Results for "Patricia de la Presa"

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Gold Nanoparticles Generated in Ethosome Bilayers, As Revealed by Cryo-Electron-TomographyNov 20 2009Gold nanoparticles have been synthesized inside ethosomes, vesicles composed of phospholipid, ethanol and water, which could be very efficient not only in delivery probes to the skin but also as diagnostic and therapeutic multimodal agents. High efficiency ... More
Versatile Hall magnetometer with variable sensitivity assembly for characterization of the magnetic properties of nanoparticlesMay 14 2019A Hall magnetometer with variable sensitivity is constructed to measure the magnetic properties of magnetic nanoparticles manufactured by different methods. This novel magnetometer can also be used to measure bulk materials and samples in liquids. The ... More
Magnetic capsules for NMR imaging: Effect of magnetic nanoparticles spatial distribution and aggregationMar 13 2011Magnetic and NMR relaxivity properties of {\gamma}-Fe2O3 nanoparticles embedded into the walls of polyelectrolyte multilayer capsules and freely dispersed in a sodium borate buffer solution have been investigated. The different geometric distribution ... More
Synthesis and characterization of FePt/Au core-shell nanoparticlesNov 25 2009In this work, the structural and magnetic properties of the gold-coated FePt nanoparticles synthesized from high-temperature solution phase are presented. The amount of gold was optimized to obtain most of the FePt particles coated. The particle diameter ... More
Hyperthermia HeLa cell treatment with silica coated manganese oxide nanoparticlesJul 19 2009Nov 21 2009The effect of a high frequency alternating magnetic field on HeLa tumour cells incubated with ferromagnetic nanoparticles of manganese oxide perovskite La0.56(SrCa)0.22MnO3 have been studied. The particles were subjected to a size selection process and ... More
A tale of a rich cluster at z$\sim$0.8 as seen by the Star Formation Histories of its ETGsOct 20 2014We present a detailed stellar population analysis for a sample of 24 early-type galaxies belonging to the rich cluster RXJ0152.7-1357 at z=0.83. We have derived the age, metallicity, abundance pattern and star formation history for each galaxy individually, ... More
Polarized synchrotron emissionJul 20 2006Galactic synchrotron emission represents the most relevant foreground contamination in cosmic microwave background (CMB) anisotropy observations at angular scales $\theta \gsim 1^\circ$ and frequencies $\nu \lsim 70$ GHz. The accurate understanding of ... More
Young ages and other intriguing properties of massive compact galaxies in the Local UniverseMar 12 2012We characterize the kinematics, morphology, stellar populations and star formation histories of a sample of massive compact galaxies in the nearby Universe, which might provide a closer look to the nature of their high redshift (z > 1.0) massive counterparts. ... More
A class of non-fillable contact structuresNov 13 2006Nov 28 2006A geometric obstruction, the so called "plastikstufe", for a contact structure to not being fillable has been found by K. Niederkruger. This generalizes somehow the concept of overtwisted structure to dimensions higher than 3. This paper elaborates on ... More
Submanifolds of symplectic manifolds with contact borderJul 06 2000We construct symplectic submanifolds of symplectic manifolds with contact border. The boundary of such submanifolds is shown to be a contact submanifold of the contact border. We also give a topological characterization of the constructed submanifolds ... More
Lefschetz type pencils on contact manifoldsJul 06 2000We define the concept of Lefschetz contact pencil and we show the existence of such structures on any contact manifold. The main idea of the proof is a generalization of the Donaldson arguments used in the symplectic case. We will analyze some of the ... More
On norms taking integer values on the integer latticeApr 06 2016We present a new proof of Thurston's theorem that the unit ball of a seminorm on $\mathbf{R}^d$ taking integer values on $\mathbf{Z}^d$ is a polyhedra defined by finitely many inequalities with integer coefficients.
