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Over the past decades, mesoporous silica has emerged as a new material with interesting physical and chemical properties, such as high surface-to-volume ratio, stability, and the feasibility of surface functionalization, amongst others. Mesoporous silica provides an opportunity to improve conventional commercial catalyst supports, and sorbent due to its low-cost synthesis. In this research field, investigations on various materials prepared by different techniques as potential support have been reported. The main objective of the studies was to produce highly stable mesoporous materials for energy and environmental applications using simple and low-cost synthesis. In this thesis, we utilized the sol-gel and self-templating processes in synthesizing three types of highly porous silica nanomaterials, mainly aerogels (SiO2 AG), xerogel (SiO2 XG), and nanosheets (SiO2 NS). SiO2 AG and SiO2 XG were synthesized using the sol-gel method, while SiO2 NS was synthesized using the soft-templating hydrothermal technique. SiO2 AG, SiO2, XG, and SiO2 NS are explored as catalyst support for low-temperature carbon monoxide (CO) oxidation and compared to commercial Fumed Silica. The synthesized materials are investigated as metal support materials (M/SiO2) for environmental applications such as CO oxidation and carbon dioxide (CO2) adsorption. The morphology of the synthesized materials was investigated experimentally using several characterization techniques such as X-ray Diffraction (XRD), X-ray Photo-electron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), Thermo-Gravimetry-Differential Scanning Calorimetry (TGA-DSC), gas adsorption by Brunauer–Emmett–Teller (BET) method, Fourier Transform Infra-Red spectroscopy (FTIR), UV-Vis spectroscopy, and Temperature Programmed Reduction (TPR) for understanding the surface chemistry of supports. The M/SiO2 was subjected to a detailed study of the morphology before, during, and after the low-temperature CO oxidation reaction unde, Under de senaste decennierna har mesoporöst kisel uppstått som ett nytt material med intressanta fysikaliska och kemiska egenskaper, såsom hög yta-till-volym-förhållande, stabilitet och möjligheten till ytterligare funktionalisering av ytan, bland annat. Mesoporöst kisel ger en möjlighet att förbättra konventionella kommersiella katalystbärare och adsorbenter på grund av dess kostnadseffektiva syntes. Inom detta forskningsområde har undersökningar av olika material framställda med olika tekniker som potentiella bärare rapporterats. Det primära målet med studierna var att producera högstabila mesoporösa material för energi- och miljöapplikationer med hjälp av enkel och kostnadseffektiv syntes. I denna avhandling använde vi sol-gel och självtemplateringsprocesser för att syntetisera tre typer av högporösa kiselnanomaterial, huvudsakligen aerogeler (SiO2 AG), xerogeler (SiO2 XG) och nanoskikt (SiO2 NS). SiO2 AG och SiO2 XG syntetiserades med hjälp av sol-gelmetoden, medan SiO2 NS syntetiserades med hjälp av den mjuka templaterings hydrotermiska tekniken. SiO2 AG, SiO2 XG och SiO2 NS utforskades som katalysatorbärare för kolmonoxid (CO) oxidation vid låga temperaturer och jämfördes med kommersiell Fumed Silica. De syntetiserade materialen undersöktes som metallbärarmaterial (M/SiO2) för miljöapplikationer såsom CO-oxidation och koldioxid (CO2) adsorption. Morfologin hos de syntetiserade materialen undersöktes experimentellt med hjälp av flera karaktäriseringsmetoder såsom röntgendiffraktion (XRD), röntgenfotoelektronspektroskopi (XPS), transmissions elektronmikroskopi (TEM), termogravimetrisk-differential scanning kalorimetri (TGA-DSC), gasadsorption med Brunauer-Emmett-Teller (BET) metoden, Fourier-transform-infraröd spektroskopi (FTIR), UV-Vis spektroskopi och temperaturprogrammerad reduktion (TPR) för att förstå ytkemin hos bärarna. M/SiO2 utsattes för en detaljerad studie av morfologin före, under och efter CO-oxidationsreaktionen vid låga temperatu, QC 2024-08-30

