This master thesis explores the challenge of algorithmic hypothesis generation and its connection to potential inductive biases. In the scientific method, hypotheses are formulated and tested against data for validity. The process of hypothesis generation is, however, not explicitly formulated. A structured approach to hypothesis generation would allow for a near algorithmic process that could scale far beyond the current capabilities of science. The thesis explored the concepts of entropy, symmetry and minimum description length for use as inductive biases. Two algorithms were implemented and evaluated: one for symmetry finding and one for symbolic regression. The theoretical results show a strong connection between entropy and minimum description length with a weaker connection to symmetry. Both implementations indicate potential paths exist to partial or full automation of the hypothesis generation process. In general, there do not seem to exist fundamental issues in automating the process besides the challenge of its implementation. Thus, the thesis demonstrates a clear path forward towards partial or complete automation of the scientific method for physical research.

LiDAR is a remote sensing technology that uses a laser to map the surrounding environment. With its many applications, for example in autonomous vehicles, LiDAR is a growing field within technology and research. The silicon photomultiplier (SiPM) is a solid state device commonly used in the receiving system of a LiDAR. However, ambient light from sun or other light sources is also seen by the photodetector which creates noise in the receiving system. The purpose of this work is to examine how the performance of a 1D LiDAR with a SiPM receiver can be predicted, given a certain level of ambient light, target reflectance and measuring distance. This was carried through by working with mathematical models and comparing the outcomes to lab measurements of a certain LiDAR model. The outcome showed that describing the performance of the particular LiDAR by a model based on incident photon rate was difficult mainly due to the unknown relation between how the voltage signal threshold in the receiving electric circuit for when the LiDAR stops the time measurement relates to the number of microcells activated in the SiPM during a time span. However, the results obtained suggest a threshold value of between around 20 and 60 microcells activated within a 1 ns time interval, but further tests are needed in order to confirm or reject this. Of the two other approaches tried, the signal voltage model gave reasonable results for the values tested but in a rather indirect way. The other approach, describing the connection between DC noise and AC RMS noise in the receiving system gave results deviating between 40% and 320% from the lab results, i.e. not so good match. / LiDAR är en fjärranalysteknik som använder laser för att kartlägga ett geografiskt område. Med flertalet användningsområden, bland annat inom industrin för självstyrande fordon, är LiDAR ett växande teknik- och forskningsområde. Kisel-fotomultiplikatorn är en halvledarapparat som ofta används i LiDAR-mottagarsystemet. Bakgrundsljus från omgivningen detekteras dock också av fotodetektorn vilket orsakar  brus i mottagarsystemet. Detta arbete syftar till att testa metoder för hur prestandan hos en 1D LiDAR med en kisel-fotomultiplikator i mottagaren kan estimeras, i en viss nivå av bakgrundsljus, med en viss målreflektans på ett visst mätavstånd. Detta utfördes genom att arbeta med matematiska modeller och jämföra dess resultat med resultat från laborativa tester på en viss LiDAR-modell. Det visade sig vara svårt att beskriva prestandan för denna LiDAR enligt en modell baserad på fotonflöde, huvudsakligen på grund av den okända kopplingen mellan tröskelnivån i termer av voltsignal i mottagarkretsen då tidmätningen stoppas och antalet aktiverade mikroceller i kisel-fotomultiplikatorn under ett visst tidsintervall. De resultat som erhölls visar dock på en träskelnivå någonstans mellan 20 och 60 mikroceller inom ett 1 ns tidsintervall, men ytterligare tester bör genomföras för att konfirmera eller förkasta detta. Av de övriga två angreppssätten prövade, gav modellen baserad på voltsignal rimliga resultat för värdena testade men på ett relativt indirekt sätt. Försök till beskrivning av sambandet mellan DC brus och AC RMS brus i mottagarsystemet gav resultat med mellan 40% och 320% avvikelse från de laborativa mätningarna, relativt dåligt alltså.

