A density--functional study of interfacial properties of colloid--polymer mixtures

Interfacial properties of colloid--polymer mixtures are examined within an effective one--component representation, where the polymer degrees of freedom are traced out, leaving a fluid of colloidal particles interacting via polymer--induced depletion forces. Restriction is made to zero, one and two--body effective potentials, and a free energy functional is used which treats colloid excluded volume correlations within Rosenfeld's Fundamental Measure Theory, and depletion--induced attraction within first--order perturbation theory. This functional allows a consistent treatment of both ideal and interacting polymers. The theory is applied to surface properties near a hard wall, to the depletion interaction between two walls, and to the fluid--fluid interface of demixed colloid--polymer mixtures. The results of the present theory compare well with predictions of a fully two--component representation of mixtures of colloids and ideal polymers (the Asakura--Oosawa model), and allow a systematic investigation of the effects of polymer--polymer interactions on interfacial properties. In particular, the wall surface tension is found to be significantly larger for interacting than for ideal polymers, while the opposite trend is predicted for the fluid--fluid interfacial tension.Comment: submitted to J. Phys. Chem. B, special issue in honour of David Chandle

A Chronology of International Business Cycles Through Non-parametric Decoding

This paper introduces a new empirical strategy for the characterization of business cycles. It combines non-parametric decoding methods that classify a series into expansions and recessions but does not require specification of the underlying stochastic process generating the data. It then uses network analysis to combine the signals obtained from different economic indicators to generate a unique chronology. These methods generate a record of peak and trough dates comparable, and in one sense superior, to the NBER’s own chronology. The methods are then applied to 22 OECD countries to obtain a global business cycle chronology.decoding, hierarchical factor segmentation, network analysis, business cycles

Millimetre continuum observations of comet C/2009 P1 (Garradd)

Little is known about the physical properties of the nuclei of Oort cloud comets. Measuring the thermal emission of a nucleus is one of the few means for deriving its size and constraining some of its thermal properties. We attempted to measure the nucleus size of the Oort cloud comet C/2009 P1 (Garradd). We used the Plateau de Bure Interferometer to measure the millimetric thermal emission of this comet at 157 GHz (1.9 mm) and 266 GHz (1.1 mm). Whereas the observations at 266 GHz were not usable due to bad atmospheric conditions, we derived a 3-sigma upper limit on the comet continuum emission of 0.41 mJy at 157 GHz. Using a thermal model for a spherical nucleus with standard thermal parameters, we found an upper limit of 5.6 km for the radius. The dust contribution to our signal is estimated to be negligible. Given the water production rates measured for this comet and our upper limit, we estimated that Garradd was very active, with an active fraction of its nucleus larger than 50%.Comment: Accepted for publication in Astronomy & Astrophysics. 5 pages, 2 figure

Tingley's problem for p-Schatten von Neumann classes

[EN] Let H and H' be the complex Hilbert spaces. For p is an element of] 1, infinity[\{2} we consider the Banach space C-p(H) of all p-Schatten von Neumann operators, whose unit sphere is denoted by S(C-p(H)). In this paper we prove that every surjective isometry Delta: S(C-p(H)) -> S(C-p(H')) can be extended to a complex linear or to a conjugate linear surjective isometry T: C-p(H) -> C-p(H').The first and third authors were partially supported by the Spanish Ministry of Science, Innovation and Universities (MICINN) and European RegionalDevelopment Fund project no. PGC2018-093332-B-I00, Programa Operativo FEDER 2014-2020 and Consejeria de Economia y Conocimiento de la Junta de Andalucia grant number A-FQM-242-UGR18, and Junta de Andalucia grant FQM375. The second author was partially supported by the project MTM2016-76647-P.Fernández-Polo, FJ.; Jorda Mora, E.; Peralta, AM. (2020). Tingley's problem for p-Schatten von Neumann classes. Journal of Spectral Theory. 10(3):809-841. https://doi.org/10.4171/JST/313S80984110

Supercyclicity of weighted composition operators on spaces of continuous functions

