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CERN Document Server latest documents in Articles & PreprintsenMon, 30 Nov 2015 08:01:04 GMTInvenio 1.1.3.1106-62468cds.support@cern.ch3601216917125https://cds.cern.ch/img/site_logo_rss.pngCERN Document Server
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Revision of the classical nucleation theory for supersaturated solutions
https://cds.cern.ch/record/2109247
During the processes of nucleation and growth of a precipitate cluster from a supersaturated solution, the diffusion flux between the cluster and the solution changes the solute concentration near the cluster-solution interface from its average bulk value. This feature affects the rates of attachment and detachment of solute atoms at the interface and, therefore, alters the entire nucleation kinetics. Unless quite obvious, this effect has been ignored in the classical nucleation theory. To illustrate the results of this new approach, for the case of homogeneous nucleation, we calculate the total solubility (including the contribution from heterophase fluctuations) and the nucleation rate as functions of two parameters of the model and compare these results to the classical ones. One can conclude that discrepancies with the classical nucleation theory are great in the diffusion-limited regime, when the bulk diffusion mobility of solute atoms is small compared to the interfacial one, while in the opposite interface-limited case they vanish.Borisenko, AlexanderMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08765https://cds.cern.ch/record/2109247['arXiv:1511.08765']arXiv:1511.08765An accurate Rb density measurement method for a plasma wakefield accelerator experiment using a novel Rb reservoir
https://cds.cern.ch/record/2109246
A method to accurately measure the density of Rb vapor is described. We plan on using this method for the Advanced Wakefield (AWAKE)~\cite{bib:awake} project at CERN , which will be the world's first proton driven plasma wakefield experiment. The method is similar to the hook~\cite{bib:Hook} method and has been described in great detail in the work by W. Tendell Hill et. al.~\cite{bib:densitymeter}. In this method a cosine fit is applied to the interferogram to obtain a relative accuracy on the order of $1\%$ for the vapor density-length product. A single-mode, fiber-based, Mach-Zenhder interferometer will be built and used near the ends of the 10 meter-long AWAKE plasma source to be able to make accurate relative density measurement between these two locations. This can then be used to infer the vapor density gradient along the AWAKE plasma source and also change it to the value desired for the plasma wakefield experiment. Here we describe the plan in detail and show preliminary results obtained using a prototype 8 cm long novel Rb vapor cell.Öz, EBatsch, FMuggli, PMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08763https://cds.cern.ch/record/2109246['arXiv:1511.08763']arXiv:1511.08763Probe-based data storage
https://cds.cern.ch/record/2109245
Probe-based data storage attracted many researchers from academia and industry, resulting in unprecendeted high data-density demonstrations. This topical review gives a comprehensive overview of the main contributions that led to the major accomplishments in probe-based data storage. The most investigated technologies are reviewed: topographic, phase-change, magnetic, ferroelectric and atomic and molecular storage. Also, the positioning of probes and recording media, the cantilever arrays and parallel readout of the arrays of cantilevers are discussed. This overview serves two purposes. First, it provides an overview for new researchers entering the field of probe storage, as probe storage seems to be the only way to achieve data storage at atomic densities. Secondly, there is an enormous wealth of invaluable findings that can also be applied to many other fields of nanoscale research such as probe-based nanolithography, 3D nanopatterning, solid-state memory technologies and ultrafast probe microscopy.Koelmans, Wabe WEngelen, Johan B CAbelmann, LMon, 30 Nov 2015 06:40:02 GMT25 Nov 2015arXiv:1511.08755https://cds.cern.ch/record/2109245['arXiv:1511.08755']arXiv:1511.08755What does Big Data tell? Sampling the social network by communication channels
https://cds.cern.ch/record/2109244
