Singlet-doublet fermion and triplet scalar dark matter with radiative neutrino masses

We present a detailed study of a combined singlet-doublet fermion and triplet scalar model for dark matter. These models have only been studied separately in the past. Together, they form a simple extension of the Standard Model that can account for dark matter and explain the existence of neutrino masses, which are generated radiatively. This holds even if singlet-doublet fermions and triplet scalars never contribute simultaneously to the dark matter abundance. However, this also implies the existence of lepton flavour violating processes. In addition, this particular model allows for gauge coupling unification. The new fields are odd under a new $\mathbb{Z}_2$ symmetry to stabilise the dark matter candidate. We analyse the dark matter, neutrino mass and lepton flavour violation aspects both separately and in conjunction, exploring the viable parameter space of the model. This is done using a numerical random scan imposing successively the neutrino mass and mixing, relic density, Higgs mass, direct detection, collider and lepton flavour violation constraints. We find that dark matter in this model is fermionic for masses below about 1 TeV and scalar above. The narrow mass regions found previously for the two separate models are enlarged by their coupling. While coannihilations of the weak isospin partners are sizeable, this is not the case for fermions and scalars despite their often similar masses due to the relatively small coupling of the two sectors, imposed by the small neutrino masses. We observe a high degree of complementarity between direct detection and lepton flavour violation experiments, which should soon allow to fully probe the fermionic dark matter sector and at least partially the scalar dark matter sector.Comment: 24 pages, 12 figures; version accepted by and published in JHE

Singlet-doublet/triplet dark matter and neutrino masses

In these proceedings, we present a study of a combined singlet--doublet fermion and triplet scalar model for dark matter (DM). Together, these models form a simple extension of the Standard Model (SM) that can account for DM and explain the existence of neutrino masses, which are generated radiatively. However, this also implies the existence of lepton flavour violating (LFV) processes. In addition, this particular model allows for gauge coupling unification. The new fields are odd under a new $\mathbb{Z}_2$ symmetry to stabilise the DM candidate. We analyse the DM, neutrino mass and LFV aspects, exploring the viable parameter space of the model. This is done using a numerical random scan imposing successively the neutrino mass and mixing, relic density, Higgs mass, direct detection, collider and LFV constraints. We find that DM in this model is fermionic for masses below about 1 TeV and scalar above. We observe a high degree of complementarity between direct detection and LFV experiments, which should soon allow to fully probe the fermionic DM sector and at least partially the scalar DM sector.Comment: 4 pages, 1 figure; contribution to the 2019 EW session of the 54th Rencontres de Moriond (summary of arXiv:1812.11133

Scalable data abstractions for distributed parallel computations

The ability to express a program as a hierarchical composition of parts is an essential tool in managing the complexity of software and a key abstraction this provides is to separate the representation of data from the computation. Many current parallel programming models use a shared memory model to provide data abstraction but this doesn't scale well with large numbers of cores due to non-determinism and access latency. This paper proposes a simple programming model that allows scalable parallel programs to be expressed with distributed representations of data and it provides the programmer with the flexibility to employ shared or distributed styles of data-parallelism where applicable. It is capable of an efficient implementation, and with the provision of a small set of primitive capabilities in the hardware, it can be compiled to operate directly on the hardware, in the same way stack-based allocation operates for subroutines in sequential machines

