25,967 research outputs found
A characterization of hyperbolic rational maps
We give a topological characterization of rational maps with disconnected Julia sets. Our results extend Thurstonâs characterization of postcritically finite rational maps. In place of iteration on TeichmĂŒller space, we use quasiconformal surgery and Thurstonâs original result
Rotation in galaxy clusters from MUSIC simulations with the kinetic Sunyaev-Zel'dovich effect
We propose in this work its application for the detection of possible coherent rotational motions in the hot intra-cluster medium. We select a sample of massive, relaxed and rotating galaxy clusters from Marenostrum-mUltidark SImulations of galaxy Clusters (MUSIC), and we produce mock maps of the temperature distortion produced by the kinetic Sunyaev-Zel'dovich effect by exploring six different lines of sight, in the best observational condition. These maps are compared with the expected signal computed from a suitable theoretical model in two cases: (i) focusing only on the contribution from the rotation, and (ii) accounting also for the cluster bulk motion. We find that the parameters of the model assumed for the radial profile of the rotational velocity, averaged over the considered lines of sight, are in agreement within two standard deviations at most with independent estimates from the simulation data, without being significantly affected by the presence of the cluster bulk term. The amplitude of the rotational signal is, on average, of the order of 23 per cent of the total signal accounting also for the cluster bulk motion, and its values are consistent with the literature. The projected bulk velocity of the cluster is also recovered at the different lines of sight, with values in agreement with the simulation dataASB acknowledges funding from Sapienza UniversitĂ di Roma - Progetti per Avvio alla Ricerca Anno 2017, prot. AR11715C82402BC
Characterizing Diffused Stellar Light in simulated galaxy clusters
[Abridged] In this paper, we carry out a detailed analysis of the performance
of two different methods to identify the diffuse stellar light in cosmological
hydrodynamical simulations of galaxy clusters. One method is based on a
dynamical analysis of the stellar component. The second method is closer to
techniques commonly employed in observational studies. Both the dynamical
method and the method based on the surface brightness limit criterion are
applied to the same set of hydrodynamical simulations for a large sample about
80 galaxy clusters.
We find significant differences between the ICL and DSC fractions computed
with the two corresponding methods, which amounts to about a factor of two for
the AGN simulations, and a factor of four for the CSF set. We also find that
the inclusion of AGN feedback boosts the DSC and ICL fractions by a factor of
1.5-2, respectively, while leaving the BCG+ICL and BCG+DSC mass fraction almost
unchanged. The sum of the BCG and DSC mass stellar mass fraction is found to
decrease from ~80 per cent in galaxy groups to ~60 per cent in rich clusters,
thus in excess of what found from observational analysis.
We identify the average surface brightness limits that yields the ICL
fraction from the SBL method close to the DSC fraction from the dynamical
method. These surface brightness limits turn out to be brighter in the CSF than
in the AGN simulations. This is consistent with the finding that AGN feedback
makes BCGs to be less massive and with shallower density profiles than in the
CSF simulations. The BCG stellar component, as identified by both methods, are
slightly older and more metal-rich than the stars in the diffuse component.Comment: 18 Pages, 15 figures. Matches to MNRAS published versio
Intra-day variability observations and the VLBI structure analysis of quasar S4 0917+624
The IDV observations of S4 0917+624 were carried out monthly, from August
2005 to January 2010, with the Urumqi 25m radio telescope at 4.8 GHz. The
quasar S4 0917+624 exhibits only very weak or no IDV during our 4.5 year
observing interval. Prior to the year 2000, the source S4 0917+624 was one of
the most prominent IDV sources. Our new data indicate that the previous strong
IDV has ceased. We analyzed the long-term VLBI structural variability using
Gaussian model-fitting. From this we obtained the flux densities and the
deconvolved sizes of core and inner-jet components of the source. We studied
the properties such as core fraction, angular size, spectral index, and
brightness temperature of VLBI core for S4 0917+624, as well as the time delay
between 5 and 15 GHz variations, and compared them with the IDV properties of
S4 0917+624. The source shows ejection of several jet components that are
suspected to have partially reduced the IDV amplitude of S4 0917+624. However,
