A characterization of hyperbolic rational maps

We give a topological characterization of rational maps with disconnected Julia sets. Our results extend Thurston’s characterization of postcritically finite rational maps. In place of iteration on Teichmüller space, we use quasiconformal surgery and Thurston’s 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 Università 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 C═N double bond isomerization. The internal conversion of the resulting S1 cis-keto species is initiated by an out-of-plane motion around the C–C 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 C–C 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 $R$. Based on the finite-$U$ 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 $R$; (2) appearance of a "hump" in the $R$-dependent behavior for odd parity. $R$-induced reverse of the persistent current direction is also observed for odd parity.Comment: 7 pages,6 figures, to be published by Europhys. Let