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Search for bottom squark pair production in proton--proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
https://cds.cern.ch/record/2194976
The result of a search for pair production of the supersymmetric partner of the Standard Model bottom quark ($\tilde{b}_1$) is reported. The search uses 3.2 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}=13$ TeV collected by the ATLAS experiment at the Large Hadron Collider in 2015. Bottom squarks are searched for in events containing large missing transverse momentum and exactly two jets identified as originating from $b$-quarks. No excess above the expected Standard Model background yield is observed. Exclusion limits at 95\% confidence level on the mass of the bottom squark are derived in phenomenological supersymmetric $R$-parity-conserving models in which the $\tilde{b}_1$ is the lightest squark and is assumed to decay exclusively via $\tilde{b}_1 \rightarrow b \tilde{\chi}_1^0$, where $\tilde{\chi}_1^0$ is the lightest neutralino. The limits significantly extend previous results; bottom squark masses up to 800 (840) GeV are excluded for the $\tilde{\chi}_1^0$ mass below 360 (100) GeV whilst differences in mass above 100 GeV between the $\tilde{b}_1$ and the \tilde{\chi}_1^0$ are excluded up to a $\tilde{b}_1$ mass of 500 GeV.ATLAS CollaborationTue, 28 Jun 2016 15:07:44 GMT28 Jun 2016CERN-EP-2016-138https://cds.cern.ch/record/21949762016138Amplitude analysis of $B^+\to J/\psi \phi K^+$ decays
https://cds.cern.ch/record/2194962
The first full amplitude analysis of $B^+\to J/\psi \phi K^+$ with $J/\psi\to\mu^+\mu^-$, $\phi\to K^+K^-$ decays is performed with a data sample of 3 fb$^{-1}$ of $pp$ collision data collected at $\sqrt{s}=7$ and $8$ TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into $\phi K^+$, and four $J/\psi\phi$ structures are observed, each with significance over $5$ standard deviations. The quantum numbers of these structures are determined with significance of at least $4$ standard deviations. The lightest is best described as a $D_s^{\pm}D_s^{*\mp}$ cusp, but a resonant interpretation is also possible with mass consistent with, but width much larger than, previous measurements of the claimed $X(4140)$ state. The model includes significant contributions from a number of expected kaon excitations, including the first observation of the $K^{*}(1680)^+\to\phi K^+$ transition.LHCb CollaborationTue, 28 Jun 2016 13:21:53 GMT28 Jun 2016CERN-EP-2016-156https://cds.cern.ch/record/21949622016156Observation of $J/\psi\phi$ structures consistent with exotic states from amplitude analysis of $B^+\to J/\psi \phi K^+$ decays
https://cds.cern.ch/record/2194961
The first full amplitude analysis of $B^+\to J/\psi \phi K^+$ with $J/\psi\to\mu^+\mu^-$, $\phi\to K^+K^-$ decays is performed with a data sample of 3 fb$^{-1}$ of $pp$ collision data collected at $\sqrt{s}=7$ and $8$ TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into $\phi K^+$, and four $J/\psi\phi$ structures are observed, each with significance over $5$ standard deviations. The quantum numbers of these structures are determined with significance of at least $4$ standard deviations. The lightest is best described as a $D_s^{\pm}D_s^{*\mp}$ cusp, but a resonant interpretation is also possible with mass consistent with, but width much larger than, previous measurements of the claimed $X(4140)$ state.LHCb CollaborationTue, 28 Jun 2016 13:17:37 GMT28 Jun 2016CERN-EP-2016-155https://cds.cern.ch/record/21949612016155Density functional theory with quantum nuclei
https://cds.cern.ch/record/2194914
