3,737 research outputs found
Numbers of donors and acceptors from transport measurements in graphene
A method is suggested to separately determine the surface density of
positively and negatively charged impurities that limit the mobility in a
graphene monolayer. The method is based on the exact result for the transport
cross-section, according to which the massless carriers are scattered more
strongly when they are attracted to a charged impurity than when they are
repelled from it.Comment: 3 pages, 1 figur
Hydrodynamic Flow as Congruence of Geodesic Lines in Riemannian Space-Time
It is shown that small elements of perfect fluid in adiabatic processes move
along geodesic lines of a Riemannian space-time.Comment: 5 pages, Latex. Final versio
The electrification of spacecraft
Physical and applied aspects of the electrification of space vehicles and natural celestial objects are discussed, the factors resulting in electrification of spacecraft are analyzed, and methods of investigating various phenomena associated with this electrification and ways of protecting spacecraft against the influence of static electricity are described. The booklet is intended for the general reader interested in present day questions of space technology
Groebner-Shirshov basis for HNN extensions of groups and for the alternating group
In this paper, we generalize the Shirshov's Composition Lemma by replacing
the monomial order for others. By using Groebner-Shirshov bases, the normal
forms of HNN extension of a group and the alternating group are obtained
Qualitative Criterion for Interception in a Pursuit/Evasion Game
A qualitative account is given of a differential pursuit/evasion game. A
criterion for the existence of an intercept solution is obtained using future
cones that contain all attainable trajectories of target or interceptor
originating from an initial position. A sufficient and necessary conditon that
an opportunity to intercept always exist is that, after some initial time, the
future cone of the target be contained within the future cone of the
interceptor. The sufficient condition may be regarded as a kind of Nash
equillibrium.Comment: 8 pages; revsions and corrigend
Temperature-dependent Drude transport in a two-dimensional electron gas
We consider transport of dilute two-dimensional electrons, with temperature
between Fermi and Debye temperatures. In this regime, electrons form a
nondegenerate plasma with mobility limited by potential disorder. Different
kinds of impurities contribute unique signatures to the resulting
temperature-dependent Drude conductivity, via energy-dependent scattering. This
opens up a way to characterize sample disorder composition. In particular,
neutral impurities cause a slow decrease in conductivity with temperature,
whereas charged impurities result in conductivity growing as a square root of
temperature. This observation serves as a precaution for literally interpreting
metallic or insulating conductivity dependence, as both can be found in a
classical metallic system.Comment: 5 pages, 2 figures, published versio
Devil's staircase of incompressible electron states in a nanotube
It is shown that a periodic potential applied to a nanotube can lock
electrons into incompressible states. Depending on whether electrons are weakly
or tightly bound to the potential, excitation gaps open up either due to the
Bragg diffraction enhanced by the Tomonaga - Luttinger correlations, or via
pinning of the Wigner crystal. Incompressible states can be detected in a
Thouless pump setup, in which a slowly moving periodic potential induces
quantized current, with a possibility to pump on average a fraction of an
electron per cycle as a result of interactions.Comment: 4 pages, 1 figure, published versio
Dirac fermion wave guide networks on topological insulator surfaces
Magnetic texturing on the surface of a topological insulator allows the
design of wave guide networks and beam splitters for domain-wall Dirac
fermions. Guided by simple analytic arguments we model a Dirac fermion
interferometer consisting of two parallel pathways, whereby a newly developed
staggered-grid leap-frog discretization scheme in 2+1 dimensions with absorbing
boundary conditions is employed. The net transmission can be tuned between
constructive to destructive interference, either by variation of the
magnetization (path length) or an applied bias (wave length). Based on this
principle, a Dirac fermion transistor is proposed. Extensions to more general
networks are discussed.Comment: Submitted to PR
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