Spaces of closed subgroups of locally compact groupsJul 13 2008Nov 12 2008The set $\Cal C(G)$ of closed subgroups of a locally compact group $G$ has a natural topology which makes it a compact space. This topology has been defined in various contexts by Vietoris, Chabauty, Fell, Thurston, Gromov, Grigorchuk, and many others. ... More
The large charge expansion at large NMay 01 2018The scaling dimensions of charged operators in conformal field theory have recently been predicted to exhibit universal behavior in the large charge limit. We verify this behavior in the 2+1 dimensional CPN model. Specifically, we numerically compute ... More
An introduction to joinings in ergodic theoryJul 21 2005Dec 22 2005Since their introduction by Furstenberg in 1967, joinings have proved a very powerful tool in ergodic theory. We present here some aspects of the use of joinings in the study of measurable dynamical systems, emphasizing on - the links between the existence ... More
A shorter proof of a result by Potapov and Sukochev on Lipschtiz functions on $S^p$May 07 2009In this short note we give a short proof of a recent result by Potapov and Sukochev (arXiv:0904.4095v1), stating that a Lipschitz function on the real line remains Lipschitz on the (self-adjoint part of) non-commutative $L_p$ spaces with $1<p<\infty$. ... More
Strong property (T) for higher rank latticesNov 06 2017Oct 04 2018We prove that every lattice in a product of higher rank simple Lie groups or higher rank simple algebraic groups over local fields has Vincent Lafforgue's strong property (T). Over non-archimedean local fields, we also prove that they have strong Banach ... More
Coloring GridsSep 18 2014A structure $\mathcal{A}=\left(A;E_i\right)_{i\in n}$ where each $E_i$ is an equivalence relation on $A$ is called an $n$-grid if any two equivalence classes coming from distinct $E_i$'s intersect in a finite set. A function $\chi: A \to n$ is an acceptable ... More
A local characterization of Kazhdan projections and applicationsApr 06 2016Feb 22 2018We give a local characterization of the existence of Kazhdan projections for arbitary families of Banach space representations of a compactly generated locally compact group $G$. We also define and study a natural generalization of the Fell topology to ... More
Strong Haagerup inequality with operator coefficientsMar 02 2009Jun 10 2009We prove a Strong Haagerup inequality with operator coefficients. If for an integer d, H_d denotes the subspace of the von Neumann algebra of a free group F_I spanned by the words of length d in the generators (but not their inverses), then we provide ... More
Brouwer degree, domination of manifolds, and groups presentable by productsSep 21 2016For oriented connected closed manifolds of the same dimension, there is a transitive relation: $M$ dominates $N$, or $M \ge N$, if there exists a continuous map of non-zero degree from $M$ onto $N$. Section 1 is a reminder on the notion of degree (Brouwer, ... More
Towards Strong Banach property (T) for SL(3,R)Jul 09 2013Jul 04 2014We prove that SL(3,R) has Strong Banach property (T) in Lafforgue's sense with respect to the Banach spaces that are $\theta>0$ interpolation spaces (for the complex interpolation method) between an arbitrary Banach space and a Banach space with sufficiently ... More
Bootstrapping mixed correlators in the 2D Ising modelApr 22 2019Bootstrapping mixed correlators in three dimensional conformal field theories with a $\mathbb Z_2$ global symmetry has previously led to a closed allowed region in ($\Delta_\sigma$, $\Delta_\epsilon$) space surrounding the 3D Ising model. We repeat that ... More
Numerical study of a flow of regular planar curves that develop singularities at finite timeDec 05 2008In this paper, we will study the following geometric flow, obtained by Goldstein and Petrich while considering the evolution of a vortex patch in the plane under Euler's equations, X_t = -k_s n - (1/2) k^2 T, with s being the arc-length parameter and ... More
The Fuglede-Kadison determinant, theme and variationsJul 06 2011Jul 07 2012We review the definition of determinants for finite von Neumann algebras, due to Fuglede and Kadison (1952), and a generalisation for appropriate groups of invertible elements in Banach algebras, from a paper by Skandalis and the author (1984). After ... More
Extraction of the $i^{th}$ Elementary Symmetric Polynomial from a Product in Binomial Form ${{m_1+...+m_n}\choose i}$Sep 17 2014The $i^{th}$ elementary symmetric polynomial of the set of $n$ variables $\mathcal{R}=\{m_1,m_2,m_3,...,m_n\}$ is isolated from the expansion of the $i^{th}$ binomial product ${{m_1+...+m_n}\choose i}$ via an alternating sum.
