This paper uses the Pantheon+ data set that consists of 1701 light curves of 1550 unique type IaSupernova to find constraints on various cosmological models and compare them with a varying darkenergy model proposed by Chevallier, Polarski and Linder in the early 2000s and analyze it deeper.The results show a tipping point from a decelerating universe to an accelerating one at a redshift ofz = 0.35, and a second tipping point back to a decelerating universe in the future at z = −0.19. The flatChevallier-Polarski-Linder (CPL) model leads to a matter dominated universe with Ωm = 0.52 ± 0.08while the relative dark energy density Ωde = 0.48±0.08. Finally, taking all these models and comparingthem with the results that are found from Taylor expanding the distance relation shows that they aremostly consistent with a deceleration parameter around q0 = −0.28.

This work is a preliminary study of the background of a search for dark, long-lived particles in the IceCube detector. The high flux of atmospheric muons in IceCube is considered background to the detector's primary science goal, which is to detect astrophysical neutrinos through the emission of Cherenkov radiation. However, high muon rates may break fresh ground for the detection of hypothetical dark particles. These could be created during the Bremsstrahlung-like interaction of an energetic muon and decay into a muon and an electron. Such an event is expected to produce a characteristic signal in the detector: A track-like signal produced by the Cherenkov-photon emitting muon, followed by a gap due to the electric neutrality of the dark particle. The subsequent decay of the dark particle into a muon produces a further track-like signal. In order to probe the success rate of this endeavor, two precursory statistical analyses are made using simulated data provided by CORSIKA. In order to obtain a clear track-gap signature that is not diluted by other particles, atmospheric muons should preferably travel in a bundle of few to no other muons. The muon multiplicity in incident bundles is estimated. The study reveals that 50% of all muons are single muons at the point of production, while their relative number increases to 70% by the time they reach the detector boundary. A possible background to this search is assumed to be produced by a collinear neutrino interacting after a stop of the muon. The muon may stop due to energy loss or spontaneous decay. In that case, the resulting signal is expected to be identical to the desired track-gap signature. A preliminary background rate is obtained by performing an event selection. The resulting background rate after the selection process is 5e-5 Hz, which is a reasonable result given a neutrino flux of mHz. A more thorough selection taking into account the particle energies as well as IceCube's limited energy resolution is expected to lower the rate.

Aims. The aim of this work is to investigate any presence of transit timing variations (TTVs) in a sample of observed targets that has light curves in both K2 mission data and TESS mission data.  Methods. The original sample utilised here was one from the doctoral thesis of D. Soto (2020) with candidates from K2 data. Cross-referencing for corresponding light curves in TESS was done with a customised Python script created for the purposes of this work, automating the process of obtaining light curves using only one mission ID. A transit search was performed on the light curves of each mission separately with the Python software package OpenTS. The candidates with transits in both light curves were subjected to a TTV search using the Python software package PyTTV. The PyTTV software utilises both mission light curves in creating a joint light curve.  Results. Orbital periods, Porb, and transit center times, t0, for 30 targets were updated using joint light curves from the K2 and TESS missions. Seventeen of these systems are found to have non-linear trends in their transit times. These also have constraints for the periods and amplitudes of the TTVs.  The disposition distribution of the 30 systems is that 19 candidates are unregistered candidates, ten are registered planetary candidates or TOIs and eight are registered known planets.  Conclusions. Out of the reference sample by D. Soto (2020) consisting of 564 targets, 257 targets had a corresponding TESS light curve. Out of the 257 targets, a new sample of 45 targets was contrived through a transit search where they all show distinct transits in both missions light curves. Out of these, fifteen targets were not suitable for a TTV search. A final sample of 30 targets are presented, with seventeen targets showing signs of TTVs and thirteen targets showing a linear trend. The parameters of orbital period and transit centre times are updated for all 30 final candidates. Seventeen candidates are shown to have variations in the transit times and are presented with diagnostics. The candidates with transit timing variations should be further investigated for potential validation or follow-up observations. The unregistered candidates as well as the planetary candidates and TOIs should be considered for follow-up observations or similar validation, to confirm or discard a planetary status.

