Updated cosmic-ray and radio constraints on light dark matter: Implications for the GeV gamma-ray excess at the Galactic center

The apparent gamma-ray excess in the Galactic center region and inner Galaxy has attracted considerable interest, notably because both its spectrum and radial distribution are consistent with an interpretation in terms of annihilating dark matter particles with a mass of about 10-40 GeV. We confront such an interpretation with an updated compilation of various indirect dark matter detection bounds, which we adapt to the specific form required by the observed signal. We find that cosmic-ray positron data strongly rule out dark matter annihilating to light leptons, or 'democratically' to all leptons, as an explanation of the signal. Cosmic-ray antiprotons, for which we present independent and significantly improved limits with respect to previous estimates, are already in considerable tension with DM annihilation to any combination of quark final states; the first set of AMS-02 data will thus be able to rule out or confirm the DM hypothesis with high confidence. For reasonable assumptions about the magnetic field in the Galactic center region, radio observations independently put very severe constraints on a DM interpretation of the excess, in particular for all leptonic annihilation channels.Comment: 23 pages revtex, 19 figures, 1 table. Extended discussion of antiproton limits and added references. Matches published versio

Enhanced Line Signals from Annihilating Kaluza-Klein Dark Matter

Monochromatic gamma ray lines have long been known to provide potential smoking gun signals for annihilating dark matter. Here, we demonstrate that the situation is particularly interesting for Kaluza-Klein dark matter because resonant annihilation is generically expected for small, but not necessarily vanishing relative velocities of the annihilating particles. We calculate the contribution from those hitherto neglected resonances and show that the annihilation rate into monochromatic photons can be significantly enhanced, in a way that is much more pronounced than for the associated production of continuum photons. For favorable astrophysical conditions, this leads to promising prospects for the detection of TeV-scale Kaluza-Klein dark matter. We also point out that the situation may be even more interesting in the vicinity of black holes, like the supermassive black hole at the center of our Galaxy, where in principle center-of-mass energies much larger than the rest mass are available. In this case, annihilating Kaluza-Klein dark matter may show the striking and unique signature of several gamma ray lines, with an equidistant spacing corresponding to twice the compactification radius of the extra dimension

Misperceiving Economic Success: Experimental Evidence on Meritocratic Beliefs and Inequality Acceptance

Most people tend to equate success with merit, a tendency that is particularly pronounced among conservatives. However, in practice it is exceedingly difficult to discern the relative impact of luck and effort to economic success. Based on a large-scale online study that samples the general US population, we investigate whether individuals misperceive the importance of luck for success, and how this mediates their meritocratic beliefs and acceptance of inequality. We randomly assign participants in pairs to compete in an easy or hard work assignment. The tasks are structured such that working on the easy work assignment almost certainly results in better performance and economic success. We show that economically successful participants overweight the role of effort in their success, perceiving high income as more deserved than unsuccessful participants. Subsequently, they demand less redistributive taxation, and they also show little interest in receiving information about the true determinants of their success. These general findings hold true regardless of political orientation. Successful liberals are as meritocratic as conservatives are, sharing the same beliefs in deservingness and preferences for low redistributive taxes

Synchrotron Emission from Dark Matter in Galactic Subhalos. A Look into the Smith Cloud

One of the key predictions of the WIMP paradigm for Dark Matter (DM) is that DM particles can annihilate into charged particles. These annihilations will proceed in e.g. Galactic subhalos such as dwarf Galaxies or, as recently pointed out, high velocity clouds such as the "Smith Cloud". In this note, we focus on the radio emission associated with DM annihilations into electrons and positrons occurring in the Smith Cloud. The phenomenology of this emission is discussed in quite some detail. We argue that the uncertainties in the propagation can be captured by the typical diffusion-loss length parameter (Syrovatskii variable) but that the angle-integrated radio fluxes are independent of the propagation. We conclude that if the Smith Cloud is indeed dominated by DM, radio signals from DM annihilation stand out amongst other messengers. Furthermore, low frequencies such as the ones observed by e.g. the Low Frequency Array (LOFAR) and the next-generation Square Kilometre Array (SKA) are optimal for searches for DM in the Smith Cloud. As a practical application, we set conservative constraints on dark matter annihilation cross section using data of continuum radio emission from the Galaxy at 22 MHz and at 1.4 GHz. Stronger constraints could be reached by background subtraction, exploiting the profile and frequency dependence of the putative DM signal. We set stronger but tentative limits using the median noise in brightness temperature from the Green Bank Telescope and the LOFAR sensitivities.Comment: 23 pages, 17 figures. Extended discussion on how the limits/forecasts are obtained. Matches published versio

The Value of Verbal Feedback in Allocation Decisions

Depending on the context at hand, people’s preference for receiving feedback might differ. Especially in allocation decisions that directly concern another individual, feedback from the affected person can have positive or negative value. We study such preferences in a laboratory experiment by eliciting the willingness-to-pay to receive or to avoid verbal feedback from subjects that were previously affected by an allocation decision. We find that most decision makers exhibit a positive willingness-to-pay for having control about whether feedback occurs or not. Specifically, decision makers that equally shared their endowment with the recipient revealed a positive willingness-to-pay for receiving, but not for avoiding feedback. By contrast, among decision makers that behaved selfishly, we identify both: subjects that were willing to pay for receiving and subjects that were willing to pay for avoiding feedback. The stated motivations indicate that curiosity, the desire to receive social approval and giving the recipient the chance to express his/her feelings are the main reasons for feedback acquisition, while shame and fear of negative feedback are the main reasons for avoidance