An extension which is relatively twofold mixing but not threefold mixingJul 27 2004We give an example of a dynamical system which is mixing relative to one of its factors, but for which relative mixing of order three does not hold.
Complete isometries between subspaces of noncommutative Lp-spacesJul 03 2007Dec 04 2007We prove some noncommutative analogues of a theorem by Plotkin and Rudin about isometries between subspaces of Lp-spaces. Let 0<p<\infty, p not an even integer. The main result of this paper states that in the category of unital subspaces of noncommutative ... More
Operator space valued Hankel matricesSep 28 2009If $E$ is an operator space, the non-commutative vector valued $L^p$ spaces $S^p[E]$ have been defined by Pisier for any $1 \leq p \leq \infty$. In this paper a necessary and sufficient condition for a Hankel matrix of the form $(a_{i+j})_{0 \le i,j}$ ... More
On dually almost MRD codesDec 13 2016In this paper we define and study a family of codes which come close to be MRD codes, so we call them AMRD codes (almost MRD). An AMRD code is a code with rank defect equal to 1. AMRD codes whose duals are AMRD are called dually AMRD. Dually AMRD codes ... More
Topologie, théorie des groupes et problèmes de décision. Célébration d'un article de Max Dehn de 1910Apr 05 2010Jun 25 2010This paper, in French, is a celebration of Max Dehn, and an essay of describing some of his results published in the beginning of the 1910's, and their offspring. It has been written up for a winter school in Les Diablerets, March 7-12, 2010: Geometry, ... More
2-fold and 3-fold mixing: why 3-dot-type counterexamples are impossible in one dimensionMar 07 2006V.A. Rohlin asked in 1949 whether 2-fold mixing implies 3-fold mixing for a stationary process indexed by Z, and the question remains open today. In 1978, F. Ledrappier exhibited a counterexample to the 2-fold mixing implies 3-fold mixing problem, the ... More
Identification of a Proliferation Gene Cluster Associated with HPV E6/E7 Expression Level and Viral DNA Load in Invasive Cervical CarcinomaNov 15 2005Specific HPV DNA sequences are associated with more than 90% of invasive carcinomas of the uterine cervix. Viral E6 and E7 oncogenes are key mediators in cell transformation by disrupting TP53 and RB pathways. To investigate molecular mechanisms involved ... More
The Morphology of Hα emission in CALIFA galaxiesOct 19 2018We have determined the H{\alpha} emission line radial profiles for a sample of 86 face-on galaxies observed in the CALIFA survey and analyzed with the Pipe3D pipeline. From a visual analysis we propose a two step classification of these profiles. Initially, ... More
The Evolution of Primordial Binary Open Star Clusters: Mergers, Shredded Secondaries and Separated TwinsJun 27 2010Jun 29 2010The basic properties of the candidate binary cluster population in the Magellanic Clouds and Galaxy are similar. The fraction of candidate binary systems is $\sim$10% and the pair separation histogram exhibits a bimodal distribution commonly attributed ... More
A trio of horseshoes: past, present and future dynamical evolution of Earth co-orbital asteroids 2015 XX169, 2015 YA and 2015 YQ1Mar 08 2016It is widely accepted that a quasi-steady-state flux of minor bodies moving in and out of the co-orbital state with the Earth may exist. Some of these objects are very good candidates for future in situ study due to their favourable dynamical properties. ... More
Far from random: dynamical groupings among the NEO populationDec 07 2015Dec 19 2015Among the near-Earth object (NEO) population there are comets and active asteroids which are sources of fragments that initially move together; in addition, some NEOs follow orbits temporarily trapped in a web of secular resonances. These facts contribute ... More
Asteroid 2015 DB216: a recurring co-orbital companion to UranusJul 27 2015Aug 10 2015Minor bodies trapped in 1:1 co-orbital resonances with a host planet could be relevant to explain the origin of captured satellites. Among the giant planets, Uranus has one of the smallest known populations of co-orbitals, three objects, and all of them ... More
