5,830 research outputs found
Size confinement effect in graphene grown on 6H-SiC (0001) substrate
We have observed the energy structure in the density of occupied states of
graphene grown on n-type 6H-SiC (0001). The structure revealed with
photoelectron spectroscopy is described by creation of the quantum well states
whose number and the energy position (E1 = 0.3 eV, E2 = 1.2 eV, E3 = 2.6 eV )
coincide with the calculated ones for deep (V = 2.9 eV) and narrow (d = 2.15 A)
quantum well formed by potential relief of the valence bands in the structure
graphene/n-SiC. We believe that the quantum well states should be formed also
in graphene on dielectric and in suspended graphene.Comment: 7 pages, 4 figure
Comment on ``Damping of energetic gluons and quarks in high-temperature QCD''
Burgess and Marini have recently pointed out that the leading contribution to
the damping rate of energetic gluons and quarks in the QCD plasma, given by
, can be obtained by simple arguments obviating the need
of a fully resummed perturbation theory as developed by Braaten and Pisarski.
Their calculation confirmed previous results of Braaten and Pisarski, but
contradicted those proposed by Lebedev and Smilga. While agreeing with the
general considerations made by Burgess and Marini, I correct their actual
calculation of the damping rates, which is based on a wrong expression for the
static limit of the resummed gluon propagator. The effect of this, however,
turns out to be cancelled fortuitously by another mistake, so as to leave all
of their conclusions unchanged. I also verify the gauge independence of the
results, which in the corrected calculation arises in a less obvious manner.Comment: 5 page
Dynamics of Two-Level System Interacting with Random Classical Field
The dynamics of a particle interacting with random classical field in a
two-well potential is studied by the functional integration method. The
probability of particle localization in either of the wells is studied in
detail. Certain field-averaged correlation functions for quantum-mechanical
probabilities and the distribution function for the probabilities of final
states (which can be considered as random variables in the presence of a random
field) are calculated. The calculated correlators are used to discuss the
dependence of the final state on the initial state. One of the main results of
this work is that, although the off-diagonal elements of density matrix
disappear with time, a particle in the system is localized incompletely
(wave-packet reduction does not occur), and the distribution function for the
probability of finding particle in one of the wells is a constant at infinite
time.Comment: 5 page
Entanglement in a Noninteracting Mesoscopic Structure
We study the time dependent electron-electron and electron-hole correlations
in a mesoscopic device which is splitting an incident current of free fermions
into two spatially separated particle streams. We analyze the appearance of
entanglement as manifested in a Bell inequality test and discuss its origin in
terms of local spin-singlet correlations already present in the initial channel
and the action of post-selection during the Bell type measurement. The time
window over which the Bell inequality is violated is determined in the
tunneling limit and for the general situation with arbitrary transparencies. We
compare our results with alternative Bell inequality tests based on coincidence
probabilities.Comment: 9 pages, 2 figure
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