during 2005-2006, the VLBI core size was comparable to the size before the year
2000, but no strong IDV was detected in the period, suggesting that the
quenching effect due to source size changes may not be responsible for the lack
of strong IDV after the year 2000. The refractive scattering properties for the
strong IDV phase of S4 0917+624 before the year 2000 are discussed. The
disappearance of strong IDV in S4 0917+624 after the year 2000 is a mystery and
cannot be explained via the quenching effect by changes in the observable VLBI
structure. However, it may be caused by changes in the interstellar medium,
i.e. by interstellar weather, which induces changes in the scintillation
pattern on timescales of several years. Further coordinated multi-frequency
observations will be required to distinguish between the effect of
source-intrinsic variability and changing properties of the interstellar
medium.Comment: 8 pages, 6 figures, accepted for publication in A&
Vector magnetic field sensing by single nitrogen vacancy center in diamond
In this Letter, we proposed and experimentally demonstrated a method to
detect vector magnetic field with a single nitrogen vacancy (NV) center in
diamond. The magnetic field in parallel with the axis of the NV center can be
obtained by detecting the electron Zeeman shift, while the Larmor precession of
an ancillary nuclear spin close to the NV center can be used to measure the
field perpendicular to the axis. Experimentally, both the Zeeman shift and
Larmor precession can be measured through the fluorescence from the NV center.
By applying additional calibrated magnetic fields, complete information of the
vector magnetic field can be achieved with such a method. This vector magnetic
field detection method is insensitive to temperature fluctuation and it can be
applied to nanoscale magnetic measurement.Comment: 5 pages, 5 figure
Photodynamics of Schiff Base Salicylideneaniline: Trajectory Surface-Hopping Simulations
We report a computational study on the photochemistry of the prototypical aromatic Schiff base salicylideneaniline in the gas phase using static electronic structure calculations (TDDFT, OM2/MRCI) and surface-hopping dynamics simulations (OM2/MRCI). Upon photoexcitation of the most stable cis-enol tautomer into the bright S1 state, we find an ultrafast excited-state proton transfer that is complete within tens of femtoseconds, without any CâN double bond isomerization. The internal conversion of the resulting S1 cis-keto species is initiated by an out-of-plane motion around the CâC single bond, which guides the molecule toward a conical intersection that provides an efficient deactivation channel to the ground state. We propose that the ease of this CâC single bond rotation regulates fluorescence quenching and photocoloration in condensed-phase environments. In line with previous work, we find the S1 cis-keto conformer to be responsible for fluorescence, especially in rigid surroundings. The S0 cis-keto species is a transient photoproduct, while the stable S0 trans-keto photoproduct is responsible for photochromism. The trajectory calculations yield roughly equal amounts of the S0 cis-enol and trans-keto photoproducts. Methodologically, full-dimensional nonadiabatic dynamics simulations are found necessary to capture the preferences among competitive channels and to gain detailed mechanistic insight into Schiff base photochemistry
Dynamics of Entanglement and Bell-nonlocality for Two Stochastic Qubits with Dipole-Dipole Interaction
We have studied the analytical dynamics of Bell nonlocality as measured by
CHSH inequality and entanglement as measured by concurrence for two noisy
qubits that have dipole-dipole interaction. The nonlocal entanglement created
by the dipole-dipole interaction is found to be protected from sudden death for
certain initial states
Mesoscopic Kondo effect of a quantum dot embedded in an Aharonov-Bohm ring with intradot spin-flip scattering
We study the Kondo effect in a quantum dot embedded in a mesoscopic ring
taking into account intradot spin-flip scattering . Based on the finite-
slave-boson mean-field approach, we find that the Kondo peak in the density of
states is split into two peaks by this coherent spin-flip transition, which is
responsible for some interesting features of the Kondo-assisted persistent
current circulating the ring: (1) strong suppression and crossover to a sine
function form with increasing ; (2) appearance of a "hump" in the
-dependent behavior for odd parity. -induced reverse of the persistent
current direction is also observed for odd parity.Comment: 7 pages,6 figures, to be published by Europhys. Let
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