This paper presents a systematic approach to derive physical bounds for passive systems, or equivalently for positive real (PR) functions, directly in the time-domain (TD). As a generic, canonical example we explore the TD dielectric response of a passive material. We will furthermore revisit the theoretical foundation regarding the Brendel-Bormann (BB) oscillator model which is reportedly very suitable for the modeling of thin metallic films in high-speed optoelectronic devices. To this end, an important result here is to re-establish the physical realizability of the BB model by showing that it represents a passive and causal system. The theory is based on Cauer's representation of an arbitrary PR function together with associated sum rules (moments of the measure) and exploits the unilateral Laplace transform to derive rigorous bounds on the TD response of a passive system. Similar bounds have recently been reported for more general casual systems with other a priori assumptions. To this end, it is important to note here that the existence of useful sum rules and related physical bounds rely heavily on an assumption about the PR functions having a low- or high-frequency asymptotic expansion at least of odd order 1. As a particular numerical example, we consider here the electric susceptibility of gold (Au) which is commonly modeled by well established Drude or BB models. Explicit physical bounds are given as well as an efficient fast-Fourier transform -based numerical procedure to compute the TD impulse response associated with the nonrational BB model.

The purpose of this study was to compute the classical Compton amplitude by solving the equations of motion through perturbative expansion for scalar QED. The interaction of interest was that of a massive charged relativistic point particle without spin scattering off of a photon. The tree-level classical Compton amplitude was then extracted by projection of the solved photon field onto the outgoing polarization vector, and the resulting amplitude was consistent with recent work and literature. The applied theory, being the framework of worldline QFT, applied to this simpler scalar QED case has in previous studies proven to provide insight into more complex gravitational problems where e.g. spin too is considered., Syftet med denna studie var att beräkna den klassiska Comptonamplituden genom att lösa rörelseekvationerna via perturbativ expansion inom skalär kvantelektrodynamik. Interaktionen av intresse var en massiv laddad relativistisk punktpartikel utan spinn som sprider sig mot en foton. Den klassiska loopfria Comptonamplituden extraherades sedan genom projektion av det lösta fotonfältet på den utgående polarisationsvektorn, och den resulterande amplituden stämde överens med tidigare arbete och litteratur. Den tillämpade teorin, vilket är ramverket av worldline QFT, för detta enklare kvantelektrodynamikfall har tidigare påvisats ge insikt i mer komplexa problem med gravitation där exempelvis även spinn beaktas.

A theoretical symmetry between bosons and fermions, supersymmetry, turns out to provide satisfying solutions to some of the problems with the standard model. No experiments have yet shown any indication of its existence. Supersymmetric quantum mechanics (SUSY QM) was originally studied in the context of broken supersymmetry, as an environment for testing methods for quantum field theory. SUSY QM soon became a field of study of its own, and several applications of it were found beyond the testing for supersymmetry breaking. In this thesis, supersymmetric quantum mechanics is presented. The main formulas are derived and the interpretation of the mathematical formalism as a boson-fermion symmetry is discussed. Two of the aforementioned applications, shape invariant potentials and quasi-solvable systems, are investigated. It is found that SUSY QM provides a concise method for classifying and solving potentials, which is a property connected to shape invariance. Two known solvable potentials are shown to be shape invariant. Furthermore, it is shown how SUSY QM can be used to solve and find new quasi-solvable potentials. Finally, the two applications are used as motivating examples to argue that there is an incentive to study supersymmetric quantum mechanics., En teoretisk symmetri mellan bosoner och fermioner, supersymmetri, visar sig ge tillfredsställande lösningar på några av de problem som finns med standardmodellen. Inga experiment har hittills indikerat att symmetrin existerar. Supersymmetrisk kvantmekanik (SUSY QM) studerades från början för att pröva metoder inom kvantfältteori relaterade till supersymmetribrott. SUSY QM började snart studeras som ett eget område, och flera applikationer hittades utöver att testa för supersymmetribrott. I den här uppsatsen presenteras supersymmetrisk kvantmekanik. De huvudsakliga formlerna härleds och tolkningen av den matematiska formalismen som en boson-fermion symmetri diskuteras. Två av de tidigare nämnda applikationerna, forminvarianta potentialer och kvasi-lösbara system, undersöks. Det visar sig att SUSY QM ger oss en koncis metod för att klassificera och lösa potentialer, vilket är en egenskap som är kopplad till forminvarians. Två kända lösbara potentialer visas vara forminvarianta. Vidare visas hur SUSY QM kan användas för att lösa och hitta nya kvasi-lösbara potentialer. Slutligen används dessa två applikationer som motiverande exempel för att argumentera för att det finns anledning att studera supersymmetrisk kvantmekanik.