Structure formation in quantum-wave dark matter cosmologies

Although the so-called standard model of cosmology has been able to make successful predictions on many physical length scales, it does not provide an explanation for its two central components: (Cold) dark matter and dark energy (in the form of a cosmological constant). This “dark universe”, which makes up more than 95 % of the total cosmic energy budget, still eludes our grasp: It is not known which elementary physical components it is composed of. Particularly with regard to dark matter, the focus has shifted in the recent past, since there has been no trace of the candidates favored thus far even after decades of intensive experimental and observational search using particle- and astrophysical approaches. Ultra-light scalar particles represent an alternative to these candidates, offering intriguing possibilities for their potential detection due to their rich astrophysical phenomenology. Because of their extremely small masses, they do not behave as individual particles, but collectively as waves. This results in a multitude of wave phenomena, such as the formation of solitons and interference patterns or transient, oscillating density fluctuations which are rather reminiscent of quantum-mechanical effects than macroscopic structures. In the course of this dissertation, I will consider cosmological models in which dark matter is composed of exactly such ultra-light bosons. To this end, I employ extensive numerical simulations of cosmic structure formation, which are capable of discerning key physical differences between this model of dark matter and the standard model by means of the non-linear evolution of structure in the universe. As an important goal and tool within the dissertation, I developed the AxiREPO code, which numerically solves the corresponding equations of motions for ultra-light dark matter and can thus compute simulations of the expected formation of cosmic structure. Using this code, I designed, executed and analyzed large simulations of ultra-light and cold dark matter. In particular, different initial conditions were used in order to be able to study and compare both the influence of differences in the primordial density fluctuations as opposed to those which originate due to the dynamics of the equations of motions, as well as different values for the masses of the ultra-light bosons and accounting for baryonic matter.Obwohl das sogenannte kosmologische Standardmodell auf vielen physikalischen Längenskalen erfolgreiche Vorhersagen macht, liefert es keine Erklärung für seine beiden zentralen Bestandteile: Die (kalte) dunkle Materie und die dunkle Energie (in Form einer kosmologischen Konstante). Dieses „dunkle Universum“, welches über 95 % des gesamten kosmischen Energiebudgets ausmacht, entzieht sich unserer Kenntnis: Es ist nicht bekannt, aus welchen elementaren physikalischen Komponenten es besteht. Speziell bezüglich der dunklen Materie hat sich der Fokus in der näheren Vergangenheit verschoben, da nach Jahrzehnten intensiver teilchen- und astrophysikalischer Suche keine Spur von den bisher favorisierten Kandidaten zu finden ist. Ultraleichte Skalarteilchen stellen eine Alternative zu diesen Kandidaten dar, die durch ihre reichhaltige astrophysikalische Phänomenologie interessante Möglichkeiten für ihre potentielle Entdeckung liefern. Aufgrund ihrer extrem geringen Masse verhalten sie sich auf astrophysikalischen Skalen nicht als individuelle Teilchen, sondern kollektiv als Wellen. Dies resultiert in einer Vielzahl von Wellenphänomenen, wie etwa die Bildung von Solitonen und Interferenzmustern oder auf kurzen Zeitskalen oszillierende Dichtefluktuationen, die eher an quantenmechanische Effekte als an makroskopische Strukturen erinnern. Im Rahmen dieser Dissertation befasse ich mich mit kosmologischen Modellen, in denen die dunkle Materie aus ebensolchen ultraleichten Bosonen besteht. Zu diesem Zweck setze ich umfangreiche numerische Simulationen der kosmischen Strukturbildung ein, die in der Lage sind, anhand der nicht-linearen Evolution von Strukturen im Universum entscheidende physikalische Unterschiede zwischen diesem Modell dunkler Materie und dem Standardmodell hervorzuheben. Als ein wichtiges Ziel und Werkzeug der Dissertation habe ich dementsprechend das Programm AxiREPO entwickelt, das die entsprechenden Bewegungsgleichungen ultraleichter dunkler Materie numerisch löst und so Simulationen der erwarteten kosmischen Strukturbildung berechnen kann. Mithilfe dieses Programms habe ich große Simulationen ultraleichter und kalter dunkler Materie geplant, durchgeführt und analysiert. Hierbei wurden insbesondere verschiedene Anfangsbedingungen verwendet, um sowohl den Einfluss von Unterschieden in den primordialen Dichtefluktuationen im Vergleich zu solchen, die von der Dynamik der zu lösenden Bewegungsgleichungen herrühren, als auch verschiedene Werte für die Masse der ultraleichten Bosonen sowie die Berücksichtigung von baryonischer Materie untersuchen und vergleichen zu können

minimal-lagrangians: Generating and studying dark matter model Lagrangians with just the particle content

