Adaptive Tag Selection for Image Annotation

Not all tags are relevant to an image, and the number of relevant tags is image-dependent. Although many methods have been proposed for image auto-annotation, the question of how to determine the number of tags to be selected per image remains open. The main challenge is that for a large tag vocabulary, there is often a lack of ground truth data for acquiring optimal cutoff thresholds per tag. In contrast to previous works that pre-specify the number of tags to be selected, we propose in this paper adaptive tag selection. The key insight is to divide the vocabulary into two disjoint subsets, namely a seen set consisting of tags having ground truth available for optimizing their thresholds and a novel set consisting of tags without any ground truth. Such a division allows us to estimate how many tags shall be selected from the novel set according to the tags that have been selected from the seen set. The effectiveness of the proposed method is justified by our participation in the ImageCLEF 2014 image annotation task. On a set of 2,065 test images with ground truth available for 207 tags, the benchmark evaluation shows that compared to the popular top-$k$ strategy which obtains an F-score of 0.122, adaptive tag selection achieves a higher F-score of 0.223. Moreover, by treating the underlying image annotation system as a black box, the new method can be used as an easy plug-in to boost the performance of existing systems

Leptophilic dark matter in gauged U(1)Le−LμU(1)_{L_e-L_\mu} model in light of DAMPE cosmic ray e++e−e^+ + e^- excess

Motivated by the very recent cosmic-ray electron+positron excess observed by DAMPE collaboration, we investigate a Dirac fermion dark matter (DM) in the gauged $L_e - L_\mu$ model. DM interacts with the electron and muon via the $U(1)_{e-\mu}$ gauge boson $Z^{'}$. The model can explain the DAMPE data well. Although a non-zero DM-nucleon cross section is only generated at one loop level and there is a partial cancellation between $Z^{'}ee$ and $Z^{'}\mu\mu$ couplings, we find that a large portion of $Z^{'}$ mass is ruled out from direct DM detection limit leaving the allowed $Z^{'}$ mass to be close to two times of the DM mass. Implications for $pp \to Z^{'} \to 2\ell$ and $pp \to 2\ell + Z^{'}$ , and muon $g-2$ anomaly are also studied.Comment: Discussions added, version accepted by EPJ

t→cVt\to cV via SUSY FCNC couplings in the unconstrained MSSM

We recalculate the branching ratios for $t\to cV$ ($V=g,\gamma,Z$) induced by SUSY FCNC couplings within the general unconstrained MSSM framework using mass eigenstate approach. Our results show that the branching ratios for these decays are larger than ones reported in previous literatures in the MSSM with R-parity conservation, and they can reach $\sim 10^{-4}$, $\sim 10^{-6}$, and $\sim 10^{-6}$, respectively, for favorable parameter values allowed by current precise experiments. Thus, the branching ratios for $t\to cg$ and $t\to c\gamma$ may be measurable at the LHC.Comment: 15 pages, 3 figures, minor changs in the Table

Multivariable Scaling for the Anomalous Hall Effect

We derive a general scaling relation for the anomalous Hall effect in ferromagnetic metals involving multiple competing scattering mechanisms, described by a quadratic hypersurface in the space spanned by the partial resistivities. We also present experimental findings, which show strong deviation from previously found scaling forms when different scattering mechanism compete in strength but can be nicely explained by our theory