686 research outputs found
SUSY-QCD corrections to stop annihilation into electroweak final states including Coulomb enhancement effects
We present the full supersymmetric QCD corrections
for stop-anti-stop annihilation into electroweak final states within the
Minimal Supersymmetric Standard Model (MSSM). We also incorporate Coulomb
corrections due to gluon exchange between the incoming stops. Numerical results
for the annihilation cross sections and the predicted neutralino relic density
are presented. We show that the impact of the radiative corrections on the
cosmologically preferred region of the parameter space can become larger than
the current experimental uncertainty, shifting the relic bands within the
considered regions of the parameter space by up to a few tens of GeV.Comment: 20 pages, 13 figures, updated to version published in Phys. Rev.
Precision predictions for supersymmetric dark matter
The dark matter relic density has been measured by Planck and its
predecessors with an accuracy of about 2%. We present theoretical calculations
with the numerical program DM@NLO in next-to-leading order SUSY QCD and beyond,
which allow to reach this precision for gaugino and squark (co-)annihilations,
and use them to scan the phenomenological MSSM for viable regions, applying
also low-energy, electroweak and hadron collider constraints.Comment: 6 pages, 1 table, 8 figures, proceedings of ICHEP 201
Coherent Time Evolution and Boundary Conditions of Two-Photon Quantum Walks
Multi-photon quantum walks in integrated optics are an attractive controlled
quantum system, that can mimic less readily accessible quantum systems and
exhibit behavior that cannot in general be accurately replicated by classical
light without an exponential overhead in resources. The ability to observe time
evolution of such systems is important for characterising multi-particle
quantum dynamics---notably this includes the effects of boundary conditions for
walks in spaces of finite size. Here we demonstrate the coherent evolution of
quantum walks of two indistinguishable photons using planar arrays of 21
evanescently coupled waveguides fabricated in silicon oxynitride technology. We
compare three time evolutions, that follow closely a model assuming unitary
evolution, corresponding to three different lengths of the array---in each case
we observe quantum interference features that violate classical predictions.
The longest array includes reflecting boundary conditions.Comment: 7 pages,7 figure
AÂ comparison of business meeting practices in Germany and Spain
This article in the journal Gruppe. Interaktion. Organisation. (GIO) presents a study on meetings, an important part of contemporary organizational life. What happens in meetings affects individual employee experiences, team processes, and organizational functioning. However, to date little is known regarding cross-cultural differences in meeting practices. This study leverages an organizational sample (N = 488) with a German and a Spanish site to compare how pre-meeting talk, meeting design, voice in meetings, and meeting follow-up actions differ across the two cultures. Hypotheses were derived from prior intercultural theory (i.e., the GLOBE study). Following Open Science principles, the study was pre-registered. Contrary to our expectations, we found no significant differences in meeting practices between monocultural German and Spanish workplace meetings. These findings suggest that cultural differences in workplace attitudes and work practices may be diminishing in an increasingly global workplace. We sketch implications for meeting science and cross-cultural research on business practices more broadly
The nonrelativistic limit of the Majorana equation and its simulation in trapped ions
We analyze the Majorana equation in the limit where the particle is at rest.
We show that several counterintuitive features, absent in the rest limit of the
Dirac equation, do appear. Among them, Dirac-like positive energy solutions
that turn into negative energy ones by free evolution, or nonstandard
oscillations and interference between real and imaginary spinor components for
complex solutions. We also study the ultrarelativistic limit, showing that the
Majorana and Dirac equations mutually converge. Furthermore, we propose a
physical implementation in trapped ions.Comment: 7 pages, 1 figure. Proceedings of 18th Central European Workshop on
Quantum Optics (CEWQO 2011), Madrid, Spai
Algebraic Geometric Comparison of Probability Distributions
We propose a novel algebraic framework for treating probability distributions
represented by their cumulants such as the mean and covariance matrix. As an
example, we consider the unsupervised learning problem of finding the subspace
on which several probability distributions agree. Instead of minimizing an
objective function involving the estimated cumulants, we show that by treating
the cumulants as elements of the polynomial ring we can directly solve the
problem, at a lower computational cost and with higher accuracy. Moreover, the
algebraic viewpoint on probability distributions allows us to invoke the theory
of Algebraic Geometry, which we demonstrate in a compact proof for an
identifiability criterion
SPoC: A novel framework for relating the amplitude of neuronal oscillations to behaviorally relevant parameters
Previously, modulations in power of neuronal oscillations have been functionally linked to sensory, motor and cognitive operations. Such links are commonly established by relating the power modulations to specific target variables such as reaction times or task ratings. Consequently, the resulting spatio-spectral representation is subjected to neurophysiological interpretation. As an alternative, independent component analysis (ICA) or alternative decomposition methods can be applied and the power of the components may be related to the target variable. In this paper we show that these standard approaches are suboptimal as the first does not take into account the superposition of many sources due to volume conduction, while the second is unable to exploit available information about the target variable. To improve upon these approaches we introduce a novel (supervised) source separation framework called Source Power Comodulation (SPoC). SPoC makes use of the target variable in the decomposition process in order to give preference to components whose power comodulates with the target variable. We present two algorithms that implement the SPoC approach. Using simulations with a realistic head model, we show that the SPoC algorithms are able extract neuronal components exhibiting high correlation of power with the target variable. In this task, the SPoC algorithms outperform other commonly used techniques that are based on the sensor data or ICA approaches. Furthermore, using real electroencephalography (EEG) recordings during an auditory steady state paradigm, we demonstrate the utility of the SPoC algorithms by extracting neuronal components exhibiting high correlation of power with the intensity of the auditory input. Taking into account the results of the simulations and real EEG recordings, we conclude that SPoC represents an adequate approach for the optimal extraction of neuronal components showing coupling of power with continuously changing behaviorally relevant parameters
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