2MASS J06562998+3002455: Not a Cool White Dwarf Candidate, but a Population II Halo StarMay 31 20182MASS J06562998+3002455 or PSS 309-6 is a high proper-motion star that was discovered during a survey with the 2.1 m telescope at Kitt Peak National Observatory. Here, we reevaluate the status of this interesting star using Gaia DR2. Our results strongly ... More
Kozai-Lidov Resonant Behavior among Atira-class AsteroidsJun 01 2018Atira-class asteroids have aphelia greater than 0.718 au and smaller than 0.983 au. It has been found that the orbits of many of them remain relatively stable for at least 1 Myr, but it is unclear what can make them so stable when they cross the orbit ... More
Transient Co-orbitals of Venus: An UpdateNov 01 2017Venus has no known satellites, but has four known co-orbitals: (322756) 2001 CK32, 2002 VE68, 2012 XE133, and 2013 ND15. Here, we present numerical evidence suggesting that 2015 WZ12 is a possible Venus co-orbital; it might have been until recently a ... More
Pole, Pericenter, and Nodes of the Interstellar Minor Body A/2017 U1Nov 01 2017Here, we explore some peculiar orbital features of the recently discovered asteroid A/2017 U1, which is a clear outlier when considering the average value of the eccentricity of known hyperbolic comets. As for the orientation of its orbit in space, the ... More
Dynamical evolution of near-Earth asteroid 1991 VGSep 27 2017Nov 18 2017The discovery of 1991 VG on 1991 November 6 attracted an unprecedented amount of attention as it was the first near-Earth object (NEO) ever found on an Earth-like orbit. At that time, it was considered by some as the first representative of a new dynamical ... More
On the dynamical evolution of 2002 VE68Aug 22 2012Minor planet 2002 VE68 was identified as a quasi-satellite of Venus shortly after its discovery. At that time its data-arc span was only 24 days, now it is 2,947 days. Here we revisit the topic of the dynamical status of this remarkable object as well ... More
Large retrograde Centaurs: visitors from the Oort cloud?Jun 05 2014Among all the asteroid dynamical groups, Centaurs have the highest fraction of objects moving in retrograde orbits. The distribution in absolute magnitude, H, of known retrograde Centaurs with semi-major axes in the range 6-34 AU exhibits a remarkable ... More
Extreme trans-Neptunian objects and the Kozai mechanism: signalling the presence of trans-Plutonian planetsJun 03 2014Jun 16 2014The existence of an outer planet beyond Pluto has been a matter of debate for decades and the recent discovery of 2012 VP113 has just revived the interest for this controversial topic. This Sedna-like object has the most distant perihelion of any known ... More
Asteroid 2012 XE133: a transient companion to VenusMar 15 2013Apr 19 2013Apart from Mercury that has no known co-orbital companions, Venus remains as the inner planet that hosts the smallest number of known co-orbitals (two): (322756) 2001 CK32 and 2002 VE68. Both objects have absolute magnitudes 18 < H < 21 and were identified ... More
Four temporary Neptune co-orbitals: (148975) 2001 XA255, (310071) 2010 KR59, (316179) 2010 EN65, and 2012 GX17Oct 12 2012Numerical simulations suggest that Neptune primordial co-orbitals may outnumber the equivalent population hosted by Jupiter, yet the objects remain elusive. Since the first discovery in 2001 just 10 minor planets have been identified as Neptune co-orbitals. ... More
Plutino 15810 (1994 JR1), an accidental quasi-satellite of PlutoSep 14 2012In the solar system, quasi-satellites move in a 1:1 mean motion resonance going around their host body like a retrograde satellite but their mutual separation is well beyond the Hill radius and the trajectory is not closed as they orbit the Sun not the ... More
Conservation of Energy-Momentum in Teleparallel GravityMay 25 2009Jul 10 2009In a well-known paper arXiv:gr-qc/0003100 V.C. de Andrade, L. C. T. Guillen and J.G. Pereira defined a conserved gauge current, however they stated that: `` This is, we believe the farthest one can go in the direction of a tensorial definition for the ... More
Limitations of cosmography in extended theories of gravityApr 25 2016The cosmographic approach, which only relies upon the homogeneity and isotropy of the Universe on large scales, has become an essential tool in dealing with an increasing number of theoretical possibilities for explaining the late-time acceleration of ... More