Radio constraints on dark matter annihilation in Canes Venatici I with LOFAR

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Dwarf galaxies are dark matter-dominated and therefore promising targets for the search for weakly interacting massive particles (WIMPs), which are well-known candidates for dark matter. Annihilation of WIMPs produce ultra-relativistic cosmic-ray electrons and positrons that emit synchrotron radiation in the presence of magnetic fields. For typical magnetic field strengths (few $\mu$G) and $\mathcal O$(GeV-TeV) WIMP masses (and thus typical electron energies of the same order) this emission peaks at hundreds of MHz. Here, we use the non-detection of 150-MHz radio continuum emission from the dwarf spheroidal galaxy `Canes Venatici I' with the LOw-Frequency ARray (LOFAR) to derive constraints on the annihilation cross section of WIMPs into primary electron-positron and other fundamental particle-antiparticle pairs. In this first-of-its-kind LOFAR study, we obtain new constraints on annihilating WIMP dark matter (DM). Using conservative estimates for the magnetic field strengths and diffusion coefficients, we obtain limits that are comparable with those by the Fermi Large Area Telescope (Fermi-LAT) using gamma-ray observations. Assuming s-wave annihilation and WIMPs making up 100% of the DM density, our limits exclude several thermal WIMP realisations in the $[2,20]$-GeV mass range. A more ambitious multi-wavelength and multi-target LOFAR study could improve these limits by a few orders of magnitude.Peer reviewe

Möglichkeiten des Nebenfruchtanbaus bei Safrankulturen im Altenburger Land: In Kooperation mit dem Betrieb 'W hoch 3' Wandel-Werte-Wege

Safran (Crocus sativus) ist eine wertvolle Gewürzpflanze. Alleiniger Anbau führt zu Monokultur und vermehrter Verunkrautung während der Vegetationspause im Sommer. Das Ziel dieser theoretischen Studie war herauszufinden, welche Pflanzenarten zwischen den Safranreihen kultiviert werden können.:Inhaltsverzeichnis 1 Einleitung 1 2 Lagebeschreibung 2 3 Betriebsbeschreibung 3 4 Botanik Crocus sativus 7 5 Kulturverfahren 9 6 Nebenfruchtanbau 11 6.1 Gemüse und Obst 13 6.2 Zierpflanzen 15 6.3 Getreide 17 6.4 Leguminosen 19 6.5 Ölpflanzen 22 6.6 Kräuter 25 7 Diskussion 27 7.1 Gemüse- und Obst 28 7.2 Zierpflanzen 31 7.3 Getreide 34 7.4 Leguminosen 36 7.5 Ölpflanzen 38 7.6 Kräuter 40 8 Zusammenfassung 43 9 Anhang 44 10 Literaturverzeichnis 51Saffron (Crocus sativus) is a valuable spice plant. Sole cultivation of saffron leads to monoculture and increases weed growth in the vegetative dormancy period. The aim of this theoretical study was to determine which plants species could be cultivated between saffron rows.:Inhaltsverzeichnis 1 Einleitung 1 2 Lagebeschreibung 2 3 Betriebsbeschreibung 3 4 Botanik Crocus sativus 7 5 Kulturverfahren 9 6 Nebenfruchtanbau 11 6.1 Gemüse und Obst 13 6.2 Zierpflanzen 15 6.3 Getreide 17 6.4 Leguminosen 19 6.5 Ölpflanzen 22 6.6 Kräuter 25 7 Diskussion 27 7.1 Gemüse- und Obst 28 7.2 Zierpflanzen 31 7.3 Getreide 34 7.4 Leguminosen 36 7.5 Ölpflanzen 38 7.6 Kräuter 40 8 Zusammenfassung 43 9 Anhang 44 10 Literaturverzeichnis 5

Bidirectional gray matter changes after complex motor skill learning

Long-term motor skill learning has been consistently shown to result in functional as well as structural changes in the adult human brain. However, the effect of short learning periods on brain structure is not well understood. In the present study, subjects performed a sequential pinch force task (SPFT) for 20 min on 5 consecutive days. Changes in brain structure were evaluated with anatomical magnetic resonance imaging (MRI) scans acquired on the first and last day of motor skill learning. Behaviorally, the SPFT resulted in sequence-specific learning with the trained (right) hand. Structural gray matter (GM) alterations in left M1, right ventral premotor cortex (PMC) and right dorsolateral prefrontal cortex (DLPFC) correlated with performance improvements in the SPFT. More specifically we found that subjects with strong sequence-specific performance improvements in the SPFT also had larger increases in GM volume in the respective brain areas. On the other hand, subjects with small behavioral gains either showed no change or even a decrease in GM volume during the time course of learning. Furthermore, cerebellar GM volume before motor skill learning predicted (A) individual learning-related changes in the SPFT and (B) the amount of structural changes in left M1, right ventral PMC and DLPFC. In summary, we provide novel evidence that short-term motor skill learning is associated with learning-related structural brain alterations. Additionally, we showed that practicing a motor skill is not exclusively accompanied by increased GM volume. Instead, bidirectional structural alterations explained the variability of the individual learning success