6,882 research outputs found
Observable Dirac-type singularities in Berry's phase and the monopole
The physical reality and observability of 2n\pi Berry phases, as opposed to
the usually considered modulo 2\pi topological phases is demonstrated with the
help of computer simulation of a model adiabatic evolution whose parameters are
varied along a closed loop in the parameter space. Using the analogy of Berry's
phase with the Dirac monopole, it is concluded that an interferometer loop
taken around a magnetic monopole of strength n/2 yields an observable 2n\pi
phase shift, where n is an integer. An experiment to observe the effect is
proposed.Comment: 12 pages Latex, 3 postscript figures; submitted to Physical Review
Letters 15 September 2000; revised 19 November 200
Growth, debt, and sovereign risk in a small, open economy
The continuing debt crisis that many developing countries have faced in the current decade has underscored the need to understand the relationships between debt accumulation and growth, as well as the need to develop policy approaches that foster adjustment in the external account while maintaining the growth of output. The purpose of this paper is to develop a macroeconomic model for a small open developing economy that borrows abroad. This model will assist in studying the dynamic interaction between debt and growth, as well as the impact of various policies and exogenous shocks on the rate of capital accumulation, the current account and debt. From this analysis, the authors make the following conclusions. An upward shift in the supply of debt leads to a long run decline in external debt, a higher domestic interest rate, less capital stock, and a reduced trade surplus. An increase in the marginal cost of debt may or may not lower long run external debt as well. An increase in productivity raises the long run stock of capital but leaves the level of external debt and the interest rate unchanged in the long run. Finally, fiscal expansion has almost no effect in either the short run or the long run.Economic Theory&Research,Environmental Economics&Policies,Strategic Debt Management,Banks&Banking Reform,Financial Intermediation
Geochemistry of K/T boundaries in India and contributions of Deccan volcanism
Three possible Cretaceous/Tertiary (K/T) boundary sections in the Indian subcontinent were studied for their geochemical and fossil characteristics. These include two marine sections of Meghalaya and Zanskar and one continental section of Nagpur. The Um Sohryngkew river section of Meghalaya shows a high iridium, osmium, iron, cobalt, nickel and chromium concentration in a 1.5 cm thick limonitic layer about 30 cm below the planktonic Cretaceous-Palaeocene boundary identified by the characteristic fossils. The Bottaccione and Contessa sections at Gubbio were also analyzed for these elements. The geochemical pattern at the boundary at the Um Sohryngkew river and Gubbio sections are similar but the peak concentrations and the enrichment factors are different. The biological boundary is not as sharp as the geochemical boundary and the extinction appears to be a prolonged process. The Zanskar section shows, in general, similar concentration of the siderophile, lithophile and rare earth elements but no evidence of enrichment of siderophiles has so far been observed. The Takli section is a shallow inter-trappean deposit within the Deccan province, sandwiched between flow 1 and flow 2. The geochemical stratigraphy of the inter-trappeans is presented. The various horizons of ash, clay and marl show concentration of Fe and Co, generally lower than the adjacent basalts. Two horizons of slight enrichment of iridium are found within the ash layers, one near the contact of flow 1 and other near the contact of flow 2, where iridium occurs at 170 and 260 pg/g. These levels are lower by a factor of 30 compared to Ir concentration in the K/T boundary in Meghalaya section. If the enhanced level of some elements in a few horizons of the ash layer are considered as volcanic contribution by some fractionation processes than the only elements for which it occurs are REE, Ir and possibly Cr
Relation between geometric phases of entangled bi-partite systems and their subsystems
This paper focuses on the geometric phase of entangled states of bi-partite
systems under bi-local unitary evolution. We investigate the relation between
the geometric phase of the system and those of the subsystems. It is shown that
(1) the geometric phase of cyclic entangled states with non-degenerate
eigenvalues can always be decomposed into a sum of weighted non-modular pure
state phases pertaining to the separable components of the Schmidt
decomposition, though the same cannot be said in the non-cyclic case, and (2)
the geometric phase of the mixed state of one subsystem is generally different
from that of the entangled state even by keeping the other subsystem fixed, but
the two phases are the same when the evolution operator satisfies conditions
where each component in the Schmidt decomposition is parallel transported
Thermoelectric studies of KxFe2-ySe2: weakly correlated superconductor
We report thermal transport measurement of KxFe2-ySe2 superconducting single
crystal. Significant peak anomaly in thermal conductivity is observed at nearly
TC/2 indicating a large phonon mean-free-path in the superconducting state. The
zero-temperature extrapolated thermoelectric power is smaller than the value in
typical strongly correlated superconductors, implying large normalized Fermi
temperature. In contrast to other iron superconductors, thermoelectric power in
our sample does not exhibit significant anomalies. These findings indicate that
KxFe2-ySe2 is a weakly or intermediately correlated superconductor without
significant Fermi surface nesting.Comment: Revised version, 5 pages, 5 figures, Will appear in Physical Review
SRA: Fast Removal of General Multipath for ToF Sensors
A major issue with Time of Flight sensors is the presence of multipath
interference. We present Sparse Reflections Analysis (SRA), an algorithm for
removing this interference which has two main advantages. First, it allows for
very general forms of multipath, including interference with three or more
paths, diffuse multipath resulting from Lambertian surfaces, and combinations
thereof. SRA removes this general multipath with robust techniques based on
optimization. Second, due to a novel dimension reduction, we are able to
produce a very fast version of SRA, which is able to run at frame rate.
Experimental results on both synthetic data with ground truth, as well as real
images of challenging scenes, validate the approach
Is Our Model for Contention Resolution Wrong?
Randomized binary exponential backoff (BEB) is a popular algorithm for
coordinating access to a shared channel. With an operational history exceeding
four decades, BEB is currently an important component of several wireless
standards. Despite this track record, prior theoretical results indicate that
under bursty traffic (1) BEB yields poor makespan and (2) superior algorithms
are possible. To date, the degree to which these findings manifest in practice
has not been resolved.
To address this issue, we examine one of the strongest cases against BEB:
packets that simultaneously begin contending for the wireless channel. Using
Network Simulator 3, we compare against more recent algorithms that are
inspired by BEB, but whose makespan guarantees are superior. Surprisingly, we
discover that these newer algorithms significantly underperform. Through
further investigation, we identify as the culprit a flawed but common
abstraction regarding the cost of collisions. Our experimental results are
complemented by analytical arguments that the number of collisions -- and not
solely makespan -- is an important metric to optimize. We believe that these
findings have implications for the design of contention-resolution algorithms.Comment: Accepted to the 29th ACM Symposium on Parallelism in Algorithms and
Architectures (SPAA 2017
Description of a new species cephaline gregarine Stenophora bristili (Apicomplexa, Sporozoea) from Millipede (Chondromorpha severini) in Aurangabad district (M.S), India
The study of the endoparasitic cephaline gregarine in the gut content of millipede (Chondromorpha severini) was found to be infested with a new species (Stenophora bristili) of genus Stenophora (Labee, 1899). It differs from all the earlier reported species. The shape of the body of cephalont small elongated, slightly curved and rounded posterior end. Potomerite consists of fine bundle of bristles. The Sporont is elongated curved, slightly tapering and rounded posterior end, having brush like broader in between protomerite and deutomerite, Nucleus isspherical with ecentric karyosome. The different developmental stages including cephalont, sporont, gametocyst and sporocyst have been observed
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