Generalization of the second trace form of central simple algebras in characteristic twoOct 09 2004Let F be a field with characteristic two. We generalize the second trace form for central simple algebras with odd degree over F. We determine the second trace form and the Arf invariant and Clifford invariant for tensor products of central simple algebras. ... More
Dynamically correlated minor bodies in the outer Solar systemOct 20 2017Dec 04 2017The organization of the orbits of most minor bodies in the Solar system seems to follow random patterns, the result of billions of years of chaotic dynamical evolution. Much as heterogeneous orbital behaviour is ubiquitous, dynamically coherent pairs ... More
Asteroid 2017 FZ2 et al.: signs of recent mass-shedding from YORP?Sep 27 2017The first direct detection of the asteroidal YORP effect, a phenomenon that changes the spin states of small bodies due to thermal reemission of sunlight from their surfaces, was obtained for (54509) YORP 2000 PH5. Such an alteration can slowly increase ... More
Evidence for a possible bimodal distribution of the nodal distances of the extreme trans-Neptunian objects: avoiding a trans-Plutonian planet or just plain bias?Jun 21 2017Aug 07 2017It is a well-known fact that the presence of a massive perturber interacting with a population of minor bodies following very eccentric orbits can strongly affect the distribution of their nodal distances. The details of this process have been explored ... More
Asteroid 2014 OL339: yet another Earth quasi-satelliteSep 19 2014Oct 07 2014Our planet has one permanently bound satellite -the Moon-, a likely large number of mini-moons or transient irregular natural satellites, and three temporary natural retrograde satellites or quasi-satellites. These quasi-moons -(164207) 2004 GU9, (277810) ... More
Reconstructing the Chelyabinsk event: pre-impact orbital evolutionMay 28 2014Jun 11 2014The Chelyabinsk superbolide was the largest known natural object to enter the Earth's atmosphere since the Tunguska event in 1908 and it has become a template to understand, manage and mitigate future impacts. Although the event has been documented in ... More
The Chelyabinsk superbolide: a fragment of asteroid 2011 EO40?Jul 30 2013Aug 10 2013Bright fireballs or bolides are caused by meteoroids entering the Earth's atmosphere at high speed. On 2013 February 15, a superbolide was observed in the skies near Chelyabinsk, Russia. Such a meteor could be the result of the decay of an asteroid and ... More
Finding Planet Nine: a Monte Carlo approachMar 21 2016Apr 04 2016Planet Nine is a hypothetical planet located well beyond Pluto that has been proposed in an attempt to explain the observed clustering in physical space of the perihelia of six extreme trans-Neptunian objects or ETNOs. The predicted approximate values ... More
From horseshoe to quasi-satellite and back again: the curious dynamics of Earth co-orbital asteroid 2015 SO2Nov 26 2015Dec 02 2015Earth co-orbitals of the horseshoe type are interesting objects to study for practical reasons. They are relatively easy to access from our planet and that makes them attractive targets for sample return missions. Here, we show that near-Earth asteroid ... More
Recent multi-kiloton impact events: are they truly random?Sep 01 2014Oct 29 2014It is customarily assumed that Earth-striking meteoroids are completely random, and that all the impacts must be interpreted as uncorrelated events distributed according to Poisson statistics. If this is correct, their impact dates must be uniformly spread ... More
On the angular distribution of IceCube high-energy eventsAug 06 2015Aug 13 2015The detection of high-energy astrophysical neutrinos of extraterrestrial origin by the IceCube neutrino observatory in Antarctica has opened a unique window to the cosmos that may help to probe both the distant Universe and our cosmic backyard. The arrival ... More
Dancing with Venus in the shadow of the Earth: a pair of genetically related near-Earth asteroids trapped in a mean-motion resonanceNov 12 2018Dec 04 2018YORP-induced fission events may form dynamically coherent pairs or even families of asteroids. The outcome of this process is well documented among members of the main asteroid belt, but not in the case of the near-Earth asteroid (NEA) population because ... More
