2,665 research outputs found

    Hawking Radiation of Black p-Branes from Gravitational Anomaly

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    We investigate the Hawking radiation of black pp-branes of superstring theories using the method of anomaly cancelation, specially, we use the method of [S. Iso, H. Umetsu and F. Wilczek, {\sl Phys. Rev. Lett.} {\bf 96}, 151302 (2006); {\sl Phys. Rev. D} {\bf 74}, 044017 (2006)]. The metrics of black pp-branes are spherically symmetric, but not the Schwarzschild type. In order to simplify the calculation, we first make a coordinate transformation to transform the metric to the Schwarzschild type. Then we calculate its energy-momentum flux from the method of anomaly cancelation of the above mentioned references. The obtained energy-momentum flux is equal to a black body radiation, the thermodynamic temperature of the radiation is equal to its Hawking temperature. And we find that the results are not changed for the original non-Schwarzschild type spherically symmetric metric.Comment: 19 pages Latex, some mistakes correcte

    Non-Markovian effect on the quantum discord

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    We study the non-Markovian effect on the dynamics of the quantum discord by exactly solving a model consisting of two independent qubits subject to two zero-temperature non-Markovian reservoirs, respectively. Considering the two qubits initially prepared in Bell-like or extended Werner-like states, we show that there is no occurrence of the sudden death, but only instantaneous disappearance of the quantum discord at some time points, in comparison to the entanglement sudden death in the same range of the parameters of interest. It implies that the quantum discord is more useful than the entanglement to describe quantum correlation involved in quantum systems.Comment: 5 pages, 5 figure

    Constraints on holographic dark energy models using the differential ages of passively evolving galaxies

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    Using the absolute ages of passively evolving galaxies observed at different redshifts, one can obtain the differential ages, the derivative of redshift zz with respect to the cosmic time tt (i.e. dz/dt{\rm d} z/{\rm d}t). Thus, the Hubble parameter H(z)H(z) can be measured through the relation H(z)=(dz/dt)/(1+z)H(z)=-({\rm d} z/{\rm d}t)/(1+z). By comparing the measured Hubble parameter at different redshifts with the theoretical one containing free cosmological parameters, one can constrain current cosmological models. In this paper, we use this method to present the constraint on a spatially flat Friedman-Robert-Walker Universe with a matter component and a holographic dark energy component, in which the parameter cc plays a significant role in this dark energy model. Firstly we consider three fixed values of cc=0.6, 1.0 and 1.4 in the fitting of data. If we set cc free, the best fitting values are c=0.26c=0.26, Ωm0=0.16\Omega_{\rm m0}=0.16, h=0.9998h=0.9998. It is shown that the holographic dark energy behaves like a quintom-type at the 1σ1\sigma level. This result is consistent with some other independent cosmological constrains, which imply that c<1.0c<1.0 is favored. We also test the results derived from the differential ages using another independent method based on the lookback time to galaxy clusters and the age of the universe. It shows that our results are reliable.Comment: 18 pages including 7 figures and 1 tables. Final version for publication in Modern Physics Letters A (MPLA)[minor revision to match the appear version

    China’s emerging tax regime: Devolution, fiscal federalism, or tax farming?

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    China like other transition economies needs to establish a tax regime compatible with a market economy. The paper singles out the general and China-specific features by which national legislation attempts to accompany economic transformation. Based on an empirical study in two provinces this paper shows that without including local government agencies and their budgets, China’s fiscal federalism cannot be analysed. This paper argues that China’s emerging tax regime depends on the institutional design that shapes the interaction between firms (as major tax payers at the local level), local government agencies, and the national tax administration

