10,773 research outputs found
Anelastic relaxation process of polaronic origin in La{2-x}Sr{x}CuO{4}: interaction between the charge stripes and pinning centers
The evolution of an anelastic relaxation process occurring around 80 K in
La{2-x}Sr{x}CuO{4} at a measuring frequency of ~1 kHz has been followed from x
= 0.0075 to the overdoped region, x = 0.2, where it disappears. The dependence
of the peak intensity on doping is consistent with a polaronic mechanism,
identified with the disordered charge stripes overcoming pinning centers. A
marked decrease of the peak amplitude occurs at x > 0.045, the same doping
range where a change of the stripe order from parallel to diagonal with respect
to the Cu-O bonds has been observed by neutron diffraction. Both the energy
barrier and peak amplitude also exhibit a rise near x = 1/8.Comment: 5 pages, 4 figure
The weight of words: textual data versus sentiment analysis in stock returns prediction
The focus of this paper is to understand whether the words contained in a text corpus improves the explained variance of stock returns better than the use of the polarity of the same texts, obtained through a sentiment analysis using a generic ontological dictionary. The empirical analysis is based on the content of a weekly column in the most important Italian financial newspaper, which published past information and analysts’ recommendations on listed companies. The use of textual data clearly increases the explained variance of stock returns but, through comparisons between data mining techniques, we observed minor differences in terms of MSE, by adding a selection of specific terms as features. In this context, the text mining approach proved to be very useful to improve the explanatory power of forecasting models, while it emerged the limited explanatory power of an automatic sentiment analysis based on a generic lexicon
Testing for redshift evolution of Type Ia supernovae using the strongly lensed PS1-10afx at
The light from distant supernovae (SNe) can be magnified through
gravitational lensing when a foreground galaxy is located along the line of
sight. This line-up allows for detailed studies of SNe at high redshift that
otherwise would not be possible. Spectroscopic observations of lensed
high-redshift Type Ia supernovae (SNe Ia) are of particular interest since they
can be used to test for evolution of their intrinsic properties. The use of SNe
Ia for probing the cosmic expansion history has proven to be an extremely
powerful method for measuring cosmological parameters. However, if systematic
redshift-dependent properties are found, their usefulness for future surveys
could be challenged. We investigate whether the spectroscopic properties of the
strongly lensed and very distant SN Ia PS1-10afx at deviates from the
well-studied populations of normal SNe Ia at nearby or intermediate distance.
We created median spectra from nearby and intermediate-redshift
spectroscopically normal SNe Ia from the literature at -5 and +1 days from
light-curve maximum. We then compared these median spectra to those of
PS1-10afx. We do not find signs of spectral evolution in PS1-10afx. The
observed deviation between PS1-10afx and the median templates are within what
is found for SNe at low- and intermediate-redshift. There is a noticeable broad
feature centred at ~\AA{}, which is present only to a
lesser extent in individual low and intermediate redshift SN Ia spectra. From a
comparison with a recently developed explosion model, we find this feature to
be dominated by iron peak elements, in particular, singly ionized cobalt and
chromium.Comment: accepted for publication in section 4. Extragalactic astronomy of
Astronomy and Astrophysic
Evidence for pseudogap and phase-coherence gap separation by Andreev reflection experiments in Au/La_{2-x}Sr_{x}CuO_4 point-contact junctions
We present new Au/La_{2-x}Sr_{x}CuO_{4} (LSCO) point-contact conductance
measures as a function of voltage and temperature in samples with 0.08 <= x <=
0.2. Andreev reflection features disappear at about the bulk Tc, giving no
evidence of gap for T > Tc. The fit of the normalized conductance at any T < Tc
supports a (s + d)-wave symmetry of the gap, whose dominant low-T s component
follows the Tc(x) curve in contrast with recent angle-resolved photoemission
spectroscopy and quasiparticle tunneling data. These results prove the
separation between pseudogap and phase-coherence superconducting gap in LSCO at
x <= 0.2.Comment: 4 pages, 4 eps figures, 1 table (RevTeX). Labels added to Fig. 1;
Fig. 3 resized; references added; short discussion about ballistic contact
regime adde
Beta-functions in Yang-Mills Theory from Non-critical String
The renormalization group equations of the Yang-Mills theory are examined in
the non-critical string theory according to the framework of the holography.
Under a simple ansatz for the tachyon, we could find several interesting
solutions which are classified by the value of the tachyon potential at the
vacuum. We show two typical, asymptotic-free solutions which are different in
their infrared behaviors. For both types of solutions, we could obtain
quark-confinement potential from the Wilson-loop. The stability of the tachyon
and the ZigZag symmetry are also discussed for these solutions.Comment: 16 pages, 5 figure
First principle theory of correlated transport through nano-junctions
We report the inclusion of electron-electron correlation in the calculation
of transport properties within an ab initio scheme. A key step is the
reformulation of Landauer's approach in terms of an effective transmittance for
the interacting electron system. We apply this framework to analyze the effect
of short range interactions on Pt atomic wires and discuss the coherent and
incoherent correction to the mean-field approach.Comment: 5 pages, 3 figure
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