13,010 research outputs found
Generalized Noiseless Quantum Codes utilizing Quantum Enveloping Algebras
A generalization of the results of Rasetti and Zanardi concerning avoiding
errors in quantum computers by using states preserved by evolution is
presented. The concept of dynamical symmetry is generalized from the level of
classical Lie algebras and groups to the level of dynamical symmetry based on
quantum Lie algebras and quantum groups (in the sense of Woronowicz). A natural
connection is proved between states preserved by representations of a quantum
group and states preserved by evolution with dynamical symmetry of the
appropriate universal enveloping algebra. Illustrative examples are discussed.Comment: 10 pages, LaTeX, 2 figures Postscrip
Search for and strangeonium-like structures
Theoretically, it has been presumed from an effective Lagrangian calculation
that there could exist two charged strangeonium-like molecular states
and , with and
configurations respectively. In the framework of QCD sum rules, we predict that
masses of () and ()
are and respectively, which are both above
their respective two meson thresholds. We suggest to put in practice the search
for these two charged strangeonium-like structures in future experiments.Comment: 7 pages, 4 eps figures; the version accepted for publication in PRD.
arXiv admin note: text overlap with arXiv:1203.070
A General SU(2) Formulation for Quantum Searching with Certainty
A general quantum search algorithm with arbitrary unitary transformations and
an arbitrary initial state is considered in this work. To serach a marked state
with certainty, we have derived, using an SU(2) representation: (1) the
matching condition relating the phase rotations in the algorithm, (2) a concise
formula for evaluating the required number of iterations for the search, and
(3) the final state after the search, with a phase angle in its amplitude of
unity modulus. Moreover, the optimal choices and modifications of the phase
angles in the Grover kernel is also studied.Comment: 8 pages, 2 figure
Inseparability criterion for continuous variable systems
An inseparability criterion based on the total variance of a pair of
Einstein-Podolsky-Rosen type operators is proposed for continuous variable
systems. The criterion provides a sufficient condition for entanglement of any
two-party continuous variable states. Furthermore, for all the Gaussian states,
this criterion turns out to be a necessary and sufficient condition for
inseparability.Comment: minor changes in the introduction and ref
Origin of magnetic interactions and their influence on the structural properties of Ni2MnGa and related compounds
In this work, we perform first principles DFT calculations to investigate the
interplay between magnetic and structural properties in Ni2MnGa. We demonstrate
that the relative stability of austenite (cubic) and non-modulated martensite
(tetragonal) phases depends critically on the magnetic interactions between Mn
atoms. While standard approximate DFT functionals stabilize the latter phase, a
more accurate treatment of electronic localization and magnetism, obtained with
DFT+U, suppresses the non-modulated tetragonal structure for the stoichiometric
compound, in better agreement with the experiments. We show that the Anderson
impurity model, with Mn atoms treated as magnetic impurities, can explain this
observation and that the fine balance between super-exchange RKKY type
interactions mediated by Ni d and Ga p orbitals determines the equilibrium
structure of the crystal. The Anderson model is also demonstrated to capture
the effect of the number of valence electrons per unit cell on the structural
properties, often used as an empirical parameter to tune the behavior of
Ni2MnGa based alloys. Finally, we show that off-stoichiometric compositions
with excess Mn promote transitions to a non-modulated tetragonal structure, in
agreement with experiments.Comment: 16 pages, 25 figure
Class of exactly solvable SO(n) symmetric spin chains with matrix product ground states
We introduce a class of exactly solvable SO(n) symmetric Hamiltonians with
matrix product ground states. For an odd case, the ground state is a
translational invariant Haldane gap spin liquid state; while for an even case, the ground state is a spontaneously dimerized state with twofold
degeneracy. In the matrix product ground states for both cases, we identify a
hidden antiferromagnetic order, which is characterized by nonlocal string order
parameters. The ground-state phase diagram of a generalized SO(n) symmetric
bilinear-biquadratic model is discussed.Comment: 11 pages, 5 figure
Coupled-Bunch Beam Breakup due to Resistive-Wall Wake
The coupled-bunch beam breakup problem excited by the resistive wall wake is
formulated. An approximate analytic method of finding the asymptotic behavior
of the transverse bunch displacement is developed and solved.Comment: 8 page
Two-channel Kondo model as a generalized one-dimensional inverse square long-range Haldane-Shastry spin model
Majorana fermion representations of the algebra associated with spin, charge,
and flavor currents have been used to transform the two-channel Kondo
Hamiltonian. Using a path integral formulation, we derive a reduced effective
action with long-range impurity spin-spin interactions at different imaginary
times. In the semiclassical limit, it is equivalent to a one-dimensional
Heisenberg spin chain with two-spin, three-spin, etc. long-range interactions,
as a generalization of the inverse-square long-range Haldane-Shastry spin
model. In this representation the elementary excitations are "semions", and the
non-Fermi-liquid low-energy properties of the two-channel Kondo model are
recovered.Comment: 4 pages, no figure, to be published in J. Phys.: Condens. Matter,
200
Partonic effects on anisotropic flows at RHIC
We report recent results from a multiphase transport (AMPT) model on the
azimuthal anisotropies of particle momentum distributions in heavy ion
collisions at the Relativistic Heavy Ion Collider. These include higher-order
anisotropic flows and their scaling, the rapidity dependence of anisotropic
flows, and the elliptic flow of charm quarks.Comment: 7 pages, 5 figures, talk given at "Hot Quarks 2004", July 18-24,
2004, Taos Valley, NM, US
X-ray Observation and Analysis of The Composite Supernova Remnant G327.1-1.1
Based on the data from the observation of the SNR G327.1-1.1 by ASCA and
ROSAT, we find that G327.1-1.1 is a composite remnant with both a nonthermal
emission component and a diffuse thermal emission component. The nonthermal
component is well fitted by a power-law model with photon index about 2.2. This
component is attributed to the emission from the synchrotron nebula powered by
an undiscovered central pulsar. The thermal component has a temperature of
about 0.4 keV. We attribute it to the emission from the shock-heat swept-up
ISM. Its age, explosion energy and density of ambient medium are derived from
the observed thermal component. Some charactistics about the synchrotron nebula
are also derived. We search for the pulsed signal, but has not found it. The
soft X-ray(0.4 - 2 keV) and hard X-ray(2 - 10 keV) images are different, but
they both elongate in the SE-NW direction. And this X-ray SE-NW elongation is
in positional coincidence with the radio ridge in MOST 843MHz radio map. We
present a possibility that the X-ray nonthermal emission mainly come from the
trail produced by a quickly moving undiscoverd pulsar, and the long radio ridge
is formed when the pulsar is moving out of the boundary of the plerionic
structure.Comment: 20 pages, 4 Postscript figures, aasms4.sty and psfig.sty, to be
published in Astrophysical Journal, January 20, 1999, Vol. 51
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