Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the 4D Eigenvector 1 (4DE1) parameter space which implies restricted geometry/physics/kinematics for this subclass compared to the radio-quiet (RQ) majority of quasars. We discus
s how this restricted domain for the LD RL parent population supports the notion for a RQ-RL dichotomy among Type 1 sources. 3C 57 is an atypical RL quasar that shows both uncertain radio morphology and falls in a region of 4DE1 space where RL quasars are rare. We present new radio flux and optical spectroscopic measures designed to verify its atypical optical/UV spectroscopic behaviour and clarify its radio structure. The former data confirms that 3C 57 falls off the 4DE1 quasar main sequence with both extreme optical FeII emission (R_{FeII} ~ 1) and a large CIV 1549 profile blueshift (~ -1500 km/s). These parameter values are typical of extreme Population A sources which are almost always RQ. New radio measures show no evidence for flux change over a 50+ year timescale consistent with compact steep-spectrum (CSS or young LD) over core-dominated morphology. In the 4DE1 context where LD RL are usually low L/L_{Edd} quasars we suggest that 3C 57 is an evolved RL quasar (i.e. large Black Hole mass) undergoing a major accretion event leading to a rejuvenation reflected by strong FeII emission, perhaps indicating significant heavy metal enrichment, high bolometric luminosity for a low redshift source and resultant unusually high Eddington ratio giving rise to the atypical CIV 1549.
Recent studies have presented evidence that the Milky Way global potential may be nonspherical. In this case, the assembling process of the Galaxy may have left long lasting stellar halo kinematic fossils due to the shape of the dark matter halo, pot
entially originated by orbital resonances. We further investigate such possibility, considering now potential models further away from $Lambda$CDM halos, like scalar field dark matter halos, MOND, and including several other factors that may mimic the emergence and permanence of kinematic groups, such as, a spherical and triaxial halo with an embedded disk potential. We find that regardless of the density profile (DM nature), kinematic groups only appear in the presence of a triaxial halo potential. For the case of a MOND like gravity theory no kinematic structure is present. We conclude that the detection of these kinematic stellar groups could confirm the predicted triaxiality of dark halos in cosmological galaxy formation scenarios.
The Carnot cycle imposes a fundamental upper limit to the efficiency of a macroscopic motor operating between two thermal baths. However, this bound needs to be reinterpreted at microscopic scales, where molecular bio-motors and some artificial micro
-engines operate. As described by stochastic thermodynamics, energy transfers in microscopic systems are random and thermal fluctuations induce transient decreases of entropy, allowing for possible violations of the Carnot limit. Despite its potential relevance for the development of a thermodynamics of small systems, an experimental study of microscopic Carnot engines is still lacking. Here we report on an experimental realization of a Carnot engine with a single optically trapped Brownian particle as working substance. We present an exhaustive study of the energetics of the engine and analyze the fluctuations of the finite-time efficiency, showing that the Carnot bound can be surpassed for a small number of non-equilibrium cycles. As its macroscopic counterpart, the energetics of our Carnot device exhibits basic properties that one would expect to observe in any microscopic energy transducer operating with baths at different temperatures. Our results characterize the sources of irreversibility in the engine and the statistical properties of the efficiency -an insight that could inspire novel strategies in the design of efficient nano-motors.
It is widely believed that the swimming speed, $v$, of many flagellated bacteria is a non-monotonic function of the concentration, $c$, of high-molecular-weight linear polymers in aqueous solution, showing peaked $v(c)$ curves. Pores in the polymer s
olution were suggested as the explanation. Quantifying this picture led to a theory that predicted peaked $v(c)$ curves. Using new, high-throughput methods for characterising motility, we have measured $v$, and the angular frequency of cell-body rotation, $Omega$, of motile Escherichia coli as a function of polymer concentration in polyvinylpyrrolidone (PVP) and Ficoll solutions of different molecular weights. We find that non-monotonic $v(c)$ curves are typically due to low-molecular weight impurities. After purification by dialysis, the measured $v(c)$ and $Omega(c)$ relations for all but the highest molecular weight PVP can be described in detail by Newtonian hydrodynamics. There is clear evidence for non-Newtonian effects in the highest molecular weight PVP solution. Calculations suggest that this is due to the fast-rotating flagella `seeing a lower viscosity than the cell body, so that flagella can be seen as nano-rheometers for probing the non-Newtonian behavior of high polymer solutions on a molecular scale.
