Results for "N. Bartolo"

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Possibly Large Corrections to the Inflationary ObservablesNov 26 2007We point out that the theoretical predictions for the inflationary observables may be generically altered by the presence of fields which are heavier than the Hubble rate during inflation and whose dynamics is usually neglected. They introduce corrections ... More
The simplest curvaton modelMar 06 2002Apr 29 2002We analyze the simplest possible realization of the curvaton scenario, where a nearly scale-invariant spectrum of adiabatic perturbations is generated by conversion of an isocurvature perturbation generated during inflation, rather than the usual inflationary ... More
Electromagnetic field fluctuations near a dielectric-vacuum boundary and surface divergences in the ideal conductor limitApr 29 2012Jul 30 2012We consider the electric and magnetic field fluctuations in the vacuum state in the region external to a half-space filled with a homogeneous non-dissipative dielectric. We discuss an appropriate limit to an ideal metal and concentrate our interest on ... More
Canonical Horizontal Visibility Graphs are uniquely determined by their degree sequenceMay 17 2016Horizontal visibility graphs (HVGs) are graphs constructed in correspondence with number sequences that have been introduced and explored recently in the context of graph-theoretical time series analysis. In most of the cases simple measures based on ... More
Non-Gaussianity and the Cosmic Microwave Background AnisotropiesJan 22 2010We review in a pedagogical way the present status of the impact of non-Gaussianity (NG) on the Cosmic Microwave Background (CMB) anisotropies. We first show how to set the initial conditions at second-order for the (gauge invariant) CMB anisotropies when ... More
On Non-Gaussianity in the Curvaton ScenarioSep 03 2003Nov 28 2003Since a positive future detection of non-linearity in the cosmic microwave background anisotropy pattern might allow to descriminate among different mechanisms giving rise to cosmological adiabatic perturbations, we study the evolution of the second-order ... More
The Full Second-Order Radiation Transfer Function for Large-Scale CMB AnisotropiesDec 19 2005We calculate the full second-order radiation transfer function for Cosmic Microwave Background anisotropies on large angular scales in a flat universe filled with matter and cosmological constant. It includes (i) the second-order generalization of the ... More
Enhancement of Non-Gaussianity after InflationAug 06 2003Apr 05 2004We study the evolution of cosmological perturbations on large scales, up to second order, for a perfect fluid with generic equation of state. Taking advantage of super-horizon conservation laws, it is possible to follow the evolution of the non-Gaussianity ... More
Non-Gaussianity in the Cosmic Microwave Background Anisotropies at Recombination in the Squeezed limitSep 09 2011Sep 13 2011We estimate analytically the second-order cosmic microwave background temperature anisotropies at the recombination epoch in the squeezed limit and we deduce the contamination to the primordial local non-Gaussianity. We find that the level of contamination ... More
Non-Gaussianity of Large-Scale Cosmic Microwave Background Anisotropies beyond Perturbation TheoryJun 17 2005Aug 31 2005We compute the fully non-linear Cosmic Microwave Background (CMB) anisotropies on scales larger than the horizon at last-scattering in terms of only the curvature perturbation, providing a generalization of the linear Sachs-Wolfe effect at any order in ... More
Evolution of Second-Order Cosmological Perturbations and Non-GaussianitySep 25 2003Oct 06 2003We present a second-order gauge-invariant formalism to study the evolution of curvature perturbations in a Friedmann-Robertson-Walker universe filled by multiple interacting fluids. We apply such a general formalism to describe the evolution of the second-order ... More
Oscillations During Inflation and the Cosmological Density PerturbationsJun 01 2001Jun 07 2001Adiabatic (curvature) perturbations are produced during a period of cosmological inflation that is driven by a single scalar field, the inflaton. On particle physics grounds -- though -- it is natural to expect that this scalar field is coupled to other ... More
Adiabatic and Isocurvature Perturbations from Inflation: Power Spectra and Consistency RelationsJul 26 2001We study adiabatic and isocurvature perturbations produced during a period of cosmological inflation. We compute the power spectra and cross spectra of the curvature and isocurvature modes, as well as the tensor perturbation spectrum in terms of the slow-roll ... More
Post-inflation increase of the cosmological tensor-to-scalar perturbation ratioJul 25 2005Sep 10 2005We investigate the possibility that the amplitude of scalar density perturbations may be damped after inflation. This would imply that CMB anisotropies do not uniquely fix the amplitude of the perturbations generated during inflation and that the present ... More
