23 research outputs found
Pentaquark Masses in Chiral Perturbation Theory
Heavy baryon chiral perturbation theory for pentaquarks is applied beyond
leading order. The mass splitting in the pentaquark anti-decuplet is calculated
up to NNLO. An expansion in the coupling of pentaquarks to non-exotic baryons
simplifies calculations and makes the pentaquark masses insensitive to the
pentaquark-nucleon mass difference. The possibility of determining coupling
constants in the chiral Lagrangian on the lattice is discussed. Both positive
and negative parities are considered.Comment: 11 pages; reference added, minor changes in wordin
Bounded Model Checking of State-Space Digital Systems: The Impact of Finite Word-Length Effects on the Implementation of Fixed-Point Digital Controllers Based on State-Space Modeling
The extensive use of digital controllers demands a growing effort to prevent
design errors that appear due to finite-word length (FWL) effects. However,
there is still a gap, regarding verification tools and methodologies to check
implementation aspects of control systems. Thus, the present paper describes an
approach, which employs bounded model checking (BMC) techniques, to verify
fixed-point digital controllers represented by state-space equations. The
experimental results demonstrate the sensitivity of such systems to FWL effects
and the effectiveness of the proposed approach to detect them. To the best of
my knowledge, this is the first contribution tackling formal verification
through BMC of fixed-point state-space digital controllers.Comment: International Symposium on the Foundations of Software Engineering
201
Dirac Particles in Twisted Tubes
We consider the dynamics of a relativistic Dirac particle constrained to move
in the interior of a twisted tube by confining boundary conditions, in the
approximation that the curvature of the tube is small and slowly varying. In
contrast with the nonrelativistic theory, which predicts that a particle's spin
does not change as the particle propagates along the tube, we find that the
angular momentum eigenstates of a relativistic spin-1/2 particle may behave
nontrivially. For example, a particle with its angular momentum initially
polarized in the direction of propagation may acquire a nonzero component of
angular momentum in the opposite direction on turning through 2 \pi radians.
Also, the usual nonrelativistic effective potential acquires an additional
factor in the relativistic theory.Comment: 16 pages, 3 EPS figures, REVTeX using BoxedEPS package; email to
[email protected]
Chiral Soliton Model vs Pentaquark Structure for \Theta (1540)
The exotic baryon (1540 MeV)\omega - \phi$ mixing.Comment: 11 pages, references added, final published versio
In2Se3 Visible/Near-IR Photodetector With Observation of Band-Edge in Spectral Response
We report on the demonstration of visible/near-IR high-performance photodetector based on exfoliated beta-Indium selenide (In2Se3) on sapphire with a clear signature of band edge in spectral responsivity at a wavelength of similar to 850-900 nm. Room temperature photoluminescence (PL) measurements also indicated a peak at similar to 900 nm confirming the band-edge. Devices with inter-digitated metal-semiconductor-metal (MSM) geometry exhibited a responsivity of 3.8 A/W (normalized to device area). A low dark current of 0.80 nA and a photo to dark current ratio of similar to 52 were measured when illuminated with 650 nm A specific detectivity of 1 x 10(10) cm Hz(0.5) W-1 at 650 nm and 6 x 10(8) cm Hz(0.5) W-1 at the band-edge of 900 nm were estimated. These results indicate the promise of beta-(In2Se3) for visible/near-IR detector applications
Gain mechanism and carrier transport in high responsivity AlGaN-based solar blind metal semiconductor metal photodetectors
We report on the highest responsivity for III-nitride Metal Semiconductor Metal solar-blind photodetectors on sapphire. Devices on unintentionally doped AlGaN epilayers grown by Metal Organic Chemical Vapor Deposition exhibited sharp absorption cut-off in the range of 245-290 nm. Very high responsivity >5 A/W at 10V bias was achieved with visible rejection exceeding three orders of magnitude for front illumination. Compared to the responsivity values reported in the literature for state-of-the-art solar-blind photodetectors, this work presents the highest values of responsivity at a given bias and up to sub-250 nm detection threshold. The high responsivity is attributed to an internal gain mechanism operating on these devices. The reverse-bias leakage current across these samples was found to be dominated by thermionic field emission at low biases and Poole-Frenkel emission from a deep trap level (0.7 eV from the conduction band-edge for Al0.50Ga0.50N) at high biases. Published by AIP Publishing