6,632 research outputs found
Thermal Dissipation and Variability in Electrical Breakdown of Carbon Nanotube Devices
We study high-field electrical breakdown and heat dissipation from carbon
nanotube (CNT) devices on SiO2 substrates. The thermal "footprint" of a CNT
caused by van der Waals interactions with the substrate is revealed through
molecular dynamics (MD) simulations. Experiments and modeling find the
CNT-substrate thermal coupling scales proportionally to CNT diameter and
inversely with SiO2 surface roughness (~d/{\Delta}). Comparison of diffuse
mismatch modeling (DMM) and data reveals the upper limit of thermal coupling
~0.4 W/K/m per unit length at room temperature, and ~0.7 W/K/m at 600 C for the
largest diameter (3-4 nm) CNTs. We also find semiconducting CNTs can break down
prematurely, and display more breakdown variability due to dynamic shifts in
threshold voltage, which metallic CNTs are immune to; this poses a fundamental
challenge for selective electrical breakdowns in CNT electronics
Biaxial spin-nematic phase of two dimensional disordered rotor models and spin-one bosons in optical lattices
We show that the ground state of disordered rotor models with quadrupolar
interactions can exhibit biaxial nematic ordering in the disorder-averaged
sense. We present a mean-field analysis of the model and demonstrate that the
biaxial phase is stable against small quantum fluctuations. We point out the
possibility of experimental realization of such rotor models using ultracold
spin-one Bose atoms in a spin-dependent and disordered optical lattice in the
limit of a large number of atoms per site and also suggest an imaging
experiment to detect the biaxial nematicity in such systems.Comment: revtex file 7 pages, 2 figures, version published in PR
The Wide-Field X and Gamma-Ray Telescope ECLAIRs aboard the Gamma-Ray Burst Multi-Wavelength Space Mission SVOM
The X and Gamma-ray telescope ECLAIRs is foreseen to be launched on a low
Earth orbit (h=630 km, i=30 degrees) aboard the SVOM satellite (Space-based
multi-band astronomical Variable Objects Monitor), a French-Chinese mission
with Italian contribution. Observations are expected to start in 2013. It has
been designed to detect and localize Gamma-Ray Bursts (GRBs) or persistent
sources of the sky, thanks to its wide field of view (about 2 sr) and its
remarkable sensitivity in the 4-250 keV energy range, with enhanced imaging
sensitivity in the 4-70 keV energy band. These characteristics are well suited
to detect highly redshifted GRBs, and consequently to provide fast and accurate
triggers to other onboard or ground-based instruments able to follow-up the
detected events in a very short time from the optical wavelength bands up to
the few MeV Gamma-Ray domain.Comment: Proccedings of the "2008 Nanjing GRB Conference", June 23-27 2008,
Nanjing, Chin
Fermion Pairing Dynamics in the Relativistic Scalar Plasma
Using many-body techniques we obtain the time-dependent Gaussian
approximation for interacting fermion-scalar field models. This method is
applied to an uniform system of relativistic spin-1/2 fermion field coupled,
through a Yukawa term, to a scalar field in 3+1 dimensions, the so-called
quantum scalar plasma model. The renormalization for the resulting Gaussian
mean-field equations, both static and dynamical, are examined and initial
conditions discussed. We also investigate solutions for the gap equation and
show that the energy density has a single minimum.Comment: 21 pages, latex, 4 postscript figures, new sections, some literary
changes, notation corrections, accepted for publication in Phys. Rev
Scheme for demonstrating Bell theorem in tripartite entanglement between atomic ensembles
We propose an experimentally feasible scheme to demonstrate quantum
nonlocality, using Greenberger-Horne-Zeilinger (GHZ) and entanglement
between atomic ensembles generated by a new developed method based on laser
manipulation and{} single-photon detection.Comment: 10 pages, 4 figure
Anomalous Spin Dynamics of Hubbard Model on Honeycomb Lattices
In this paper, the honeycomb Hubbard model in optical lattices is
investigated using O(3) non-linear sigma model. A possible quantum non-magnetic
insulator in a narrow parameter region is found near the metal-insulator
transition. We study the corresponding dynamics of magnetic properties, and
find that the narrow region could be widened by hole doping.Comment: 9 pages, 12 figure
Classical Dynamics of Anyons and the Quantum Spectrum
In this paper we show that (a) all the known exact solutions of the problem
of N-anyons in oscillator potential precisely arise from the collective degrees
of freedom, (b) the system is pseudo-integrable ala Richens and Berry. We
conclude that the exact solutions are trivial thermodynamically as well as
dynamically.Comment: 19 pages, ReVTeX, IMSc/93/0
Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
We present a high resolution spectroscopic analysis of 62 red giants in the
Milky Way globular cluster NGC5286. We have determined abundances of
representative light proton-capture, alpha, Fe-peak and neutron-capture element
groups, and combined them with photometry of multiple sequences observed along
the colour-magnitude diagram. Our principal results are: (i) a broad, bimodal
distribution in s-process element abundance ratios, with two main groups, the
s-poor and s-rich groups; (ii) substantial star-to-star Fe variations, with the
s-rich stars having higher Fe, e.g. _s-rich - _s-poor ~
0.2~dex; and (iii) the presence of O-Na-Al (anti-)correlations in both stellar
groups. We have defined a new photometric index, c_{BVI}=(B-V)-(V-I), to
maximise the separation in the colour-magnitude diagram between the two stellar
groups with different Fe and s-element content, and this index is not
significantly affected by variations in light elements (such as the O-Na
anticorrelation). The variations in the overall metallicity present in NGC5286
add this object to the class of "anomalous" GCs. Furthermore, the chemical
abundance pattern of NGC5286 resembles that observed in some of the anomalous
GCs, e.g. M22, NGC1851, M2, and the more extreme Omega Centauri, that also show
internal variations in s-elements, and in light elements within stars with
different Fe and s-elements content. In view of the common variations in
s-elements, we propose the term s-Fe-anomalous GCs to describe this sub-class
of objects. The similarities in chemical abundance ratios between these objects
strongly suggest similar formation and evolution histories, possibly associated
with an origin in tidally disrupted dwarf satellites.Comment: 28 pages, 21 figures, accepted for publication in MNRA
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