This thesis focuses on the connection between knot theory and Chern-Simons theory. In this regard, knot theory is explored and the Chern-Simons theory is discussed in terms of principle bundles. By quantising Chern-Simons theory a link invariant emerges: the vacuum expectation value, up to a factor of the partition function, of the product of a collection of Wilson loops. This link invariant depends on the gauge group and the representation, and relates to other link invariants, such as the Jones Polynomial, the HOMFLY-PT polynomial and the Kauffman polynomial. The discovery of this by Witten led to an intrinsically 3-dimensional way to calculate knot invariants. Moreover, by considering complexified tangent bundles and self-dual Lorentz connections on trivial complex tangent bundles, a solution to the Wheeler-De Witt equation was given, called the the Chern-Simons state. Furthermore, quantum states are considered as link invariants in terms of the components of self-dual Lorentz connections and their conjugate momentum., Denna avhandling fokuserar på kopplingen mellan knutteori och Chern-Simons teori. För att göra detta så utforskas knutteori och Chern-Simons teori samt G-buntar. Chern-Simons teori kvantiseras och då dyker det upp en länkinvariant: det onormaliserade vakuum väntevärdet av en samling Wilson loopar. Länkinvarianten beror på vilken gauge grupp och representation som används och har ett samband med andra länkinvarianter t.ex. Jones polynomet, HOMFLY-PT polynomet och Kauffman polynomet. Wittens upptäckt av detta ledde till ett 3-dimensionellt sätt att kalkylera länkinvarianter. Genom att fokusera på komplexifierade tangentbuntar och självduala Lorentz buntanslutning på triviala komplexa tangentbuntar så kan en lösning till Wheeler-De Witt ekvationen hittas. Denna lösning kallas för Chern-Simons tillståndet. I termer av komponenterna av självduala Lorentz buntanslutningar och deras generaliserade rörelsemängd så utforskar lösningarna till Wheeler-De Witt ekvationen i termer av länkinvarianter.

Many applications of quantum mechanics depend on how the geometry of some space of quantum states alters the state's evolution.Mixed states are common in applications and their evolution is thus of interest.The Sjöqvist metric [Phys. Rev. Research 2, 013344 (2020)] describes how a mixed state evolves and has before been used to analyse the path on which a mixed two-dimensional state evolves along.In this thesis, we will use the Sjöqvist metric to find the Lagrangian governing the evolution of a mixed three-dimensional state along the shortest path and discuss the non-trivial singularities introduced by the metric, which may span some hyper-surface in an eight-dimensional space, and the similarity to black holes., Flertalet tillämplingar av kvantmekaniken beror på hur geometrin i något kvantmekanisk tillståndsrum påverkar tidsutvecklingen av de tillhörande tillstånden.Blandade tillstånd är förekommande i tillämpningar och därmed är deras utveckling av intresse. Sjöqvist metriken [Phys. Rev. Research 2, 013344 (2020)] beskriver hur ett blandat tillstånd utvecklas och har tidigare använts för att undersöka den väg vilket ett två-dimensionellt tillstånd utvecklas längs med. I denna uppsats används Sjöqvist metriken för att finna Lagrangianen som styr tidsutvecklingen av ett tre-dimensionellt blandat tillstånd längs den kortaste vägen och diskutera de icke-triviala singulariteterna som introduceras av metriken, vilka kan spänna upp någon hyperyta i ett åtta-dimensionellt rum, och likheterna med svarta hål.

This thesis project explores period doubling in optical frequency combs, an area with limited prior research. An optical frequency comb can be used in telecommunications and high-precision metrologyand is a coherent set of discrete, equidistant frequency components generated from a central pumplaser frequency. To simulate the combs and the evolution of the intracavity field, the Ikeda map and two coupled mean-field equations for the period doubling regime are employed. The equations ofthese mathematical models are first derived, followed by an analytical investigation of the modulationinstability in the period doubling regime. Furthermore, the period doubling regime is simulated numerically to investigate stability and the generation of various comb patterns. During the simulations, the initial pump power is held constant while the detuning is varied. It is found that the energy was highest where the eigenvalue had the biggest real part from the analytical investigation. Additionalinstabilities is shown in results from simulations with normal dispersion.

