9,109 research outputs found
Parity independence of the zero-bias conductance peak in a nanowire based topological superconductor-quantum dot hybrid device
We explore the signatures of Majorana fermions in a nanowire based
topological superconductor-quantum dot-topological superconductor hybrid device
by charge transport measurements. The device is made from an epitaxially grown
InSb nanowire with two superconductor Nb contacts on a Si/SiO substrate. At
low temperatures, a quantum dot is formed in the segment of the InSb nanowire
between the two Nb contacts and the two Nb contacted segments of the InSb
nanowire show superconductivity due to the proximity effect. At zero magnetic
field, well defined Coulomb diamonds and the Kondo effect are observed in the
charge stability diagram measurements in the Coulomb blockade regime of the
quantum dot. Under the application of a finite, sufficiently strong magnetic
field, a zero-bias conductance peak structure is observed in the same Coulomb
blockade regime. It is found that the zero-bias conductance peak is present in
many consecutive Coulomb diamonds, irrespective of the even-odd parity of the
quasi-particle occupation number in the quantum dot. In addition, we find that
the zero-bias conductance peak is in most cases accompanied by two differential
conductance peaks, forming a triple-peak structure, and the separation between
the two side peaks in bias voltage shows oscillations closely correlated to the
background Coulomb conductance oscillations of the device. The observed
zero-bias conductance peak and the associated triple-peak structure are in line
with the signatures of Majorana fermion physics in a nanowire based topological
superconductor-quantum dot-topological superconductor system, in which the two
Majorana bound states adjacent to the quantum dot are hybridized into a pair of
quasi-particle states with finite energies and the other two Majorana bound
states remain as the zero-energy modes located at the two ends of the entire
InSb nanowire.Comment: 6 pages, 4 figure
An M-theory solution generating technique and SL(2,R)
In this paper we generalize the O(p+1,p+1) solution generating technique
(this is a method used to deform Dp-branes by turning on a NS-NS B-field) to
M-theory, in order to be able to deform M5-brane supergravity solutions
directly in eleven dimensions, by turning on a non zero three form A. We find
that deforming the M5-brane, in some cases, corresponds to performing certain
SL(2,R) transformations of the Kahler structure parameter for the three-torus,
on which the M5-brane has been compactified. We show that this new M-theory
solution generating technique can be reduced to the O(p+1,p+1) solution
generating technique with p=4. Further, we find that it implies that the open
membrane metric and generalized noncommutativity parameter are manifestly
deformation independent for electric and light-like deformations. We also
generalize the O(p+1,p+1) method to the type IIA/B NS5-brane in order to be
able to deform NS5-branes with RR three and two forms, respectively. In the
type IIA case we use the newly obtained solution generating technique and
deformation independence to derive a covariant expression for an open D2-brane
coupling, relevant for OD2-theory.Comment: 24 pages, Latex. v2:Sections 3.2 and 3.3 improved. v3:Some
clarifications added. Version published in JHE
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The identification and psychological treatment of panic disorder in adolescents: a survey of CAMHS clinicians
Background
Panic disorder is experienced by around 1% of adolescents, and has a significant impact on social and academic functioning. Preliminary evidence supports the effectiveness of panic disorder specific treatment in adolescents with panic disorder, however panic disorder may be overlooked in adolescents due to overlapping symptoms with other anxiety disorders and other difficulties being more noticeable to others. The aim of this study was to establish what training National Health Service (NHS) Child and Adolescent Mental Health Services (CAMHS) clinicians have received in psychological therapies and panic disorder and how they identify and treat panic disorder in adolescents.
Method
CAMHS clinicians from a range of professions (n = 427), who were delivering psychological treatments to children and adolescents with anxiety disorders, participated. They completed a cross-sectional, online survey, including a vignette describing an adolescent with panic disorder, and were asked to identify the main diagnosis or presenting problem.
Results
Less than half the clinicians (48.6%) identified panic disorder or panic symptoms as the main presenting problem from the vignette. The majority of clinicians suggested CBT would be their treatment approach. However, few identified an evidence-based treatment protocol for working with young people with panic disorder. Almost half the sample had received no training in cognitive behaviour therapy (CBT) and around a fifth had received no training in delivering psychological treatments.