It is proved that the ground state energy of an electron-nuclear system is a variational functional of the conditional electronic density n_R(r), the nuclear wavefunction \chi(R) and the quantum geometric tensor of the conditional electronic wavefunction $T_{\mu\nu}(R) = \langle \partial_{\mu} \Phi_R | (1-|\Phi_R\rangle \langle \Phi_R|) |\partial_{\nu} \Phi_R \rangle$ over nuclear configuration space, where $\Phi_R(r)$ and \chi(R) are derived from the exact factorization $\Psi(r,R)=\Phi_R(r) \chi(R)$ of the electron-nuclear wavefunction with electronic coordinates r = r_1, r_2, ... and nuclear coordinates R = R_1, R_2, ... The ground state (n_R,\chi,$T_{\mu\nu}$) can be calculated by solving self-consistently (i) conditional Kohn-Sham equations containing an effective potential v_s(r) that depends parametrically on R, (ii) the Schroedinger equation for \chi(R) and (iii) a set of Euler-Lagrange equations that determine the tensor $T_{\mu\nu}$, whose imaginary part is the Berry curvature. The theory is applied to the E x e Jahn-Teller model.Requist, RyanGross, E K UTue, 28 Jun 2016 06:08:07 GMT27 Jun 2016arXiv:1606.08424https://cds.cern.ch/record/2194914['arXiv:1606.08424']arXiv:1606.08424Revisiting the Lie-group symmetry method for turbulent channel flow with wall transpiration
https://cds.cern.ch/record/2194913
The Lie-group-based symmetry analysis, as first proposed in Avsarkisov et al. (2014) and then later modified in Oberlack et al. (2015), to generate invariant solutions in order to predict the scaling behavior of a channel flow with uniform wall transpiration, is revisited. By focusing first on the results obtained in Avsarkisov et al. (2014), we failed to reproduce two key results: (i) For different transpiration rates at a constant Reynolds number, the mean velocity profiles (in deficit form) do not universally collapse onto a single curve as claimed. (ii) The universally proposed logarithmic scaling law in the center of the channel does not match the direct numerical simulation (DNS) data for the presented parameter values. In fact, no universal scaling behavior in the center of the channel can be detected from their DNS data, as it is misleadingly claimed in Avsarkisov et al. (2014). Moreover, we will demonstrate that the assumption of a Reynolds-number independent symmetry analysis is not justified for the flow conditions considered therein. Only when including also the viscous terms, an overall consistent symmetry analysis can be provided. This has been attempted in their subsequent study Oberlack et al. (2015). But, also the (viscous) Lie-group-based scaling theory proposed therein is inconsistent, apart from the additional fact that this study of Oberlack et al. (2015) is also technically flawed. The reason for this permanent inconsistency is that their symmetry analysis constantly involves several unphysical statistical symmetries that are incompatible to the underlying deterministic description of Navier-Stokes turbulence.Khujadze, GeorgeFrewer, MichaelTue, 28 Jun 2016 06:08:07 GMT27 Jun 2016arXiv:1606.08396https://cds.cern.ch/record/2194913['arXiv:1606.08396']arXiv:1606.08396Singular effective slip length for longitudinal flow over a dense bubble mattress
https://cds.cern.ch/record/2194912
We consider the effective hydrophobicity of a Cassie-state liquid above a periodically grooved surface, with trapped shear-free bubbles protruding between no-slip ridges at a pi/2 contact angle. Specifically, we carry out a singular-perturbation analysis in the limit where the bubbles are closely separated, finding the effective slip length for longitudinal flow along the the ridges as a[pi*sqrt(a/d) - 2.53 + o(1)], a being the bubble radius and d the width of the no-slip segments; the square-root divergence with a/d highlights the strong hydrophobic character of this configuration. The leading singular term follows from a local analysis of the gap regions between the bubbles, together with general matching considerations and a global relation linking the applied shear, the protrusion geometry, and the variation of the flow speed transverse to the no-slip ridges. The corrective constant term is found as an integral quantity of the leading-order "outer" problem, where the bubbles appear to be touching. We find excellent agreement between our slip-length formula and a numerical scheme recently derived using a "uniform-transform" method (D. Crowdy, IMA J. Appl. Math., 80 1902, 2015). The comparison demonstrates that our approximation, together with the diametric "dilute-limit" approximation (D. Crowdy, J. Fluid Mech., 791 R7, 2016), provides an elementary analytical description for essentially arbitrary no-slip fractions. We briefly discuss the case of contact angles less than pi/2, where scaling arguments imply that the slip-length singularity becomes logarithmic.Schnitzer, OryTue, 28 Jun 2016 06:08:07 GMT27 Jun 2016arXiv:1606.08387https://cds.cern.ch/record/2194912['arXiv:1606.08387']arXiv:1606.08387Non-destructive monitoring of Bloch oscillations in an optical cavity
