42,661 research outputs found
On the nature of the lightest scalar resonances
We briefly review the recent progresses in the new unitarization approach
being developed by us. Especially we discuss the large
scatterings by making use of the partial wave matrix parametrization form.
We find that the pole may move to the negative real axis on the second
sheet of the complex plane, therefore it raises the interesting question
that this `' pole may be related to the in the linear
model.Comment: Talk presented by Zheng at ``Quark Confinement and Hadron
Spectroscopy VI'', 21--25 Sept. 2004, Cagliari, Italy. 3 pages with 2 figure
Flame Instability and Transition to Detonation in Supersonic Reactive Flows
Multidimensional numerical simulations of a homogeneous, chemically reactive
gas were used to study ignition, flame stability, and
deflagration-to-detonation transition (DDT) in a supersonic combustor. The
configuration studied was a rectangular channel with a supersonic inflow of
stoichiometric ethylene-oxygen and a transimissive outflow boundary. The
calculation is initialized with a velocity in the computational domain equal to
that of the inflow, which is held constant for the duration of the calculation.
The compressible reactive Navier-Stokes equations were solved by a high-order
numerical algorithm on an adapting mesh. This paper describes two calculations,
one with a Mach 3 inflow and one with Mach 5.25. In the Mach 3 case, the
fuel-oxidizer mixture does not ignite and the flow reaches a steady-state
oblique shock train structure. In the Mach 5.25 case, ignition occurs in the
boundary layers and the flame front becomes unstable due to a Rayleigh-Taylor
instability at the interface between the burned and unburned gas. Growth of the
reaction front and expansion of the burned gas compress and preheat the
unburned gas. DDT occurs in several locations, initiating both at the flame
front and in the unburned gas, due to an energy-focusing mechanism. The growth
of the flame instability that leads to DDT is analyzed using the Atwood number
parameter
Local spin polarisation of electrons in Rashba semiconductor nanowires: effects of the bound state
The local spin polarisation (LSP) of electrons in two typical semiconductor
nanowires under the modulation of Rashba spin-orbit interaction (SOI) is
investigated theoretically. The influence of both the SOI- and
structure-induced bound states on the LSP is taken into account via the
spin-resolved lattice Green function method. It is discovered that high
spin-density islands with alternative signs of polarisation are formed inside
the nanowires due to the interaction between the bound states and the Rashba
effective magnetic field. Further study shows that the spin-density islands
caused by the structure-induced bound state exhibit a strong robustness against
disorder. These findings may provide an efficient way to create local magnetic
moments and store information in semiconductors.Comment: 8 pages, 3 figure
Study on the mechanism of open-flavor strong decays
The open-flavor strong decays are studied based on the interaction of
potential quark model. The decay process is related to the s-channel
contribution of the same scalar confinment and one-gluon-exchange(OGE)
interaction in the quark model. After we adopt the prescription of massive
gluons in time-like region from the lattice calculation, the approximation of
four-fermion interaction is applied. The numerical calculation is performed to
the meson decays in , , light flavor sector. The analysis of the
ratios of and show
that the scalar interaction should be dominant in the open-flavor decays
Sputtered Gold as an Effective Schottky Gate for Strained Si/SiGe Nanostructures
Metallization of Schottky surface gates by sputtering Au on strained Si/SiGe
heterojunctions enables the depletion of the two dimensional electron gas
(2DEG) at a relatively small voltage while maintaining an extremely low level
of leakage current. A fabrication process has been developed to enable the
formation of sub-micron Au electrodes sputtered onto Si/SiGe without the need
of a wetting layer.Comment: 3 pages, 3 figure
Pomeron loops in zero transverse dimensions
We analyze a toy model which has a structure similar to that of the recently
found QCD evolution equations, but without transverse dimensions. We develop
two different but equivalent methods in order to compute the leading-order and
next-to-leading order Pomeron loop diagrams. In addition to the leading-order
result which has been derived from Mueller's toy model~\cite% {Mueller:1994gb},
we can also calculate the next-to-leading order contribution which provides the
correction. We interpret this result and discuss its
possible implications for the four-dimensional QCD evolution.Comment: 11 pages, 4 figure
Squeezed-state generation in optical bistability
Experiments to generate squeezed states of light are described for a collection of two-level atoms within a high-finesse cavity. The investigation is conducted in a regime for which the weak-field coupling of atoms to the cavity mode produces a splitting in the normal mode structure of the atom-field system that is large compared with the atomic linewidth. Reductions in photocurrent noise of 30% (-1.55 dB) below the noise level set by the vacuum state of the field are observed in a balanced homodyne detector. A degree of squeezing of approximately 50% is inferred for the field state in the absence of propagation and detection losses. The observed spectrum of squeezing extends over a very broad range of frequencies (~±75 MHz), with the frequency of best squeezing corresponding to an offset from the optical carrier given by the normal mode splitting
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