Conclusions
Only half of CAMHS clinicians identified panic disorder from a vignette and although CBT treatments are widely offered, only a minority of adolescents with panic disorder are receiving treatments developed for, and evaluated with young people with panic disorder. There is a vital need for clinician training, the use of tools that aid identification and the implementation of evidence-based treatments within CAMHS
The Dynamics of Radiative Shock Waves: Linear and Nonlinear Evolution
The stability properties of one-dimensional radiative shocks with a power-law
cooling function of the form are the main
subject of this work. The linear analysis originally presented by Chevalier &
Imamura, is thoroughfully reviewed for several values of the cooling index
and higher overtone modes. Consistently with previous results, it is
shown that the spectrum of the linear operator consists in a series of modes
with increasing oscillation frequency. For each mode a critical value of the
cooling index, , can be defined so that modes with are unstable, while modes with
are stable. The perturbative analysis is complemented by several numerical
simulations to follow the time-dependent evolution of the system for different
values of . Particular attention is given to the comparison between
numerical and analytical results (during the early phases of the evolution) and
to the role played by different boundary conditions. It is shown that an
appropriate treatment of the lower boundary yields results that closely follow
the predicted linear behavior. During the nonlinear regime, the shock
oscillations saturate at a finite amplitude and tend to a quasi-periodic cycle.
The modes of oscillations during this phase do not necessarily coincide with
those predicted by linear theory, but may be accounted for by mode-mode
coupling.Comment: 33 pages, 12 figures, accepted for publication on the Astrophysical
Journa
VLA 3.5 cm continuum sources in the Serpens cloud core
We present VLA 3.5 cm continuum observations of the Serpens cloud core. 22
radio continuum sources are detected. 16 out of the 22 cm sources are suggested
to be associated with young stellar objects (Class 0, Class I, flat-spectrum,
and Class II) of the young Serpens cluster. The rest of the VLA sources
plausibly are background objects. Most of the Serpens cm sources likely
represent thermal radio jets; on the other hand, the radio continuum emission
of some sources could be due to a gyrosynchroton mechanism arising from
coronally active young stars. The Serpens VLA sources are spatially distributed
into two groups; one of them located towards the NW clump of the Serpens core,
where only Class 0 and Class I protostars are found to present cm emission, and
a second group located towards the SE clump, where radio continuum sources are
associated with objects in evolutionary classes from Class 0 to Class II. This
subgrouping is similar to that found in the near IR, mid-IR and mm wavelength
regimes.Comment: 2 figures, accepted by Astronomical journa
Deformation independent open brane metrics and generalized theta parameters
We investigate the consequences of generalizing certain well established
properties of the open string metric to the conjectured open membrane and open
Dp-brane metrics. By imposing deformation independence on these metrics their
functional dependence on the background fields can be determined including the
notorious conformal factor. In analogy with the non-commutativity parameter
in the string case, we also obtain `generalized' theta
parameters which are rank q+1 antisymmetric tensors (polyvectors) for open
Dq-branes and rank 3 for the open membrane case. The expressions we obtain for
the open membrane quantities are expected to be valid for general background
field configurations, while the open D-brane quantities are only valid for one
parameter deformations. By reducing the open membrane data to five dimensions,
we show that they, modulo a subtlety with implications for the relation between
OM-theory and NCYM, correctly generate the open string and open D2-data.Comment: 24 pages, LaTe
Suzaku observations of Markarian 335: evidence for a distributed reflector
We report on a 151 ks net exposure Suzaku observation of the Narrow Line
Seyfert 1 galaxy Mrk 335. The 0.5-40 keV spectrum contains a broad Fe line, a
strong soft excess below about 2 keV and a Compton hump around 20-30 keV. We
find that a model consisting of a power law and two reflectors provides the
best fit to the time-averaged spectrum. In this model, an ionized, heavily
blurred, inner reflector produces most of the soft excess, while an almost
neutral outer reflector (outside ~40 r_g) produces most of the Fe line
emission. The spectral variability of the observation is characterised by
spectral hardening at very low count rates. In terms of our power-law +
two-reflector model it seems like this hardening is mainly caused by pivoting
of the power law. The rms spectrum of the entire observation has the curved
shape commonly observed in AGN, although the shape is significantly flatter
when an interval which does not contain any deep dip in the lightcurve is
considered. We also examine a previous 133 ks XMM-Newton observation of Mrk
335. We find that the XMM-Newton spectrum can be fitted with a similar
two-reflector model as the Suzaku data and we confirm that the rms spectrum of
the observation is flat. The flat rms spectra, as well as the high-energy data
from the Suzaku PIN detector, disfavour an absorption origin for the soft
excess in Mrk 335.Comment: 13 pages, 13 figures. Accepted for publication in MNRA
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