Searching for the lost Unicorn: a prominent feature in the radial velocity distribution of stars in Vela from Gaia DR2 dataAug 29 2018Sep 11 2018Stellar streams are ubiquitous in the Galactic halo and they can be used to improve our understanding of the formation and evolution of the Milky Way as a whole. The so-called Monoceros Ring might have been the result of satellite accretion. Guglielmo ... More
Understanding the evolution of Atira-class asteroid 2019 AQ3, a major step towards the future discovery of the Vatira populationMay 21 2019May 22 2019Orbiting the Sun at an average distance of 0.59 au and with the shortest aphelion of any known minor body, at 0.77 au, the Atira-class asteroid 2019 AQ3 may be an orbital outlier or perhaps an early indication of the presence of a new population of objects: ... More
A quantum arrow of timeNov 09 2014It is shown that position-momentum correlation is never decreasing and therefore it is a good candidate as a quantum arrow of time devoid of shortcomings of other proposals.
A one-dimensional lattice model for a quantum mechanical free particleMay 10 1999Two types of particles, A and B with their corresponding antiparticles, are defined in a one dimensional cyclic lattice with an odd number of sites. In each step of time evolution, each particle acts as a source for the polarization field of the other ... More
The quantum field theory interpretation of quantum mechanicsMar 02 2015It is shown that adopting the \emph{Quantum Field} ---extended entity in space-time build by dynamic appearance propagation and annihilation of virtual particles--- as the primary ontology the astonishing features of quantum mechanics can be rendered ... More
Relativity of representations in quantum mechanicsSep 25 2001Only the position representation is used in introductory quantum mechanics and the momentum representation is not usually presented until advanced undergraduate courses. To emphasize the relativity of the representations of the abstract formulation of ... More
Teleparallel DarknessOct 08 2013Feb 15 2014First a review of Teleparallel theory is done with special emphasis in the derivation of conservation equations within this theory and in particular of energy-momentum conservation. Given that we are allowed to speak about the existence of negative energy, ... More
Spectral methods for bivariate Markov processes with diffusion and discrete components and a variant of the Wright-Fisher modelJul 19 2011The aim of this paper is to study differential and spectral properties of the infinitesimal operator of two dimensional Markov processes with diffusion and discrete components. The infinitesimal operator is now a second-order differential operator with ... More
Distances on the tropical line determined by two pointsOct 01 2013Apr 10 2014Let $p',q'\in R^n$. Write $p'\sim q'$ if $p'-q'$ is a multiple of $(1,\ldots,1)$. Two different points $p$ and $q$ in $R^n/\sim$ uniquely determine a tropical line $L(p,q)$, passing through them, and stable under small perturbations. This line is a balanced ... More
On tropical Kleene star matrices and alcoved polytopesOct 05 2012Sep 20 2013In this paper we give a short, elementary proof of a known result in tropical mathematics, by which the convexity of the column span of a zero--diagonal real matrix $A$ is characterized by $A$ being a Kleene star. We give applications to alcoved polytopes, ... More
Quantum annealingApr 09 2014Brief description on the state of the art of some local optimization methods: Quantum annealing Quantum annealing (also known as alloy, crystallization or tempering) is analogous to simulated annealing but in substitution of thermal activation by quantum ... More
On the Third-Degree Continuous Cohomology of Simple Lie GroupsNov 14 2018We show that the class of connected, simple Lie groups that have non-vanishing third-degree continuous cohomology with trivial $\mathbb{R}$-coefficients consists precisely of all simple complex Lie groups and of $\widetilde{\mathrm{SL}_2(\mathbb{R})}$. ... More