Relativistic effects and primordial non-Gaussianity in the galaxy biasNov 19 2010Apr 19 2011When dealing with observables, one needs to generalize the bias relation between the observed galaxy fluctuation field to the underlying matter distribution in a gauge-invariant way. We provide such relation at second-order in perturbation theory adopting ... More
CMB Anisotropies at Second Order IApr 19 2006May 05 2006We present the computation of the full system of Boltzmann equations at second-order describing the evolution of the photon, baryon and cold dark matter fluids. These equations allow to follow the time evolution of the Cosmic Microwave Background (CMB) ... More
Gauge-Invariant Temperature Anisotropies and Primordial Non-GaussianityJul 23 2004Nov 03 2004We provide the gauge-invariant expression for large-scale cosmic microwave background temperature fluctuations at second-order in perturbation theory. It enables to unambiguously define the nonlinearity parameter f_NL which is used by experimental collaborations ... More
Signatures of Primordial Non-Gaussianity in the Large-Scale Structure of the UniverseJan 27 2005Dec 21 2005We discuss how primordial (e.g. inflationary) non-Gaussianity in the cosmological perturbations is left imprinted in the Large-Scale Structure of the universe. Our findings show that the information on the primordial non-Gaussianity set on super-Hubble ... More
Non-Gaussianity from InflationDec 19 2001Mar 18 2002Correlated adiabatic and isocurvature perturbation modes are produced during inflation through an oscillation mechanism when extra scalar degrees of freedom other than the inflaton field are present. We show that this correlation generically leads to ... More
Exact results for Schrödinger cats in driven-dissipative systems and their feedback controlJan 12 2016May 25 2016In quantum optics, photonic Schr\"odinger cats are superpositions of two coherent states with opposite phases and with a significant number of photons. Recently, these states have been observed in the transient dynamics of driven-dissipative resonators ... More
The Maximal Amount of Gravitational Waves in the Curvaton ScenarioMay 29 2007Sep 24 2007The curvaton scenario for the generation of the cosmological curvature perturbation on large scales represents an alternative to the standard slow-roll scenario of inflation in which the observed density perturbations are due to fluctuations of the inflaton ... More
Non-Gaussianity from Inflation: Theory and ObservationsJun 17 2004Jul 28 2004This is a review of models of inflation and of their predictions for the primordial non-Gaussianity in the density perturbations which are thought to be at the origin of structures in the Universe. Non-Gaussianity emerges as a key observable to discriminate ... More
CMB temperature anisotropies from third order gravitational perturbationsJul 19 2007Dec 14 2007In this paper we present a complete computation of the Cosmic Microwave Background (CMB) anisotropies up to third order from gravitational perturbations accounting for scalar, vector and tensor perturbations. We then specify our results to the large scale ... More
On the Physical Significance of Infra-red Corrections to Inflationary ObservablesNov 27 2007Dec 04 2007Inflationary observables, like the power spectrum, computed at one- and higher-order loop level seem to be plagued by large infra-red corrections. In this short note, we point out that these large infra-red corrections appear only in quantities which ... More
Measuring chiral gravitational waves in Chern-Simons gravity with CMB bispectraSep 28 2018Jan 25 2019Chern-Simons gravity coupled to the scalar sector through a generic coupling function $f(\phi)$ can be tested at the very high energies of the inflationary period. In 1706.04627, we computed the theoretical parity breaking signatures of the $\langle \gamma ... More
Some open questions on arithmetic Zariski pairsJun 17 2015In this paper, complement-equivalent arithmetic Zariski pairs will be exhibited answering in the negative a question by Eyral-Oka on these curves and their groups. A complement-equivalent arithmetic Zariski pair is a pair of complex projective plane curves ... More
Studies of h/e Aharonov-Bohm Photovoltaic Oscillations in Mesoscopic Au RingsSep 20 1996We have investigated a mesoscopic photovoltaic (PV) effect in micron-size Au rings in which a dc voltage Vdc is generated in response to microwave radiation. The effect is due to the lack of inversion symmetry in a disordered system. Aharonov-Bohm PV ... More
An Estimator for statistical anisotropy from the CMB bispectrumJul 21 2011Jan 19 2012Various data analyses of the Cosmic Microwave Background (CMB) provide observational hints of statistical isotropy breaking. Some of these features can be studied within the framework of primordial vector fields in inflationary theories which generally ... More
