15,332 research outputs found
Family Unification, Exotic States and Light Magnetic Monopoles
Models with fermions in bifundamental representations can lead naturally to
family unification as opposed to family replication. Such models typically
predict (exotic) color singlet states with fractional electric charge, and
magnetic monopoles with multiple Dirac charge. The exotics may be at the TeV
scale, and relatively light magnetic monopoles (greater than about 10^7 GeV)
can be present in the galaxy with abundance near the Parker bound. We focus on
three family SU(4)XSU(3)XSU(3) models.Comment: 37 page
Graph-Based Shape Analysis Beyond Context-Freeness
We develop a shape analysis for reasoning about relational properties of data
structures. Both the concrete and the abstract domain are represented by
hypergraphs. The analysis is parameterized by user-supplied indexed graph
grammars to guide concretization and abstraction. This novel extension of
context-free graph grammars is powerful enough to model complex data structures
such as balanced binary trees with parent pointers, while preserving most
desirable properties of context-free graph grammars. One strength of our
analysis is that no artifacts apart from grammars are required from the user;
it thus offers a high degree of automation. We implemented our analysis and
successfully applied it to various programs manipulating AVL trees,
(doubly-linked) lists, and combinations of both
Social learning in otters
The use of information provided by others to tackle life's challenges is widespread, but should not be employed indiscriminately if it is to be adaptive. Evidence is accumulating that animals are indeed selective and adopt ‘social learning strategies’. However, studies have generally focused on fish, bird and primate species. Here we extend research on social learning strategies to a taxonomic group that has been neglected until now: otters (subfamily Lutrinae). We collected social association data on captive groups of two gregarious species: smooth-coated otters (Lutrogale perspicillata), known to hunt fish cooperatively in the wild, and Asian short-clawed otters (Aonyx cinereus), which feed individually on prey requiring extractive foraging behaviours. We then presented otter groups with a series of novel foraging tasks, and inferred social transmission of task solutions with network-based diffusion analysis. We show that smooth-coated otters can socially learn how to exploit novel food sources and may adopt a ‘copy when young’ strategy. We found no evidence for social learning in the Asian short-clawed otters. Otters are thus a promising model system for comparative research into social learning strategies, while conservation reintroduction programmes may benefit from facilitating the social transmission of survival skills in these vulnerable specie
Uncertainty Principle Enhanced Pairing Correlations in Projected Fermi Systems Near Half Filling
We point out the curious phenomenon of order by projection in a class of
lattice Fermi systems near half filling. Enhanced pairing correlations of
extended s-wave Cooper pairs result from the process of projecting out s-wave
Cooper pairs, with negligible effect on the ground state energy. The Hubbard
model is a particularly nice example of the above phenomenon, which is revealed
with the use of rigorous inequalities including the Uncertainty Principle
Inequality. In addition, we present numerical evidence that at half filling, a
related but simplified model shows ODLRO of extended s-wave Cooper pairs.Comment: RevTex 11 pages + 1 ps figure. Date 19 September 1996, Ver.
Sarcoidosis of the hypothalamus and pituitary stalk
We report a rare case of sarcoidosis of the hypothalamic and suprasellar region, with clinical course and the magnetic resonance imaging follow-up
Silicon Atomic Quantum Dots Enable Beyond-CMOS Electronics
We review our recent efforts in building atom-scale quantum-dot cellular
automata circuits on a silicon surface. Our building block consists of silicon
dangling bond on a H-Si(001) surface, which has been shown to act as a quantum
dot. First the fabrication, experimental imaging, and charging character of the
dangling bond are discussed. We then show how precise assemblies of such dots
can be created to form artificial molecules. Such complex structures can be
used as systems with custom optical properties, circuit elements for
quantum-dot cellular automata, and quantum computing. Considerations on
macro-to-atom connections are discussed.Comment: 28 pages, 19 figure
Convergence and stability theorems for the Picard-Mann hybrid iterative scheme for a general class of contractive-like operators
In this paper we use the general class of contractive-like operators introduced by
Bosede and Rhoades (J. Adv. Math. Stud. 3(2):1-3, 2010) to prove strong convergence
and stability results for Picard-Mann hybrid iterative schemes considered in a real
normed linear space. We establish the strong convergence and stability of the Picard
iterative scheme as a corollary. Our results generalize and improve a multitude of
results in the literature, including the recent results of Chidume (Fixed Point Theory
Appl. 2014:233, 2014)
Proton Driven Plasma Wakefield Acceleration
Plasma wakefield acceleration, either laser driven or electron-bunch driven,
has been demonstrated to hold great potential. However, it is not obvious how
to scale these approaches to bring particles up to the TeV regime. In this
paper, we discuss the possibility of proton-bunch driven plasma wakefield
acceleration, and show that high energy electron beams could potentially be
produced in a single accelerating stage.Comment: 13 pages, 4 figure
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