2,748 research outputs found
Transport Equations and Spin-Charge Propagating Mode in the Two Dimensional Hole Gas
We find that the spin-charge motion in a strongly confined two-dimensional
hole gas (2DHG) supports a propagating mode of cubic dispersion apart from the
diffusive mode due to momentum scattering. Propagating modes seem to be a
generic property of systems with spin-orbit coupling. Through a rigorous
Keldysh approach, we obtain the transport equations for the 2DHG, we analyze
the behavior of the hole spin relaxation time, the diffusion coefficients, and
the spin-charge coupled motion
Zero sound in triplet-correlated superfluid neutron matter
The linear response of a superfluid neutron liquid onto external vector field
is studied for the case of ^{3}P_{2}-\,^{3}F_{2} pairing. The consideration
is limited to the case when the wave-length of the perturbation is large as
compared to the coherence length in the superfluid matter and the transferred
energy is small in comparison with the gap amplitude. The obtained results are
used to analyse the collisionless phonon-like excitations of the condensate of
superfluid neutrons. In particular, we analyze the case of neutron condensation
into the state with which is conventionally considered as the
preferable one in the bulk matter of neutron stars. Zero sound (if it exists)
is found to be anisotropic and undergoes strong decrement below some
temperature threshold depending substantially on the intensity of Fermi-liquid
interactions.Comment: 16 pages, 2 figure
Apollo experience report: Onboard navigational and alignment software
The onboard navigational and alignment routines used during the nonthrusting phases of an Apollo mission are discussed as to their limitations, and alternate approaches that have more desirable capabilities are presented. A more efficient procedure for solving Kepler's equation, which is used in the calculation of Kepler's problem and Lambert's problem is included, and a sixth-order predictor scheme with a Runge-Kutta starter is recommended for numerical integration. The extension of the rendezvous navigation state to include angle biases and the use of a fixed coordinate system is also evaluated
Electric-field correlations in quantum charged fluids coupled to the radiation field
In a recent paper [S.El Boustani, P.R.Buenzli, and Ph.A.Martin, Phys.Rev. E
73, 036113 (2006) cond-mat/0511537], about quantum charges in equilibrium with
radiation, among other things the asymptotic form of the electric-field
correlation has been obtained by a microscopic calculation. It has been found
that this correlation has a long-range algebraic decay (except in the classical
limit). The macroscopic approach, in the Course of Theoretical Physics of
Landau and Lifshitz, gives no such long-range algebraic decay. In this Brief
Report, we revisit and complete the macroscopic approach of Landau and
Lifshitz, we confirm their result, and suggest that, perhaps, the use of a
classical electromagnetic field by El Boustani et al. was not justified.Comment: 10 pages. Title changed. Minor modifications, including a better
justification of eq.(8
Particle linear theory on a self-gravitating perturbed cubic Bravais lattice
Discreteness effects are a source of uncontrolled systematic errors of N-body
simulations, which are used to compute the evolution of a self-gravitating
fluid. We have already developed the so-called "Particle Linear Theory" (PLT),
which describes the evolution of the position of self-gravitating particles
located on a perturbed simple cubic lattice. It is the discrete analogue of the
well-known (Lagrangian) linear theory of a self-gravitating fluid. Comparing
both theories permits to quantify precisely discreteness effects in the linear
regime. It is useful to develop the PLT also for other perturbed lattices
because they represent different discretizations of the same continuous system.
In this paper we detail how to implement the PLT for perturbed cubic Bravais
lattices (simple, body and face-centered) in a cubic simulation box. As an
application, we will study the discreteness effects -- in the linear regime --
of N-body simulations for which initial conditions have been set-up using these
different lattices.Comment: 9 pages, 4 figures and 4 tables. Minor corrections to match published
versio
The Dynamic Structure Factor of the 1D Bose Gas near the Tonks-Girardeau Limit
While the 1D Bose gas appears to exhibit superfluid response under certain
conditions, it fails the Landau criterion according to the elementary
excitation spectrum calculated by Lieb. The apparent riddle is solved by
calculating the dynamic structure factor of the Lieb-Liniger 1D Bose gas. A
pseudopotential Hamiltonian in the fermionic representation is used to derive a
Hartree-Fock operator, which turns out to be well-behaved and local. The
Random-Phase approximation for the dynamic structure factor based on this
derivation is calculated analytically and is expected to be valid at least up
to first order in , where is the dimensionless interaction
strength of the model. The dynamic structure factor in this approximation
clearly indicates a crossover behavior from the non-superfluid Tonks to the
superfluid weakly-interacting regime, which should be observable by Bragg
scattering in current experiments.Comment: 4 pages, 2 figures misprints in formulas correcte
Fourier transform pure nuclear quadrupole resonance by pulsed field cycling
We report the observation of Fourier transform pure NQR by pulsed field cycling. For deuterium, well resolved spectra are obtained with high sensitivity showing the low frequency nu0 lines and allowing assignments of quadrupole couplings and asymmetry parameters to inequivalent deuterons. The technique is ideally applicable to nuclei with low quadrupolar frequencies (e.g., 2D, 7Li, 11B, 27Al, 23Na, 14N) and makes possible high resolution structure determination in polycrystalline or disordered materials
Nonlinear screening of charge impurities in graphene
It is shown that a ``vacuum polarization'' induced by Coulomb potential in
graphene leads to a strong suppression of electric charges even for undoped
case (no charge carriers). A standard linear response theory is therefore not
applicable to describe the screening of charge impurities in graphene. In
particular, it overestimates essentially the contributions of charge impurities
into the resistivity of graphene.Comment: 3 pages, 1 figure; final version as published in the journa
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