20,909 research outputs found
Atomic scale lattice distortions and domain wall profiles
We present an atomic scale theory of lattice distortions using strain related
variables and their constraint equations. Our approach connects constrained
{\it atomic length} scale variations to {\it continuum} elasticity and
describes elasticity at several length scales. We apply the approach to a
two-dimensional square lattice with a monatomic basis, and find the elastic
deformations and hierarchical atomic relaxations in the vicinity of a domain
wall between two different homogeneous strain states. We clarify the
microscopic origin of gradient terms, some of which are included
phenomenologically in Ginzburg-Landau theory, by showing that they are
anisotropic.Comment: 6 figure
The Primary Spin-4 Casimir Operators in the Holographic SO(N) Coset Minimal Models
Starting from SO(N) current algebra, we construct two lowest primary higher
spin-4 Casimir operators which are quartic in spin-1 fields. For N is odd, one
of them corresponds to the current in the WB_{\frac{N-1}{2}} minimal model. For
N is even, the other corresponds to the current in the WD_{\frac{N}{2}} minimal
model. These primary higher spin currents, the generators of wedge subalgebra,
are obtained from the operator product expansion of fermionic (or bosonic)
primary spin-N/2 field with itself in each minimal model respectively. We
obtain, indirectly, the three-point functions with two real scalars, in the
large N 't Hooft limit, for all values of the 't Hooft coupling which should be
dual to the three-point functions in the higher spin AdS_3 gravity with matter.Comment: 65 pages; present the main results only and to appear in JHEP where
one can see the Appendi
The Operator Product Expansion of the Lowest Higher Spin Current at Finite N
For the N=2 Kazama-Suzuki(KS) model on CP^3, the lowest higher spin current
with spins (2, 5/2, 5/2,3) is obtained from the generalized GKO coset
construction. By computing the operator product expansion of this current and
itself, the next higher spin current with spins (3, 7/2, 7/2, 4) is also
derived. This is a realization of the N=2 W_{N+1} algebra with N=3 in the
supersymmetric WZW model. By incorporating the self-coupling constant of lowest
higher spin current which is known for the general (N,k), we present the
complete nonlinear operator product expansion of the lowest higher spin current
with spins (2, 5/2, 5/2, 3) in the N=2 KS model on CP^N space. This should
coincide with the asymptotic symmetry of the higher spin AdS_3 supergravity at
the quantum level. The large (N,k) 't Hooft limit and the corresponding
classical nonlinear algebra are also discussed.Comment: 62 pages; the footnotes added, some redundant appendices removed, the
presentations in the whole paper improved and to appear in JHE
Modulation Doping near Mott-Insulator Heterojunctions
We argue that interesting strongly correlated two-dimensional electron
systems can be created by modulation doping near a heterojunction between Mott
insulators. Because the dopant atoms are remote from the carrier system, the
electronic system will be weakly disordered. We argue that the competition
between different ordered states can be engineered by choosing appropriate
values for the dopant density and the setback distance of the doping layer. In
particular larger setback distances favor two-dimensional antiferromagnetism
over ferromagnetism. We estimate some key properties of modulation-doped Mott
insulator heterojunctions by combining insights from Hartree-Fock-Theory and
Dynamical-Mean-Field-Theory descriptions and discuss potentially attractive
material combinations.Comment: 9 pages, 9 figures, submitte
Pairing in the quantum Hall system
We find an analogy between the single skyrmion state in the quantum Hall
system and the BCS superconducting state and address that the quantum
mechanical origin of the skyrmion is electronic pairing. The skyrmion phase is
found to be unstable for magnetic fields above the critical field at
temperature , which is well represented by the relation .Comment: revtex, two figures, to appear in Phys. Rev. B (Rapid Communications
The Large N 't Hooft Limit of Kazama-Suzuki Model
We consider N=2 Kazama-Suzuki model on CP^N=SU(N+1)/SU(N)xU(1). It is known
that the N=2 current algebra for the supersymmetric WZW model, at level k, is a
nonlinear algebra. The N=2 W_3 algebra corresponding to N=2 was recovered from
the generalized GKO coset construction previously. For N=4, we construct one of
the higher spin currents, in N=2 W_5 algebra, with spins (2, 5/2, 5/2, 3). The
self-coupling constant in the operator product expansion of this current and
itself depends on N as well as k explicitly. We also observe a new higher spin
primary current of spins (3, 7/2, 7/2, 4). From the behaviors of N=2, 4 cases,
we expect the operator product expansion of the lowest higher spin current and
itself in N=2 W_{N+1} algebra. By taking the large (N, k) limit on the various
operator product expansions in components, we reproduce, at the linear order,
the corresponding operator product expansions in N=2 classical
W_{\infty}^{cl}[\lambda] algebra which is the asymptotic symmetry of the higher
spin AdS_3 supergravity found recently.Comment: 44 pages; the two typos in the first paragraph of page 23 corrected
and to appear in JHE
On quantum error-correction by classical feedback in discrete time
We consider the problem of correcting the errors incurred from sending
quantum information through a noisy quantum environment by using classical
information obtained from a measurement on the environment. For discrete time
Markovian evolutions, in the case of fixed measurement on the environment, we
give criteria for quantum information to be perfectly corrigible and
characterize the related feedback. Then we analyze the case when perfect
correction is not possible and, in the qubit case, we find optimal feedback
maximizing the channel fidelity.Comment: 11 pages, 1 figure, revtex
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