DeepKSPD: Learning Kernel-matrix-based SPD Representation for Fine-grained Image Recognition

Being symmetric positive-definite (SPD), covariance matrix has traditionally been used to represent a set of local descriptors in visual recognition. Recent study shows that kernel matrix can give considerably better representation by modelling the nonlinearity in the local descriptor set. Nevertheless, neither the descriptors nor the kernel matrix is deeply learned. Worse, they are considered separately, hindering the pursuit of an optimal SPD representation. This work proposes a deep network that jointly learns local descriptors, kernel-matrix-based SPD representation, and the classifier via an end-to-end training process. We derive the derivatives for the mapping from a local descriptor set to the SPD representation to carry out backpropagation. Also, we exploit the Daleckii-Krein formula in operator theory to give a concise and unified result on differentiating SPD matrix functions, including the matrix logarithm to handle the Riemannian geometry of kernel matrix. Experiments not only show the superiority of kernel-matrix-based SPD representation with deep local descriptors, but also verify the advantage of the proposed deep network in pursuing better SPD representations for fine-grained image recognition tasks

Chemical Segregation in Hot Cores With Disk Candidates: An investigation with ALMA

In the study of high-mass star formation, hot cores are empirically defined stages where chemically rich emission is detected toward a massive YSO. It is unknown whether the physical origin of this emission is a disk, inner envelope, or outflow cavity wall and whether the hot core stage is common to all massive stars. We investigate the chemical make up of several hot molecular cores to determine physical and chemical structure. We use high spectral and spatial resolution Cycle 0 ALMA observations to determine how this stage fits into the formation sequence of a high mass star. We observed the G35.20-0.74N and G35.03+0.35 hot cores at 350 GHz. We analyzed spectra and maps from four continuum peaks (A, B1, B2 and B3) in G35.20, separated by 1000-2000 AU, and one continuum peak in G35.03. We made all possible line identifications across 8 GHz of spectral windows of molecular emission lines and determined column densities and temperatures for as many as 35 species assuming local thermodynamic equilibrium. In comparing the spectra of the four peaks, we find each has a distinct chemical composition expressed in over 400 different transitions. In G35.20, B1 and B2 contain oxygen- and sulfur-bearing organic and inorganic species but few nitrogen-bearing species whereas A and B3 are strong sources of O, S, and N-bearing species (especially those with the CN-bond). CH$_2$DCN is clearly detected in A and B3 with D/H ratios of 8 and 13$\%$, respectively, but is much weaker at B1 and undetected at B2. No deuterated species are detected in G35.03, but similar molecular abundances to G35.20 were found in other species. We also find co-spatial emission of HNCO and NH$_2$CHO in both sources indicating a strong chemical link between the two species. The chemical segregation between N-bearing organic species and others in G35.20 suggests the presence of multiple protostars, surrounded by a disk or torus.Comment: 14 pages with 13 figures main text, 54 pages appendi

Self-organization of ultrasound in viscous fluids

We report the theoretical and experimental demonstration of pattern formation in acoustics. The system is an acoustic resonator containing a viscous fluid. When the system is driven by an external periodic force, the ultrasonic field inside the cavity experiences different pattern-forming instabilities leading to the emergence of periodic structures. The system is also shown to possess bistable regimes, in which localized states of the ultrasonic field develop. The thermal nonlinearity in the viscous fluid, together with the far-from-equilibrium conditions, are is the responsible of the observed effects