High-grade gliomas (HGGs) are a type of malignant brain cancer, which include glioblastomas (GBMs). In adults, GBM is the most common malignant primary brain cancer. Attempts to treat patients with GBMs have been conducted for over a century, but the prognosis has only marginally improved. Current standard treatment involves surgical resection of the gross tumor volume (GTV), followed by radiotherapy and chemotherapy. Despite the efforts, the median survival for patients diagnosed with GBMs is less than 15 months. The inability to accurately determine the full extent of the tumor invaded regions in the brain is assumed to be the reason for the incurability of GBMs.  In radiotherapy, the microscopic infiltration of normal tissue by tumor cells in the vicinity of the GTV is accounted for by extending the target into a clinical target volume (CTV). Current recommended margin widths for GBMs range from 15 to 30 mm. Despite a generous margin, the persistent recurrence of GBMs following treatment indicates that the CTV delineations currently used might fail to encompass the entirety of the tumor cell distribution, leaving clonogenic tumor cells untreated. To improve the CTV delineation and possibly treatment of GBMs, novel approaches in determining the tumor infiltrated regions have been suggested in the form of mathematical modeling.  The aim of this project is to develop a mathematical model for the infiltration of glioma cells into normal brain tissue and implement it into a framework for predicting the full extent of tumor-invaded tissue for HGGs.    This thesis is comprised of papers I–II, an overview of the methodology, results, and discussion of the work. The work herein is presented in order of: 1) model development; 2) model verification. Paper I explores the robustness and results of a mathematical model for tumor spread in terms of its input parameters. By applying the model to a large dataset, the behavior of the model could be investigated statistically, and optimal input parameters determined. The results of the tumor invasion simulations were compared in terms of volumes to the conventionally delineated CTVs, which were found not to adhere to the pathways of the simulated spread. Paper II used the resulting simulated invasions from paper I to predict the overall survival (OS) of the same cohort of cases. OS prediction was better predicted by the simulated volumes of the tumor spread than the size of the GTV. The results showed the potential of improving OS prediction and furthermore demonstrated a new methodology for indirect model verification that does not rely on histopathological data. Planned future work will revolve around dose prescription and plan optimization based on the simulated tumor spread, model investigation using artificial intelligence methods, and finally, practical implementation of the model into research versions of treatment planning systems.

Scanning Electron Microscopy combined with Energy Dispersive X-ray Spectroscopy (SEM-EDS) is a widely applied elemental microanalysis method. The integration of silicon drift detectors (SDDs) has notably enhanced EDS performance, enabling precise elemental identification due to its large sensitive area and low output capacitance.  Accurate simulations of SDDs can provide insights that enable the design and optimization of future models without the need for costly and time-consuming experimental iterations. Moreover, the current model-based quantification methods for EDS applications have reached their maximum predictive accuracy. As such, creating a more accurate simulation model could help achieve a higher level of precision in these quantification models, which would be immensely valuable for all EDS applications.  With this objective in mind, a simulation framework for modeling SDDs in EDS was developed based on Geant4, Allpix Squared, and COMSOL Multiphysics. The simulation encompasses the entire physics pipeline, including characteristic X-ray emission from the target sample and its absorption in the detector. The generated charge carriers within the detector are propagated through the internal electric field of the SDD, and their individual charge contribution is measured to simulate EDS spectra. The simulated model was compared to existing literature and in-house experimental measurements, showing strong agreement in the case of a well-tuned SDD. Limitations of the simulation framework are discussed, and further research to enhance accuracy and speed is explored.

The Swampland program is way of sorting effective field theories based on conjectures of how an effective field theory consistent with quantum gravity should look like. In this thesis we take a closer look at the No Global Symmetries Conjecture, the Weak Gravity Conjecture, the de Sitter Conjecture and the Trans-Planckian Censorship Conjecture. The Weak Gravity Conjecture generalized to arbitrary dimensions and p-forms is tested under dimensional reduction and its sharpened version is used to discuss how under this conjecture non-supersymmetric AdS geometries are unstable. The de Sitter Conjecture and the Trans-Planckian Censorship Conjecture are compared to show that they give similar predictions based on different assumptions. Lastly we provide an example of a theory emerging from the swampland that utilizes the instability of AdS geometries to model our universe as the boundary of a higher dimensional expanding bubble. / Swampland-programmet är ett sätt att sortera effektiva fältteorier baserat på antaganden om hur en effektiv fältteori förenlig med kvantgravitation bör se ut. I den här avhandlingen tittar vi närmare på No Global Symmetries-antagandet, Weak Gravity-antagandet, de Sitter-antagandet och Trans-Planckian Censorship-antagandet. Weak gravity-antagandet generaliserat till godtyckliga dimensioner och p-former testas under dimensionsreduktion och dess skärpta version används för att diskutera hur man via detta antagande finner en instabilitet i icke-supersymmetriska AdS-geometrier. De sitter-antagandet och Trans-Planckian Censorship-antagandet jämförs för att visa att de ger liknande förutsägelser baserat på olika frågeställningar. Slutligen ger vi ett exempel på en teori som växer fram ur programmet som använder instabiliteten hos AdS-geometrier genom att modellera vårt universum som randen på en expanderande bubbla i högre dimensioner.

