Black Holes, Entropy Bound and Causality Violation

The gravity/gauge theory duality has provided us a way of studying QCD at short distances from straightforward calculations in classical general relativity. Among numerous results obtained so far, one of the most striking is the universality of the ratio of the shear viscosity to the entropy density. For all gauge theories with Einstein gravity dual, this ratio is \eta/s=1/4\pi. However, in general higher-curvature gravity theories, including two concrete models under discussion - the Gauss-Bonnet gravity and the (Riemann)^2 gravity - the ratio \eta/s can be smaller than 1/4\pi (thus violating the conjecture bound), equal to 1/4\pi or even larger than 1/4\pi. As we probe spacetime at shorter distances, there arises an internal inconsistency in the theory, such as a violation of microcausality, which is correlated with a classical limit on black hole entropy.Comment: 8 pages, no figures; Invited contribution to appear in the Proceedings of the 75 Years since Solvay, Singapore, Nov 2008, (World Scientific, Singapore, 2009

Wideband performance comparison between the 40 GHz and 60 GHz frequency bands for indoor radio channels

B

How Well Does AdS/QCD Describe QCD?

AdS/QCD is an extra-dimensional approach to modeling hadronic physics, motivated by the AdS/CFT correspondence in string theory. AdS/QCD models are often more accurate than would have been expected at energies below a few GeV. We address the question of why these models are so successful, and respond to some of the criticisms that have been waged against these models.Comment: To appear in proceedings of Crossing the Boundaries: Gauge Dynamics at Strong Coupling (Shifmania), Minnesota, May 14-17, 2009. 12 pages, 2 eps figure

Politics or profits along the “Silk Road”: what drives Chinese farms in Tajikistan and helps them thrive?

China’s influence in neighboring Central Asian states is growing at a fast pace. Since the launch of the One Belt, One Road (OBOR) initiative to accelerate China’s engagement in Central Asia and beyond, nearly all Chinese activity in this region has been gathered under OBOR. OBOR now seems to cover a plethora of spatially and temporally expanding state and privately driven projects. In this paper, I discuss large- and small-scale Chinese farm enterprises in Tajikistan, in which discussions around China’s “global land investments” and OBOR intersect. Beneath abstract conceptualizations of OBOR and the Chinese presence in Central Asia, my analysis shows that Chinese land investments in Tajikistan are shaped by Chinese dynamics of agrarian change and are contingent upon country-specific conditions. Rather than state-led endeavors as is often assumed, the main Chinese actors in Tajik agriculture are capitalist yet partially state-embedded enterprises driven by profit-oriented goals. Chinese farm enterprises tap into specific market demands that are either unanswered or underdeveloped in Tajikistan, or which have emerged due to the growing number of Chinese consumers in Tajikistan. The nature and drivers of Chinese land acquisitions in Tajikistan shed light on the various, sometimes competing, factors driving China’s broader foreign “land rush,” in Central Asia (and beyond).Asian Studie

AKSZ-BV Formalism and Courant Algebroid-induced Topological Field Theories

We give a detailed exposition of the Alexandrov-Kontsevich-Schwarz- Zaboronsky superfield formalism using the language of graded manifolds. As a main illustarting example, to every Courant algebroid structure we associate canonically a three-dimensional topological sigma-model. Using the AKSZ formalism, we construct the Batalin-Vilkovisky master action for the model.Comment: 13 pages, based on lectures at Rencontres mathematiques de Glanon 200

Mean first passage time for fission potentials having structure

A schematic model of over-damped motion is presented which permits one to calculate the mean first passage time for nuclear fission. Its asymptotic value may exceed considerably the lifetime suggested by Kramers rate formula, which applies only to very special, favorable potentials and temperatures. The additional time obtained in the more general case is seen to allow for a considerable increment in the emission of light particles.Comment: 7 pages, LaTex, 7 postscript figures; Keywords: Decay rate, mean first passage tim

Assessment of Scholarly Publications of Nigerian Health Sciences Researchers in MEDLINE/PubMed (1996-2007)

Scholarly publications are outcome of research and are important channels for dissemination of research findings by researchers. The main objective of this study was to assess the scholarly publications of Nigerian health sciences’ researchers and the journals in which they publish. Health science researchers are health care providers, faculty, medical scientists and other allied health professionals who conduct research in health related fields. Research articles written by Nigerian health sciences’ researchers published during 1996-2007 were accessed through the MEDLINE/PubMed database. Both the author affiliation in Address field and Publication date field were used to obtain data on the number and characteristics of publications by the researchers. A total of 7030 articles were published during the period. The number of publications increased from 338 in 1996 to 952 in 2007. Of the 7,030 citations, 2,124 (31%) were published in nine Nigerian journals with the African Journal of Medicine and Medical Sciences having the highest (660). However, 17 articles were published in four international multidisciplinary journals namely: British Medical Journal (BMJ), Journal of the American Medical Association (JAMA), Lancet and New England Journal of Medicine (NEJM). Approximately 80% of the publications were Original Research Articles. Nigerian health sciences’ researchers are productive in terms of scholarly publications. However, their publications are concentrated more in national journals, some of which are not indexed in any bibliographic database; others are print only, not widely circulated thereby limiting the impact of their research. Development of a national bibliographc database to index articles published in Nigerian journals and publication of more journal in electronic format is recommended.Keywords: Biomedical journals, Nigerian health science researchers, Publication output, Scientific publication

Adding Fundamental Matter to ``Chiral Rings and Anomalies in Supersymmetric Gauge Theory''

We consider a supersymmetric U(N) gauge theory with matter fields in the adjoint, fundamental and anti-fundamental representations. As in the framework which was put forward by Dijkgraaf and Vafa, this theory can be described by a matrix model. We analyze this theory along the lines of [F. Cachazo, M. Douglas, N.S. and E. Witten, ``Chiral Rings and Anomalies in Supersymmetric Gauge Theory'' hep-th/0211170] and show the equivalence of the gauge theory and the matrix model. In particular, the anomaly equations in the gauge theory is identified with the loop equations in the matrix model.Comment: 14 page

Fast and slow strategies in multiplication

In solving multiplication problems, children use both fast retrieval-based processes and slower computational processes. In the current study, we explore the possibility of disentangling these strategies using information contained in the observed response latencies using a method that is applicable in large data sets. We used a tree-based item response-modeling framework (De Boeck & Partchev, 2012) to investigate whether the proposed qualitative distinctions in fast and slow strategies can be detected. This so-called fast-slow model was applied to responses to a set of multiplication items, totalling more than 180,000 responses, collected in an online computer-adaptive training environment for mathematics. Parameters describing person characteristics (ability) and item characteristics (easiness) are estimated with the model. Both item and person characteristics differed between fast and slow processes and match predictions from substantive models of multiplication. Moreover, the parameters allowed us to describe the fast and slow strategies in more detail. Results emphasize the utility of the fast-slow model in the detection of strategies in multiplication but also in other areas of cognition and learning where strategies are expected