Sweden's nuclear power industry plays a crucial role in meeting future energy needs and achieving climate goals where nuclear power is essential to this success. However, one of the biggest challenges in nuclear power is the management of spent nuclear fuel, which must be stored safely for long periods to protect people and the environment from radioactive radiation. To address this, Svensk Kärnbränslehantering AB (SKB) plans to build a capsule factory for encapsulating spent nuclear fuel. The capsule factory is a key component of the Swedish KBS-3 system for the final disposal of nuclear waste, where copper capsules will be used to safely seal and store the spent nuclear fuel for over 100,000 years, 500 meters underground. The purpose of this study was to evaluate two main scenarios for the construction of the capsule factory: an early construction, and a later construction, as well as to examine the opportunities and risks of reusing existing encapsulation equipment compared to investing in new equipment. To address the research questions and achieve the objectives of the report, the methods consisted of SWOT-analyses, surveys, risk assessments, and statistical analysis of the risks to evaluate the scenarios. The results show that an early construction start can reduce overall risks and enable a more efficient transition to full-scale production by the year 2036. A later construction start can reduce initial costs but may involve an increased risk of delays. Reusing existing equipment can also lower costs but may require extensive inspections and upgrades as it becomes outdated. New investments in equipment entail higher initial costs but offer more modern and efficient solutions with lower long-term maintenance requirements. In summary, an early construction start of the capsule factory is recommended, with a thorough assessment of the possibility of reusing existing equipment to maximize cost-effectiveness and minimize risks.

The theory of loop quantum gravity is an attempt at reconciling general relativity and quantum mechanics by studying the quantum behavior of spacetime at the Planck scale. By finding a geometrical picture of discrete spacetime the theory aims for a full quantum theory with a Hilbert Space H, a setof observables O and governing laws of dynamics. The dynamics in questionare described in terms of transition amplitudes W where the shift from different geometrical configurations of spacetime is the main focal point. Thisproject outlines the theoretical background and describes the construction ofthe set (H, O, W) needed for a full quantum picture including the construction of spin networks. Since the theory describes nature at the Planck scaleit is far away from being experimentally feasible and so one must turn tosimulations. For this purpose I discuss and conduct experimental quantumsimulations on real quantum hardware with a focus on the construction anddynamics of spin networks and show how today’s quantum technologies canalready be used to perform meaningful computations.

This thesis project aims to model a quadcopter and design a linear quadratic regulator (LQR) by means of Matlab/Simulink. To this purpose, the LQR-based optimal control theory for controllinga quadcopter is first studied which includes state-space representation (SSR) of a dynamicprocess or system, cost function, LQR, quadcopter flight dynamics and system linearization. A quadcopter model is developed in Matlab/Simulink, followed by the implementation of a LQR-based control system. The LQR parameters are tuned and the system is tested under various flight conditions (wind disturbance, in the simulation, specific/simplified model, etc.). The simulation results show that the LQR is an effective controller for maintaining stable hover at a height straight up and compensating for wind disturbances. However, when the quadcopter moves to a new position, oscillations occur, highlighting the limitations of the LQR due to its reliance on a simplified and linearized model. Additionally, modifications to the model parameters, such as mass and inertia, impact the system performance, indicating potential robustness issues with the controller. It can be concluded that Matlab/Simulink is an effective tool for quadcopter modeling, LQR designing and LQR performance analyzing. In this thesis project, only the LQR method is used for controlling a quadcopter and the LQR tuning process is not efficient. In future work other techniques such as regional linearization and alternative non-linear controllers, like model predictive control (MPC) or sliding mode control (SMC), can be explored. Development of optimization algorithms for LQR tuning in the LQR method is highly recommended.

