Late-time expansion in the semiclassical theory of the Hawking radiation

We give a detailed treatment of the back-reaction effects on the Hawking spectrum in the late-time expansion within the semiclassical approach to the Hawking radiation. We find that the boundary value problem defining the action of the modes which are regular at the horizon admits in general the presence of caustics. We show that for radii less that a certain critical value $r_c$ no caustic occurs for all values of the wave number and time and we give a rigorous lower bound on such a critical value. We solve the exact system of non linear equations defining the motion, by an iterative procedure rigorously convergent at late times. The first two terms of such an expansion give the $O(\omega/M)$ correction to the Hawking spectrum.Comment: 17 pages, 1 figure, LaTex, typos corrected, one intermediate formula adde

Large Chiral Diffeomorphisms on Riemann Surfaces and W-algebras

The diffeomorphism action lifted on truncated (chiral) Taylor expansion of a complex scalar field over a Riemann surface is presented in the paper under the name of large diffeomorphisms. After an heuristic approach, we show how a linear truncation in the Taylor expansion can generate an algebra of symmetry characterized by some structure functions. Such a linear truncation is explicitly realized by introducing the notion of Forsyth frame over the Riemann surface with the help of a conformally covariant algebraic differential equation. The large chiral diffeomorphism action is then implemented through a B.R.S. formulation (for a given order of truncation) leading to a more algebraic set up. In this context the ghost fields behave as holomorphically covariant jets. Subsequently, the link with the so called W-algebras is made explicit once the ghost parameters are turned from jets into tensorial ghost ones. We give a general solution with the help of the structure functions pertaining to all the possible truncations lower or equal to the given order. This provides another contribution to the relationship between KdV flows and W-diffeomorphimsComment: LaTeX file, 31 pages, no figure. Version to appear in J. Math. Phys. Work partly supported by Region PACA and INF

The Phoenix Pluto Probe

A design proposal for an unmanned probe to Pluto is presented. The topics covered include: (1) scientific instrumentation; (2) mission management, planning, and costing; (3) power and propulsion system; (4) structural subsystem; (5) command, control, and communication; and (6) attitude and articulation control

Hα\alpha Emission From Active Equal-mass, Wide M Dwarf Binaries

We identify a sample of near-equal mass wide binary M dwarf systems from the SLoWPoKES catalog of common proper-motion binaries and obtain follow-up observations of their chromospheric activity as measured by the H$\alpha$ emission line. We present optical spectra for both components of 48 candidate M dwarf binaries, confirming their mid-M spectral types. Of those 48 coeval pairs, we find eight with H$\alpha$ emission from both components, three with weak emission in one component and no emission in the other, and 37 with two inactive components. We find that of the eleven pairs with at least one active component, only three follow the net trend of decreasing activity strength $L_{\rm H\alpha}/L_{\rm bol}$ with later spectral type. The difference in quiescent activity strength between the A and B components is larger than what would be expected based on the small differences in color (mass). For five binaries with two active components, we present 47 hours of time-resolved spectroscopy, observed on the ARC 3.5-m over twelve different nights. For four of the five pairs, the slightly redder (B) component exhibits a higher level of H$\alpha$ emission during the majority of the observations and the redder objects are the only components to flare. The full range of H$\alpha$ emission observed on these variable mid-M dwarfs is comparable to the scatter in H$\alpha$ emission found in single-epoch surveys of mid-M dwarfs, indicating that variability could be a major factor in the spread of observed activity strengths. We also find that variability is independent of both activity strength and spectral type.Comment: 10 pages, 6 figures, accepted for publication in PAS

Toda Fields on Riemann Surfaces: remarks on the Miura transformation

We point out that the Miura transformation is related to a holomorphic foliation in a relative flag manifold over a Riemann Surface. Certain differential operators corresponding to a free field description of $W$--algebras are thus interpreted as partial connections associated to the foliation.Comment: AmsLatex 1.1, 10 page

Nanostructural changes in cell wall pectins during strawberry fruit ripening assessed by atomic force microscopy

Rapid loss of firmness occurs during strawberry (Fragaria × ananassa Duch) ripening, resulting in a short shelf life and high economic losses. The disassembly of cell walls is considered the main responsible for fruit softening, being pectins extensively modified during strawberry ripening (Paniagua et al. 2014). Atomic force microscopy allows the analysis of individual polymer chains at nanostructural level with a minimal sample preparation (Morris et al., 2001). The main objective of this research was to compare pectins of green and red ripe strawberry fruits at the nanostructural level to shed light on structural changes that could be related to softening. Cell walls from strawberry fruits were extracted and fractionated with different solvents to obtain fractions enriched in a specific component. The yield of cell wall material, as well as the amount of the different fractions, decreased in ripe fruits. CDTA and Na2CO3 fractions underwent the largest decrements, being these fractions enriched in pectins supposedly located in the middle lamella and primary cell wall, respectively. Uronic acid content also decreased significantly during ripening in both pectin fractions, but the amount of soluble pectins, those extracted with phenol:acetic acid:water (PAW) and water increased in ripe fruits. Monosaccharide composition in CDTA and Na2CO3 fractions was determined by gas chromatography. In both pectin fractions, the amount of Ara and Gal, the two most abundant carbohydrates, decreased in ripe fruits. The nanostructural characteristics of CDTA and Na2CO3 pectins were analyzed by AFM. Isolated pectic chains present in the CDTA fraction were significantly longer and more branched in samples from green fruits than those present in samples obtained from red fruit. In spite of slight differences in length distributions, Na2CO3 samples from unripe fruits displayed some longer chains at low frequency that were not detected in ripe fruits. Pectin aggregates were more frequently observed in green fruit samples from both fractions. These results support that pectic chain length and the nanostructural complexity of the pectins present in CDTA and Na2CO3 fractions diminish during strawberry fruit development, and these changes, jointly with the loss of neutral sugars, could contribute to the solubilization of pectins and fruit softening. Paniagua et al. (2014). Ann Bot, 114: 1375-1383 Morris et al. (2001). Food Sci Tech 34: 3-10 This research was supported by FEDER EU Funds and the Ministerio de Educación y Ciencia of Spain (grant reference AGL2011-24814)Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

From the 'cinematic' to the 'anime-ic': Issues of movement in anime

This is the author's accepted manuscript. The final published article is available from the link below.This article explores the way that movement is formally depicted in anime. Drawing on Thomas Lamarre's concepts of the `cinematic' and the `anime-ic', the article interrogates further the differences in movement and action in anime from traditional filmic form. While often considered in terms of `flatness', anime offers spectacle, character development and, ironically, depth through the very form of movement put to use in such texts.The article questions whether the modes of address at work in anime are unique to this form of animation.Taking into account how the terms `cinematic' and `anime-ic' can be understood (and by extension the cinematic and animatic apparatus), the article also begins to explore how viewers might identify with such images

The Digital Flynn Effect: Complexity of Posts on Social Media Increases over Time

Parents and teachers often express concern about the extensive use of social media by youngsters. Some of them see emoticons, undecipherable initialisms and loose grammar typical for social media as evidence of language degradation. In this paper, we use a simple measure of text complexity to investigate how the complexity of public posts on a popular social networking site changes over time. We analyze a unique dataset that contains texts posted by 942, 336 users from a large European city across nine years. We show that the chosen complexity measure is correlated with the academic performance of users: users from high-performing schools produce more complex texts than users from low-performing schools. We also find that complexity of posts increases with age. Finally, we demonstrate that overall language complexity of posts on the social networking site is constantly increasing. We call this phenomenon the digital Flynn effect. Our results may suggest that the worries about language degradation are not warranted