548 research outputs found
On the extra phase correction to the semiclassical spin coherent-state propagator
The problem of an origin of the Solary-Kochetov extra-phase contribution to
the naive semiclassical form of a generalized phase-space propagator is
addressed with the special reference to the su(2) spin case which is the most
important in applications. While the extra-phase correction to a flat
phase-space propagator can straightforwardly be shown to appear as a difference
between the principal and the Weyl symbols of a Hamiltonian in the
next-to-leading order expansion in the semiclassical parameter, the same
statement for the semiclassical spin coherent-state propagator holds provided
the Holstein-Primakoff representation of the su(2) algebra generators is
employed.Comment: 19 pages, no figures; a more general treatment is presented, some
references are added, title is slightly changed; submitted to JM
Electronic properties of disclinated flexible membrane beyond the inextensional limit: Application to graphene
Gauge-theory approach to describe Dirac fermions on a disclinated flexible
membrane beyond the inextensional limit is formulated. The elastic membrane is
considered as an embedding of 2D surface into R^3. The disclination is
incorporated through an SO(2) gauge vortex located at the origin, which results
in a metric with a conical singularity. A smoothing of the conical singularity
is accounted for by replacing a disclinated rigid plane membrane with a
hyperboloid of near-zero curvature pierced at the tip by the SO(2) vortex. The
embedding parameters are chosen to match the solution to the von Karman
equations. A homogeneous part of that solution is shown to stabilize the
theory. The modification of the Landau states and density of electronic states
of the graphene membrane due to elasticity is discussed.Comment: 15 pages, Journal of Physics:Condensed Matter in pres
Thermal, fire, and mechanical properties of solvent-free processed BN/boehmite-filled prepregs
On representation of the t-J model via spin-charge variables
We show that the t-J Hamiltonian is not in general reduced to H(S,f), where S
and f stand for independent ([S,f]=0) SU(2) (spin) generators and spinless
fermionic (hole) field, respectively. The proof is based upon an identification
of the Hubbard operators with the generators of the su(2|1) superalgebra in the
degenerate fundamental representation and ensuing SU(2|1) path integral
representation of the partition function.Comment: 15 pages, latex, no figure
Classical and quantum dynamics of a spin-1/2
We reply to a comment on `Semiclassical dynamics of a spin-1/2 in an
arbitrary magnetic field'.Comment: 4 pages, submitted to Journal of Physics
Two-oscillator model of trapped-modes interaction in a nonlinear bilayer fish-scale metamaterial
We discuss the similarity between the nature of resonant oscillations in two
nonlinear systems, namely, a chain of coupled Duffing oscillators and a bilayer
fish-scale metamaterial. In such systems two different resonant states arise
which differ in their spectral lines. The spectral line of the first resonant
state has a Lorentzian form, while the second one has a Fano form. This
difference leads to a specific nonlinear response of the systems which
manifests itself in appearance of closed loops in spectral lines and bending
and overlapping of resonant curves. Conditions of achieving bistability and
multistability are found out.Comment: 14 pages, 6 figure
Electronic Structure of Disclinated Graphene in an Uniform Magnetic Field
The electronic structure in the vicinity of the 1-heptagonal and 1-pentagonal
defects in the carbon graphene plane is investigated. Using a continuum gauge
field-theory model the local density of states around the Fermi energy is
calculated for both cases. In this model, the disclination is represented by an
SO(2) gauge vortex and corresponding metric follows from the elasticity
properties of the graphene membrane. To enhance the interval of energies, a
self-consistent perturbation scheme is used. The Landau states are investigated
and compared with the predicted values.Comment: keywords: graphene, heptagonal defect, elasticity, carbon nanohorns,
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