Second-Order Cosmological Perturbations from InflationSep 09 2002Dec 19 2002We present the first computation of the cosmological perturbations generated during inflation up to second order in deviations from the homogeneous background solution. Our results, which fully account for the inflaton self-interactions as well as for ... More
Second-order matter perturbations in a LambdaCDM cosmology and non-GaussianityFeb 19 2010We obtain exact expressions for the effect of primordial non-Gaussianity on the matter density perturbation up to second order in a LambdaCDM cosmology, fully accounting for the general relativistic corrections arising on scales comparable with the Hubble ... More
The impact of cosmic neutrinos on the gravitational-wave backgroundMay 21 2008Oct 23 2008We obtain the equation governing the evolution of the cosmological gravitational-wave background, accounting for the presence of cosmic neutrinos, up to second order in perturbation theory. In particular, we focus on the epoch during radiation dominance, ... More
Critical behavior of dissipative two-dimensional spin latticesSep 09 2016We explore critical properties of two-dimensional lattices of spins interacting via an anisotropic Heisenberg Hamiltonian and subject to incoherent spin flips. We determine the steady-state solution of the master equation for the density matrix via the ... More
Wirtinger curves, Artin groups, and hypocycloidsMay 09 2017Aug 31 2017The computation of the fundamental group of the complement of an algebraic plane curve has been theoretically solved since Zariski-van Kampen, but actual computations are usually cumbersome. In this work, we describe the notion of Wirtinger presentation ... More
Fundamental groups of real arrangements and torsion in the lower central series quotientsApr 13 2017Jan 11 2018By using computer assistance, we prove that the fundamental group of the complement of a real complexified line arrangement is not determined by its intersection lattice, providing a counter-example for a problem of Falk and Randell. We also deduce that ... More
Quasiperiodic graphs: structural design, scaling and entropic propertiesMar 16 2012A novel class of graphs, here named quasiperiodic, are constructed via application of the Horizontal Visibility algorithm to the time series generated along the quasiperiodic route to chaos. We show how the hierarchy of mode-locked regions represented ... More
Characteristic varieties of graph manifolds and quasi-projectivity of fundamental groups of algebraic linksApr 01 2019The present paper studies the structure of characteristic varieties of fundamental groups of graph manifolds. As a consequence, a simple proof of Papadima's question is provided on the characterization of algebraic links that have quasi-projective fundamental ... More
CMB Circular and B-mode Polarization from New InteractionsMar 11 2019Standard models describing the radiation transfer of the Cosmic Microwave Background (CMB) through Compton scattering predict that cosmological scalar perturbations at linear order are not able to source V and B polarization modes. In this work we investigate ... More
Triangular curves and cyclotomic Zariski tuplesApr 19 2019The purpose of this paper is to exhibit infinite families of conjugate projective curves in a number field whose complement have the same abelian fundamental group, but are non-homeomorphic. In particular, for any $d>3$ we find Zariski tuples parametrized ... More
Arrangements of hypersurfaces and Bestvina-Brady groupsJul 02 2012Jun 08 2015We show that quasi-projective Bestvina-Brady groups are fundamental groups of complements to hyperplane arrangements. Furthermore we relate other normal subgroups of right-angled Artin groups to complements to arrangements of hypersurfaces. We thus obtain ... More
Depth of cohomology support loci for quasi-projective varieties via orbifold pencilsMar 12 2012The present paper describes a relation between the quotient of the fundamental group of a smooth quasi-projective variety by its second commutator and the existence of maps to orbifold curves. It extends previously studied cases when the target was a ... More
Orbifold groups, quasi-projectivity and coversMar 07 2012We discuss properties of complex algebraic orbifold groups, their characteristic varieties, and their abelian covers. In particular, we deal with the question of (quasi)-projectivity of orbifold groups. We also prove a structure theorem for the variety ... More
Computation-free presentation of the fundamental group of generic $(p,q)$-torus curvesJan 16 2012In this note, we present a new method for computing fundamental groups of curve complements using a variation of the Zariski-Van Kampen method on general ruled surfaces. As an application we give an alternative (computation-free) proof for the fundamental ... More
Essential coordinate components of characteristic varietiesNov 06 2002In this note we give an algebraic and topological interpretation of essential coordinate components of characteristic varieties and illustrate their importance with an example.