https://cds.cern.ch/record/2194911
Bloch oscillations are a hallmark of coherent wave dynamics in periodic potentials. They occur as the response of quantum mechanical particles in a lattice if a weak force is applied. In optical lattices with their perfect periodic structure they can be readily observed and employed as a quantum mechanical force sensor, for example, for precise measurements of the gravitational acceleration. However, the destructive character of the measurement process in previous experimental implementations poses serious limitations for the precision of such measurements. In this article we show that the use of an optical cavity operating in the regime of strong cooperative coupling allows one to directly monitor Bloch oscillations of a cloud of cold atoms in the light leaking out of the cavity. Hence, with a single atomic sample the Bloch oscillation dynamics can be mapped out, while in previous experiments, each data point required the preparation of a new atom cloud. The use of a cavity-based monitor should greatly improve the precision of Bloch oscillation measurements for metrological purposes.Keßler, HKlinder, JVenkatesh, B PGeorges, ChHemmerich, ATue, 28 Jun 2016 06:08:06 GMT27 Jun 2016arXiv:1606.08386https://cds.cern.ch/record/2194911['arXiv:1606.08386']arXiv:1606.08386Resolving a discrepancy between experimental and theoretical lifetimes in atomic negative ions
https://cds.cern.ch/record/2194909
Recently the lifetime of the excited $^{2}P_{1/2}$-state of S$^-$ was measured to be $503\pm 54$ s (B\"ackstr\"om \textit{et al.} Phys. Rev. Lett. 114, 143003 (2015)). The earlier theoretical lifetime of $436$ s was clearly outside the experimental error bars. To investigate this discrepancy we have performed systematic and large-scale Multi-configuration Dirac-Hartree-Fock calculations for this system. After including a careful treatment of correlation and relativistic effects, we predict a well-converged value of $492$ s for this lifetime, with an uncertainty considerably less than 1 \%, thereby removing the apparent conflict between theory and experiment. We also show that this result corresponds to the non-relativistic limit in the $LS$-approximation for the M1-transition within this $^2P$-term. This approach for the M1-transition yields lifetimes for several $^2P$ fine-structure transitions in negative ions, which only depends on the transition energy and shows excellent agreement with recent lifetime measurements, when the transition energy is known. We propose that measurements of these lifetimes could be used to confirm the spectroscopic identification of these transitions. This becomes an important tool since atomic anions, in general, have few bound states, and therefore only a few photon signals from bound-bound transitions, thereby making traditional spectroscopic analyses impossible. In addition to this, in cases where the lifetime, but not the transition energy, is known, the latter can be determined from the former by using the simple energy dependence of the lifetime.Brage, TomasGrumer, JonTue, 28 Jun 2016 06:08:06 GMT27 Jun 2016arXiv:1606.08361https://cds.cern.ch/record/2194909['arXiv:1606.08361']arXiv:1606.08361Collective excitations of dipolar gases based on local tunneling in ultracold superlattices
https://cds.cern.ch/record/2194908
