. We find that the
emission from the HCN(1-0) and HCO+(1-0) transitions, both indicators of dense
molecular gas, trace regions which are non-distinguishable within the
uncertainties of our observations. Even though the continuum flux varies by
more than a factor 10 across the starburst disk, the HCN/HCO+ ratio is constant
throughout the disk, and we derive an average ratio of 1.1+/-0.2. From an
excitation analysis we find that all lines from both molecules are subthermally
excited and that they are optically thick. This subthermal excitation implies
that the observed HCN/HCO+ line ratio is sensitive to the underlying chemistry.
The constant line ratio thus implies that there are no strong abundance
gradients across the starburst disk of NGC253. This finding may also explain
the variations in L'(HCN)/L'(HCO+) between different star forming galaxies both
nearby and at high redshifts.Comment: 9 pages, 12 figures, ApJ in press (volume 666 September
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