This thesis investigates the application of two different modeling techniques for simulating nuclear fuel rods: Constructive Solid Geometry (CSG) with Boolean operations in Serpent and mesh-based modeling in OpenFOAM. The purpose of the study was to evaluate how a mesh-based model performs compared to a CSG-based model when conducting simulations on a relatively simple geometric configuration. The reasons for using mesh-based geometry include the ability to couple Serpent with OpenFOAM, enabling simulations in both codes using the same geometry, and accommodating users who might be more comfortable with mesh-based software. By performing a direct comparison between the results from the two modeling methods, the project aimed to assess the accuracy, efficiency, and practical usability of mesh-based geometry in nuclear simulations. The results indicate that mesh-based modeling, particularly with finer mesh, can achieve a level of detail and accuracy comparable to that of CSG models. However, the simulations with finer mesh took significantly longer to complete, highlighting the need for careful consideration of mesh size depending on the specific requirements of the simulation. The study encompasses several critical aspects, including computational speed and the precision of the resulting simulation data. The analysis demonstrates that while mesh-based modeling offers high precision and flexibility, it is more computationally intensive. In contrast, CSG is faster and simpler to implement for less complex geometries, but may not adequately capture more intricate details. The conclusions suggest that mesh-based modeling can be a viable alternative for complex simulations, provided that the computational resources are available. By highlighting the potential and limitations of mesh-based modeling in comparison to traditional CSG techniques, the study provides valuable insights. Utilizing mesh-based models is highly advantageous when CFD simulations are planned, as it avo

In the 1970s, the tandem shaped charge was developed to overcome countermeasures like active armor and thicker armor. It uses a leading charge to clear a path for the main trailing charge, theoretically improving penetration. However, disturbances from shock waves can cause under-performance. To address this, the leading charge's shock waves must be minimized to protect the main charge. Designing a part with shock wave attenuating properties can help achieve this.There is limited information on grenade structures that reduce shock wave stresses from impact and detonation. Most studies on shock wave attenuation focus on protecting buildings and humans, with few addressing structures designed to withstand and then halt the transmission of shock waves. Here we report on simulations in IMPETUS Afea where an explicit FEM solver approach have been made to compare four different concepts to an original structure. Physical theories about attenuation of shock waves in solids has been applied. The first concept utilize a mass with different area increases in the propagation path of the shock wave. The second concept use the characteristics of interfaces between two different materials, with different shock wave impedance which will reflect and transmit the incoming wave. The third concept incorporate a brittle ceramic which should shatter when a shock wave propagates to it, if the brittle structure fracture, no more shock waves can be transmitted. The fourth concept utilize the properties of porous metals. All concepts shows shock wave attenuating effects, but only the third concept which totally disconnects the leading shaped charge to the main charge might be a full solution. The fourth concept compared to the third has other advantages, it attenuate the shock wave to more than 90%, not halt the transmission. Configuration of the porosity in the structural part can be made to have characteristics that can solve the problem. Concept three and four are the main recommendation, På 1970-talet utvecklades tandem-RSV laddningar för att övervinna motmedel som aktivt pansar och tjockare pansar. De använder en förladdning för att skapa en väg för den efterföljande huvudladdningen, vilket teoretiskt sett förbättrar prestandan. Störningar från tryckvågor från olika källor orsaka prestandaförluster. För att hantera detta måste islagets och förladdningens tryckvågor minimeras för att skydda huvudladdningen. Att designa en mellandel med egenskaper som dämpar tryckvågor kan hjälpa till att uppnå detta. Information om granatstrukturer som minskar tryckvågsbelastningar från islag och detonation är begränsad. De flesta studier om dämpning av tryckvågor fokuserar på att skydda byggnader och människor, med få som behandlar strukturer designade för att motstå och sedan stoppa överföringen av tryckvågor. Här rapporterar vi om simuleringar genomförda i IMPETUS Afea med en explicit FEM-lösare för att jämföra fyra olika koncept mot en originalstruktur. Fysiska teorier om dämpning av tryckvågor i fasta material har tillämpats. Det första konceptet utnyttjar en massa med olika areaökningar i tryckvågens propagationsväg. Det andra konceptet använder egenskaperna hos gränsytor mellan två olika material med olika tryckvågsimpedanser som kommer att reflektera och transmittera den inkommande tryckvågen. I det tredje konceptet appliceras en spröd keram som bör splittras när en tryckvåg fortplantas till den. Om den spröda strukturen spricker kan då inga fler tryckvågor överföras genom strukturen. Det fjärde konceptet utnyttjar egenskaperna hos porösa metaller. Alla koncept visar tryckvågsdämpande effekter. Men endast det tredje konceptet som helt kopplar bort förladdningen från huvudladdningen kan vara en fullständig lösning. Det fjärde konceptet jämfört med det tredje har andra fördelar; det dämpar tryckvågen till mer än 90%, men stoppar inte överföringen helt. Konfigurationen av porositeten i den strukturella delen kan utformas för att ha egenskaper som kan lösa probl

