Universal symmetry-protected topological invariants for symmetry-protected topological states

Symmetry-protected topological (SPT) states are short-range entangled states with a symmetry G. They belong to a new class of quantum states of matter which are classified by the group cohomology $H^{d+1}(G,\mathbb{R}/\mathbb{Z})$ in d-dimensional space. In this paper, we propose a class of symmetry- protected topological invariants that may allow us to fully characterize SPT states with a symmetry group G (ie allow us to measure the cocycles in $H^{d+1}(G,\mathbb{R}/\mathbb{Z})$ that characterize the SPT states). We give an explicit and detailed construction of symmetry-protected topological invariants for 2+1D SPT states. Such a construction can be directly generalized to other dimensions.Comment: 12 pages, 11 figures. Added reference

Quantized topological terms in weak-coupling gauge theories with symmetry and their connection to symmetry enriched topological phases

We study the quantized topological terms in a weak-coupling gauge theory with gauge group $G_g$ and a global symmetry $G_s$ in $d$ space-time dimensions. We show that the quantized topological terms are classified by a pair $(G,\nu_d)$, where $G$ is an extension of $G_s$ by $G_g$ and $\nu_d$ an element in group cohomology \cH^d(G,\R/\Z). When $d=3$ and/or when $G_g$ is finite, the weak-coupling gauge theories with quantized topological terms describe gapped symmetry enriched topological (SET) phases (i.e. gapped long-range entangled phases with symmetry). Thus, those SET phases are classified by \cH^d(G,\R/\Z), where $G/G_g=G_s$. We also apply our theory to a simple case $G_s=G_g=Z_2$, which leads to 12 different SET phases in 2+1D, where quasiparticles have different patterns of fractional $G_s=Z_2$ quantum numbers and fractional statistics. If the weak-coupling gauge theories are gapless, then the different quantized topological terms may describe different gapless phases of the gauge theories with a symmetry $G_s$, which may lead to different fractionalizations of $G_s$ quantum numbers and different fractional statistics (if in 2+1D).Comment: 13 pages, 2 figures, PRB accepted version with added clarification on obtaining G_s charge for a given PSG with non-trivial topological terms. arXiv admin note: text overlap with arXiv:1301.767

Complexity growth rates for AdS black holes in massive gravity and f(R)f(R) gravity

The "complexity = action" duality states that the quantum complexity is equal to the action of the stationary AdS black holes within the Wheeler-DeWitt patch at late time approximation. We compute the action growth rates of the neutral and charged black holes in massive gravity and the neutral, charged and Kerr-Newman black holes in $f(R)$ gravity to test this conjecture. Besides, we investigate the effects of the massive graviton terms, higher derivative terms and the topology of the black hole horizon on the complexity growth rate.Comment: 11 pages, no figur

Broadband enhancement of light harvesting in luminescent solar concentrator

Luminescent solar concentrator (LSC) can absorb large-area incident sunlight, then emit luminescence with high quantum efficiency, which finally be collected by a small photovoltaic (PV) system. The light-harvesting area of the PV system is much smaller than that of the LSC system, potentially improving the efficiency and reducing the cost of solar cells. Here, based on Fermi-golden rule, we present a theoretical description of the luminescent process in nanoscale LSCs where the conventional ray-optics model is no longer applicable. As an example calculated with this new model, we demonstrate that a slot waveguide consisting of a nanometer-sized low-index slot region sandwiched by two high-index regions provides a broadband enhancement of light harvesting by the luminescent centers in the slot region. This is because the slot waveguide can (1) greatly enhance the spontaneous emission due to the Purcell effect, (2) dramatically increase the effective absorption cross-section of luminescent centers, and (3) strongly improve the quantum efficiency of luminescent centers. It is found that about 80% solar photons can be ultimately converted to waveguide-coupled luminescent photons even for a low luminescent quantum efficiency of 0.5. This LSC is potential to construct a tandem structure which can absorb nearly full-spectrum solar photons, and also may be of special interest for building integrated nano-PV applications

Enterprise Technology Management Maturity Model and Application

In retrospect the human history, the economic development is concerned with technology. Technology is the huge force that pushes forward the economic development. In the current knowledge-economic period, technology has become an important asset in an organization, especially in an enterprise. Consequently, technology management has emerged as an issue that managers have to deal with. Therefore, this paper aims to construct a technology management maturity model to evaluate the differences of enterprises’ technology management practices. An enterprise will be taken as an example to illustrate the application of this model and discuss how to support the practices at each maturity level in a certain enterprise by using this model. Key words: technology management, maturity model, technology management process Résumé: Dans la rétrospection de l’histoire humaine, on constate que le développement économique se rapporte toujours avec la technologie. Celle-ci est une force considérable encourageant le développement de l’économie. Dans la période actuell de l’économie du savoir, la technologie est déja devenue un capital important pour une organisation, en particulier pour une entreprise. En conséquence, le management de la technologie émerge comme un problème que les gérants sont obligés de résoudre. Ainsi, l’article présent vise à construire un modèle mûr du management technologique afin d’évaluer les différences de pratiques des entreprises dans ce domaine. Une entreprise sera donné comme exemple pour illustrer l’application de ce modèle et discuter comment supporter les pratiques à chaque niveau de maturité dans une certaine entreprise en applicant ce modèle. Mots-Clés: management technologique, modèle mûr, processus du management technologiqu