25,957 research outputs found
Some Issues in a Gauge Model of Unparticles
We address in a recent gauge model of unparticles the issues that are
important for consistency of a gauge theory, i.e., unitarity and Ward identity
of physical amplitudes. We find that non-integrable singularities arise in
physical quantities like cross section and decay rate from gauge interactions
of unparticles. We also show that Ward identity is violated due to the lack of
a dispersion relation for charged unparticles although the Ward-Takahashi
identity for general Green functions is incorporated in the model. A previous
observation that the unparticle's (with scaling dimension d) contribution to
the gauge boson self-energy is a factor (2-d) of the particle's has been
extended to the Green function of triple gauge bosons. This (2-d) rule may be
generally true for any point Green functions of gauge bosons. This implies that
the model would be trivial even as one that mimics certain dynamical effects on
gauge bosons in which unparticles serve as an interpolating field.Comment: v1:16 pages, 3 figures. v2: some clarifications made and presentation
improved, calculation and conclusion not modified; refs added and updated.
Version to appear in EPJ
Modulation efficiency of LiNbO<sub>3</sub> waveguide electro-optic intensity modulator operating at high microwave frequency
The modulation efficiency, at high-frequency microwave modulation, of a LiNbO3 waveguide electro-optic modulator is shown to be degraded severely, especially when it is used as a frequency translator in a Brillouin-distributed fiber-sensing system. We derive an analytical expression for this attenuation regarding the phase-velocity mismatch and the impedance mismatch during the modulation process. Theoretical results are confirmed by experimental results based on a 15 Gb/s LiNbO3 optical intensity modulator
From the chiral magnetic wave to the charge dependence of elliptic flow
The quark-gluon plasma formed in heavy ion collisions contains charged chiral
fermions evolving in an external magnetic field. At finite density of electric
charge or baryon number (resulting either from nuclear stopping or from
fluctuations), the triangle anomaly induces in the plasma the Chiral Magnetic
Wave (CMW). The CMW first induces a separation of the right and left chiral
charges along the magnetic field; the resulting dipolar axial charge density in
turn induces the oppositely directed vector charge currents leading to an
electric quadrupole moment of the quark-gluon plasma. Boosted by the strong
collective flow, the electric quadrupole moment translates into the charge
dependence of the elliptic flow coefficients, so that
(at positive net charge). Using the latest quantitative simulations of the
produced magnetic field and solving the CMW equation, we make further
quantitative estimates of the produced splitting and its centrality
dependence. We compare the results with the available experimental data.Comment: Contains 12 pages, 6 figures, written as a proceeding for the talk of
Y. Burnier at the conference "P and CP-odd Effects in Hot and Dense Matter
2012" held in BN
Deep Learning for Single Image Super-Resolution: A Brief Review
Single image super-resolution (SISR) is a notoriously challenging ill-posed
problem, which aims to obtain a high-resolution (HR) output from one of its
low-resolution (LR) versions. To solve the SISR problem, recently powerful deep
learning algorithms have been employed and achieved the state-of-the-art
performance. In this survey, we review representative deep learning-based SISR
methods, and group them into two categories according to their major
contributions to two essential aspects of SISR: the exploration of efficient
neural network architectures for SISR, and the development of effective
optimization objectives for deep SISR learning. For each category, a baseline
is firstly established and several critical limitations of the baseline are
summarized. Then representative works on overcoming these limitations are
presented based on their original contents as well as our critical
understandings and analyses, and relevant comparisons are conducted from a
variety of perspectives. Finally we conclude this review with some vital
current challenges and future trends in SISR leveraging deep learning
algorithms.Comment: Accepted by IEEE Transactions on Multimedia (TMM
Patrones de distribución de individuos longevos de plantas relictas en los alrededores de la montana Fanjingshan en China: implicaciones para su conservación in situ