Big Data has become the primary source of understanding the structure and dynamics of the society at large scale. The network of social interactions can be considered as a multiplex, where each layer corresponds to one communication channel and the aggregate of all them constitutes the entire social network. However, usually one has information only about one of the channels, which should be considered as a sample of the whole. Here we show by simulations and analytical methods that this sampling may lead to bias. For example, while it is expected that the degree distribution of the whole social network has a maximum at a value larger than one, we get with reasonable assumptions about the sampling process a monotonously decreasing distribution as observed in empirical studies of single channel data. Also we find, that assortativity may occur or get strengthened due to the sampling process. We analyze the far-reaching consequences of our findings.Török, JánosMurase, YohsukeJo, Hang-HyunKertész, JánosKaski, KimmoMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08749https://cds.cern.ch/record/2109244['arXiv:1511.08749']arXiv:1511.08749The approach to chaos in ultracold atomic and molecular physics: statistics of near-threshold bound states for Li+CaH and Li+CaF
https://cds.cern.ch/record/2109243
We calculate near-threshold bound states for the highly anisotropic systems Li+CaH and Li+CaF and perform statistical analysis on the resulting level positions to compare with the predictions of random matrix theory. For Li+CaH with total angular momentum $J=0$ we find fully chaotic behavior in both the nearest-neighbor spacing distribution and the level number variance. However, for $J>0$ we find different behavior due to the presence of a nearly conserved quantum number. Li+CaF ($J=0$) also shows apparently reduced levels of chaotic behavior despite its stronger effective coupling. We suggest this may indicate the development of another good quantum number relating to a bending motion of the complex. However, continuously varying the rotational constant over a wide range shows unexpected structure in the degree of chaotic behavior, including a dramatic reduction around the rotational constant of CaF. This demonstrates the complexity of the relationship between coupling and chaotic behaviour.Frye, Matthew DMorita, MasatoVaillant, Christophe LGreen, Dermot GHutson, Jeremy MMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08744https://cds.cern.ch/record/2109243['arXiv:1511.08744']arXiv:1511.08744Well-balanced nodal discontinuous Galerkin method for Euler equations with gravity
https://cds.cern.ch/record/2109242
We present a well-balanced nodal discontinuous Galerkin (DG) scheme for compressible Euler equations with gravity. The DG scheme makes use of discontinuous Lagrange basis functions supported at Gauss-Lobatto-Legendre (GLL) nodes together with GLL quadrature using the same nodes. The well-balanced property is achieved by a specific form of source term discretization that depends on the nature of the hydrostatic solution, together with the GLL nodes for quadrature of the source term. The scheme is able to preserve isothermal and polytropic stationary solutions upto machine precision on any mesh composed of quadrilateral cells and for any gravitational potential. It is applied on several examples to demonstrate its well-balanced property and the improved resolution of small perturbations around the stationary solution.Chandrashekar, PraveenZenk, MarkusMon, 30 Nov 2015 06:40:02 GMT25 Nov 2015arXiv:1511.08739https://cds.cern.ch/record/2109242['arXiv:1511.08739']arXiv:1511.08739Relativity Theory Refounded
https://cds.cern.ch/record/2109241
We put forward a new view of relativity theory that makes the existence of a flow of time compatible with the four-dimensional block universe. To this end, we apply the creation-discovery view elaborated for quantum mechanics to relativity theory and in such a way that time and space become creations instead of discoveries and an underlying non-temporal and non-spatial reality comes into existence. We study the nature of this underlying non-temporal and non-spatial reality and reinterpret many aspects of the theory within this new view. We show that data of relativistic measurements are sufficient to derive the three-dimensionality of physical space. The nature of light and massive entities is reconsidered, and an analogy with human cognition is worked out.Aerts, DiederikMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08735https://cds.cern.ch/record/2109241['arXiv:1511.08735']arXiv:1511.08735Capillary rise dynamics of liquid hydrocarbons in mesoporous silica as explored by gravimetry, optical and neutron imaging: Nano-rheology and determination of pore size distributions from the shape of imbibition fronts