Pencils and Infinite Dihedral covers of P^2Nov 23 2004In this work we study the connection between the existence of finite dihedral covers of the projective plane ramified along an algebraic curve C, infinite dihedral covers, and pencils of curves containing C.
Testing Primordial Black Holes as Dark Matter through LISAOct 29 2018Feb 22 2019The idea that primordial black holes (PBHs) can comprise most of the dark matter of the universe has recently reacquired a lot of momentum. Observational constraints, however, rule out this possibility for most of the PBH masses, with a notable exception ... More
Dipolar-Induced Resonance for Ultracold Bosons in a Quasi-1D Optical LatticeMar 13 2013Aug 16 2013We study the role of the Dipolar-Induced Resonance (DIR) in a quasi-one-dimensional system of ultracold bosons. We first describe the effect of the DIR on two particles in a harmonic trap. Then, we consider a deep optical lattice loaded with ultracold ... More
The Primordial Black Hole Dark Matter - LISA SerendipityOct 29 2018Feb 22 2019The last few years have witnessed a renewed interest in the possibility that primordial black holes (PBHs) constitute the dark matter of the universe. Current observational constraints leave only a few PBH mass ranges for this possibility. One of them ... More
Matter waves in two-dimensional arbitrary atomic crystalsSep 17 2014We present a general scheme to realize a cold-atom quantum simulator of bidimensional atomic crystals. Our model is based on the use of two independently trapped atomic species: the first one, subject to a strong in-plane confinement, constitutes a two-dimensional ... More
One-loop graviton corrections to the curvature perturbation from inflationJul 17 2008Nov 14 2008We compute one-loop corrections to the power spectrum of the curvature perturbation in single-field slow-roll inflation arising from gravitons and inflaton interactions. The quantum corrections due to gravitons to the power spectrum of the inflaton field ... More
Shaking-induced motility in suspensions of soft active particlesNov 19 2009We investigate theoretically the collective dynamics of soft active particles living in a viscous fluid. We focus on a minimal model for active but non-motile particles consisting of $N>1$ elastic dimers deformed by active stresses and interacting hydrodynamically. ... More
No many-scallop theorem: Collective locomotion of reciprocal swimmersMay 05 2008To achieve propulsion at low Reynolds number, a swimmer must deform in a way that is not invariant under time-reversal symmetry; this result is known as the scallop theorem. We show here that there is no many-scallop theorem. We demonstrate that two active ... More
Revisiting the Saffman-Taylor experiment: imbibition patterns and liquid-entrainment transitionsApr 09 2014We revisit the Saffman-Taylor experiment focusing on the forced-imbibition regime where the displacing fluid wets the confining walls. We demonstrate a new class of invasion patterns that do not display the canonical fingering shapes. We evidence that ... More
ISW effect in Unified Dark Matter Scalar Field Cosmologies: an analytical approachJul 28 2007Feb 13 2008We perform an analytical study of the Integrated Sachs-Wolfe (ISW) effect within the framework of Unified Dark Matter models based on a scalar field which aim at a unified description of dark energy and dark matter. Computing the temperature power spectrum ... More
Bonabeau hierarchy models revisitedNov 11 2005What basic processes generate hierarchy in a collective? The Bonabeau model provides us a simple mechanism based on randomness which develops self-organization through both winner/looser effects and relaxation process. A phase transition between egalitarian ... More
Phase transition in the Countdown problemJun 13 2012Here we present a combinatorial decision problem, inspired by the celebrated quiz show called the countdown, that involves the computation of a given target number T from a set of k randomly chosen integers along with a set of arithmetic operations. We ... More
Detecting series periodicity with horizontal visibility graphsAug 08 2011The horizontal visibility algorithm has been recently introduced as a mapping between time series and networks. The challenge lies in characterizing the structure of time series (and the processes that generated those series) using the powerful tools ... More
Emergence of linguistic laws in human voiceOct 09 2016Linguistic laws constitute one of the quantitative cornerstones of modern cognitive sciences and have been routinely investigated in written corpora, or in the equivalent transcription of oral corpora. This means that inferences of statistical patterns ... More
Flowing active liquids in a pipe: Hysteretic response of polar flocks to external fieldsMar 28 2018We investigate the response of colloidal flocks to external fields. We first show that individual colloidal rollers align with external flows as would a classical spin with magnetic fields. Assembling polar active liquids from colloidal rollers, we experimentally ... More
Vacuum Casimir energy densities and field divergences at boundariesOct 06 2014May 14 2015We consider and review the emergence of singular energy densities and field fluctuations at sharp boundaries or point-like field sources in the vacuum. The presence of singular energy densities of a field may be relevant from a conceptual point of view, ... More
