Dynamical Linear Response of TDDFT with LDA+U Functional: strongly hybridized Frenkel excitons in NiO

Within the framework of time-dependent density-functional theory (TDDFT), we derive the dynamical linear response of LDA+U functional and benchmark it on NiO, a prototypical Mott insulator. Formulated using real-space Wannier functions, our computationally inexpensive framework gives detailed insights into the formation of tightly bound Frenkel excitons with reasonable accuracy. Specifically, a strong hybridization of multiple excitons is found to significantly modify the exciton properties. Furthermore, our study exposes a significant generic limitation of adiabatic approximation in TDDFT with hybrid functionals and in existing Bethe-Salpeter-equation approaches, advocating the necessity of strongly energy-dependent kernels in future development.Comment: 5 pages, 2 figure

Prediction of the CPCP asymmetry C00C_{00} in B0→D0D0‾B^0 \to D^0\overline{D^0} decay

Of all $B \to D \overline{D}$ decays, the $B^0 \to D^0 \overline{D^0}$ decay has the smallest observed branching ratio as it takes place primarily via the suppressed $W$-exchange diagram. The $CP$ asymmetry for this mode is yet to be measured experimentally. By exploiting the relationship among the decay amplitudes of $B \to D\overline{D}$ decays (using isospin and topological amplitudes) we are able to relate the $CP$ asymmetries and branching ratios by a simple expression. This enables us to predict the $CP$ asymmetry $C_{00}$ in $B^0 \to D^0 \overline{D^0}$. While the predicted central values of $C_{00}$ are outside the physically allowed region, they are currently associated with large uncertainties owing to the large errors in the measurements of the $B^0 \to D^0 \overline{D^0}$ branching ratio ($B_{00}$), the other $CP$ asymmetries $C_{+-}$ (of $B^0 \to D^+ D^-$) and $A_{\text{CP}}$ (of $B^+ \to D^+ \overline{D^0}$). With a precise determination of $B_{00}$, $C_{+-}$ and $A_{\text{CP}}$, one can use our analytical result to predict $C_{00}$ with a reduced error and compare it with the experimental measurement when it becomes available. The correlation between $B_{00}$ and $C_{00}$ is an interesting aspect that can be probed in ongoing and future particle physics experiments such as LHCb and Belle II.Comment: 21 pages, 6 figures, accepted for publication in JHE

SSD: Single Shot MultiBox Detector

We present a method for detecting objects in images using a single deep neural network. Our approach, named SSD, discretizes the output space of bounding boxes into a set of default boxes over different aspect ratios and scales per feature map location. At prediction time, the network generates scores for the presence of each object category in each default box and produces adjustments to the box to better match the object shape. Additionally, the network combines predictions from multiple feature maps with different resolutions to naturally handle objects of various sizes. Our SSD model is simple relative to methods that require object proposals because it completely eliminates proposal generation and subsequent pixel or feature resampling stage and encapsulates all computation in a single network. This makes SSD easy to train and straightforward to integrate into systems that require a detection component. Experimental results on the PASCAL VOC, MS COCO, and ILSVRC datasets confirm that SSD has comparable accuracy to methods that utilize an additional object proposal step and is much faster, while providing a unified framework for both training and inference. Compared to other single stage methods, SSD has much better accuracy, even with a smaller input image size. For $300\times 300$ input, SSD achieves 72.1% mAP on VOC2007 test at 58 FPS on a Nvidia Titan X and for $500\times 500$ input, SSD achieves 75.1% mAP, outperforming a comparable state of the art Faster R-CNN model. Code is available at https://github.com/weiliu89/caffe/tree/ssd .Comment: ECCV 201

Modulation Doping near Mott-Insulator Heterojunctions

We argue that interesting strongly correlated two-dimensional electron systems can be created by modulation doping near a heterojunction between Mott insulators. Because the dopant atoms are remote from the carrier system, the electronic system will be weakly disordered. We argue that the competition between different ordered states can be engineered by choosing appropriate values for the dopant density and the setback distance of the doping layer. In particular larger setback distances favor two-dimensional antiferromagnetism over ferromagnetism. We estimate some key properties of modulation-doped Mott insulator heterojunctions by combining insights from Hartree-Fock-Theory and Dynamical-Mean-Field-Theory descriptions and discuss potentially attractive material combinations.Comment: 9 pages, 9 figures, submitte

Fast Single Shot Detection and Pose Estimation

For applications in navigation and robotics, estimating the 3D pose of objects is as important as detection. Many approaches to pose estimation rely on detecting or tracking parts or keypoints [11, 21]. In this paper we build on a recent state-of-the-art convolutional network for slidingwindow detection [10] to provide detection and rough pose estimation in a single shot, without intermediate stages of detecting parts or initial bounding boxes. While not the first system to treat pose estimation as a categorization problem, this is the first attempt to combine detection and pose estimation at the same level using a deep learning approach. The key to the architecture is a deep convolutional network where scores for the presence of an object category, the offset for its location, and the approximate pose are all estimated on a regular grid of locations in the image. The resulting system is as accurate as recent work on pose estimation (42.4% 8 View mAVP on Pascal 3D+ [21] ) and significantly faster (46 frames per second (FPS) on a TITAN X GPU). This approach to detection and rough pose estimation is fast and accurate enough to be widely applied as a pre-processing step for tasks including high-accuracy pose estimation, object tracking and localization, and vSLAM

Collective Excitations, Nambu-Goldstone Modes and Instability of Inhomogeneous Polariton Condensates

We study non-equilibrium microcavity-polariton condensates (MPCs) in a harmonic potential trap theoretically. We calculate and analyze the steady state, collective-excitation modes and instability of MPCs. Within excitation modes, there exist Nambu-Goldstone modes that can reveal the pattern of the spontaneous symmetry breaking of MPCs. Bifurcation of the stable and unstable modes is identified in terms of the pumping power and spot size. The unstable mechanism associated with the inward supercurrent flow is characterized by the existence of a supersonic region within the condensate.Comment: 16 pages, 3 figure

Study of Radiative Leptonic D Meson Decays

We study the radiative leptonic $D$ meson decays of D^+_{(s)}\to \l^+\nu_{\l}\gamma (\l=e,\mu,\tau), $D^0\to \nu\bar{\nu}\gamma$ and D^0\to \l^+\l^-\gamma ($l=e,\mu$) within the light front quark model. In the standard model, we find that the decay branching ratios of $D^+_{(s)}\to e^+\nu_e\gamma$, $D^+_{(s)}\to\mu^+\nu_{\mu}\gamma$ and $D^+_{(s)}\to\tau^+\nu_{\tau}\gamma$ are $6.9\times 10^{-6}$ ($7.7\times 10^{-5}$), $2.5\times 10^{-5}$ ($2.6\times 10^{-4}$), and $6.0\times 10^{-6}$ ($3.2\times 10^{-4}$), and that of D^0\to\l^+\l^-\gamma (\l=e,\mu) and $D^0\to\nu\bar{\nu}\gamma$ are $6.3\times 10^{-11}$ and $2.7\times 10^{-16}$, respectively.Comment: 23 pages, 6 Figures, LaTex file, a reference added, to be published in Mod. Phys. Lett.