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.

Quantum holonomies are non-Abelian Geometric Phases predominantly observed in adiabatic, non-adiabatic, or measurement-based quantum evolutions. Their significance lies in their potential utility within quantum computing due to their robustness against noise throughout the parameter path. In this report, we detail the foundational methods necessary for constructing holonomic non-Abelian gates specifically designed for tripartite states <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%7CW%3E" data-classname="equation" data-title="" />and <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%7C%5Cbar%7BW%7D%3E" data-classname="equation" data-title="" />, which serve as the logical qubits in our project. Given that the existence of a universal set of gates has already been demonstrated for each of these evolution types, our project delves into the advantages of applying these basis states across the three evolution categories. We have reformulated the Nuclear Quadrupole Resonance (NQR) Hamiltonian to be exclusively composed of two-body terms, thus rendering it more experimentally feasible. Furthermore, we have connected the W states with the remaining tripartite states to construct a four-level model system and generalized gates within this framework. Lastly, we introduce a measurement-based method that maintains its non-Abelian attributes even in the Zeno limit, where the process of projective measurement gradually approaches the adiabatic model. / Icke-Abelska geometriska faser, så kallade kvantholonomier, observeras huvudsakligen i adiabatiska, icke-adiabatiska eller mätningsbaserade manipulationer av kvanttillstånd. De har stor potential till användning inom kvantdatorberäkningar på grund av deras robusthet mot olika typer av brus. I den här rapporten beskriver vi de grundläggande metoderna som är nödvändiga för att konstruera holonoma kvantgrindar som är speciellt utformade för trekroppstillstånden <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%7CW%3E" data-classname="equation" /> och <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%7C%5Cbar%7BW%7D%3E" data-classname="equation" data-title="" />, som fungerar som de logiska kvantbitarna i projektet, givet att det är redan bevisat att alla dessa modeller kan klara kraven för universalitet. Den här rapporten fokuserar på fördelarna med att tillämpa dessa logiska kvantbitar för tre olika evolutionskategorier. Vi har omformulerat kärnkvadrupolresonans Hamiltonianen så att den uteslutande består av tvåkroppstermer, vilket gör den mer experimentellt genomförbar för att realisera adiabatiska holonoma kvantgrindar. Vidare har vi kopplat <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?W" data-classname="equation" data-title="" />-tillstånden med andra trekroppstillstånden för att konstruera ett så kallat sammanflätat <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5CLambda" data-classname="equation" data-title="" />-system och icke-adiabatiska holonoma kvantgrindar inom detta ramverk. Slutligen introducerar vi en mätningsbaserad metod som, till skillnad från tidigare resultat, bibehåller sina icke-Abelska attribut även i Zeno-gränsen, där processen med projektiv mätning gradvis närmar sig den adiabatiska kärnkvadrupolresonans-modellen.

In this study, the weather impact on lidar signals has been researched. A lidar system was placed with a target at approximately 90 m and has together with a weather station collected data for about a year before this study. By using the raw detector data from the lidar, the full waveform can be obtained and the amplitude of the return pulse can be calculated. Atmospheric attenuation of lidar signals is often modeled using the lidar equation, which predicts an exponential decrease in energy over the distance. The factor in the exponent is referred to as the extinction coefficient and it is the main property studied in this thesis. By utilizing models for the extinction coefficient under different weather conditions, it is possible to simulate the performance of the lidar.  The extinction coefficient was calculated using different empirical models. The empirical models investigated in this thesis are the Kim and Kruse models for known visibility, the Al Naboulsi model for different types of fog with known visibility, the Carbonneau model for known precipitation amount in rainy conditions, and a similar model for snowy conditions. For the case of rain, a physical model was also used, which is derived through Mie theory. The physical model requires a particle size distribution, which is the number of particles of a certain radius per unit volume. A particle size distribution for rain was generated using the Ulbrich raindrop size distribution, using the precipitation amount recorded by the weather station. Particle size distributions for radiation and advection fog were also simulated.  The measured attenuation in lidar signals was compared to the predicted attenuation that was calculated using different models for the extinction coefficient in the lidar equation. Generally, the models tend to underestimate the amplitude of the return pulse. This can partially be explained by the assumptions used to derive the lidar equation, which neglects all augmentation of the beam. The visibility models gave more accurate results compared to the precipitation models. This was expected, since visibility is defined as a measure of attenuation and precipitation amount is not.  When a lidar signal is emitted, the light will be reflected from optical surfaces within the lidar and cause a pulse to be detected. This pulse is referred to as the zeropulse. In the first couple of meters of the transmission, we expect to see some backscattered light from adverse weather, since the detector has a larger solid angle at shorter distances. This returned light will be combined with the zeropulse and cause it to expand in width. By examining the zeropulse, it was possible to observe a difference between the average zeropulse under some different weather conditions. This leads to the conclusion that it may be possible to extract some information about current weather conditions from the zeropulse data, given that there is little ambient light and snowy weather conditions.  By integrating the zeropulse, variations in the shape of the zeropulse could be described by a single value. Then by separating the data into low and high visibility populations, the zeropulse integral could be used to predict the visibility. The conclusion was that the zeropulse integral can accurately predict whether visibility is above or below a threshold value, given that there is little ambient light and the visibility is known to be below 19950 m.

