Cosmology and prospects for sub-MeV dark matter in electron recoil experiments

Dark matter is poorly constrained by direct detection experiments at masses below 1 MeV. This is an important target for the next generation of experiments, and several methods have been proposed to probe this mass range. One class of such experiments will search for dark matter--electron recoils. However, simplified models with new light degrees of freedom coupled to electrons face significant pressure from cosmology, and the extent of these restrictions more generally is poorly understood. Here, we perform a systematic study of cosmological constraints on models with a heavy mediator in the context of an effective field theory. We include constraints from (i) disruption of primordial nucleosynthesis, (ii) overproduction of dark matter, and (iii) the effective number of neutrino species at recombination. We demonstrate the implications of our results for proposed electron recoil experiments, and highlight scenarios which may be amenable to direct detection.Comment: 21 pages, 7 figures. Matched published versio

Black hole remnants are not too fast to be dark matter

We comment on recent claims that recoil in the final stages of Hawking evaporation gives black hole remnants large velocities, rendering them inviable as a dark matter candidate. We point out that due to cosmic expansion, such large velocities at the final stages of evaporation are not in tension with the cold dark matter paradigm so long as they are attained at sufficiently early times. In particular, the predicted recoil velocities are robustly compatible with observations if the remnants form before the epoch of big bang nucleosynthesis, a requirement which is already imposed by the physics of nucleosynthesis itself.Comment: 1.5 pages + reference

Clear Shores: Enhancing Water Quality Monitoring

Mission goal: Improve monitoring of the quality of water in and around Aotearoa New Zealand for researchers, decision makers and the public at large through innovative space technolog

Connecting direct and indirect detection with a dark spike in the cosmic-ray electron spectrum

Multiple space-borne cosmic ray detectors have detected line-like features in the electron and positron spectra. Most recently, the DAMPE collaboration reported the existence of such a feature at 1.4 TeV, sparking interest in a potential dark matter origin. Such quasi-monochromatic features, virtually free of any astrophysical background, could be explained by the annihilation of dark matter particles in a nearby dark matter clump. Here, we explore the consistency of producing such spectral features with dark matter annihilation from the standpoint of dark matter substructure statistics, constraints from anisotropy, and constraints from gamma-ray emission. We demonstrate that if indeed a high-energy, line-like feature in the electron-positron spectrum originates from dark matter annihilation in a nearby clump, a significant or even dominant fraction of the dark matter in the Solar System likely stems from the clump, with dramatic consequences for direct dark matter searches.Comment: 30 pages, 11 figure

Connecting direct and indirect detection with a dark spike in the cosmic-ray electron spectrum

Multiple space-borne cosmic ray detectors have detected line-like features in the electron and positron spectra. Most recently, the DAMPE collaboration reported the existence of such a feature at 1.4 TeV, sparking interest in a potential dark matter origin. Such quasi-monochromatic features, virtually free of any astrophysical background, could be explained by the annihilation of dark matter particles in a nearby dark matter clump. Here, we explore the consistency of producing such spectral features with dark matter annihilation from the standpoint of dark matter substructure statistics, constraints from anisotropy, and constraints from gamma-ray emission. We demonstrate that if indeed a high-energy, line-like feature in the electron-positron spectrum originates from dark matter annihilation in a nearby clump, a significant or even dominant fraction of the dark matter in the Solar System likely stems from the clump, with dramatic consequences for direct dark matter searches.Comment: 30 pages, 11 figure

Cosmological implications of the KOTO excess

The KOTO experiment has reported an excess of $K_L\to\pi^0\nu\bar\nu$ events above the standard model prediction, in tension with the Grossman--Nir bound. The GN bound heavily constrains new physics interpretations of an excess in this channel, but another possibility is that the observed events originate from a different process entirely: a decay of the form $K_L\to\pi^0X$, where $X$ denotes one or more new invisible species. We introduce a class of models to study this scenario with two light scalars playing the role of $X$, and we examine the possibility that the lighter of the two new states may also account for cosmological dark matter. We show that this species can be produced thermally in the presence of additional interactions apart from those needed to account for the KOTO excess. Conversely, in the minimal version of the model, dark matter must be produced non-thermally. In this case, avoiding overproduction imposes constraints on the structure of the low-energy theory. Moreover, this requirement carries significant implications for the scale of reheating in the early universe, generically preferring a low but observationally-permitted reheating temperature of O(10 MeV). We discuss astrophysical and terrestrial signatures that will allow further tests of this paradigm in the coming years.Comment: 43 pages, 10 figure

