2,466 research outputs found
Comment on: ``Zero temperature conductance of parallel T-shape double quantum dots'' [Physica E 39 (2007) 214, arXiv:0708.1842v1]
In a recent paper [Physica E 39 (2007) 214, arXiv:0708.1842v1] Crisan, Grosu
and Tifrea revisited the problem of the conductance through a double quantum
dot molecule connected to electrodes in a T-shape configuration. The authors
obtained an expression for the conductance that disagrees with previous results
in the literature. We point out an error in their derivation of the conductance
formula and show that it gives unphysical results even for non-interacting
quantum dots.Comment: 2 pages, no figure
Evaluating CAVM: A New Search-Based Test Data Generation Tool for C
We present CAVM (pronounced “ka-boom”), a new search-based test data generation tool for C. CAVM is developed to augment an existing commercial tool, CodeScroll, which uses static analysis and input partitioning to generate test data. Unlike the current state-of-the-art search-based test data generation tool for C, Austin, CAVM handles dynamic data structures using purely search-based techniques. We compare CAVM against CodeScroll and Austin using 49 C functions, ranging from small anti-pattern case studies to real world open source code and commercial code. The results show that CAVM can cover branches that neither CodeScroll nor Austin can, while also exclusively achieving the highest branch coverage for 20 of the studied functions
Higher dimensional dust collapse with a cosmological constant
The general solution of the Einstein equation for higher dimensional (HD)
spherically symmetric collapse of inhomogeneous dust in presence of a
cosmological term, i.e., exact interior solutions of the Einstein field
equations is presented for the HD Tolman-Bondi metrics imbedded in a de Sitter
background. The solution is then matched to exterior HD Scwarschild-de Sitter.
A brief discussion on the causal structure singularities and horizons is
provided. It turns out that the collapse proceed in the same way as in the
Minkowski background, i.e., the strong curvature naked singularities form and
that the higher dimensions seem to favor black holes rather than naked
singularities.Comment: 7 Pages, no figure
Suppression of Superconducting Critical Current Density by Small Flux Jumps in Thin Films
By doing magnetization measurements during magnetic field sweeps on thin
films of the new superconductor , it is found that in a low temperature
and low field region small flux jumps are taking place. This effect strongly
suppresses the central magnetization peak leading to reduced nominal
superconducting critical current density at low temperatures. A borderline for
this effect to occur is determined on the field-temperature (H-T) phase
diagram. It is suggested that the small size of the flux jumps in films is due
to the higher density of small defects and the relatively easy thermal
diffusion in thin films in comparison with bulk samples.Comment: 7 figures Phys. Rev. B accepted scheduled issue: 01 Feb 200
Asymmetry sum rule for molecular predissociation
© 2000 American Physical SocietyIn the case of weak diatomic molecular predissociation by noninteracting, optically inactive continuum states, it is demonstrated that the predissociation line shape is more accurately represented by a Beutler-Fano profile than by a Lorentzian. The weak asymmetry that is found to occur is due principally to interactions with neighboring vibrational resonances. For this type of predissociation in the case of multiple continua, a sum rule for the corresponding line-shape asymmetry is derived. This sum rule is verified numerically using single-channel and multichannel coupled Schrödinger-equation calculations for the Schumann-Runge band system of O2. Similar results are presented for the case of optically active continua.F. T. Hawes, L. W. Torop, B. R. Lewis and S. T. Gibso
Black hole thermodynamics with generalized uncertainty principle
In the standard viewpoint, the temperature of a stationary black hole is
proportional to its surface gravity, . This is a
semiclassical result and the quantum gravity effects are not taken into
consideration. This Letter explores a unified expression for the black hole
temperature in the sense of a generalized uncertainty principle(GUP). Our
discussion involves a heuristic analysis of a particle which is absorbed by the
black hole. Besides a class of static and spherically symmetric black holes, an
axially symmetric Kerr-Newman black hole is considered. Different from the
existing literature, we suggest that the black hole's irreducible mass
represent the characteristic size in the absorption process. The information
capacity of a remnant is also discussed by Bousso's D-bound in de Sitter
spacetime.Comment: 18 pages, great improvement on the first version; a Kerr-Newman black
hole is considere
Supersymmetry and Branes in M-theory Plane-waves
We study brane embeddings in M-theory plane-waves and their supersymmetry.
The relation with branes in AdS backgrounds via the Penrose limit is also
explored. Longitudinal planar branes are originated from AdS branes while giant
gravitons of AdS spaces become spherical branes which are realized as fuzzy
spheres in the massive matrix theory.Comment: 17 pages, JHEP style, references added, typos correcte
Pumping in quantum dots and non-Abelian matrix Berry phases
We have investigated pumping in quantum dots from the perspective of
non-Abelian (matrix) Berry phases by solving the time dependent Schr{\"o}dinger
equation exactly for adiabatic changes. Our results demonstrate that a pumped
charge is related to the presence of a finite matrix Berry phase. When
consecutive adiabatic cycles are performed the pumped charge of each cycle is
different from the previous ones
Thermodynamics of a black hole based on a generalized uncertainty principle
We study thermodynamic quantities and the stability of a black hole in a
cavity using the Euclidean action formalism by Gibbons and Hawking based on the
generalized uncertainty relation which is extended in a symmetric way with
respect to the space and momentum without loss of generality. Two parameters in
the uncertainty relation affect the thermodynamical quantities such as energy,
entropy, and the heat capacity. In particular, it can be shown that the small
black hole is unstable and it may decay either into a minimal black hole or a
large black hole. We discuss a constraint for a large black hole comparable to
the size of the cavity in connection with the critical mass.Comment: 12 pages, 4 figures; v2. to appear in JHE
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