https://cds.cern.ch/record/2109240
We present gravimetrical, optical, and neutron imaging measurements of the capillarity-driven infiltration of mesoporous silica glass by hydrocarbons. Square-root-of-time Lucas-Washburn invasion kinetics are found for linear alkanes from n-decane (C10) to n-hexacontane (C60) and for squalane, a branched alkane, in porous Vycor with 6.5 nm or 10 nm pore diameter, respectively. Humidity-dependent experiments allow us to study the influence on the imbibition kinetics of water layers adsorbed on the pore walls. Except for the longest molecule studied, C60, the invasion kinetics can be described by bulk fluidity and bulk capillarity, provided we assume a sticking, pore-wall adsorbed boundary layer, i.e. a monolayer of water covered by a monolayer of flat-laying hydrocarbons. For C60, however, an enhanced imbibition speed compared to the value expected in the bulk is found. This suggests the onset of velocity slippage at the silica walls or a reduced shear viscosity due to the transition towards a polymer-like flow in confined geometries. Both, light scattering and neutron imaging indicate a pronounced roughening of the imbibition fronts. Their overall shape and width can be resolved by neutron imaging. The fronts can be described by a superposition of independent wetting fronts moving with pore size-dependent square-root-of-time laws and weighted according to the pore size distributions obtained from nitrogen gas sorption isotherms. This finding indicates that the shape of the imbibition front in a porous medium, such as Vycor glass, with interconnected, elongated pores, is solely determined by independent movements of liquid menisci. These are dictated by the Laplace pressure and hydraulic permeability variations and thus the pore size variation at the invasion front. Our results suggest that pore size distributions can be derived from the broadening of imbibition fronts.Gruener, SimonHermes, Helen ESchillinger, BurkhardEgelhaaf, Stefan UHuber, PatrickMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08728https://cds.cern.ch/record/2109240['arXiv:1511.08728']arXiv:1511.08728Study on Coulomb explosions of ion mixtures
https://cds.cern.ch/record/2109239
The paper presents a theoretical work on the dynamics of Coulomb explosion for spherical nanoplasmas composed by two different ion species. Particular attention has been dedicated to study the energy spectra of the ions with the larger charge-to-mass ratio. The connection between the formation of shock shells and the energy spread of the ions has been the object of a detailed analysis, showing that under particular conditions the width of the asymptotic energy spectrum tends to become very narrow, which leads to a multi-valued ion phase-space. The conditions to generate a quasi mono-energetic ion spectrum have been rigorously demonstrated and verifed by numerical simulations, using a technique that, exploiting the spherical symmetry of the problem, allows one to obtain very accurate and precise results.Boella, EParadisi, B PeirettiD'Angola, ACoppa, GSilva, L OMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08717https://cds.cern.ch/record/2109239['arXiv:1511.08717']arXiv:1511.08717A stochastic evolutionary model generating a mixture of exponential distributions
https://cds.cern.ch/record/2109238
Recent interest in human dynamics has stimulated the investigation of the stochastic processes that explain human behaviour in various contexts, such as mobile phone networks and social media. In this paper, we extend the stochastic urn-based model proposed in \cite{FENN15} so that it can generate mixture models,in particular, a mixture of exponential distributions. The model is designed to capture the dynamics of survival analysis, traditionally employed in clinical trials, reliability analysis in engineering, and more recently in the analysis of large data sets recording human dynamics. The mixture modelling approach, which is relatively simple and well understood, is very effective in capturing heterogeneity in data. We provide empirical evidence for the validity of the model, using a data set of popular search engine queries collected over a period of 114 months. We show that the survival function of these queries is closely matched by the exponential mixture solution for our model.Fenner, TrevorLevene, MarkLoizou, GeorgeMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08712https://cds.cern.ch/record/2109238['arXiv:1511.08712']arXiv:1511.08712On Reflection and Refraction of the Laser Light Pulse at the Vacuum-Medium Interface