The Maximal-Density Mass Function for Primordial Black Hole Dark Matter

The advent of gravitational wave astronomy has rekindled interest in primordial black holes (PBH) as a dark matter candidate. As there are many different observational probes of the PBH density across different masses, constraints on PBH models are dependent on the functional form of the PBH mass function. This complicates general statements about the mass functions allowed by current data, and, in particular, about the maximum total density of PBH. Numerical studies suggest that some forms of extended mass functions face tighter constraints than monochromatic mass functions, but they do not preclude the existence of a functional form for which constraints are relaxed. We use analytical arguments to show that the mass function which maximizes the fraction of the matter density in PBH subject to all constraints is a finite linear combination of monochromatic mass functions. We explicitly compute the maximum fraction of dark matter in PBH for different combinations of current constraints, allowing for total freedom of the mass function. Our framework elucidates the dependence of the maximum PBH density on the form of observational constraints, and we discuss the implications of current and future constraints for the viability of the PBH dark matter paradigm.Comment: 19 pages, 3 figures. Matched published versio

The flexible world of the Simpsons

Die Simpsons sorgen seit mehr als 20 Jahren für subversive Unterhaltung im Zeichentrickformat. Die Serie verbindet realistische Themen mit dem abnormen Witz von Cartoons. Diese Flexibilität ist ein bestimmendes Element in Springfield und erstreckt sich über verschiedene Bereiche der Serie. Die flexible Welt der Simpsons wird in dieser Arbeit unter Berücksichtigung der Auswirkungen auf den Wiedersehenswert der Serie untersucht

ICE-EXTENT VARIATIONS AND POST-GLACIAL EROSION IN THE MONT BLANC MASSIF

Afin d’appr´ehender l’effet des variations climatiques sur les environnements alpins, il est n´ecessaire d’´etudier le pass´e des syst`emes montagneux. Depuis le dernier maximum glaciaire (LGM), il y a environ 20 000 ans, les glaciers alpins se sont retir´es des r´egions de plaine et de leurs zones d’accumulation en altitude. Cette transition modifia consid´erablement la g´eographie alpine en allimentant de grands lac d’eau douce, en lib´erant de consid´erable quan- tit´ee de s´ediments et en exposant d’importantes ´etendues de surfaces rocheuses. Pourtant, les reconstitutions des conditions environnementales depuis le LGM restent peu document´ees. Une des principales limitations est le manque de contraintes temporelles pr´ecises dans la reconstruction des extensions glaciaires pass´ees. Diff´erentes m´ethodes g´eochronologiques ont ´et´e d´evelopp´ees et appliqu´ees pour dater les marqueurs g´eomorphologiques ou s´edimentaires sp´ecifiques de la dynamique des glaciers. R´ecemment, la datation de l’exposition de surface par luminescence stimul´ee optiquement (OSL) a ´et´e d´evelopp´ee, offrant l’occasion d’am´eliorer les reconstructions des extensions glaciaires pass´ees. Cette m´ethode est bas´ee sur la sensibilit´e du signal OSL des min´eraux `a la lumi´ere. Lors d’une exposition le signal OSL est remis `a z´ero dans les premiers mil- lim`etres sup´erieurs de la surface rocheuse expos´ee. Dans cette th`ese, j’´etudie le potentiel de la datation d’exposition de surface OSL `a partir de polis glaciaires sur les flancs de la Mer de Glace, glacier embl´ematique du massif du Mont- Blanc. Je montre tout d’abord que cette m´ethode permet de reconstruire les ´epaisseurs pass´ees du glacier depuis le Petit Aˆge Glaciaire, c’est `a dire depuis la deuxime moiti´e du XIXe si`ecle. Je montre ensuite que sur de plus longues p´eriodes, la m´ethode est sensible `a l’´erosion de surface. En la combinant avec une autre m´ethode de datation: la datation par cosmog´enie nucl´eide, je montre qu’il est possible de contraindre l’´evolution de l’´erosion de surface et des variations d’´epaisseur du glacier depuis 20 000 ans. En appliquant cette nouvelle approche sur des profiles verticaux de surfaces de roches mou- ton´ees sur les bords de la Mer de Glace, je d´emontre que l’intensit´e de l’´erosion varie avec l’altitude. Plus les surfaces sont haute, plus l’´erosion est faible. De plus, les r´esultats mon- trent des intensit´es d’´erosion tr`es fortes par rapport `a ce qui est g´en´eralement admis dans ces environnements de montagnes. La distribution vertical et l’intentist´e des taux d’´erosion pour- raient la cons´equence des facteurs morphom`etrique et climatiques propres aux environnement de haute montagne, comme la pente des surfaces rocheuses ou la distribution du manteau neigeux. Enfin, les reconstitutions glaciaires sugg`erent des secnarios d’amincissement glaciaire potentiellement rapide `a la fin du dernier maximum glaciaire