11,843 research outputs found
Tight-binding study of bilayer graphene Josephson junctions
Using highly efficient simulations of the tight-binding Bogoliubov-de Gennes
model we solved self-consistently for the pair correlation and the Josephson
current in a Superconducting-Bilayer graphene-Superconducting Josephson
junction. Different doping levels for the non-superconducting link are
considered in the short and long junction regime. Self-consistent results for
the pair correlation and superconducting current resemble those reported
previously for single layer graphene except in the Dirac point where remarkable
differences in the proximity effect are found as well as a suppression of the
superconducting current in long junction regime. Inversion symmetry is broken
by considering a potential difference between the layers and we found that the
supercurrent can be switched if junction length is larger than the Fermi
length
Automorphism Group of : Applications to the Bosonic String
This paper is concerned with the formulation of a non-pertubative theory of
the bosonic string. We introduce a formal group which we propose as the
``universal moduli space'' for such a formulation. This is motivated because
establishes a natural link between representations of the Virasoro algebra
and the moduli space of curves. Among other properties of it is shown that
a ``local'' version of the Mumford formula holds on .Comment: 29 page
Nonequilibrium wetting of finite samples
As a canonical model for wetting far from thermal equilibrium we study a
Kardar-Parisi-Zhang interface growing on top of a hard-core substrate.
Depending on the average growth velocity the model exhibits a non-equilibrium
wetting transition which is characterized by an additional surface critical
exponent theta. Simulating the single-step model in one spatial dimension we
provide accurate numerical estimates for theta and investigate the distribution
of contact points between the substrate and the interface as a function of
time. Moreover, we study the influence of finite-size effects, in particular
the time needed until a finite substrate is completely covered by the wetting
layer for the first time.Comment: 17 pages, 8 figures, revisio
The very faint hard state of the persistent neutron star X-ray binary SLX 1737-282 near the Galactic centre
We report on a detailed study of the spectral and temporal properties of the
neutron star low mass X-ray binary SLX 1737-282, which is located only ~1degr
away from Sgr A. The system is expected to have a short orbital period, even
within the ultra-compact regime, given its persistent nature at low X-ray
luminosities and the long duration thermonuclear burst that it has displayed.
We have analysed a Suzaku (18 ks) observation and an XMM-Newton (39 ks)
observation taken 7 years apart. We infer (0.5-10 keV) X-ray luminosities in
the range 3-6 x10^35erg s-1, in agreement with previous findings. The spectra
are well described by a relatively cool (kTbb = 0.5 keV) black body component
plus a Comptonized emission component with {\Gamma} ~1.5-1.7. These values are
consistent with the source being in a faint hard state, as confirmed by the ~
20 per cent fractional root mean square amplitude of the fast variability (0.1
- 7 Hz) inferred from the XMM-Newton data. The electron temperature of the
corona is >7 keV for the Suzaku observation, but it is measured to be as low as
~2 keV in the XMM-Newton data at higher flux. The latter is significantly lower
than expected for systems in the hard state. We searched for X-ray pulsations
and imposed an upper limit to their semi-amplitude of 2 per cent (0.001 - 7
Hz). Finally, we investigated the origin of the low frequency variability
emission present in the XMM-Newton data and ruled out an absorption dip origin.
This constraint the orbital inclination of the system to 65 degr unless the
orbital period is longer than 11 hr (i.e. the length of the XMM-Newton
observation).Comment: 7 pages, 4 figures, 1 table. Accepted for publication in MNRA
Experimental phase functions of mm-sized cosmic dust grains
We present experimental phase functions of three types of millimeter-sized
dust grains consisting of enstatite, quartz and volcanic material from Mount
Etna, respectively. The three grains present similar sizes but different
absorbing properties. The measurements are performed at 527 nm covering the
scattering angle range from 3 to 170 degrees. The measured phase functions show
two well defined regions i) soft forward peaks and ii) a continuous increase
with the scattering angle at side- and back-scattering regions. This behavior
at side- and back-scattering regions are in agreement with the observed phase
functions for the Fomalhaut and HR 4796A dust rings. Further computations and
measurements (including polarization) for millimeter sized-grains are needed to
draw some conclusions about the fluffy or compact structure of the dust grains
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