https://cds.cern.ch/record/2109237
By generalizing the well known results for reflection and refraction of plane waves at the vacuum-medium interface to Gaussian light beams, we obtain analytic formulas for reflection and refraction of the TM and TE laser light pulses. This enables us to give a possible explanation why no reflection was observed in light pulse photographs in some vicinity of the air-resin interface, given in L. Gao, J. Liang, C. Li, and L. V. Wang, Nature 516 (2014) 74-77. We suggest how to modify the experimental setup so as to observe the reflected pulse.Żakowicz, WSkorupski, A AMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08709https://cds.cern.ch/record/2109237['arXiv:1511.08709']arXiv:1511.08709Visibility of Young's interference fringes: Scattered light from small ion crystals
https://cds.cern.ch/record/2109236
We observe the interference in the light scattered from trapped 40Ca+ ion crystals. Varying the intensity of the excitation laser we study the influence of elastic and inelastic scattering on the visibility of the fringe pattern and discriminate its effect from that of the ion temperature and wave-packet localization. In this way we determine the complex degree of coherence and the mutual coherence of light fields produced by individual atoms. We obtain interference fringes from crystals consisting of two, three and four ions in a harmonic trap. Controlling of the trapping potential allows for adjusting the interatomic distances and thus to form linear arrays of atoms serving as a regular grating of microscopic scatterers.Wolf, SebastianWechs, Julianvon Zanthier, JoachimSchmidt-Kaler, FerdinandMon, 30 Nov 2015 06:40:02 GMT27 Nov 2015arXiv:1511.08697https://cds.cern.ch/record/2109236['arXiv:1511.08697']arXiv:1511.08697Cascading failures in coupled networks with both inner-dependency and interdependency links
https://cds.cern.ch/record/2109235
We study the percolation of coupled networks with both inner-dependency and interdependency links, where the inner-dependency links represent the dependencies between the nodes in the same network and the interdependency links represent the dependencies between the nodes in different networks. By tuning an introduced parameter $\beta$ that controls the fraction of nodes with interdependency links, we find a nontrivial relation between the percolation transition points and the fraction of nodes with interdependency links $\beta$, which is that there exists an optimal parameter value of $\beta$ leading to the most robust coupled networks. More interestingly, we also find that the coupled system has two tricritical points of $\beta$ through which the type of percolation transition changes. However, the two tricritical points can merge together and the system makes a discontinuous (first-order) percolation transition for any given value of $\beta$ when the average degrees $\langle k\rangle$ of the networks are less than a certain value $\langle\tilde{k}\rangle$. We also develop an approach to analyze this model, and obtain the exact solutions for the size of the giant component and the critical points. Numerical computations and theoretical analysis agree with each other well, which ensures the reliability of the research.Liu, Run-RanLi, MingJia, Chun-XiaoWang, Bing-HongMon, 30 Nov 2015 06:40:01 GMT27 Nov 2015arXiv:1511.08661https://cds.cern.ch/record/2109235['arXiv:1511.08661']arXiv:1511.08661Path-integral simulation of ice VII: Pressure and temperature effects
https://cds.cern.ch/record/2109234
