105,538 research outputs found
Energy levels of a parabolically confined quantum dot in the presence of spin-orbit interaction
We present a theoretical study of the energy levels in a parabolically
confined quantum dot in the presence of the Rashba spin-orbit interaction
(SOI). The features of some low-lying states in various strengths of the SOI
are examined at finite magnetic fields. The presence of a magnetic field
enhances the possibility of the spin polarization and the SOI leads to
different energy dependence on magnetic fields applied. Furthermore, in high
magnetic fields, the spectra of low-lying states show basic features of
Fock-Darwin levels as well as Landau levels.Comment: 6 pages, 4 figures, accepted by J. Appl. Phy
Over-Bias Light Emission due to Higher Order Quantum Noise of a Tunnel Junction
Understanding tunneling from an atomically sharp tip to a metallic surface
requires to account for interactions on a nanoscopic scale. Inelastic tunneling
of electrons generates emission of photons, whose energies intuitively should
be limited by the applied bias voltage. However, experiments by Schull et al.
[Phys. Rev. Lett. 102, 057401 (2009)] indicate that more complex processes
involving the interaction of electrons with plasmon polaritons lead to photon
emission characterized by over-bias energies. We propose a model of this
observation in analogy to dynamical Coulomb blockade, originally developed for
treating the electronic environment in mesoscopic circuits. We explain the
experimental finding quantitatively by the correlated tunneling of two
electrons interacting with an LRC circuit modeling the local plasmon-polariton
mode. To explain the over-bias emission, the non-Gaussian statistics of the
tunneling dynamics of the electrons is essential.Comment: 5 pages, 4 figure
Higher-spin Realisations of the Bosonic String
It has been shown that certain algebras can be linearised by the
inclusion of a spin--1 current. This provides a way of obtaining new
realisations of the algebras. Recently such new realisations of were
used in order to embed the bosonic string in the critical and non-critical
strings. In this paper, we consider similar embeddings in and
strings. The linearisation of is already known, and can be
achieved for all values of central charge. We use this to embed the bosonic
string in critical and non-critical strings. We then derive the
linearisation of using a spin--1 current, which turns out to be
possible only at central charge . We use this to embed the bosonic
string in a non-critical string.Comment: 8 pages. CTP TAMU-10/95
Liouville and Toda Solitons in M-theory
We study the general form of the equations for isotropic single-scalar,
multi-scalar and dyonic -branes in superstring theory and M-theory, and show
that they can be cast into the form of Liouville, Toda (or Toda-like)
equations. The general solutions describe non-extremal isotropic -branes,
reducing to the previously-known extremal solutions in limiting cases. In the
non-extremal case, the dilatonic scalar fields are finite at the outer event
horizon.Comment: Latex, 10 pages. Minor corrections to text and titl
Physical Conditions and Star Formation Activity in the Intragroup Medium of Stephan's Quintet
New multi-band observations of the famous compact group of galaxies Stephan's
Quintet (SQ) are presented and analyzed. These include far infrared (FIR)
images at 60 and 100 (ISOPHOT C-100 camera), radio continuum
images at 1.4 GHz (VLA B-array) and 4.86 GHz (VLA C-array), and long-slit
optical spectrographs (Palomar telescope). With these new data, we aim
to learn more about the X-ray/radio ridge in the middle of the intragroup
medium (IGM) and the IGM starburst SQ-A, both are likely to be caused by the
high speed collision ( km s) between the intruder galaxy NGC
7318b ( km s) and the IGM ( km s).Comment: 31 pages text, 17 figures. Accepted by ApJ. A PS file including all
figures can be found in
http://spider.ipac.caltech.edu/staff/cxu/preprints/sq/apj_sq.ps.g
Basic physical and chemical processes in space radiation effects on polymers
The effects of space ionizing radiation on polymers is investigated in terms of operative physical and chemical processes. A useful model of charged particle impact with a polymer was designed. Principle paths of molecular relaxation were identified and energy handling processes were considered. The focus of the study was on energy absorption and the immediately following events. Further study of the radiation degradation of polymers is suggested
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