    Fulvic acid affects pepper antioxidant activity and fruit quality

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    Fulvic acid has been considered as a valuable fertilizer for sustainable agriculture. The present investigation  was undertaken to evaluate the effect of fulvic acid (FA) on antioxidant compounds and fruit quality of pepper  under field conditions. Plants were grown in the Department of Horticulture Farm, Ferdowsi University of  Mashhad, Iran (latitude 36‹ 17Œ N, longitude 59‹ 35Œ E and 985 m elevation). The experiment was designed in randomized block design with three replications. Treatments consisted of five levels of fulvic acid (0, 25, 100, 175 and 250 mg kg-1). The results indicate that fruit antioxidant activity, total phenolic, carbohydrate,  capsaicin and carotenoids contents were influenced by fulvic acid, but total flavonoid and ascorbic acid  contents were not affected significantly by fulvic acid treatments applications. FA applied at 25 mg kg-1 resulted in the highest carbohydrate content, lycopene and ƒÀ-carotene contents, while the lowest values  were recorded in the control. Fulvic acid treatments positively affected fruit quality (total soluble solids and titratable acidity); total soluble solids and titratable acidity significantly increased in response to FA  treatments. These results confirm that the use of fulvic acid have a positive effect on antioxidant activity and quality of hot pepper under field conditions.Key words: Fulvic acid, antioxidant activity, quality, pepper

    (D* to D + gamma) and (B* to B + gamma) as derived from QCD Sum Rules

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    The method of QCD sum rules in the presence of the external electromagnetic FμνF_{\mu\nu} field is used to analyze radiative decays of charmed or bottomed mesons such as DDγD^{\ast}\to D\gamma and BBγB^{\ast}\to B\gamma, with the susceptibilities obtained previously from the study of baryon magnetic moments. Our predictions on DD^{\ast} decays agree very well with the experimental data. There are differences among the various theoretical predictions on BB^{\ast} decays but the data are not yet available.Comment: 11 pages, Late

    The influence of slope and peatland vegetation type on riverine dissolved organic carbon and water colour at different scales

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    Peatlands are important sources of fluvial carbon. Previous research has shown that riverine dissolved organic carbon (DOC) concentrations are largely controlled by soil type. However, there has been little work to establish the controls of riverine DOC within blanket peatlands that have not undergone major disturbance from drainage or burning. A total of 119 peatland catchments were sampled for riverine DOC and water colour across three drainage basins during six repeated sampling campaigns. The topographic characteristics of each catchment were determined from digital elevation models. The dominant vegetation cover was mapped using 0.5 m resolution colour infrared aerial images, with ground-truthed validation revealing 82 % accuracy. Forward and backward stepwise regression modelling showed that mean slope was a strong (and negative) determinant of DOC and water colour in blanket peatland river waters. There was a weak role for plant functional type in determining DOC and water colour. At the basin scale, there were major differences between the models depending on the basin. The dominance of topographic predictors of DOC found in our study, combined with a weaker role of vegetation type, paves the way for developing improved planning tools for water companies operating in peatland catchments. Using topographic data and aerial imagery it will be possible to predict which tributaries will typically yield lower DOC concentrations and which are therefore more suitable and cost-effective as raw water intakes

    Anatomical Region-Specific In Vivo Wireless Communication Channel Characterization

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    In vivo wireless body area networks (WBANs) and their associated technologies are shaping the future of healthcare by providing continuous health monitoring and noninvasive surgical capabilities, in addition to remote diagnostic and treatment of diseases. To fully exploit the potential of such devices, it is necessary to characterize the communication channel which will help to build reliable and high-performance communication systems. This paper presents an in vivo wireless communication channel characterization for male torso both numerically and experimentally (on a human cadaver) considering various organs at 915 MHz and 2.4 GHz. A statistical path loss (PL) model is introduced, and the anatomical region-specific parameters are provided. It is found that the mean PL in dB scale exhibits a linear decaying characteristic rather than an exponential decaying profile inside the body, and the power decay rate is approximately twice at 2.4 GHz as compared to 915 MHz. Moreover, the variance of shadowing increases significantly as the in vivo antenna is placed deeper inside the body since the main scatterers are present in the vicinity of the antenna. Multipath propagation characteristics are also investigated to facilitate proper waveform designs in the future wireless healthcare systems, and a rootmean- square (RMS) delay spread of 2.76 ns is observed at 5 cm depth. Results show that the in vivo channel exhibit different characteristics than the classical communication channels, and location dependency is very critical for accurate, reliable, and energy-efficient link budget calculations
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