316 research outputs found
Dynamical role of system-environment correlations in non-Markovian dynamics
We analyse the role played by system-environment correlations in the
emergence of non-Markovian dynamics. By working within the framework developed
in Breuer et al., Phys. Rev. Lett. 103, 210401 (2009), we unveil a fundamental
connection between non-Markovian behaviour and dynamics of system-environment
correlations. We derive an upper bound to the rate of change of the
distinguishability between different states of the system that explicitly
depends on the development and establishment of correlations between system and
environment. We illustrate our results using a fully solvable spin-chain model,
which allows us to gain insight on the mechanisms triggering non-Markovian
evolution.Comment: 5 pages, 2 figure
Quantitative aspects of entanglement in the optically driven quantum dots
We present a novel approach to look for the existence of maximum entanglement
in a system of two identical quantum dots coupled by the Forster process and
interacting with a classical laser field. Our approach is not only able to
explain the existing treatments, but also provides further detailed insights
into the coupled dynamics of quantum dots systems. The result demonstrates that
there are two ways for generating maximum entangled states, one associated with
far off-resonance interaction, and the other associated with the weak field
limit. Moreover, it is shown that exciton decoherence results in the decay of
entanglement.Comment: 13 pages, 4 figure
NuSTAR observation of the Supergiant Fast X-ray Transient IGR J11215-5952 during its 2017 outburst
We report on the results of a NuSTAR observation of the Supergiant Fast X-ray
Transient pulsar IGRJ11215-5952 during the peak of its outburst in June 2017.
IGRJ11215-5952 is the only SFXT undergoing strictly periodic outbursts, every
165 days. NuSTAR caught several X-ray flares, spanning a dynamic range of 100,
and detected X-ray pulsations at 187.0 s, consistent with previous
measurements. The spectrum from the whole observation is well described by an
absorbed power-law (with a photon index of 1.4) modified, above 7 keV, by a
cutoff with an e-folding energy of 24 keV. A weak emission line is present at
6.4 keV, consistent with Kalpha emission from cold iron in the supergiant wind.
The time-averaged flux is 1.5E-10 erg/cm2/s (3-78 keV, corrected for the
absorption), translating into an average luminosity of about 9E35 erg/s (1-100
keV, assuming a distance of 6.5 kpc). The NuSTAR observation allowed us to
perform the most sensitive search for cyclotron resonant scattering features in
the hard X-ray spectrum, resulting in no significant detection in any of the
different spectral extractions adopted (time-averaged, temporally-selected,
spin-phase-resolved and intensity-selected spectra). The pulse profile showed
an evolution with both the energy (3-12 keV energy range compared with 12-78
keV band) and the X-ray flux: a double peaked profile was evident at higher
fluxes (and in both energy bands), while a single peaked, sinusoidal profile
was present at the lowest intensity state achieved within the NuSTAR
observations (in both energy bands). The intensity-selected analysis allowed us
to observe an anti-correlation of the pulsed fraction with the X-ray
luminosity. The pulse profile evolution can be explained by X-ray photon
scattering in the accreting matter above magnetic poles of a neutron star at
the quasi-spherical settling accretion stage.Comment: Accepted for publication in Astronomy & Astrophysics (Received 3
April 2020 / Accepted 17 April 2020). 14 pages, 5 Tables, 9 Figure
Tidal evolution of exo-planetary systems: WASP-50, GJ 1214 and CoRoT-7
We perform numerical simulations to investigate tidal evolution of two
single-planet systems, that is, WASP-50 and GJ 1214 and a two-planet system
CoRoT-7. The results of orbital evolution show that tidal decay and
circularization may play a significant role in shaping their final orbits,
which is related to the initial orbital data in the simulations. For GJ 1214
system, different cases of initial eccentricity are also considered as only an
upper limit of its eccentricity (0.27) is shown, and the outcome suggests a
possible maximum initial eccentricity (0.4) in the adopted dynamical model.