The collective dynamics of a dipolar fermionic quantum gas confined in a one-dimensional double-well superlattice is explored. The fermionic gas resides in a paramagnetic-like ground state in the weak interaction regime, upon which a new type of collective dynamics is found when applying a local perturbation. This dynamics is composed of the local tunneling of fermions in separate supercells, and is a pure quantum effect, with no classical counterpart. Due to the presence of the dipolar interactions the local tunneling transports through the entire superlattice, giving rise to a collective dynamics. A well-defined momentum-energy dispersion relation is identified in the ab-initio simulations demonstrating the phonon-like behavior. The phonon-like characteristic is also confirmed by an analytical description of the dynamics within a semiclassical picture.Cao, LMistakidis, S IDeng, XSchmelcher, PTue, 28 Jun 2016 06:08:06 GMT27 Jun 2016arXiv:1606.08358https://cds.cern.ch/record/2194908['arXiv:1606.08358']arXiv:1606.08358First-principles structure search for the stable isomers of stoichiometric WS2 nano-clusters
https://cds.cern.ch/record/2194907
In this paper, we employ evolutionary algorithm along with the full-potential density functional theory (DFT) computations to perform a comprehensive search for the stable structures of stoichiometric (WS2)n nano-clusters (n=1-9), within three different exchange-correlation functionals. Our results suggest that n=3, 5, 8 are possible candidates for the low temperature magic sizes of WS2 nano-clusters while at temperatures above 600 Kelvin, n=5 and 7 exhibit higher relative stability among the studied systems. The electronic properties and energy gap of the lowest energy isomers were computed within several schemes, including semilocal PBE and BLYP functionals, hybrid B3LYP functional, many body based DFT+GW approach, and time dependent DFT calculations. Vibrational spectra of the lowest lying isomers, computed by the force constant method, are used to address IR spectra and thermal free energy of the clusters. Time dependent density functional calculation in real time domain is applied to determine the full absorption spectra and optical gap of the lowest energy isomers of the WS2 nano-clusters.Hafizi, RoohollahHashemifar, S JavadAlaei, MojtabaJangrouei, MohammadRezaAkbarzadeh, HadiTue, 28 Jun 2016 06:08:06 GMT27 Jun 2016arXiv:1606.08355https://cds.cern.ch/record/2194907['arXiv:1606.08355']arXiv:1606.08355Superfluid (quantum) turbulence and distributed chaos
https://cds.cern.ch/record/2194906
Properties of distributed chaos in superfluid (quantum) turbulence have been studied using the data of recent direct numerical simulations (HVBK two-fluid model for He II, and a moving grid in the frames of Gross-Pitaevskii model of the Bose-Einstein condensates at low temperatures). It is found that for the viscous (normal) component of the velocity field in He II the viscosity dominates the distributed chaos with the stretched exponential spectrum $\exp(-k/k_{\beta})^{\beta}$ and $\beta = 2/3$. For the superfluid component the distributed chaos is dominated by the vorticity correlation integral with $\beta =1/2$ (the soft spontaneous breaking of the space translational symmetry - homogeneity). For very low temperature the distributed chaos is tuned to the large-scale coherent motions: the viscous (normal) component is tuned to the fundamental mode, whereas the superfluid component is subharmonically tuned. For the Gross-Pitaevskii superfluid turbulence incompressible part of the energy spectrum (containing the vortices contribution) also indicates the distributed chaos dominated by the vorticity correlation integral ($\beta =1/2$) and the subharmonic tuning to the large-scale coherent motions.Bershadskii, ATue, 28 Jun 2016 06:08:06 GMT27 Jun 2016arXiv:1606.08351https://cds.cern.ch/record/2194906['arXiv:1606.08351']arXiv:1606.08351Raman scattering with strongly coupled vibron-polaritons
https://cds.cern.ch/record/2194905