minimal-lagrangians is a Python program which allows one to specify the field content of an extension of the Standard Model of particle physics and, using this information, to generate the most general renormalizable Lagrangian that describes such a model. As the program was originally created for the study of minimal dark matter models with radiative neutrino masses, it can handle additional scalar or Weyl fermion fields which are $\mathrm{SU}(3)_{\mathrm{C}}$ singlets, $\mathrm{SU}(2)_{\mathrm{L}}$ singlets, doublets or triplets, and can have arbitrary $\mathrm{U}(1)_{\mathrm{Y}}$ hypercharge. It is also possible to enforce an arbitrary number of global $\mathrm{U}(1)$ symmetries (with $\mathbb{Z}_2$ as a special case) so that the new fields can additionally carry such global charges. In addition to human-readable and $\mathrm{\LaTeX}$ output, the program can generate SARAH model files containing the computed Lagrangian, as well as information about the fields after electroweak symmetry breaking (EWSB), such as vacuum expectation values (VEVs) and mixing matrices. This capability allows further detailed investigation of the model in question, with minimal-lagrangians as the first component in a tool chain for rapid phenomenological studies of "minimal" dark matter models requiring little effort and no unnecessary input from the user.Comment: 40 pages, 1 figure; version accepted by and published in CPC; code is available at https://gitlab.com/Socob/minimal-lagrangian

Influenced transplantation:a study into emerging Mafia groups in the United States pre-1920

The current literature on mafia transplantation into the US does not address the relationship between Italian mafia groups and United States mafia groups in the pre-prohibition era; any connection between the two is assumed rather than proven. This thesis argues that mafia transplantation theory, showing that the operation of an overseas outpost by an Italian mafia is insufficient in explaining the movement of mafiosi from Italy to the United States and the formation of groups in the United States. Instead, it suggests that members of groups in the United States used knowledge obtained in Italy, but in the form of imitation rather than control. This imitation was based on elements of cultural heritage with which the mafioso would be familiar, helping define the structure, relationships, rituals and modus operandi of the US groups.The research involved examining records from various archives; newspaper, police, immigration records, personal records, etc., in order to find proof of transplantation outposts operations, influence or of home-grown mafia. The thesis tackles transplantation in three areas; migration, markets and operations. It shows that generalised migration was not a factor in determining the transplantation of a mafia group and shows that individual Mafiosi travelled often as the result of increased law enforcement efforts against them rather than as part of a strategy. The thesis demonstrates that the markets in which these migrated Mafiosi operated in the United States were not comparable in a way that suggests the running of an outpost from Italy, but instead that these mafiosi’s groups adapted to changing conditions in the United States. At an operational level, the groups in the US fed off the reputation of their Italian counterparts but were imitating their practices rather than being subservient to their control. Overall the thesis shows that the Mafia groups in the US were not operating as an outpost under control of an Italian organisation and instead were made up of close affiliations of individuals with the relevant skills to take advantage of and adapt to the local American conditions in a form influenced by their Italian counterparts

The future of sustainable cities: governance, policy and knowledge

The aim of this special issue is to address a conceptual and empirical gap in the existing literature on sustainable cities. Uniquely, it brings together questions about the “what” (in this case, the content and representation of urban policy) of research on urban sustainability with “how” (the social organisation of knowledge and action) through the results of collaborative and comparative work. The special issue contains curated contributions that draw upon the findings of a comparative international project funded by Mistra (Swedish Foundation for Strategic Environmental Research) through the Mistra Urban Futures Centre, based in Gothenburg. The project sought to bring together two questions that are usually treated as separate in existing research approaches. They are the “what” and “how” of sustainable cities’ debates. By working in partnership with local policy-makers, practitioners and universities, each local area entered into a process of collaborative design in order to examine assumptions, expectations, processes and the outcomes of knowledge co-production. This paper introduces the conceptual ideas behind this initiative and so provides a frame for the reader to situate the contributions. It then outlines those articles to draw connections between them and concludes with a short summary of what research and societal lessons can be learnt from the project

Sedimentological, geomorphological and geochronological studies on Holocene tsunamis in the Lefkada / Preveza area (NW Greece) and their implications for coastal evolution