The determination of the solar oxygen abundance is a topic that has long beenunder debate, where the exact value has varied between researchers. These variationsin the oxygen abundance have implications on our understanding of the Sun and itsinterior as well as our understanding of other stars. The aim of this report is to explorethe di erences between three observations; the Liège, Hamburg and SST, and their effecton the solar oxygen abundance calculated from the 777 nm triplet. In the reportit was found that the abundance from the Liège and SST data was lower and in betteragreement (A(O) ≈ 8.709 dex) compared to the Hamburg data (A(O) ≈ 8.732 dex).One of the potential reasons for these di erences explored in the thesis were the e ectsof magnetic  elds. After comparing the di erences it was argued that the SST dataset as well as the Liège could be considered more reliable compared to the Hamburg.The argued abundance was therefore of a somewhat lower value which does not helplessen the inconsistency between solar models and helioseismology. / Bestämningen av mängden syre i solen har länge varit ett debatterat område där det exakta numeriska värdet varierat bland forskare. Dessa variationer av mängden syre ger konsekvenser för vår förståelse av solen och dess inre samt för vår förståelse av andra stjärnor. Syftet med denna rapport är att utforska skillnaderna mellan tre observationer; från Liège, Hamburg och SST, samt deras påverkan på mängden syre i solen beräknad från 777 nm tripletten. Rapporten fann att mängden syre beräknad från Liège- och SST-datan både var lägre samt stämde bättre överens (A(O) ≈ 8.709 dex) i jämförelse med mängden från Hamburg observationen (A(O) ≈ 8.732 dex). En potentiell anledning till skillnaden i resultat som utforskades i denna uppsats var påverkan av magnetiska fält. Efter jämförelse av skillnaderna kunde det konstateras att datan från SST så väl som från Liège kan anses mer pålitliga i förhållande till Hamburg-datan. Den förespråkade mängden syre var åt det lägre hållet vilket inte bidrar till minskningen av avvikelserna mellan modeller av solen och mätningar via helioseismologi.

Detecting neutrinos, especially ultra-high-energy (UHE) neutrinos, is inherently challenging. Highly sensitive detection devices are required to effectively capture these rare particles, which often results in significant noise in the data. This project focuses on enhancing the detection sensitivity of UHE neutrinos interacting with glacier ice by employing deep learning and transformer models. These models are trained on simulated data that mimics the radio signals produced by neutrino interactions in ice. The developed models have demonstrated improved performance compared to current hardware implementations, offering a promising advancement in neutrino detection technology.

40 light years from Earth an Earth sized exoplanet called Trappist 1d orbits the M-dwarf star called Trappist 1. Trappist 1d is located in the habitable zone where liquid water could exist on the surface of the planet which raises the question: Could Trappist 1d be habitable? Since it is not known what the planet looks like, several simulations of potentially habitable climates were made including different water levels and atmospheric pressures with Earth-like atmospheres. Real observations with JWST and VLT are currently being made for the light passing through Trappist 1d’s potential atmosphere. In order to interpret the data and make any conclusions about the habitability of Trappist 1d, simulated spectra need to be made for the different scenarios. The goal of this project was to produce radiance spectrum of how observations viewed through different instruments would look like for the different planetary scenarios. The result of the project gave spectra that were quite similar, but differed specifically in the depths of the lines, meaning that in theory it could be possible to distinguish between the planetary scenarios via observations. In reality, because of uncertainties in the observations, it is probably not possible to distinguish between the different planetary models, but it might be enough to conclude if the planet has an Earth like atmosphere containing CO2 and H2O or not. / 40 ljusår bort från jorden kretsar en jordlik planet vid namn Trappist 1d runt en röd dvärgstjärna. Trappist 1d ligger i den så kallade beboeliga zonen där det är möjligt för flytande vatten att existera på planetens yta. Detta medför frågan: Finns det förutsättningar för liv på Trappist 1d? Eftersom det inte är känt hur det ser ut på planeten har flera potentiellt beboeliga klimat simulerats för olika vattennivåer och atmosfärstryck med en jordlik atmosfär. Olika instrument på teleskopen JWST och VLT samlar för tillfället in data för observationer genom Trappist 1d:s potentiella atmosfär. För att kunna tolka datan och dra slutsatser om förutsättningarna för liv på Trappist 1d behövs simulerade spektrum att jämföra med. Målet med det här projektet är att producera simulerade radians spektrum för hur observationer med de olika instrumenten hade sett ut för de olika scenarierna. Resultatet gav spektrum som främst skiljde sig i djupet av linjerna i graferna, vilket betyder att i teorin är det möjligt att skilja mellan de olika scenariona för en observation. På grund av osäkerheter i observationen, är det troligtvis inte möjligt i praktiken att se exakt vilket scenario det tillhör, men det kan vara tillräckligt för att säga ifall planeten har en jordlik atmosfär som innehåller vatten och koldioxid eller ej.

In this report, we present a novel Bayesian inference framework to reconstruct the three-dimensional initial conditions of cosmic structure formation from data. To achieve this goal, we leverage deep learning technologies to create a generative model of cosmic initial conditions paired with a fast machine learning surrogate model emulating the complex gravitational structure formation. According to the cosmological paradigm, all observable structures were formed from tiny primordial quantum fluctuations generated during the early stages of the Universe. As time passed, these seed fluctuations grew via gravitational aggregation to form the presently observed cosmic web traced by galaxies. For this reason, the specific shape of a configuration of the observed galaxy distribution retains a memory of its initial conditions and the physical processes that shaped it. To recover this information, we develop a novel machine learning approach that leverages the hierarchical nature of structure formation. We demonstrate our method in a mock analysis and find that we can recover the initial conditions with high accuracy, showing the potential of our model. / I detta examensarbete presenteras ett ramverk baserat på Bayesiansk inferens för att rekonstruera de tredimensionella begynnelsevärdena av kosmisk struktur från data. För att uppnå detta har tekniker från djupinlärning använts för att skapa en generativ modell av kosmiska begynnelsevärden, vilket parats ihop med en snabb maskininlärningsmodell som efterliknar den komplexa gravitationella strukturformationen. Utifrån moderna teorier inom kosmologi skapades alla observerbara strukturer i universum från små kvantfluktuationer i det tidiga universumet. Allt eftersom tiden gick har dessa fluktuationer vuxit via gravitationella krafter för att forma det av galaxer uppspända kosmiska nät som idag kan observeras. På grund av detta bibehåller en specifik form av en konfiguration av den observerade galaxdistributionen ett minne av sina begynnelsevärden och de fysikaliska processer som formade den. För att återfå denna information presenteras en maskininlärningsmetod som utnyttjar den hierarkiska naturen av strukturformation. Metoden demonstreras genom ett modelltest som påvisar att begynnelsevärdena kan återfås med hög noggrannhet, vilket indikerar modellens potential.