Strong coupling between cavity photons and molecular vibrations can lead to the formation of vibron-polaritons. In a recent experiment with PVAc molecules in a metal-metal microcavity [A.Shalabney et al., Ang.Chem.Int.Ed. 54 7971 (2015)], such a coupling was observed to enhance the Raman scattering probability by several orders of magnitude. Inspired by this, we theoretically analyze the effect of strong photon-vibron coupling on the Raman scattering amplitude of organic molecules. This problem has recently been addressed in [J.del Pino, J.Feist and F.J.Garcia-Vidal; J.Phys.Chem.C 119 29132 (2015)] using exact numerics for a small number of molecules. In this paper we derive compact analytic results for any number of molecules, also including the ultra-strong coupling regime. Our calculations predict a division of the Raman signal into upper and lower polariton modes,with some enhancement to the lower polariton Raman amplitude due to the mode softening under strong coupling.Strashko, ArtemKeeling, JonathanTue, 28 Jun 2016 06:08:06 GMT27 Jun 2016arXiv:1606.08343https://cds.cern.ch/record/2194905['arXiv:1606.08343']arXiv:1606.08343From catastrophic acceleration to deceleration of liquid plugs in prewetted capillary tubes
https://cds.cern.ch/record/2194904
The dynamics of individual liquid plugs pushed at constant pressure head inside prewetted cylindrical capillary tubes is investigated experimentally and theoretically. It is shown that, depending on the thickness of the prewetting film and the magnitude of the pressure head, the plugs can either experience a continuous acceler ation leading to a catastrophic decrease of their size and eventually their rupture or conversely, a progressive deceleration associated with their growth. These behaviors are quantitatively reproduced with a simple nonlinear model [Baudoin et al., Proc. Nat. Ac. Sci. USA, 2013, 110, 859] adapted here for cylindrical channels. Furthermore, an analytical criterion for the transition between these two regimes is obtained and successfully compared with extensive experimental data. The implications of this work for pulmonary obstructive diseases are discussed.Magniez, J CBaudoin, MLiu, CZoueshtiagh, FTue, 28 Jun 2016 06:08:06 GMT27 Jun 2016arXiv:1606.08342https://cds.cern.ch/record/2194904['arXiv:1606.08342']arXiv:1606.08342Nonreciprocal Transverse Photonic Spin and Magnetization-Induced Electromagnetic Spin-Orbit Coupling
https://cds.cern.ch/record/2194903
A study of nonreciprocal transverse-spin angular-momentum-density shifts for evanescent waves in magneto-optic waveguide media is presented. Their functional relation to electromagnetic spin- and orbital-momenta is presented and analyzed. It is shown that the magneto-optic gyrotropy can be re-interpreted as the nonreciprocal electromagnetic spin-density shift per unit energy flux, thus providing an interesting alternative physical picture for the magneto-optic gyrotropy. The transverse spin-density shift is found to be thickness-dependent in slab optical waveguides. This dependence is traceable to the admixture of minority helicity components in the transverse spin angular momentum. It is also shown that the transverse spin is magnetically tunable. A formulation of electromagnetic spin-orbit coupling in magneto-optic media is presented, and an alternative source of spin-orbit coupling to non-paraxial optics vortices is proposed. It is shown that magnetization-induced electromagnetic spin-orbit coupling is possible, and that it leads to spin to orbital angular momentum conversion in magneto-optic media evanescent waves.Levy, MiguelKarki, DolendraTue, 28 Jun 2016 06:08:06 GMT27 Jun 2016arXiv:1606.08334https://cds.cern.ch/record/2194903['arXiv:1606.08334']arXiv:1606.08334Maps of sparse Markov chains efficiently reveal community structure in network flows with memory
https://cds.cern.ch/record/2194902
To better understand the flows of ideas or information through social and biological systems, researchers develop maps that reveal important patterns in network flows. In practice, network flow models have implied memoryless first-order Markov chains, but recently researchers have introduced higher-order Markov chain models with memory to capture patterns in multi-step pathways. Higher-order models are particularly important for effectively revealing actual, overlapping community structure, but higher-order Markov chain models suffer from the curse of dimensionality: their vast parameter spaces require exponentially increasing data to avoid overfitting and therefore make mapping inefficient already for moderate-sized systems. To overcome this problem, we introduce an efficient cross-validated mapping approach based on network flows