Alas, the dark matter structures were not that trivial

The radial density profile of dark matter structures has been observed to have an almost universal behaviour in numerical simulations, however, the physical reason for this behaviour remains unclear. It has previously been shown that if the pseudo phase-space density, rho/sigma_d^epsilon, is a beautifully simple power-law in radius, with the "golden values" epsilon=3 and d=r (i.e., the phase-space density is only dependent on the radial component of the velocity dispersion), then one can analytically derive the radial variation of the mass profile, dispersion profile etc. That would imply, if correct, that we just have to explain why rho/sigma^3_r ~r^{-alpha}, and then we would understand everything about equilibrated DM structures. Here we use a set of simulated galaxies and clusters of galaxies to demonstrate that there are no such golden values, but that each structure instead has its own set of values. Considering the same structure at different redshifts shows no evolution of the phase-space parameters towards fixed points. There is also no clear connection between the halo virialized mass and these parameters. This implies that we still do not understand the origin of the profiles of dark matter structures.Comment: 4 pages, 3 figures, accepted for publication in ApJ

Predictions for the First Parker Solar Probe Encounter

We examine Alfv\'en Wave Solar atmosphere Model (AWSoM) predictions of the first Parker Solar Probe (PSP) encounter. We focus on the 12-day closest approach centered on the 1st perihelion. AWSoM (van der Holst et al., 2014) allows us to interpret the PSP data in the context of coronal heating via Alfv\'en wave turbulence. The coronal heating and acceleration is addressed via outward-propagating low-frequency Alfv\'en waves that are partially reflected by Alfv\'en speed gradients. The nonlinear interaction of these counter-propagating waves results in a turbulent energy cascade. To apportion the wave dissipation to the electron and anisotropic proton temperatures, we employ the results of the theories of linear wave damping and nonlinear stochastic heating as described by Chandran et al. (2011). We find that during the first encounter, PSP was in close proximity to the heliospheric current sheet (HCS) and in the slow wind. PSP crossed the HCS two times, namely at 2018/11/03 UT 01:02 and 2018/11/08 UT 19:09 with perihelion occuring on the south of side of the HCS. We predict the plasma state along the PSP trajectory, which shows a dominant proton parallel temperature causing the plasma to be firehose unstable.Comment: 16 pages, 5 figures; accepted for publication in the Astrophysical Journal Letter

EXPLAINING SATISFACTION IN DOUBLE DEVIATION SCENARIOS: THE EFFECTS OF ANGER AND DISTRIBUTIVE JUSTICE

Research has shown that more than half of attempted recovery efforts only reinforce dissatisfaction, producing a ‘double deviation’ effect. Surprisingly, these double deviation effects have received little attention in service marketing literature. Yet no study has specifically investigated which are the main determinants of the formation of customer satisfaction judgments in double deviation contexts. To fill this gap, we develop and empirically test a model based on the existing service recovery literature. Specifically, we focus on two theoretical frameworks: social justice theory and theories of emotion. We examine the effect of anger with service recovery on satisfaction with service recovery, as well as the role of distributive justice on the elicitation of the specific emotion of anger with service recovery and satisfaction with service recovery. Results support the model and highlight the important role of specific recovery-related emotions in double deviation contexts. Implications for practice and future research are discussed. La investigación previa ha mostrado que más de la mitad de los esfuerzos de recuperación sólo refuerzan la insatisfacción, produciendo un efecto de desviación doble. Sorprendentemente, estos efectos de desviación doble han recibido muy poca atención en la literatura de marketing de servicios. Hasta la fecha, ningún trabajo ha investigado empíricamente cuáles son los principales determinantes en la formación de los juicios de satisfacción en contextos de desviación doble. Para cubrir este hueco, desarrollamos y analizamos empíricamente un modelo basado en la literatura de recuperación de servicios existente. Específicamente, nos basamos en dos esquemas conceptuales: la teoría de la justicia social y las teorías sobre emociones. Examinamos el efecto del enfado con la recuperación del servicio en la satisfacción con la recuperación del servicio, así como el papel de la justicia distributiva como activador de emociones específicas de enfado y como antecedente de la satisfacción con la recuperación del servicio. Los resultados confirman el modelo propuesto y ponen de manifiesto el importante papel de las emociones específicas relacionadas con la recuperación en contextos de desviación doble. Finalmente, se discuten las implicaciones de gestión y las líneas futuras de investigación.enfado con la recuperación del servicio, justicia distributiva, satisfacción con la recuperación del servicio, desviación doble, industria bancaria anger with service recovery, distributive justice, satisfaction with service recovery, double deviation, banking industry

On topological phases of spin chains

Symmetry protected topological phases of one-dimensional spin systems have been classified using group cohomology. In this paper, we revisit this problem for general spin chains which are invariant under a continuous on-site symmetry group G. We evaluate the relevant cohomology groups and find that the topological phases are in one-to-one correspondence with the elements of the fundamental group of G if G is compact, simple and connected and if no additional symmetries are imposed. For spin chains with symmetry PSU(N)=SU(N)/Z_N our analysis implies the existence of N distinct topological phases. For symmetry groups of orthogonal, symplectic or exceptional type we find up to four different phases. Our work suggests a natural generalization of Haldane's conjecture beyond SU(2).Comment: 18 pages, 7 figures, 2 tables. Version v2 corresponds to the published version. It includes minor revisions, additional references and an application to cold atom system

The search for planetary mass companions to field brown dwarfs with HST/NICMOS

We present the results of a high-resolution spectral differential imaging survey of 12 nearby, relatively young field L dwarfs (<1 Gyr) carried out with HST/NICMOS to search for planetary mass companions at small physical separations from their host. The survey resolved two brown dwarf binaries: the L dwarf system Kelu-1AB and the newly discovered L/T transition system 2MASS J031059+164815AB. For both systems common proper motion has already been confirmed in follow-up observations which have been published elsewhere. The derived separations of the binaries are smaller than 6 AU and consistent with previous brown dwarf binary statistics. Their mass ratios of q > 0.8 confirm the preference for equal mass systems similar to a large number of other surveys. Furthermore, we found tentative evidence for a companion to the L4 dwarf 2MASS W033703-175807, straddling the brown dwarf/planetary mass boundary and revealing an uncommonly low mass ratio system (q ~ 0.2) compared to the vast majority of previously found brown dwarf binaries. With a derived minimum mass of 10 - 15 Mjup, a planetary nature of the secondary cannot be ruled out yet. However, it seems more likely to be a very low mass brown dwarf secondary at the border of the spectral T/Y transition regime, primarily due to its similarities to recently found very cool T dwarfs. This would make it one of the closest resolved brown dwarf binaries (0.087" $/pm$ 0.015", corresponding to 2.52 $\pm$ 0.44 AU at a distance of 29 pc) with the coolest (Teff ~ 600-630 K) and least massive companion to any L or T dwarf.Comment: 33 pages, 8 figures, 2 tables, accepted for publication by Ap

A dual-mask coronagraph for observing faint companions to binary stars

Observations of binary stars for faint companions with conventional coronagraphic methods are challenging, as both targets will be bright enough to obscure any nearby faint companions if their scattered light is not suppressed. We propose coronagraphic examination of binary stars using an apodized pupil Lyot coronagraph and a pair of actively-controlled image plane masks to suppress both stars simultaneously. The performance is compared to imaging with a band-limited mask, a dual-mask Lyot coronagraph and with no coronagraph at all. An imaging procedure and control system for the masks are also described.Comment: 17 pages, 6 figure