In this project we search for a planet in a triple-stellar system that could be habitable and a potential host to complex, human-like life. The first step in the search for potentially habitable planets involved examining catalogs of triple-stellar systems with known exoplanets and quadruple-star systems in which one of the stars could be swapped for a planet. Then, for all the potential planets, we estimated whether they lay within the habitable zone. For all systems with planets in the habitable zone, we used previously published climate model simulations of similar systems to gain a better understanding of the potential climate of these planets. Furthermore, the simulation program VPlanet was used to check the dynamical stability of systems in which one of the stars was swapped with a planet. In total, 10 planets were found to be within the habitable zone and were closer examined, with 6 of them being already existing planets and 4 of them being fabricated. Despite all of the planets lying within the habitable zone, they showed varying degrees of suitability for hosting life, with most planets being substantially cooler than Earth. None of the existing exoplanets had a suitable climate for human-like life, and none of the fabricated systems proved to be dynamically stable. However, the fabricated system that demonstrated the highest amount of stability in simulations was the one in which the planet and the stars were most similar in size. This leads us to conclude that optimal dynamical stability is achieved when the system components are of comparable size.

This thesis investigates the archaeological material beneath the fairy tale Frau Holle through well deposits. Wells used to serve a ritual purpose, but our understanding of these rituals is limited. By bridging the gap between archaeology and ethnography, this thesis aims to uncover how fertility beliefs were ritually expressed in wells and how far back in time this tradition can be traced in the Low Countries and beyond. Three find categories are analysed: plough shares, harvesting tools and wheels. The material is approached through the theory of the biography of wells, which determines how an artefact can be interpreted based on its location within the well. Furthermore, the perspective on religion highlights two aspects of belief: the substance and the function. The continuity of the tradition is approached through this framework. The concepts of ritual and profane are in this thesis not treated as mutually exclusive. The study shows that plough shares, harvesting tools and wheels were deposited in wells with a connection to seasonality, to bridge the winter, or for land initiation. The wheels may correlate with the worship of the Germanic goddess Nerthus or related beings. The exploration of the material demonstrates that there was a cosmological continuity in the function of this religion for approximately two millennia. / Denna uppsats undersöker det arkeologiska materialet bakom sagan Frau Holle genom brunndeponeringar. Brunnar brukade ha ett rituellt syfte, men vår förståelse av dessa ritualer är begränsad. Genom att överbrygga klyftan mellan arkeologi och etnografi syftar denna uppsats till att avslöja hur fruktbarhetstro rituellt uttrycktes i brunnar och hur långt tillbaka i tiden denna tradition kan spåras i ”lågländerna” och bortom. Tre fyndkategorier analyseras: plogskär, skörderedskap och hjul. Materialet analyseras genom en teori om brunnars biografi, som avgör hur en artefakt kan tolkas utifrån dess placering i brunnen. Vidare lyfter ett perspektivet på religion fram två aspekter av tro: substansen och funktionen. Traditionens kontinuitet analyseras genom denna teori. Begreppen religiös och profan behandlas i denna uppsats inte som ömsesidigt uteslutande. Studien visar att plogskär, skörderedskap och hjul deponerades i brunnar med koppling till säsongernas förändring, för att överbrygga vintern eller för landinitiering. Hjulen kan korreleras med dyrkan av den Germanska gudinnan Nerthus eller relaterad varelser. Utforskningen av materialet visar att det fanns en kosmologisk kontinuitet i denna religions funktion under ungefär två årtusenden.

This thesis uses theoretical studies, and numerical simulations to provide results of the experimental reach to detect the QCD axion as dark matter in a Non-standard cosmological background. Assuming that the QCD axion constitutes the full CDM abundance of the universe, this thesis elaborates on its potential detection from experimental setups for the mass window of the axion. The set of results that is obtained here are the relic CDM energy density of axions produced by the vacuum realignment mechanism and the CDM energy density of axions produced from the decay of a network of cosmic strings. This thesis provides results regarding the possibility to detect a primordial gravitational wave relic, which is possible within some favorable cosmological scenarios for the background.