modeled by sparse Markov chains. To illustrate our approach, we present a map of citation flows in science with research fields that overlap in multidisciplinary journals. Compared with currently used categories in science of science studies, the research fields form better units of analysis because the map more effectively captures how ideas flow through science.Persson, ChristianBohlin, LudvigEdler, DanielRosvall, MartinTue, 28 Jun 2016 06:08:06 GMT27 Jun 2016arXiv:1606.08328https://cds.cern.ch/record/2194902['arXiv:1606.08328']arXiv:1606.08328First-Principles Correlated Electron Calculations of Photoabsorption in Small Sodium Clusters
https://cds.cern.ch/record/2194900
We present correlated electron calculations of the linear photoabsorption spectra of small neutral closed- and open-shell sodium clusters (Na$_{n}$, n=2-6), as well as closed-shell cation clusters (Na$_{n}$$^{+}$, n=3, 5). We have employed the configuration interaction (CI) methodology at the full CI (FCI) and quadruple CI (QCI) levels to compute the ground, and the low-lying excited states of the clusters. For most clusters, besides the minimum energy structures, we also consider their energetically close isomers. The photoabsorption spectra were computed under the electric-dipole approximation, employing the dipole-matrix elements connecting the ground state with the excited states of each isomer. Our calculations were tested rigorously for convergence with respect to the basis set, as well as with respect to the size of the active orbital space employed in the CI calculations. Excellent quantitative agreement is observed between our results, and experiments, where available.Priya, Pradip KumarRai, Deepak KumarShukla, AlokTue, 28 Jun 2016 06:08:05 GMT27 Jun 2016arXiv:1606.08306https://cds.cern.ch/record/2194900['arXiv:1606.08306']arXiv:1606.08306Synchronized flutter of two slender flags
https://cds.cern.ch/record/2194899
The interactions and synchronization of two parallel and slender flags in a uniform axial flow are studied in the present paper by generalizing Lighthill's Elongated Body Theory (EBT) and Lighthill's Large Amplitude Elongated Body Theory (LAEBT) to account for the hydrodynamic coupling between flags. The proposed method consists in two successive steps, namely the reconstruction of the flow created by a flapping flag within the LAEBT framework and the computation of the fluid force generated by this nonuniform flow on the second flag. In the limit of slender flags in close proximity, we show that the effect of the wakes have little influence on the long time coupled-dynamics and can be neglected in the modeling. This provides a simplified framework extending LAEBT to the coupled dynamics of two flags. Using this simplified model, both linear and large amplitude results are reported to explore the selection of the flapping regime as well as the dynamical properties of two side-by-side slender flags. Hydrodynamic coupling of the two flags is observed to destabilize the flags for most parameters, and to induce a long-term synchronization of the flags, either in-phase or out-of-phase.Mougel, JeromeDoare, OlivierMichelin, SebastienTue, 28 Jun 2016 06:08:05 GMT27 Jun 2016arXiv:1606.08305https://cds.cern.ch/record/2194899['arXiv:1606.08305']arXiv:1606.08305Surface-wave photonic quasicrystal
https://cds.cern.ch/record/2194898
In developing strategies of manipulating surface electromagnetic waves, it has been recently recognized that a complete forbidden band gap can exist in a periodic surface-wave photonic crystal, which has subsequently produced various surface-wave photonic devices. However, it is not obvious whether such a concept can be extended to a non-periodic surface-wave system that lacks translational symmetry. Here we experimentally demonstrate that a surface-wave photonic quasicrystal that lacks periodicity can also exhibit a forbidden band gap for surface electromagnetic waves. The lower cutoff of this forbidden band gap is mainly determined by the maximum separation between nearest neighboring pillars. Point defects within this band gap show distinct properties compared to a periodic photonic crystal for the absence of translational symmetry. A line-defect waveguide, which is crafted out of this surface-wave photonic quasicrystal by shortening a random row of metallic rods, is also demonstrated to guide and bend surface waves around sharp corners along an irregular waveguiding path.Gao, ZhenGao, FeiZhang, YoumingXu, HongyiZhang, BaileTue, 28 Jun 2016 06:08:05 GMT27 Jun 2016arXiv:1606.08302https://cds.cern.ch/record/2194898['arXiv:1606.08302']arXiv:1606.08302Some Surprises in Relativistic Gravity