Moreover, additional runs with alternative values of dissipation factor
are carried out to explore tidal evolution for GJ 1214b, and these
results further indicate that the real of GJ 1214b may be much
larger than its typical value, which may reasonably suggest that GJ 1214b bears
a present-day larger eccentricity, undergoing tidal circularization at a slow
rate. For the CoRoT-7 system, tidal forces make two planets migrating towards
their host star as well as producing tidal circularization, and in this process
tidal effects and mutual gravitational interactions are coupled with each
other. Various scenarios of the initial eccentricity of the outer planet have
also been done to investigate final planetary configuration. Tidal decay
arising from stellar tides may still work for each system as the eccentricity
decreases to zero, and this is in association with the remaining lifetime of
each planet used to predict its future.Comment: 9 pages, 12 figures, accepted for publication in "SCIENCE CHINA
Physics,Mechanics & Astronomy
Ginzburg-Landau Expansion in Non-Fermi Liquid Superconductors: Effect of the Mass Renormalization Factor
We reconsider the Ginzburg-Landau expansion for the case of a non-Fermi
liquid superconductor. We obtain analytical results for the Ginzburg-Landau
functional in the critical region around the superconducting phase transition,
T <= T_c, in two special limits of the model, i.e., the spin-charge separation
case and the anomalous Fermi liquid case. For both cases, in the presence of a
mass renormalization factor, we derived the form and the specific dependence of
the coherence length, penetration depth, specific heat jump at the critical
point, and the magnetic upper critical field. For both limits the obtained
results reduce to the usual BCS results for a two dimensional s-wave
superconductor. We compare our results with recent and relevant theoretical
work. The results for a d--wave symmetry order parameter do not change
qualitatively the results presented in this paper. Only numerical factors
appear additionally in our expressions.Comment: accepted for publication in Physical Review
Recommended from our members
Accelerated Identification of Proteins by Mass Spectrometry by Employing Covalent Pre-Gel Staining with Uniblue A
Background: The identification of proteins by mass spectrometry is a standard method in biopharmaceutical quality control and biochemical research. Prior to identification by mass spectrometry, proteins are usually pre-separated by electrophoresis. However, current protein staining and de-staining protocols are tedious and time consuming, and therefore prolong the sample preparation time for mass spectrometry.
Methodology and Principal Findings: We developed a 1-minute covalent pre-gel staining protocol for proteins, which does not require de-staining before the mass spectrometry analysis. We investigated the electrophoretic properties of derivatized proteins and peptides and studied their behavior in mass spectrometry. Further, we elucidated the preferred reaction of proteins with Uniblue A and demonstrate the integration of the peptide derivatization into typical informatics tools.
Conclusions and Significance: The Uniblue A staining method drastically speeds up the sample preparation for the mass spectrometry based identification of proteins. The application of this chemo-proteomic strategy will be advantageous for routine quality control of proteins and for time-critical tasks in protein analysis.Keywords: Sensitivity, Proteomics, Resistance, Electrophoresis, Digestion, Statistical model, Polyacrylamide gels, Search, Generation, Silve
Deep X-ray and radio observations of the first outburst of the young magnetar Swift J1818.0-1607
Swift J1818.0-1607 is a radio-loud magnetar with a spin period of 1.36 s and
a dipolar magnetic field strength of B~3E14 G, which is very young compared to
the Galactic pulsar population. We report here on the long-term X-ray
monitoring campaign of this young magnetar using XMM-Newton, NuSTAR, and Swift
from the activation of its first outburst in March 2020 until October 2021, as
well as INTEGRAL upper limits on its hard X-ray emission. The 1-10 keV magnetar
spectrum is well modeled by an absorbed blackbody with a temperature of
kT_BB~1.1 keV, and apparent reduction in the radius of the emitting region from
~0.6 to ~0.2 km. We also confirm the bright diffuse X-ray emission around the
source extending between ~50'' and ~110''. A timing analysis revealed large
torque variability, with an average spin-down rate nudot~-2.3E-11 Hz^2 that
appears to decrease in magnitude over time. We also observed Swift J1818.0-1607
with the Karl G. Jansky Very Large Array (VLA) on 2021 March 22. We detected
the radio counterpart to Swift J1818.0-1607 measuring a flux density of S_v =
4.38+/-0.05 mJy at 3 GHz, and a half ring-like structure of bright diffuse
radio emission located at ~90'' to the west of the magnetar. We tentatively
suggest that the diffuse X-ray emission is due to a dust scattering halo and
that the radio structure may be associated with the supernova remnant of this
young pulsar, based on its morphology.Comment: 19 pages, 8 figures, accepted for publication on Ap
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