The mountain areas in south-central China are widely recognized as refugia of relict plants during the late Neogene and Quaternary periods. In this paper, we try to explore the distribution patterns of natural habitats and to exactly locate the refugia of relict species around Fanjingshan Mountain using dendrological data of long-lived individuals (≥ 100 years old). Six typical relict plants were found around the mountain, i.e. Cyclocarya paliurus, Ginkgo biloba, Liriodendron chinense, Pinus massoniana, Podocarpus macrophyllus, and Taxus chinensis. The long-lived individuals were divided into three classes according to their ages: Class-I (≥ 500 years), Class-II (300–499 years), and Class-III (100–299 years). Our results showed that the south-west region to the mountain was the main distribution area of Class-I trees of G. biloba and T. chinensis, most of which occurring in the same small village (Yangliu Village of Yinjiang County). The north-east region harboured all the six relict species. Floristic analyses also indicated these two regions were very similar in tree growth as measured by DBH (diameter at breast height of 1.3 m). Thus, these two areas would have provided long-term suitable habitats for relict species. The south-west region, especially the small village Yangliu, should be given highest priority for in situ conservation of relict species and other rare and endangered plants. Attention should also be paid to the north-east region for its very high species diversity of relict species.Las áreas montañosas de la región centro-sur de China están ampliamente reconocidas por su papel como refugio de plantas relictas durante la última etapa del Neógeno y el Cuaternario. En el presente trabajo se intentan explorar los patrones de distribución de los hábitats naturales y la localización exacta de los refugios para especies vegetales relictas en los alrededores de la montaña Fanjinshan, mediante el empleo de datos dendrológicos de individuos longevos (≥ 100 años). En el área de estudio se encontraron seis especies vegetales tÃpicamente relictas: Cyclocarya paliurus, Ginkgo biloba, Liriodendron chinense, Pinus massoniana, Podocarpus macrophyllus y Taxus chinensis. Los individuos longevos se dividieron en tres categorÃas de acuerdo con su edad estimada: individuos de Clase I (≥ 500 años), de Clase II (300–499 años) y de Clase III (100–299 años). Nuestros resultados muestran que la región situada al suroeste de la montaña se corresponde con la principal área de distribución de los árboles de Clase I de G. biloba y T. chinensis, localizándose la mayor parte de éstos en los alrededores de una pequeña aldea (Yangliu, en el condado de Yinjiang). La región situada al noreste de Fanjinshan alberga, por su parte, las seis especies relictas, y los análisis florÃsticos muestran una elevada similaridad entre ambas regiones por lo que respecta al crecimiento arbóreo medido como DBH [diámetro a la altura del pecho (1,3 m)]. Por consiguiente, estas dos regiones habrÃan proporcionado hábitats adecuados para la supervivencia de especies relictas. La región suroeste, y en especial la aldea de Yangliu, deben recibir la máxima prioridad para la conservación in situ de especies relictas (y otras especies raras y amenazadas). La región noreste también debe priorizarse dada su elevada diversidad de especies relictas
Dynamics, space, and regional inequality in provincial China: a case study of Guangdong province
pre-printThis paper investigates the regional inequality in one of the most developed provinces in China, Guangdong, from 1979 to 2009 and follows the multi-scale and multi-mechanism framework. We have found a new round of intensifying inequality in Guangdong since the early 2000s, which is attributed to the widening gap between the core region of the Pearl River Delta (PRD) and the rest of the province (periphery) and between the urban and rural areas. The authors also apply a distribution dynamics approach and spatial Markov chains to identify the spatial-temporal dynamics of regional disparities in Guangdong. The results show that there has been a progressive bias towards a poverty trap in the province and the effect of self-reinforcing agglomeration is evident. Using a multilevel model, the study further unfolds that the regional inequality in Guangdong is sensitive to the core-periphery hierarchy of multi-mechanisms and reveals the relative influence of decentralization, marketization and globalization. We argue that the policies towards inequality-reducing in Guangdong have been constrained by the geographical barriers and the effect of self-reinforcing agglomeration in the PRD, while marketization has potential to mediate the uneven development driven by the spatial concentration of foreign investment
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