Understanding the evolution of Atira-class asteroid 2019 AQ3, a major step towards the future discovery of the Vatira populationMay 21 2019Orbiting the Sun at an average distance of 0.59 au and with the shortest aphelion of any known minor body, at 0.77 au, the Atira-class asteroid 2019 AQ3 may be an orbital outlier or perhaps an early indication of the presence of a new population of objects: ... More
Asteroid (469219) 2016 HO3, the smallest and closest Earth quasi-satelliteAug 04 2016Aug 16 2016A number of Earth co-orbital asteroids experience repeated transitions between the quasi-satellite and horseshoe dynamical states. Asteroids 2001 GO2, 2002 AA29, 2003 YN107 and 2015 SO2 are well-documented cases of such a dynamical behaviour. These transitions ... More
The analemma criterion: accidental quasi-satellites are indeed true quasi-satellitesJul 22 2016Aug 05 2016In the Solar system, a quasi-satellite is an object that follows a heliocentric path with an orbital period that matches almost exactly with that of a host body (planetary or not). The trajectory is of such nature that, without being gravitationally attached, ... More
Infrequent visitors of the Kozai kind: the dynamical lives of 2012 FC71, 2014 EK24, 2014 QD364, and 2014 URJun 04 2015Jun 16 2015Context. Asteroids with semi-major axes very close to that of a host planet can avoid node crossings when their nodal points are at perihelion and at aphelion. This layout protects the asteroids from close encounters, and eventual collisions, with the ... More
LP 543-25: a rare low-mass runaway disk starMay 16 2018LP 543-25 or PSS 544-7 is a high proper-motion star located 458 pc from the Sun in the constellation of Canis Minor; it has been argued that it could be a candidate cannonball star ejected by a star cluster. Here, we revisit the issue of the kinematics ... More
Colliding with G2 near the Galactic Centre: a geometrical approachJun 20 2013Jul 04 2013The object G2 will pass within nearly 100 au from Sgr A* in 2014. Due to its very short periapse, the study of the dynamical evolution of this object in the short-term future may offer some insight into the region surrounding the supermassive black hole ... More
Waiting to make an impact: A probable excess of near-Earth asteroids in 2018 LA-like orbitsNov 28 2018Jan 08 2019Context. The discovery and tracking of 2018 LA marks only the third instance in history that the parent body of a fireball has been identified before its eventual disintegration in our atmosphere. The subsequent recovery of meteorites from 2018 LA was ... More
Pre-airburst Orbital Evolution of Earth's Impactor 2018 LA: An UpdateJul 22 2018Apollo meteoroid 2018 LA has become only the third natural object ever to be discovered prior to causing a meteor airburst and just the second one to have its meteorites recovered (at Botswana's Central Kalahari Game Reserve). Here, we use the latest ... More
A resonant family of dynamically cold small bodies in the near-Earth asteroid beltMay 13 2013May 27 2013Near-Earth objects (NEOs) moving in resonant, Earth-like orbits are potentially important. On the positive side, they are the ideal targets for robotic and human low-cost sample return missions and a much cheaper alternative to using the Moon as an astronomical ... More
Three new stable L5 Mars TrojansMar 01 2013Mar 29 2013Mars was second to Jupiter in being recognized as the host of a population of Trojan minor bodies. Since 1990, five asteroids - 5261 Eureka, (101429) 1998 VF31, (121514) 1999 UJ7, 2001 DH47 and (311999) 2007 NS2 - have been identified as Mars Trojans, ... More
Asteroid 2014 YX49: a large transient Trojan of UranusJan 19 2017Feb 06 2017In the outer Solar system, primordial Trojan asteroids may have remained dynamically stable for billions of years. Several thousands of them accompany Jupiter in its journey around the Sun and a similarly large population may be hosted by Neptune. In ... More
A Fruit of a Different Kind: 2015 BP519 as an Outlier among the Extreme Trans-Neptunian ObjectsSep 07 2018A number of intriguing patterns have been identified in the distributions of the orbital elements of the known extreme trans-Neptunian objects or ETNOs --those with semimajor axis greater than 150 au and perihelion distance greater than 30 au. The announcement ... More