Att planera en laboration i skolan är en central del i sin lärarprofession, speciellt om man undervisar i de naturvetenskapliga ämnena. Denna undersökning har varit ett försök till att kartlägga vilka beslut lärare tar i beaktande när de planerar en laboration samt vilka konsekvenser dessa olika beslut får. För att kunna kategorisera laborationer kan man använda sig av frihetsgrader. Frihetsgrader beskriver hur mycket information som ges till eleverna när de ska genomföra en laboration. Detta har varit ett av flera användbara verktyg för att analysera olika laborationer. I denna undersökning har sex fysiklärare intervjuats där de fick svara på olika frågor om laborationer som de själva använt sig av. Dessa intervjuer har analyserats fenomenografiskt och från denna analys var det möjligt att manifestera sju huvudkategorier. Dessa huvudkategorier är en konkretisering av svaret på frågeställningen: Vilka beslut tar läraren när hen planerar sin laboration med avseende på öppenheten i laborationen? Dessa huvudkategorier är unika där lärarnas olika uttalanden enbart passar in i en av kategorierna. Ett exempel på en huvudkategori är om läraren väljer att ha med tabeller/rader som eleverna fyller i, i laborationsinstruktionen. Tabeller/rader bildar bland annat ett förtydligande i instruktionerna. Ett annat exempel är var läraren väljer att placera utrustningen. Att ha utrustningen framplockad som stationer där eleverna ska laborera gör att man sparar tid men eleverna får inte sätta ihop utrustningen på egen hand.

Systems of atoms have their kinetic energy distributed between three parts: translation, rotation and vibration. These are usually kept about the same following a Maxwell distribution, but under certain circumstances, this equilibrium might break. This would lead to, for example, ice melting anisotropically. In this report, it was determined if ice experiences anisotropic movement when it is exposed to a laser pulse in the form of an electric field. If ice experiences anisotropy, a time frame from when ice moves anisotropically until the movement is isotropic was established. This was done through molecular dynamics simulations using the GROMACS program on a system of solid ice crystals with multiple levels of field strengths. The simulations showed that anisotropy clearly exist in a solid ice structure when affected by the pulse, no matter if it's melting or not. The time period for when anisotropy existed in the ice was normally until the system had melted, which is about a minimum of 40 ps. / Varje system av atomer har tre delar som utgör deras kinetiska energi: translation, rotation och vibration. Dessa brukar hållas jämna i atomsystemen i en Maxwell fördelning, men under visa omständigheter kan detta brytas. Detta skulle leda till att t.ex. is smälts anisotropt. I denna rapport  undersöktes det ifall is som utsätts för en laserpuls, uttryckt med ett elektriskt fält, fluctuerar anisotropt. Om isen smältes anisotropt bestämdes en tidsram från när isens rörelse var anisotropt till när rörelsen blev isotrop.  Detta gjordes genom molekyldynamik simuleringar i programmet GROMACS på ett system med fasta iskristaller med varierande fältstyrka. Det som simuleringarna visade var att det tydligt finns anisotropi i isen när den blivit påverkad av en laser puls, oavsett om den var smältande eller inte. Tidsperioden denna isotropi i isen varade var till när systemet fullständigt smällt, vilket brukade ta minst 40 ps.