Matter Waves in Atomic Artificial GrapheneAug 26 2014We present a new model to realize artificial 2D lattices with cold atoms investigating the atomic artificial graphene: a 2D-confined matter wave is scattered by atoms of a second species trapped around the nodes of a honeycomb optical lattice. The system ... More
Parity breaking signatures from a Chern-Simons coupling during inflation: the case of non-Gaussian gravitational wavesJun 14 2017Jul 25 2017Considering high-energy modifications of Einstein gravity during inflation is an interesting issue. We can constrain the strength of the new gravitational terms through observations of inflationary imprints in the actual universe. In this paper we analyze ... More
Small-Worlds, Mazes and Random WalksNov 18 2002We establish a relationship between the Small-World behavior found in complex networks and a family of Random Walks trajectories using, as a linking bridge, a maze iconography. Simple methods to generate mazes using Random Walks are discussed along with ... More
On the non-Gaussianity from RecombinationNov 28 2008Feb 10 2009The non-linear effects operating at the recombination epoch generate a non-Gaussian signal in the CMB anisotropies. Such a contribution is relevant because it represents a major part of the second-order radiation transfer function which must be determined ... More
Measuring Mutual Information in Random Boolean NetworksSep 03 1999During the last few years an area of active research in the field of complex systems is that of their information storing and processing abilities. Common opinion has it that the most interesting beaviour of these systems is found ``at the edge of chaos'', ... More
Scalar-Tensor Gravity and QuintessenceAug 31 1999Scalar fields with inverse power-law effective potentials may provide a negative pressure component to the energy density of the universe today, as required by cosmological observations. In order to be cosmologically relevant today, the scalar field should ... More
The first digit frequencies of primes and Riemann zeta zeros tend to uniformity following a size-dependent generalized Benford's lawNov 20 2008Prime numbers seem to distribute among the natural numbers with no other law than that of chance, however its global distribution presents a quite remarkable smoothness. Such interplay between randomness and regularity has motivated sci- entists of all ... More
Critical mingling and universal correlations in binary active liquidsDec 08 2016Ensembles of driven or motile bodies moving along opposite directions are generically reported to self-organize into strongly anisotropic lanes. We quantitatively elucidate this behavior for binary mixtures of self-propelled bodies targeting opposite ... More
Geometrically-protected reversibility in hydrodynamic Loschmidt-echo experimentsJul 07 2014We demonstrate an archetypal Loschmidt-echo experiment involving thousands of droplets which interact in a reversible fashion via a viscous fluid. Firstly, we show that, unlike equilibrium systems, periodically driven microfluidic emulsions self-organize ... More
Elastic interaction between "hard'' or "soft" pointwise inclusions on biological membranesFeb 12 2003We calculate the induced elastic-interaction between pointwise membrane inclusions that locally interact up to quadratic order with the membrane curvature tensor. For isotropic inclusions, we recover the usual interaction proportional to the inverse fourth ... More
Lyapunov Exponents in Random Boolean NetworksJun 30 1999A new order parameter approximation to Random Boolean Networks (RBN) is introduced, based on the concept of Boolean derivative. A statistical argument involving an annealed approximation is used, allowing to measure the order parameter in terms of the ... More
Tailoring the interactions between self-propelled bodiesApr 18 2014Apr 23 2014We classify the interactions between self-propelled particles moving at a constant speed from symmetry considerations. We establish a systematic expansion for the two-body forces in the spirit of a multipolar expansion. This formulation makes it possible ... More
Braiding a flock: winding statistics of interacting flying spinsJan 30 2015Jun 26 2015When animal groups move coherently in the form of a flock, their trajectories are not all parallel, the individuals exchange their position in the group. In this Letter we introduce a measure of this mixing dynamics, which we quantify as the winding of ... More
Statistical measures of complexity for strongly interacting systemsAug 27 1999In recent studies, new measures of complexity for nonlinear systems have been proposed based on probabilistic grounds, as the LMC measure (Phys. Lett. A {\bf 209} (1995) 321) or the SDL measure (Phys. Rev. E {\bf 59} (1999) 2). All these measures share ... More
On the p-th root of a p-adic numberAug 16 2007We give a sufficient and necessary condition for a p-adic integer to have p-th root in the ring of p-adic integers. The same condition holds clearly for residues modulo p^k. We give a proof that Fermat's last theorem is false for p-adic integers and for ... More
An analytical expression for the third coefficient of the Jones PolynomialJun 22 1994An analytical expression for the third coefficient of the Jones Polynomial $P_J[\gamma,\, {\em e}^q]$ in the variable $q$ is reported. Applications of the result in Quantum Gravity are considered.