On the Pre-impact Orbital Evolution of 2018 LA, Parent Body of the Bright Fireball Observed over Botswana on 2018 June 2Jun 13 2018On 2018 June 2, meteoroid 2018 LA became the third natural body ever to be observed before entering our atmosphere ---small asteroids 2014 AA and 2008 TC3 had stricken the Earth on 2014 January 2 and 2008 October 7, respectively. Here, we explore the ... More
An independent confirmation of the future flyby of Gliese 710 to the solar system using Gaia DR2May 07 2018Gliese 710 is a K7V star located 19 pc from the Sun in the constellation of Serpens Cauda, which is headed straight for the solar system. Berski & Dybczynski (2016) used data from Gaia DR1 to show that this star will be 13366 AU from the Sun in 1.35 Myr ... More
Comet C/2017 K2 (PANSTARRS): dynamically old or new?Apr 19 2018At discovery time, C/2017 K2 (PANSTARRS) was the second most distant inbound active comet ever observed. It has been argued that this object is in the process of crossing the inner Solar System for the first time, but other authors have concluded that ... More
Crantor, a short-lived horseshoe companion to UranusJan 04 2013Stable co-orbital motion with Uranus is vulnerable to planetary migration but temporary co-orbitals may exist today. So far only two candidates have been suggested, both moving on horseshoe orbits: 83982 Crantor (2002 GO9) and 2000 SN331. (83982) Crantor ... More
Asteroid 2013 ND15: Trojan companion to Venus, PHA to the EarthJan 20 2014Feb 04 2014Venus has three known co-orbitals: (322756) 2001 CK32, 2002 VE68 and 2012 XE133. The first two have absolute magnitudes 18 < H < 21. The third one, significantly smaller at H = 23.4 mag, is a recent discovery that signals the probable presence of many ... More
On the strong orderability of overtwisted 3-foldsAug 09 2014In this article we address the existence of positive loops of contactomorphisms in overtwisted contact 3-folds. We present a construction of such positive loops in the contact fibered connected sum of certain contact 3-folds along transverse knots. In ... More
Zooming in on the large-scale geometry of locally compact groupsJun 15 2016The purpose of this survey is to describe how locally compact groups can be studied as geometric objects. We will emphasize the main ideas and skip or just sketch most proofs, often referring the reader to our much more detailed book arXiv:1403.3796
Banach space actions and $L^2$-spectral gapMay 09 2017May 16 2018\.{Z}uk proved that if a finitely generated group admits a Cayley graph such that the Laplacian on the links of this Cayley graph has a spectral gap $> \frac{1}{2}$, then the group has property (T), or equivalently, every affine isometric action of the ... More
Decompositions de groupes par produit direct et groupes de CoxeterJul 18 2005We provide examples of groups which are indecomposable by direct product, and more generally which are uniquely decomposable in direct products of indecomposable groups. Examples include Coxeter groups, for which we give an alternative approach to recent ... More
Cómo obtener curvas con formas predeterminadas a partir de circunferenciasJul 26 2013We produce several algebraic curves, some well--known, some new, out of circles, by means of two classical (mutually reciprocal) algebraic methods: blow--down and blow--up.
On expansions of non-abelian free groups by cosets of a finite index subgroupJul 10 2017Let $F$ be a finitely generated non-abelian free group and $Q$ a finite quotient. Denote by $L_Q$ the language obtained by adding unary predicates $P_q$, $q\in Q$ to the language of groups. Using a slight generalization of some of the techniques involved ... More
Classes of forms Witt equivalent to a second trace form over fields of characteristic twoOct 09 2004Let F be a field of characteristic two. We determine all non-hyperbolic quadratic forms over F that are Witt equivalent to a second trace form.
Expanded flow rate range of high-resolution nanoDMAs via improved sample flow injection at the aerosol inlet slitApr 25 2019High-resolution DMAs requiring hundreds of liters per minute of sheath gas flow Q to classify 1 nm particles have not been previously examined and optimized under the modest Q values (tens of liters per minute) needed to classify particles well above ... More