[EN] Our study is focused on the dynamics of weighted composition operators defined on a locally convex space E similar to. (C( X), tp) with X being a topological Hausdorff space containing at least two different points and such that the evaluations {dx : x. X} are linearly independent in E similar to. We prove, when X is compact and E is a Banach space containing a nowhere vanishing function, that a weighted composition operator Cw,. is never weakly supercyclic on E. We also prove that if the symbol. lies in the unit ball of A(D), then every weighted composition operator can never be tp-supercyclic neither on C( D) nor on the disc algebra A(D). Finally, we obtain Ansari-Bourdon type results and conditions on the spectrum for arbitrary weakly supercyclic operators, and we provide necessary conditions for a composition operator to be weakly supercyclic on the space of holomorphic functions defined in non necessarily simply connected planar domains. As a consequence, we show that no composition operator can be weakly supercyclic neither on the space of holomorphic functions on the punctured disc nor in the punctured plane.The authors are very thankful to the referee for his/her careful reading of the manuscript and his/her valuable comments and observations. The first and the second author were supported by MEC, MTM2016-76647-P. The third author was supported by MEC, MTM2016-75963-P and GVA/2018/110.Beltrán-Meneu, MJ.; Jorda Mora, E.; Murillo Arcila, M. (2020). Supercyclicity of weighted composition operators on spaces of continuous functions. Collectanea mathematica. 71(3):493-509. https://doi.org/10.1007/s13348-019-00274-1493509713Albanese, A., Jornet, D.: A note on supercyclic operators in locally convex spaces. Mediterr. J. Math. 16, 107 (2019). https://doi.org/10.1007/s00009-019-1386-yAleman, A., Suciu, L.: On ergodic operator means in Banach spaces. Integr. Equ. Oper. 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Anal. 159, 587–595 (1998)Bourdon, P.S., Shapiro, J.S.: Cyclic Phenomena for Composition Operators, Mem. Am. Math. Soc. 125 (1997), no. 596, Providence, Rhode IslandChan, K.C., Sanders, R.: A weakly hypercyclic operator that is not norm hypercyclic. J. Oper. Theory 52, 39–59 (2004)Duggal, B.P.: Weak supercyclicity: dynamics of paranormal operators. Rend. Circ. Mat. Palermo 65(2), 297–306 (2016)Fernández, C., Galbis, A., Jordá, E.: Dynamics and spectra of composition operators on the Schwartz space. J. Funct. Anal. 274(12), 3503–3530 (2018)Grosse-Erdmann, K.G., Mortini, R.: Universal functions for composition operators with non-automorphic symbol. J. Anal. Math. 107, 355–376 (2009)Cowen, C., MacCluer, B.: Composition Operators on Spaces of Analytic Functions, Studies in Advanced Mathematics. CRC Press, Boca Raton (1995)Garling, D.J.H.: A Course in Mathematical Analysis: Volume III, Complex analysis, Measure and Integration. Cambridge University Press, New York (2013)Garrido, M.I., Jaramillo, J.A.: Variations on the Banach–Stone theorem. In: IV Course on Banach spaces and Operators (Laredo, 2001), Extracta Math. 17, 351–383 (2002)Gadgil, S.: Dynamics on the circle-interval dynamics and rotation number. Reson. J. Sci. Educ. 8(11), 25–36 (2003)Grosse-Erdmann, K.G., Peris, A.: Linear Chaos. Springer, Berlin (2011)Gunatillake, G.: Invertible weighted composition operators. J. Funct. Anal. 261, 831–860 (2011)Herrero, D.A.: Limits of hypercyclic and supercyclic operators. J. Funct. Anal. 99(1), 179–190 (1991)Hilden, H.M., Wallen, L.J.: Some cyclic and non-cyclic vectors of certain operators. Indiana Univ. Math. J. 23, 557–565 (1974)Kalmes, T.: Dynamics of weighted composition operators on function spaces defined by local properties. Studia Math. 249(3), 259–301 (2019)Kamali, Z., Hedayatian, K., Khani Robati, B.: Non-weakly supercyclic weighted composition operators. Abstr. Appl. Anal. Art. 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P/2010 A2 LINEAR II: dynamical dust modelling

P/2010 A2 is an object on an asteroidal orbit that was observed to have an extended tail or debris trail in January 2010. In this work, we fit the outburst of P/2010 A2 with a conical burst model, and verify previous suspicions that this was a one--time collisional event rather than an sustained cometary outburst, implying that P/2010 A2 is not a new Main Belt Comet driven by ice sublimation. We find that the best--fit cone opening angle is about 40 to 50 degrees, in agreement with numerical and laboratory simulations of cratering events. Mapping debris orbits to sky positions suggests that the distinctive arc features in the debris correspond to the same debris cone inferred from the extended dust. From the velocity of the debris, and from the presence of a velocity maximum at around 15 cm/s, we infer that the surface of A2 probably has a very low strength (<1 kPa), comparable to lunar regolith.Comment: 14 pages, 25 figures; accepted by Astronomy and Astrophysic

First electron beam polarization measurements with a Compton polarimeter at Jefferson Laboratory

A Compton polarimeter has been installed in Hall A at Jefferson Laboratory. This letter reports on the first electron beam polarization measurements performed during the HAPPEX experiment at an electron energy of 3.3 GeV and an average current of 40 $\mu$A. The heart of this device is a Fabry-Perot cavity which increased the luminosity for Compton scattering in the interaction region so much that a 1.4% statistical accuracy could be obtained within one hour, with a 3.3% total error

A photon calorimeter using lead tungstate crystals for the CEBAF Hall A Compton polarimeter

The performances of the calorimeter of the Jlab Hall A Compton Polarimeter have been measured using the Mainz tagged photon beam.Comment: 13 page