Del no-lugar al cronotopos, pasando por el vestíbulo de la estación de Atocha

La estación de Atocha, por el sólo hecho de ser una estación de trenes, queda, teóricamente, dentro de la categoría que Marc Augé (1992/2000) designó como no-lugares. Augé (1992/2000) caracterizó los no-lugares como espacios carentes de historia e historias, imposibles de apropiar, que nacen de la sobremodernidad, período que comienza a finales del siglo pasado y que se caracteriza por una aceleración y exceso de acontecimientos, de espacios y un achicamiento del planeta. A través de la fotografía, asumiendo el punto de vista de Joan Fontcuberta (1990, 2009), hemos intentado buscar indicadores suficientes para entender la relación que hay entre un supuesto "no-lugar" y quienes lo transitan. Sin embargo, esta relación va más allá de una simple categoría. Hemos recurrido a la noción de cronotopos acuñada por Mijail Bajtín (1975/1989) y hemos intentado ofrecer otra mirada a las numerosas configuraciones que se pueden establecer entre las personas y los espacios. Hemos elaborado una tabla de Tipos de configuraciones espaciotemporales en un espacio concreto, en la que Cronotopoi (estables vs. efímeros) y Significación (lugar vs. no-lugar) se ponen en juego. A partir de esta tabla, hemos analizado algunos de los resultados que encontramos a lo largo de los casi cinco meses que estuvimos fotografiando el vestíbulo de Atocha y hemos hallado que las personas nos ubicamos en los espacios de diferentes modos, apropiándolos de formas peculiares que, como es lógico, van más allá de nuestras categorías de análisis.The Atocha station, by the mere fact of being a train station, is theoretically characterized by Marc Auge (1992/2000) as a non-place. Auge (1992/2000) characterizes these non-places as spaces devoid of any history or stories, impossible to appropriate, and that arise from supermodernity, a period that began at the end of the last century and is characterized by an acceleration and excess of events, spaces, and a shrinking of the planet. Through photography, according to Joan Fontcuberta's (1990, 2009) point of view, we have tried to find sufficient indicators in order to understand the relationship between a supposed "non-place" and the people that pass through it. However, this relationship goes beyond just a simple category. We have used the notion of chronotope, a concept introduced by Mikhail Bakhtin (1975/1989), in order to offer another point of view for the many configurations that can be established between people and spaces. We have developed a table of Types of Space-Time Configurations in a Specific Space, in which Chronotopoi (stable vs. ephermal) and Significance (non-place vs. place) are brought into play. From this table, we discuss some of the results found during the nearly five months that we were taking pictures of the Atocha station lobby, and we have found that people are located in spaces in different ways, appropriating in many peculiar ways, of course, beyond our categories of analysis

From the non-place to chronotope, through the lobby of the Atocha station

La estación de Atocha, por el sólo hecho de ser una estación de trenes, queda, teóricamente, dentro de la categoría que Marc Augé (1992/2000) designó como no-lugares. Augé (1992/2000) caracterizó los no-lugares como espacios carentes de historia e historias, imposibles de apropiar, que nacen de la sobremodernidad, período que comienza a finales del siglo pasado y que se caracteriza por una aceleración y exceso de acontecimientos, de espacios y un achicamiento del planeta. A través de la fotografía, asumiendo el punto de vista de Joan Fontcuberta (1990, 2009), hemos intentado buscar indicadores suficientes para entender la relación que hay entre un supuesto “no-lugar” y quienes lo transitan. Sin embargo, esta relación va más allá de una simple categoría. Hemos recurrido a la noción de cronotopos acuñada por Mijail Bajtín (1975/1989) y hemos intentado ofrecer otra mirada a las numerosas configuraciones que se pueden establecer entre las personas y los espacios. Hemos elaborado una tabla de Tipos de configuraciones espaciotemporales en un espacio concreto, en la que Cronotopoi (estables vs. efímeros) y Significación (lugar vs. no-lugar) se ponen en juego. A partir de esta tabla, hemos analizado algunos de los resultados que encontramos a lo largo de los casi cinco meses que estuvimos fotografiando el vestíbulo de Atocha y hemos hallado que las personas nos ubicamos en los espacios de diferentes modos, apropiándolos de formas peculiares que, como es lógico, van más allá de nuestras categorías de análisis.The Atocha station, by the mere fact of being a train station, is theoretically characterized by Marc Auge (1992/2000) as a non-place. Auge (1992/2000) characterizes these non-places as spaces devoid of any history or stories, impossible to appropriate, and that arise from supermodernity, a period that began at the end of the last century and is characterized by an acceleration and excess of events, spaces, and a shrinking of the planet. Through photography, according to Joan Fontcuberta’s (1990, 2009) point of view, we have tried to find sufficient indicators in order to understand the relationship between a supposed “non-place” and the people that pass through it. However, this relationship goes beyond just a simple category. We have used the notion of chronotope, a concept introduced by Mikhail Bakhtin (1975/1989), in order to offer another point of view for the many configurations that can be established between people and spaces. We have developed a table of Types of Space-Time Configurations in a Specific Space, in which Chronotopoi (stable vs. ephermal) and Significance (non-place vs. place) are brought into play. From this table, we discuss some of the results found during the nearly five months that we were taking pictures of the Atocha station lobby, and we have found that people are located in spaces in different ways, appropriating in many peculiar ways, of course, beyond our categories of analysis

Long-distance radiative corrections to the di-pion tau lepton decay

We evaluate the model-dependent piece of O(alpha) long-distance radiative corrections to tau^- \to \pi^- \pi^0\nu_{\tau} decays by using a meson dominance model. We find that these corrections to the di-pion invariant mass spectrum are smaller than in previous calculations based on chiral perturbation theory. The corresponding correction to the photon inclusive rate is tiny (-0.15%) but it can be of relevance when new measurements reach better precision.Comment: 4 pages, 2 figures. An estimate of the shift produced in the evaluation of the h.v.p. contribution to the muon anomalous magnetic moment is added. Version to appear in Phys. Rev.