Effects of pressure and temperature on structural and thermodynamic properties of ice VII have been studied by using path-integral molecular dynamics (PIMD) simulations. Temperatures between 25 and 450 K, as well as pressures up to 12 GPa were considered. Interatomic interactions were modeled by using the effective q-TIP4P/F potential for flexible water. We analyze the pressure dependence of the molar volume, bulk modulus, interatomic distances, kinetic energy, and atomic delocalization at various temperatures. Results of PIMD simulations are compared with those derived from a quasi-harmonic approximation (QHA) of vibrational modes, which helps to assess the importance of anharmonic effects, as well as the influence of the different modes on the properties of ice VII. The accuracy of the QHA for describing this high-pressure phase decreases for rising temperature, but this approximation becomes more reliable as pressure grows, since anharmonicity becomes less relevant. Comparisons with low-pressure cubic ice are presented.Herrero, Carlos PRamirez, RafaelMon, 30 Nov 2015 06:40:01 GMT27 Nov 2015arXiv:1511.08607https://cds.cern.ch/record/2109234['arXiv:1511.08607']arXiv:1511.08607Design and synthesis of aromatic molecules for probing electric-fields at the nanoscale
https://cds.cern.ch/record/2109233
We propose using halogenated organic dyes as nanoprobes for electric field and show their greatly enhanced Stark coefficients using density functional theory (DFT) calculations. We analyse halogenated variants of three molecules that have been of interest for cryogenic single molecule spectroscopy, perylene, terrylene, and dibenzoterrylene, with the zero-phonon optical transitions at blue, red, and near infrared. Out of all the combinations of halides and binding sites that are calculated, we have found that fluorination of the optimum binding site induces a dipole difference between ground and excited states larger than 0.5 D for all three molecules with the highest value of 0.69 D for fluoroperylene. We also report on synthesis of 3-fluoroterrylene and bulk spectroscopy of this compound in liquid and solid organic environments.Faez, SanliVerhart, Nico RMarkoulides, MariosBuda, FrancescoGourdon, AndréOrrit, MichelMon, 30 Nov 2015 06:40:01 GMT27 Nov 2015arXiv:1511.08597https://cds.cern.ch/record/2109233['arXiv:1511.08597']arXiv:1511.08597Criterion for sliding / rolling characterization during droplet motion over superhydrophobic surfaces
https://cds.cern.ch/record/2109232
Super hydrophobic surfaces have been the focus of research in the recent years.One of the reasons for this is the self cleaning property of these surfaces which emerges from the ability of the droplets to roll freely over them.However majority of the studies available in literature are on the static wetting behavior of liquid droplets on such surfaces and the physics of the motion of droplets has not been studied exhaustively either theoretically or experimentally.In the present study droplet motion on super hydrophobic surfaces has been modeled to analyze the sliding/ rolling characteristics of the droplet motion.A non-dimensional number is proposed to indicate whether a given droplet would tend to roll or slide more on a given super hydrophobic surface.We refer to this number as 'Slip Reynolds' number. Simulations of droplet motion were carried out with different surface and droplet characteristics leading to a unique value of this number corresponding to sliding/rolling behavior.The applicability of this number was tested with available experiments from literature.Wadgaonkar, Indrajit PSundararajan, TDas, Sarit KMon, 30 Nov 2015 06:40:01 GMT27 Nov 2015arXiv:1511.08563https://cds.cern.ch/record/2109232['arXiv:1511.08563']arXiv:1511.08563Poynting vector, orbital and spin momentum and angular momentum versus optical force and torque on arbitrary particle in generic optical fields
https://cds.cern.ch/record/2109231
We study optical force and torque on a general particle immersed in generic monochromatic free-space optical field. It is rigorously proved that the optical force can be written as a difference between the surface integrals of the orbital momentum density of light in the presence and in the absence of the particle, while the optical torque is described by the surface integral of total angular momentum (AM) density, viz the sum of the orbital and spin AM densities. It is therefore physically understood that only the orbital part of the optical momentum is responsible for the optical force, whereas the optical torque originates from both the orbital and the spin AM, clarifying in generic case the long-standing controversy about whether the orbital AM can induce a spinning torque.Jiang, YikunChen, HuajinChen, JunNg, JackLin, ZhifangMon, 30 Nov 2015 06:40:01 GMT26 Nov 2015arXiv:1511.08546https://cds.cern.ch/record/2109231['arXiv:1511.08546']arXiv:1511.08546Synchronization of Delay-coupled Micromechanical Oscillators
