38,551 research outputs found
Representation of SO(3) Group by a Maximally Entangled State
A representation of the SO(3) group is mapped into a maximally entangled two
qubit state according to literatures. To show the evolution of the entangled
state, a model is set up on an maximally entangled electron pair, two electrons
of which pass independently through a rotating magnetic field. It is found that
the evolution path of the entangled state in the SO(3) sphere breaks an odd or
even number of times, corresponding to the double connectedness of the SO(3)
group. An odd number of breaks leads to an additional phase to the
entangled state, but an even number of breaks does not. A scheme to trace the
evolution of the entangled state is proposed by means of entangled photon pairs
and Kerr medium, allowing observation of the additional phase.Comment: 4 pages, 3 figure
Globally Polarized Quark-gluon Plasma in Non-central A+A Collisions
Produced partons have large local relative orbital angular momentum along the
direction opposite to the reaction plane in the early stage of non-central
heavy-ion collisions. Parton scattering is shown to polarize quarks along the
same direction due to spin-orbital coupling. Such global quark polarization
will lead to many observable consequences, such as left-right asymmetry of
hadron spectra, global transverse polarization of thermal photons, dileptons
and hadrons. Hadrons from the decay of polarized resonances will have azimuthal
asymmetry similar to the elliptic flow. Global hyperon polarization is
predicted within different hadronization scenarios and can be easily tested.Comment: 4 pages in RevTex with 2 postscript figures, an erratum is added to
the final published versio
Discussions on Stability of Diquarks
Since the birth of the quark model, the diquark which is composed of two
quarks has been considered as a substantial structure of color anti-triplet.
This is not only a mathematical simplification for dealing with baryons, but
also provides a physical picture where the diquark would behave as a whole
object. It is natural to ask whether such a structure is sufficiently stable
against external disturbance. The mass spectra of the ground states of the
scalar and axial-vector diquarks which are composed of two-light (L-L),
one-light-one-heavy (H-L) and two-heavy quarks (H-H) respectively have been
calculated in terms of the QCD sum rules. We suggest a criterion as the
quantitative standard for the stability of the diquark. It is the gap between
the masses of the diquark and where is the threshold of the
excited states and continuity, namely the larger the gap is, the more stable
the diquark would be. In this work, we calculate the masses of the type H-H to
complete the series of the spectra of the ground state diquarks. However, as
the criterion being taken, we find that all the gaps for the various diquaks
are within a small range, especially the gap for the diquark with two heavy
quarks which is believed to be a stable structure, is slightly smaller than
that for other two types of diquarks, therefore we conclude that because of the
large theoretical uncertainty, we cannot use the numerical results obtained
with the QCD sum rules to assess the stability of diquarks, but need to invoke
other theoretical framework.Comment: 14 pages, 4 figure
Solidification of Al-Sn-Cu based immiscible alloys under intense shearing
The official published version of the Article can be accessed from the link below - Copyright @ 2009 The Minerals, Metals & Materials Society and ASM InternationalThe growing importance of Al-Sn based alloys as materials for engineering applications
necessitates the development of uniform microstructures with improved performance. Guided by the recently thermodynamically assessed Al-Sn-Cu system, two model immiscible alloys, Al-45Sn-10Cu and Al-20Sn-10Cu, were selected to investigate the effects of intensive melt shearing provided by the novel melt conditioning by advanced shear technology (MCAST) unit on the uniform dispersion of the soft Sn phase in a hard Al matrix. Our experimental results have confirmed that intensive melt shearing is an effective way to achieve fine and uniform
dispersion of the soft phase without macro-demixing, and that such dispersed microstructure can be further refined in alloys with precipitation of the primary Al phase prior to the demixing reaction. In addition, it was found that melt shearing at 200 rpm and 60 seconds will be adequate to produce fine and uniform dispersion of the Sn phase, and that higher shearing speed and prolonged shearing time can only achieve minor further refinement.This work is funded by the EPSRC and
DT
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