80,121 research outputs found
Transverse single spin asymmetry in the Drell-Yan process
We revisit the transverse single spin asymmetry in the angular distribution
of a Drell-Yan dilepton pair. We study this asymmetry by using twist-3
collinear factorization, and we obtain the same result both in covariant gauge
and in the light-cone gauge. Moreover, we have checked the electromagnetic
gauge invariance of our calculation. Our final expression for the asymmetry
differs from all the previous results given in the literature. The overall sign
of this asymmetry is as important as the sign of the Sivers asymmetry in
Drell-Yan.Comment: 9 page
Domain walls in gapped graphene
The electronic properties of a particular class of domain walls in gapped
graphene are investigated. We show that they can support mid-gap states which
are localized in the vicinity of the domain wall and propagate along its
length. With a finite density of domain walls, these states can alter the
electronic properties of gapped graphene significantly. If the mid-gap band is
partially filled,the domain wall can behave like a one-dimensional metal
embedded in a semi-conductor, and could potentially be used as a single-channel
quantum wire.Comment: 4 pgs. revte
Collins Fragmentation and the Single Transverse Spin Asymmetry
We study the Collins mechanism for the single transverse spin asymmetry in
the collinear factorization approach. The correspondent twist-three
fragmentation function is identified. We show that the Collins function
calculated in this approach is universal. We further examine its contribution
to the single transverse spin asymmetry of semi-inclusive hadron production in
deep inelastic scattering and demonstrate that the transverse momentum
dependent and twist-three collinear approaches are consistent in the
intermediate transverse momentum region where both apply.Comment: 10 pages, 2 figure
Obtaining correct orbital ground states in electron systems using a nonspherical self-interaction corrected LDA+ method
The electronic structure of lanthanide and actinide compounds is often
characterized by orbital ordering of localized -electrons.
Density-functional theory (DFT) studies of such systems using the currently
available LDA+ method are plagued by significant orbital-dependent
self-interaction, leading to erroneous orbital ground states. An alternative
scheme that modifies the exchange, not Hartree, energy is proposed as a remedy.
We show that our LDA+ approach reproduces the expected degeneracy of
and states in free ions and the correct ground states in solid PrO.
We expect our method to be useful in studying compounds of - and heavy-
elements.Comment: 11 pages, 4 figure
Quantum computation with un-tunable couplings
Most quantum computer realizations require the ability to apply local fields
and tune the couplings between qubits, in order to realize single bit and two
bit gates which are necessary for universal quantum computation. We present a
scheme to remove the necessity of switching the couplings between qubits for
two bit gates, which are more costly in many cases. Our strategy is to compute
in and out of carefully designed interaction free subspaces analogous to
decoherence free subspaces, which allows us to effectively turn off and turn on
the interactions between the encoded qubits. We give two examples to show how
universal quantum computation is realized in our scheme with local
manipulations to physical qubits only, for both diagonal and off diagonal
interactions.Comment: 5 pages, 2 figure
Towards the assignment for the meson nonet
The strong decays of the , , ,
, and as the quark-antiquark states are
investigated in the framework of the meson decay model. It is found
that the , , and appear to be the
convincing states while the assignment of the
and as the isoscalar states is not favored by their
widths. In the presence of the , , and
being the members of the meson nonet, the kaon is
phenomenologically determined to has a mass of about 2153 MeV. The width of
this unobserved kaon is expected to be about 197 MeV in the decay
model.Comment: 15 pages, 5 figures, version accepted for publication in Physical
Review
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