https://cds.cern.ch/record/2109230
Delay-coupled oscillators exhibit unique phenomena that are not present in systems without delayed coupling. In this paper, we experimentally demonstrate mutual synchronisation of two free-running micromechanical oscillators, coupled via light with a total delay 139 ns which is approximately four and a half times the mechanical oscillation time period. This coupling delay, imposed by a finite speed of propagation of light, induces multiple stable states of synchronised oscillations, each with a different oscillation frequency. These states can be accessed by varying the coupling strengths. Our result could enable applications in reconfigurable radio-frequency networks, and novel computing concepts.Shah, Shreyas YZhang, MianRand, RichardLipson, MichalMon, 30 Nov 2015 06:40:01 GMT26 Nov 2015arXiv:1511.08536https://cds.cern.ch/record/2109230['arXiv:1511.08536']arXiv:1511.08536Propagation of light through small clouds of cold interacting atoms
https://cds.cern.ch/record/2109229
We demonstrate experimentally that a cloud of cold atoms with a size comparable to the wavelength of light can induce large group delays on a laser pulse when the laser is tightly focused on it and is close to an atomic resonance. Delays as large as -10 ns are observed, corresponding to "superluminal" propagation with negative group velocities as low as -300 m/s. Strikingly, this large delay is associated with a moderate extinction owing to the very small size of the cloud and to the light-induced interactions between atoms. It implies that a large phase shift is imprinted on the continuous laser beam, and opens interesting perspectives for applications to quantum technologies.Jennewein, SSortais, Y R PGreffet, J -JBrowaeys, AMon, 30 Nov 2015 06:40:01 GMT26 Nov 2015arXiv:1511.08527https://cds.cern.ch/record/2109229['arXiv:1511.08527']arXiv:1511.08527Maths Meets Myths: Network Investigations of Ancient Narratives
https://cds.cern.ch/record/2109228
Three years ago, we initiated a programme of research in which ideas and tools from statistical physics and network theory were applied to the field of comparative mythology. The eclecticism of the work, together with the perspectives it delivered, led to widespread media coverage and academic discussion. Here we review some aspects of the project, contextualised with a brief history of the long relationship between science and the humanities. We focus in particular on an Irish epic, summarising some of the outcomes of our quantitative investigation. We also describe the emergence of a new sub-discipline and our hopes for its future.Kenna, RMac Carron, PMon, 30 Nov 2015 06:40:01 GMT26 Nov 2015arXiv:1511.08513https://cds.cern.ch/record/2109228['arXiv:1511.08513']arXiv:1511.08513Particle Conservation in Dynamical Density Functional Theory
https://cds.cern.ch/record/2109227
We present the exact adiabatic theory for the dynamics of the inhomogeneous density distribution of a classical fluid. Erroneous particle number fluctuations of dynamical density functional theory are absent, both for canonical and grand canonical initial conditions. We obtain the canonical free energy functional, which yields the adiabatic interparticle forces of overdamped Brownian motion. Using an exact and one of the most advanced approximate hard core free energy functionals, we obtain excellent agreement with simulations. The theory applies to finite systems in and out of equilibrium.Heras, Daniel de lasBrader, Joseph MFortini, AndreaSchmidt, MatthiasMon, 30 Nov 2015 06:40:01 GMT26 Nov 2015arXiv:1511.08500https://cds.cern.ch/record/2109227['arXiv:1511.08500']arXiv:1511.08500Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination
https://cds.cern.ch/record/2109226
Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at present, providing the most widespread time and frequency reference for the majority of industrial and research applications worldwide. On the other hand, the ultimate limits of the GPS presently curb further advances in high-precision, scientific and industrial applications relying on this dissemination scheme. Here, we demonstrate that these limits can be reliably overcome even in laboratories without a local atomic clock by replacing the GPS with a 642-km-long optical fiber link to a remote primary caesium frequency standard. Through this configuration we stably address the $^1$S$_0$---$^3$P$_0$ clock transition in an ultracold gas of $^{173}$Yb, with a precision that exceeds the possibilities of a GPS-based measurement, dismissing the need for a local clock infrastructure to perform high-precision tasks beyond GPS limit. We also report an improvement of two orders of magnitude in the accuracy on the transition frequency reported in literature.Clivati, CCappellini, GLivi, LPoggiali, Fde Cumis, M SicilianiMancini, MPagano, GFrittelli, MMura, ACostanzo, G ALevi, FCalonico, DFallani, LCatani, JInguscio, MMon, 30 Nov 2015 06:40:01 GMT26 Nov 2015arXiv:1511.08485https://cds.cern.ch/record/2109226['arXiv:1511.08485']arXiv:1511.08485Nonlinear dynamics and millikelvin cavity-cooling of levitated nanoparticles
https://cds.cern.ch/record/2109225
Optomechanical systems explore and exploit the coupling between light and the mechanical motion of matter. A nonlinear coupling offers access to rich new physics, in both the quantum and classical regimes. We investigate a dynamic, as opposed to the usually studied static, nonlinear optomechanical system, comprising of a nanosphere levitated and cooled in a hybrid electro-optical trap. An optical cavity offers readout of both linear-in-position and quadratic-in-position (nonlinear) light-matter coupling, whilst simultaneously cooling the nanosphere to millikelvin temperatures for indefinite periods of time in high vacuum. We observe cooling of the linear and non-linear motion, leading to a $10^5$ fold reduction in phonon number $n_p$, attaining final occupancies of $n_p = 100-1000$. This work puts cavity cooling of a levitated object to the quantum ground-state firmly within reach.Fonseca, P Z GAranas, E BMillen, JMonteiro, T SBarker, P FMon, 30 Nov 2015 06:40:01 GMT26 Nov 2015arXiv:1511.08482https://cds.cern.ch/record/2109225['arXiv:1511.08482']arXiv:1511.08482Homeostatic fluctuations of a tissue surface
https://cds.cern.ch/record/2109224
We study the surface fluctuations of a tissue with a dynamics dictated by cell-rearrangement, cell-division and cell-death processes. Surface fluctuations are calculated in the homeostatic state, where cell division and cell death equilibrate on average. The obtained fluctuation spectrum can be mapped onto several other spectra such as those characterizing incompressible fluids, compressible Maxwell elastomers or permeable membranes in appropriate asymptotic regimes. Since cell division and cell death are out-of-equilibrium processes, detailed balance is broken, but a generalized fluctuation-response relation is satisfied in terms of appropriate observables. Our work is a first step toward the description of the out-of-equilibrium fluctuations of the surface of a thick epithelium and its dynamical response to external perturbations.Risler, ThomasPeilloux, AurélienProst, JacquesMon, 30 Nov 2015 06:40:01 GMT26 Nov 2015arXiv:1511.08475https://cds.cern.ch/record/2109224['arXiv:1511.08475']arXiv:1511.08475Substrate-mediated zero backscattering from dielectric metasurfaces
https://cds.cern.ch/record/2109223
In this work, we study optical properties of all-dielectric metasurfaces on top of the high-index substrate. We show that matching the magnitudes and setting the {\pi}-phase difference of the electric and magnetic dipole moments in nanoparticles, one can obtain a suppression of reflection from the substrate coated with metasurface. In contrast to homogeneous environment, where zero backscattering, or Kerker effect, is observed when electric and magnetic moments are in-phase, the blooming of the substrate occurs when the out-of-phase condition is satisfied, i.e. for the wavelength between the resonances of electric and magnetic dipole moments. We perform numerical simulations of spherical and disk nanoparticle arrays for different permittivities of the substrate, and confirm our model by numerically separating the contributions into the total reflection from nanoparticle arrays and bare substrate. The influence of high-index substrate is crucial for designing optical metasurfaces and photovoltaic elements with nanoparticle-enhanced light trapping.Petrov, MihailBabicheva, ViktoriiaBaryshnikova, KseniiaBelov, PavelMon, 30 Nov 2015 06:40:01 GMT26 Nov 2015arXiv:1511.08473https://cds.cern.ch/record/2109223['arXiv:1511.08473']arXiv:1511.08473