Research on palaeo-tsunami and palaeo-extreme wave events aims to provide new data about former events and is of remarkable importance in the eastern Mediterranean. In general, coastal geomorphology and fine-grained near-coast geological archives store information about coastal changes over medium to long timescales, as well as short, episodic processes such as palaeo-tsunami events. In the eastern Mediterranean and particularly for the Ionian Sea and the Lefkada / Preveza coastal zone (NW Greece), strong seismic activity and a high tsunamigenic potential are evident. Thus, comprehensive geo-scientific investigations were carried out in the Lefkada / Preveza coastal zone in order to decipher coastal change throughout time, and thereby detect, verify and date the influence of tsunami events on the coastal system and coastal evolution. Herein, particular focus was set on the distinguishability of event deposits in the geological record and the evaluation of event recurrence rates - an issue of major importance in extreme wave event research. In a first step, detailed analysis of the geomorphological and geomorphodynamic situation in the study area revealed several major disturbances of the coastal system, which mark episodically occurring major impulses of coastal evolution, entailing the recurrent reorganization of coastal balance. In a second step, comprehensive geo-scientific investigations on the main near-coast geological archives provided insight into the palaeogeographical evolution and the palaeo-event history of the Lefkada / Preveza area. In the sedimentary record of the Phoukias sand spit and the washover-dominated northern Lefkada Lagoon, distinct event deposits were identified. These event deposits provide a linkage to the inferred disturbances of the coastal system and allow the dating of the main impulses in coastal evolution. Detailed analyses of the event deposits - comprising sedimentological, microfaunal and geochemical investigations as well as the interpretation of the regional geomorphologic and geographic context - strongly suggest a tsunamigenic origin of the encountered event deposits, proving the significant impact of tsunamis on the coastal system. Moreover, numerous block and boulder fields were mapped along the coastline and equally point to the impact of high energy wave events. Altogether, four major tsunamigenic disturbances were identified throughout the late Holocene. These disturbances were dated to ~1000 BC, to at around or after 300 BC and, for the main washover structures in the northern Lagoon of Lefkada, to at around or after 300 AD, the latter event most likely triggered by the 365 AD earthquake off western Crete and the related tsunami. During the younger history of coastal evolution a fourth disturbance occurred sometime before 1850 AD. In addition to the detected 365 AD event, the presented findings fit well to previous investigations in adjacent coastal zones. From a geomorphological and geomorphodynamic point of view, the major tsunami events involved the breakdown of former coastlines (the Plaka), the formation of the Phoukias sand spit and the onset of intense coastal erosion in western Aktium Headland. Moreover, the inferred tsunami events contributed to the formation of block and boulder fields, induced the evolution of ridge structures in the northern part of the Phoukias sand spit and triggered the formation of at least one, probably two washover generations in the northern Lefkada Lagoon. The episodic occurrence of tsunami events was thus responsible for the formation of major geomorphological structures and modifications of the coastal system, which are recurrently masked and mimicked by long term, gradually operating coastal processes. These marked geomorphic changes provide clear evidence that tsunami-induced disturbances exert a major control on the evolution of the coastal system in the study area. In conclusion, this study presents new geo-scientific evidence of extreme wave event deposits and will thereby expand the regional and global data pool of palaeo-event and particularly palaeo-tsunami deposits. Moreover, it contributes to ongoing research concerned with the detection of extreme wave event deposits in near-coast geological archives, ultimately enabling an improved understanding of type and degree of their impact on the evolution of coastal systems

Modeling and Detection of Ice Particle Accretion in Aircraft Engine Compression Systems

The accretion of ice particles in the core of commercial aircraft engines has been an ongoing aviation safety challenge. While no accidents have resulted from this phenomenon to date, numerous engine power loss events ranging from uneventful recoveries to forced landings have been recorded. As a first step to enabling mitigation strategies during ice accretion, a detection scheme must be developed that is capable of being implemented on board modern engines. In this paper, a simple detection scheme is developed and tested using a realistic engine simulation with approximate ice accretion models based on data from a compressor design tool. These accretion models are implemented as modified Low Pressure Compressor maps and have the capability to shift engine performance based on a specified level of ice blockage. Based on results from this model, it is possible to detect the accretion of ice in the engine core by observing shifts in the typical sensed engine outputs. Results are presented in which, for a 0.1 percent false positive rate, a true positive detection rate of 98 percent is achieved