We investigate the dynamics of single microparticles immersed in water that are driven out of equilibrium in the presence of an additional external colored noise. As a case study, we trap a single polystyrene particle in water with optical tweezers a
nd apply an external electric field with flat spectrum but a finite bandwidth of the order of kHz. The intensity of the external noise controls the amplitude of the fluctuations of the position of the particle, and therefore of its effective temperature. Here we show, in two different nonequilibrium experiments, that the fluctuations of the work done on the particle obey Crooks fluctuation theorem at the equilibrium effective temperature, given that the sampling frequency and the noise cutoff frequency are properly chosen. Our experimental setup can be therefore used to improve the design of microscopic motors towards fast and efficient devices, thus extending the frontiers of nano machinery.
A symmetry breaking (SB) involves an abrupt change in the set of microstates that a system can explore. This change has unavoidable thermodynamic implications. According to Boltzmanns microscopic interpretation of entropy, a shrinkage of the set of c
ompatible states implies a decrease of entropy, which eventually needs to be compensated by dissipation of heat and consequently requires work. Examples are the compression of a gas and the erasure of information. On the other hand, in a spontaneous SB, the available phase space volume changes without the need for work, yielding an apparent decrease of entropy. Here we show that this decrease of entropy is a key ingredient in the Szilard engine and Landauers principle and report on a direct measurement of the entropy change along SB transitions in a Brownian particle. The SB is induced by a bistable potential created with two optical traps. The experiment confirms theoretical results based on fluctuation theorems, allows us to reproduce the Szilard engine extracting energy from a single thermal bath, and shows that the signature of a SB in the energetics is measurable, providing new methods to detect, for example, the coexistence of metastable states in macromolecules.
Recently, many efforts are being put in studying three-hadron systems made of mesons and baryons and interesting results are being found. In this talk, I summarize the main features of the formalism used to study such three hadron systems with strang
eness $S=-1,0$ within a framework built on the basis of unitary chiral theories and solution of the Faddeev equations. In particular, I present the results obtained for the $pibar{K}N$, $Kbar{K}N$ and $KKbar{K}$ systems and their respective coupled channels. In the first case, we find four $Sigma$s and two $Lambda$s with spin-parity $J^P=1/2^+$, in the 1500-1800 MeV region, as two meson-one baryon s-wave resonances. In the second case, a $1/2^+$ $N^*$ around 1900 MeV is found. For the last one a kaon close to 1420 MeV is formed, which can be identified with K(1460).
We investigate the $bar KN$ and coupled channels system in a finite volume and study the properties of the $Lambda(1405)$ resonance. We calculate the energy levels in a finite volume and solve the inverse problem of determining the resonance position
in the infinite volume. We devise the best strategy of analysis to obtain the two poles of the $Lambda(1405)$ in the infinite volume case, with sufficient precision to distinguish them.
We show, using differential dynamic microscopy, that the diffusivity of non-motile cells in a three-dimensional (3D) population of motile E. coli is enhanced by an amount proportional to the active cell flux. While non-motile mutants without flagella
and mutants with paralysed flagella have quite different thermal diffusivities and therefore hydrodynamic radii, their diffusivities are enhanced to the same extent by swimmers in the regime of cell densities explored here. Integrating the advective motion of non-swimmers caused by swimmers with finite persistence-length trajectories predicts our observations to within 2%, indicating that fluid entrainment is not relevant for diffusion enhancement in 3D.
We calculate the radiative corrections to the Dalitz plot of K_{l3}^pm decays to order (alpha/pi)(q/M_1), where q is the momentum transfer and M_1 is the mass of the kaon. We restrict the analysis to the so-called four-body region, which arises when
no discrimination of real photons is made either kinematically or experimentally. We present our results in two ways: the first one with the triple integration over the photon kinematical variables ready to be performed numerically and the second one in a fully analytical form. Our results can be useful in experimental analyses of the Dalitz plot, by evaluating the model-independent coefficients of the quadratic products of the form factors; we provide some numbers as a case example. We find a small, albeit non-negligible, contribution from the four-body region to the radiative correction to the total decay rate of K_{l3}^pm decays.