https://cds.cern.ch/record/2194897
General Relativity has had tremendous success both on the theoretical and the experimental fronts for over a century now. However, the contents of the theory are far from exhausted. Only very recently, with the detection of gravitational waves from colliding black holes, we have started probing the behavior of gravity in the strongly non-linear regime. Even today, the studies of black holes keep revealing more and more paradoxes and bizarre results. In this paper, inspired by David Hilbert's startling observation, we show that, contrary to the conventional wisdom, a freely falling test particle feels gravitational repulsion by a black hole as seen by the asymptotic observer. We dig deeper into this surprising behavior of relativistic gravity and offer some explanations.Santos, N OSatheeshkumar, V HTue, 28 Jun 2016 06:08:05 GMT21 Jun 2016arXiv:1606.08300https://cds.cern.ch/record/2194897['arXiv:1606.08300']arXiv:1606.08300Ligand-receptor binding kinetics in surface plasmon resonance cells: A Monte Carlo analysis
https://cds.cern.ch/record/2194896
Surface plasmon resonance (SPR) chips are widely used to measure association and dissociation rates for the binding kinetics between two species of chemicals, e.g., cell receptors and ligands. It is commonly assumed that ligands are spatially well mixed in the SPR region, and hence a mean-field rate equation description is appropriate. This approximation however ignores the spatial fluctuations as well as temporal correlations induced by multiple local rebinding events, which become prominent for slow diffusion rates and high binding affinities. We report detailed Monte Carlo simulations of ligand binding kinetics in an SPR cell subject to laminar flow. We extract the binding and dissociation rates by means of the techniques frequently employed in experimental analysis that are motivated by the mean-field approximation. We find major discrepancies in a wide parameter regime between the thus extracted rates and the known input simulation values. These results underscore the crucial quantitative importance of spatio-temporal correlations in binary reaction kinetics in SPR cell geometries, and demonstrate the failure of a mean-field analysis of SPR cells in the regime of high association rates, where the spatio-temporal correlations due to diffusive transport and ligand-receptor rebinding events dominate the dynamics of SPR system.Carroll, JacobRaum, MatthewForsten-Williams, KimberlyTäuber, Uwe CTue, 28 Jun 2016 06:08:05 GMT27 Jun 2016arXiv:1606.08294https://cds.cern.ch/record/2194896['arXiv:1606.08294']arXiv:1606.08294Fermi golden rule for $N$-body systems in a black-body radiation
https://cds.cern.ch/record/2194895
We review the calculation of the Fermi golden rule for a system of $N$-body dipoles, magnetic or electric, weakly interacting with a black-body radiation. By using the magnetic or electric field-field correlation function evaluated in the 1960s for the black body radiation, we deduce a general formula for the transition rates and study its limiting, fully coherent or fully incoherent, regimes.Ostilli, MassimoPresilla, CarloTue, 28 Jun 2016 06:08:05 GMT27 Jun 2016arXiv:1606.08276https://cds.cern.ch/record/2194895['arXiv:1606.08276']arXiv:1606.08276Magnetic Eigenmaps for Visualization of Directed Networks
https://cds.cern.ch/record/2194894