Walking on exoplanets: Is Star Wars right?Apr 26 2016As the number of detected extrasolar planets increases, exoplanet databases become a valuable resource, confirming some details about planetary formation, but also challenging our theories with new unexpected properties.
On fundamental groups of plane curve complementsJul 29 2015In this paper we discuss some properties of fundamental groups and Alexander polynomials of plane curves. We discuss the relationship of the non-triviality of Alexander polynomials and the notion of (nearly) freeness for irreducible plane curves. We reprove ... More
Modified Mean Field approximation for the Ising ModelJun 08 2009We study a modified mean-field approximation for the Ising Model in arbitrary dimension. Instead of taking a "central" spin, or a small "drop" of fluctuating spins coupled to the effective field of their nearest neighbors as in the Mean-Field or the Bethe-Peierls-Weiss ... More
Unified Dark Matter Scalar Field ModelsAug 03 2010Mar 14 2011In this work we analyze and review cosmological models in which the dynamics of a single scalar field accounts for a unified description of the Dark Matter and Dark Energy sectors, dubbed Unified Dark Matter (UDM) models. In this framework, we consider ... More
Cosmic Microwave Background Anisotropies up to Second OrderMar 19 2007Apr 05 2007These lecture notes present the computation of the full system of Boltzmann equations describing the evolution of the photon, baryon and cold dark matter fluids up to second order in perturbation theory, as recently studied in (Bartolo, Matarrese & Riotto ... More
Canonical quantization of constrained theories on discrete space-time latticesMay 29 2002We discuss the canonical quantization of systems formulated on discrete space-times. We start by analyzing the quantization of simple mechanical systems with discrete time. The quantization becomes challenging when the systems have anholonomic constraints. ... More
Primordial trispectra and CMB spectral distortionsNov 04 2015Mar 16 2016We study the $TT\mu$ bispectrum, generated by correlations between Cosmic Microwave Background temperature (T) anisotropies and chemical potential ($\mu$) distortions, and we analyze its dependence on primordial local trispectrum parameters $g_{\rm NL}$ ... More
Phase transition in a stochastic prime number generatorJul 13 2007We introduce a stochastic algorithm that acts as a prime number generator. The dynamics of such algorithm gives rise to a continuous phase transition which separates a phase where the algorithm is able to reduce a whole set of integers into primes and ... More
Effects of intermediate bound states in dynamic force spectroscopyJul 10 2003We revisit here some aspects of the interpretation of dynamic force spectroscopy experiments. The standard theory predicts a typical unbinding force $f^*$ linearly proportional to the logarithm of the loading rate $r$ when a single energetical barrier ... More
The Effective Field Theory of Inflation Models with Sharp FeaturesJul 12 2013Oct 07 2013We describe models of single-field inflation with small and sharp step features in the potential (and sound speed) of the inflaton field, in the context of the Effective Field Theory of Inflation. This approach allows us to study the effects of features ... More
Consistent and mimetic discretizations in general relativityApr 12 2004Nov 01 2004A discretization of a continuum theory with constraints or conserved quantities is called mimetic if it mirrors the conserved laws or constraints of the continuum theory at the discrete level. Such discretizations have been found useful in continuum mechanics ... More
Spontaneous autophoretic motion of isotropic particlesNov 29 2012Jun 27 2013Suspended colloidal particles interacting chemically with a solute are able to self-propel by autophoretic motion when they are asymmetrically patterned (Janus colloids). Here we demonstrate that the chemical anisotropy is not a necessary condition to ... More
Feigenbaum graphs at the onset of chaosMay 09 2012Oct 31 2012We analyze the properties of the self-similar network obtained from the trajectories of unimodal maps at the transition to chaos via the horizontal visibility (HV) algorithm. We first show that this network is uniquely determined by the encoded sequence ... More
