287 research outputs found
Migdal Effect in Dark Matter Direct Detection Experiments
The elastic scattering of an atomic nucleus plays a central role in dark
matter direct detection experiments. In those experiments, it is usually
assumed that the atomic electrons around the nucleus of the target material
immediately follow the motion of the recoil nucleus. In reality, however, it
takes some time for the electrons to catch up, which results in ionization and
excitation of the atoms. In previous studies, those effects are taken into
account by using the so-called Migdal's approach, in which the final state
ionization/excitation are treated separately from the nuclear recoil. In this
paper, we reformulate the Migdal's approach so that the "atomic recoil" cross
section is obtained coherently, where we make transparent the energy-momentum
conservation and the probability conservation. We show that the final state
ionization/excitation can enhance the detectability of rather light dark matter
in the GeV mass range via the {\it nuclear} scattering. We also discuss the
coherent neutrino-nucleus scattering, where the same effects are expected.Comment: Integrated probability data fixed and Si.dat adde
Ridge Regression, Hubness, and Zero-Shot Learning
This paper discusses the effect of hubness in zero-shot learning, when ridge
regression is used to find a mapping between the example space to the label
space. Contrary to the existing approach, which attempts to find a mapping from
the example space to the label space, we show that mapping labels into the
example space is desirable to suppress the emergence of hubs in the subsequent
nearest neighbor search step. Assuming a simple data model, we prove that the
proposed approach indeed reduces hubness. This was verified empirically on the
tasks of bilingual lexicon extraction and image labeling: hubness was reduced
with both of these tasks and the accuracy was improved accordingly.Comment: To be presented at ECML/PKDD 201
光の連続測定による量子結合統計の物理的様相への実験的探求
広島大学(Hiroshima University)博士(理学)Doctor of Sciencedoctora
Violation of Leggett-Garg inequalities in quantum measurements with variable resolution and back-action
Quantum mechanics violates Leggett-Garg inequalities because the operator
formalism predicts correlations between different spin components that would
correspond to negative joint probabilities for the outcomes of joint
measurements. However, the uncertainty principle ensures that such joint
measurements cannot be implemented without errors. In a sequential measurement
of the spin components, the resolution and back-action errors of the
intermediate measurement can be described by random spin flips acting on an
intrinsic joint probability. If the error rates are known, the intrinsic joint
probability can be reconstructed from the noisy statistics of the actual
measurement outcomes. In this paper, we use the spin-flip model of measurement
errors to analyze experimental data on photon polarization obtained with an
interferometric setup that allows us to vary the measurement strength and hence
the balance between resolution and back-action errors. We confirm that the
intrinsic joint probability obtained from the experimental data is independent
of measurement strength and show that the same violation of the Leggett-Garg
inequality can be obtained for any combination of measurement resolution and
back-action.Comment: 17 pages, 7 figure
Susceptibility to exacerbation in COPD
The mitochondrial control region sequences of Apodemus specious used for the construction of the phylogenetic tree and network
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