12,602 research outputs found
Theory of spin blockade, charge ratchet effect, and thermoelectrical behavior in serially coupled quantum-dot system
The charge transport of a serially coupled quantum dots (SCQD) connected to
the metallic electrodes is theoretically investigated in the Coulomb blockade
regime. A closed-form expression for the tunneling current of SCQD in the
{\color{red} weak interdot hopping} limit is obtained by solving an extended
two-site Hubbard model via the Green's function method. We use this expression
to investigate spin current rectification, negative differential conductance,
and coherent tunneling in the nonlinear response regime. The current
rectification arising from the space symmetry breaking of SCQD is suppressed by
increasing temperature. The calculation of SCQD is extended to the case of
multiple parallel SCQDs for studying the charge ratchet effect and SCQD with
multiple levels. In the linear response regime, the functionalities of spin
filter and low-temperature current filter are demonstrated to coexist in this
system. It is further demonstrated that two-electron spin singlet and triplet
states can be readily resolved from the measurement of Seebeck coefficient
rather than that of electrical conductance.Comment: 11 pages, 9 figures. Revised argument, results unchanged, added
reference
Alcohol Use, Abuse, and Dependency in Shanghai
The use of alcohol for social and ceremonial occasions was recorded in Chinese history as early as 1760 B.C. during the Yin Dynasty (Ci-Hai Encyclopedia, 1979:936). The cultural tradition of ancient China placed alcoholic beverages at the center of social occasions, which presumably was the origin of the adage: Without wine, there is no li (or etiquette). Thus, the use of alcoholic beverages has always been accompanied by the concept of propriety and the discharging of one\u27s role obligations m social functions, rather than that of personal indulgence
Helicity Probabilities For Heavy Quark Fragmentation Into Excited Mesons
In the fragmentation of a heavy quark into a heavy meson whose light degrees
of freedom have angular momentum , all the helicity probabilities are
completely determined in the heavy quark limit up to a single probability
. We point out that this probability depends on the longitudinal
momentum fraction of the meson and on its transverse momentum
relative to the jet axis. We calculate as a function of scaling
variables corresponding to and for the heavy quark limit of the
perturbative QCD fragmentation functions for quark to fragment into mesons. In this model, the light degrees of freedom prefer to have
their angular momentum aligned transverse to, rather than along, the jet axis.
Implications for the production of excited heavy mesons, like and
, are discussed.Comment: 10 pages, Latex file plus 3 figures with postscript files appended at
the en
Decays of and into vector and pseudoscalar meson and the pseudoscalar glueball- mixing
We introduce a parametrization scheme for where
the effects of SU(3) flavor symmetry breaking and doubly OZI-rule violation
(DOZI) can be parametrized by certain parameters with explicit physical
interpretations. This scheme can be used to clarify the glueball-
mixing within the pseudoscalar mesons. We also include the contributions from
the electromagnetic (EM) decays of and via
. Via study of the isospin violated
channels, such as , ,
and , reasonable constraints on the EM decay
contributions are obtained. With the up-to-date experimental data for
, and , etc, we arrive at a consistent description of the mentioned
processes with a minimal set of parameters. As a consequence, we find that
there exists an overall suppression of the form factors,
which sheds some light on the long-standing " puzzle". By determining
the glueball components inside the pseudoscalar and in
three different glueball- mixing schemes, we deduce that the lowest
pseudoscalar glueball, if exists, has rather small component, and it
makes the a preferable candidate for glueball.Comment: Revised version to appear on J. Phys. G; An error in the code was
corrected. There's slight change to the numerical results, while the
conclusion is intac
Hadronic Production of S-wave and P-wave Charmed Beauty Mesons via Heavy Quark Fragmentation
At hadron colliders the dominant production mechanism of mesons
with large transverse momentum is due to parton fragmentation. We compute the
rates and transverse momentum spectra for production of S-wave and P-wave
mesons at the Tevatron via the direct fragmentation of the bottom
antiquark as well as the Altarelli-Parisi induced gluon fragmentation. Since
all the radially and orbitally excited mesons below the
flavor threshold will cascade into the pseudoscalar ground state through
electromagnetic and/or hadronic transitions, they all contribute to the
inclusive production of . The contributions of the excited S-wave and
P-wave states to the inclusive production of are 58 and 23\%,
respectively, and hence significant.Comment: Changes are made in the Discussio
Multi-Receiver Quantum Dense Coding with Non-Symmetric Quantum Channel
A two-receiver quantum dense coding scheme and an -receiver quantum dense
coding scheme, in the case of non-symmetric Hilbert spaces of the particles of
the quantum channel, are investigated in this paper. A sender can send his
messages to many receivers simultaneously. The scheme can be applied to quantum
secret sharing and controlled quantum dense coding.Comment: To appear in Journal of the Korean Physical Societ
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