Hamiltonian traffic dynamics in microfluidic-loop networksSep 28 2011Recent microfluidic experiments revealed that large particles advected in a fluidic loop display long-range hydrodynamic interactions. However, the consequences of such couplings on the traffic dynamics in more complex networks remain poorly understood. ... More
Phase Transition in Random Networks with Multiple StatesJul 23 1999The critical boundaries separating ordered from chaotic behavior in randomly wired S-state networks are calculated. These networks are a natural generalization of random Boolean nets and are proposed as on extended approach to genetic regulatory systems, ... More
Number theoretic example of scale-free topology inducing self-organized criticalitySep 12 2008Sep 17 2008In this work we present a general mechanism by which simple dynamics running on networks become self-organized critical for scale free topologies. We illustrate this mechanism with a simple arithmetic model of division between integers, the division model. ... More
Irreversibility and self-organisation in hydrodynamic echo experimentsNov 17 2008Dec 11 2008We discuss the reversible-irreversible transition in low-Reynolds hydrodynamic systems driven by external cycling actuation. We introduce a set of models with no auto-organisation, and show that a sharp crossover is obtained between a Lyapunov regime ... More
Angular dependence of primordial trispectra and CMB spectral distortionsJul 05 2016Oct 11 2016Under the presence of anisotropic sources in the inflationary era, the trispectrum of the primordial curvature perturbation has a very specific angular dependence between each wavevector that is distinguishable from the one encountered when only scalar ... More
Convexity of domains of Riemannian manifoldsApr 12 2000In this paper we analyze the problem of the geodesic connectedness of subsets of Riemannian manifolds. By using variational methods, the geodesic connectedness of open domains (whose boundaries can be not differentiable and not convex) of a smooth Riemannian ... More
Speech earthquakes: scaling and universality in human voiceAug 05 2014Speech is a distinctive complex feature of human capabilities. In order to understand the physics underlying speech production, in this work we empirically analyse the statistics of large human speech datasets ranging several languages. We first show ... More
Emergent vortices in populations of colloidal rollersJun 26 2015Coherent vortical motion has been reported in a wide variety of populations including living organisms (bacteria, fishes, human crowds) and synthetic active matter (shaken grains, mixtures of biopolymers), yet a unified description of the formation and ... More
The Trispectrum in the Effective Theory of Inflation with Galilean symmetryMay 03 2013We calculate the trispectrum of curvature perturbations for a model of inflation endowed with Galilean symmetry at the level of the fluctuations around an FRW background. Such a model has been shown to posses desirable properties such as unitarity (up ... More
Velocity Selection for Propagating Fronts in SuperconductorsJul 03 1996Using the time-dependent Ginzburg-Landau equations we study the propagation of planar fronts in superconductors, which would appear after a quench to zero applied magnetic field. Our numerical solutions show that the fronts propagate at a unique speed ... More
Halos of Unified Dark Matter Scalar FieldDec 04 2007Dec 05 2007We investigate the static and spherically symmetric solutions of Einstein's equations for a scalar field with non-canonical kinetic term, assumed to provide both the dark matter and dark energy components of the Universe. In particular, we give a prescription ... More
CMB Anisotropies at Second-Order II: Analytical ApproachOct 04 2006Jan 30 2007We provide an analytical approach to the second-order Cosmic Microwave Background (CMB) anisotropies generated by the non-linear dynamics taking place at last scattering. We study the acoustic oscillations of the photon-baryon fluid in the tight coupling ... More