We propose a framework for visualization of directed networks relying on the eigenfunctions of the magnetic Laplacian, called here Magnetic Eigenmaps. The magnetic Laplacian is a complex deformation of the well-known combinatorial Laplacian. Features such as density of links and directionality patterns are revealed by plotting the phases of the first magnetic eigenvectors. Directed networks being common in social science, biology or computer science, our visualization method may be relevant for the field of complex networks, as well as applied mathematics and machine learning. Illustrations of our method are given for both artificial and real-life networks.Fanuel, MichaëlFernández, ÁngelaAlaíz, Carlos MSuykens, Johan A KTue, 28 Jun 2016 06:08:05 GMT27 Jun 2016arXiv:1606.08266https://cds.cern.ch/record/2194894['arXiv:1606.08266']arXiv:1606.08266Electromagnetically induced transparency with Rydberg atoms across the Breit-Rabi regime
https://cds.cern.ch/record/2194893
We present experimental results on the influence of magnetic fields and laser polarization on electromagnetically induced transparency (EIT) using Rydberg levels of $^{87}$Rb atoms. The measurements are performed in a room temperature vapor cell with two counter-propagating laser beams at 480nm and 780nm in a ladder-type energy level scheme. We measure the EIT spectrum of a range of $ns_{1/2}$ Rydberg states for $n=19-27$, where the hyperfine structure can still be resolved. Our measurements span the range of magnetic fields from the low field linear Zeeman regime to the high field Paschen-Back regimes. The observed spectra are very sensitive to small changes in magnetic fields and the polarization of the laser beams. We model our observations using optical Bloch equations that take into account the full multi-level structure of the atomic states involved and the decoupling of the electronic $J$ and nuclear $I$ angular momenta in the Breit-Rabi regime. The numerical model yields excellent agreement with the observations. In addition to EIT related experiments, our results are relevant for experiments involving coherent excitation to Rydberg levels in the presence of magnetic fields.Naber, J BTauschinsky, AHeuvell, H B van Linden van denSpreeuw, R J CTue, 28 Jun 2016 06:08:05 GMT27 Jun 2016arXiv:1606.08260https://cds.cern.ch/record/2194893['arXiv:1606.08260']arXiv:1606.08260Impact of Free Carriers on Modulational Instability in Silicon-on-insulator Nanowaveguides
https://cds.cern.ch/record/2194892
We have numerically studied the effect of free-carrier-induced loss and dispersion on the modulational instability (MI) gain at low input powers in silicon-on-insulator (SOI) nanowaveguides with normal and anomalous second-order dispersion. We have shown that the free carriers affect the gain spectra even at low input powers. First time we have reported the gain in normal SOI nanowaveguides even in the absence of higher order dispersion parameters, which is due to the interaction of free-carrier-induced dispersion and nonlinearity. The MI gain in an anomalous SOI nanowaveguide vanishes even at a few milliwatt range of input power due to this interaction. We have shown that the gain could be achieved in an anomalous nanowaveguides by reducing the free carrier lifetime.Chaturvedi, DeepaKumar, AjitTue, 28 Jun 2016 06:08:05 GMT27 Jun 2016arXiv:1606.08259https://cds.cern.ch/record/2194892['arXiv:1606.08259']arXiv:1606.08259The tennis racket effect in a three-dimensional rigid body
https://cds.cern.ch/record/2194890
We propose a complete theoretical description of the tennis racket effect, which occurs in the free rotation of a three-dimensional rigid body. This effect is characterized by a flip ($\pi$- rotation) of the head of the racket when a full ($2\pi$) rotation around the unstable inertia axis is considered. We describe the asymptotics of the phenomenon and conclude about the robustness of this effect with respect to the values of the moments of inertia and the initial conditions of the dynamics. This shows the generality of this geometric property which can be found in a variety of rigid bodies. A simple analytical formula is derived to estimate the twisting effect in the general case. Different examples are discussed.Van Damme, LMardesic, PSugny, DTue, 28 Jun 2016 06:08:05 GMT27 Jun 2016arXiv:1606.08237https://cds.cern.ch/record/2194890['arXiv:1606.08237']arXiv:1606.08237