14,349 research outputs found
Novel Pressure Induced Structural Phase Transition in AgSbTe
We report a novel high pressure structural sequence for the functionally
graded thermoelectric, narrow band gap semiconductor AgSbTe, using angle
dispersive x-ray diffraction in a diamond anvil cell with synchrotron radiation
at room temperature. The compound undergoes a B1 to B2 transition; the
transition proceeds through an intermediate amorphous phase found between 17-26
GPa that is quenchable down to ambient conditions. The pressure induced
structural transition observed in this compound is the first of its type
reported in this ternary cubic family, and it is new for the B1-B2 transition
pathway reported to date. Density Functional Theory (DFT) calculations
performed for the B1 and B2 phases are in good agreement with the experimental
results.Comment: 4 pages, 3 figure
Integration of security standards in DevOps pipelines: An industry case study
In the last decade, companies adopted DevOps as a fast path to deliver software products according to customer expectations, with well aligned teams and in continuous cycles. As a basic practice, DevOps relies on pipelines that simulate factory swim-lanes. The more automation in the pipeline, the shorter a lead time is supposed to be. However, applying DevOps is challenging, particularly for industrial control systems (ICS) that support critical infrastructures and that must obey to rigorous requirements from security regulations and standards. Current research on security compliant DevOps presents open gaps for this particular domain and in general for systematic application of security standards. In this paper, we present a systematic approach to integrate standard-based security activities into DevOps pipelines and highlight their automation potential. Our intention is to share our experiences and help practitioners to overcome the trade-off between adding security activities into the development process and keeping a short lead time. We conducted an evaluation of our approach at a large industrial company considering the IEC 62443-4-1 security standard that regulates ICS. The results strengthen our confidence in the usefulness of our approach and artefacts, and in that they can support practitioners to achieve security compliance while preserving agility including short lead times.info:eu-repo/semantics/acceptedVersio
Completing Natural Inflation
If the inflaton is a pseudo-scalar axion, the axion shift symmetry can
protect the flatness of its potential from too large radiative corrections.
This possibility, known as natural inflation, requires an axion scale which is
greater than the (reduced) Planck scale. It is unclear whether such a high
value is compatible with an effective field theoretical description, and if the
global axionic symmetry survives quantum gravity effects. We propose a
mechanism which provides an effective large axion scale, although the original
one is sub-Planckian. The mechanism is based on the presence of two axions,
with a potential provided by two anomalous gauge groups. The effective large
axion scale is due to an almost exact symmetry between the couplings of the
axions to the anomalous groups. We also comment on a possible implementation in
heterotic string theory.Comment: 9 pages, 1 figur
Pairing via Index theorem
This work is motivated by a specific point of view: at short distances and
high energies the undoped and underdoped cuprates resemble the -flux phase
of the t-J model. The purpose of this paper is to present a mechanism by which
pairing grows out of the doped -flux phase. According to this mechanism
pairing symmetry is determined by a parameter controlling the quantum tunneling
of gauge flux quanta. For zero tunneling the symmetry is ,
while for large tunneling it is . A zero-temperature critical
point separates these two limits
Zero Cosmological Constant and Nonzero Dark Energy from Holographic Principle
It is shown that the first law of thermodynamics and the holographic
principle applied to an arbitrary large cosmic causal horizon naturally demand
the zero cosmological constant and non-zero dynamical dark energy in the form
of the holographic dark energy. Semiclassical analysis shows that the
holographic dark energy has a parameter and an equation of state
comparable to current observational data, if the entropy of the horizon
saturates the Bekenstein-Hawking bound. This result indicates that quantum
field theory should be modified at large scale to explain dark energy. The
relations among dark energy, quantum vacuum energy and entropic gravity are
also discussed.Comment: Revtex 7 pages 2 fig
Spin Liquid State around a Doped Hole in Insulating Cuprates
The numerically exact diagonalization study on small clusters of the t-J
model with the second- and third- neighbor hopping terms shows that a novel
spin liquid state is realized around a doped hole with momentum k=(pi,0) and
energy \sim 2J compared with that with (pi/2,pi/2) in insulating cuprates,
where the spin and charge degrees of freedom are approximately decoupled. Our
finding implies that the excitations in the insulating cuprates are mapped onto
the the d-wave resonating valence bond state.Comment: 4 pages, 4 EPS figures, to be published in J. Phys. Soc. Jpn. Vol.
69, No.1 January, 200
Non-fermi-liquid single particle lineshape of the quasi-one-dimensional non-CDW metal Li_{0.9}Mo_{6}O_{17} : comparison to the Luttinger liquid
We report the detailed non-Fermi liquid (NFL) lineshape of the dispersing
excitation which defines the Fermi surface (FS) for quasi-one-dimensional
Li_{0.9}Mo_{6}O_{17}. The properties of Li_{0.9}Mo_{6}O_{17} strongly suggest
that the NFL behavior has a purely electronic origin. Relative to the
theoretical Luttinger liquid lineshape, we identify significant similarities,
but also important differences.Comment: 5 pages, 3 eps figure
Interacting agegraphic dark energy model in tachyon cosmology coupled to matter
Scalar-field dark energy models for tachyon fields are often regarded as an
effective description of an underlying theory of dark energy. In this paper, we
propose the agegraphic dark energy model in tachyon cosmology by interaction
between the components of the dark sectors. In the formalism, the interaction
term emerges from the tachyon field nonminimally coupled to the matter
Lagrangian in the model rather than being inserted into the formalism as an
external source. The model is constrained by the observational data. Based on
the best fitted parameters in both original and new agegraphic dark energy
scenarios, the model is tested by Sne Ia data. The tachyon potential and
tachyon field are reconstructed and coincidence problem is revisited.Comment: 11 pages, 10 figures. Published in PLB (contains some changes in the
text with respect to the first version); arXiv admin note: text overlap with
arXiv:1106.2659 by same author
Hologrphy and holographic dark energy model
The holographic principle is used to discuss the holographic dark energy
model. We find that the Bekenstein-Hawking entropy bound is far from saturation
under certain conditions. A more general constraint on the parameter of the
holographic dark energy model is also derived.Comment: no figures, use revtex, v2: use iop style, some typos corrected and
references updated, will appear in CQ
Interacting Agegraphic Dark Energy
A new dark energy model, named "agegraphic dark energy", has been proposed
recently, based on the so-called K\'{a}rolyh\'{a}zy uncertainty relation, which
arises from quantum mechanics together with general relativity. In this note,
we extend the original agegraphic dark energy model by including the
interaction between agegraphic dark energy and pressureless (dark) matter. In
the interacting agegraphic dark energy model, there are many interesting
features different from the original agegraphic dark energy model and
holographic dark energy model. The similarity and difference between agegraphic
dark energy and holographic dark energy are also discussed.Comment: 10 pages, 5 figures, revtex4; v2: references added; v3: accepted by
Eur. Phys. J. C; v4: published versio
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