Over the past decades, mesoporous silica has emerged as a new material with interesting physical and chemical properties, such as high surface-to-volume ratio, stability, and the feasibility of surface functionalization, amongst others. Mesoporous silica provides an opportunity to improve conventional commercial catalyst supports, and sorbent due to its low-cost synthesis. In this research field, investigations on various materials prepared by different techniques as potential support have been reported. The main objective of the studies was to produce highly stable mesoporous materials for energy and environmental applications using simple and low-cost synthesis. In this thesis, we utilized the sol-gel and self-templating processes in synthesizing three types of highly porous silica nanomaterials, mainly aerogels (SiO2 AG), xerogel (SiO2 XG), and nanosheets (SiO2 NS). SiO2 AG and SiO2 XG were synthesized using the sol-gel method, while SiO2 NS was synthesized using the soft-templating hydrothermal technique. SiO2 AG, SiO2, XG, and SiO2 NS are explored as catalyst support for low-temperature carbon monoxide (CO) oxidation and compared to commercial Fumed Silica. The synthesized materials are investigated as metal support materials (M/SiO2) for environmental applications such as CO oxidation and carbon dioxide (CO2) adsorption. The morphology of the synthesized materials was investigated experimentally using several characterization techniques such as X-ray Diffraction (XRD), X-ray Photo-electron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), Thermo-Gravimetry-Differential Scanning Calorimetry (TGA-DSC), gas adsorption by Brunauer–Emmett–Teller (BET) method, Fourier Transform Infra-Red spectroscopy (FTIR), UV-Vis spectroscopy, and Temperature Programmed Reduction (TPR) for understanding the surface chemistry of supports. The M/SiO2 was subjected to a detailed study of the morphology before, during, and after the low-temperature CO oxidation reaction unde, Under de senaste decennierna har mesoporöst kisel uppstått som ett nytt material med intressanta fysikaliska och kemiska egenskaper, såsom hög yta-till-volym-förhållande, stabilitet och möjligheten till ytterligare funktionalisering av ytan, bland annat. Mesoporöst kisel ger en möjlighet att förbättra konventionella kommersiella katalystbärare och adsorbenter på grund av dess kostnadseffektiva syntes. Inom detta forskningsområde har undersökningar av olika material framställda med olika tekniker som potentiella bärare rapporterats. Det primära målet med studierna var att producera högstabila mesoporösa material för energi- och miljöapplikationer med hjälp av enkel och kostnadseffektiv syntes. I denna avhandling använde vi sol-gel och självtemplateringsprocesser för att syntetisera tre typer av högporösa kiselnanomaterial, huvudsakligen aerogeler (SiO2 AG), xerogeler (SiO2 XG) och nanoskikt (SiO2 NS). SiO2 AG och SiO2 XG syntetiserades med hjälp av sol-gelmetoden, medan SiO2 NS syntetiserades med hjälp av den mjuka templaterings hydrotermiska tekniken. SiO2 AG, SiO2 XG och SiO2 NS utforskades som katalysatorbärare för kolmonoxid (CO) oxidation vid låga temperaturer och jämfördes med kommersiell Fumed Silica. De syntetiserade materialen undersöktes som metallbärarmaterial (M/SiO2) för miljöapplikationer såsom CO-oxidation och koldioxid (CO2) adsorption. Morfologin hos de syntetiserade materialen undersöktes experimentellt med hjälp av flera karaktäriseringsmetoder såsom röntgendiffraktion (XRD), röntgenfotoelektronspektroskopi (XPS), transmissions elektronmikroskopi (TEM), termogravimetrisk-differential scanning kalorimetri (TGA-DSC), gasadsorption med Brunauer-Emmett-Teller (BET) metoden, Fourier-transform-infraröd spektroskopi (FTIR), UV-Vis spektroskopi och temperaturprogrammerad reduktion (TPR) för att förstå ytkemin hos bärarna. M/SiO2 utsattes för en detaljerad studie av morfologin före, under och efter CO-oxidationsreaktionen vid låga temperatu, QC 2024-08-30

Nonadiabatic holonomic quantum computation has been proposed as a method to implement quantum logic gates with robustness comparable to that of adiabatic holonomic gates but with shorter execution times. In this paper, we establish an isoholonomic inequality for quantum gates, which provides a lower bound on the lengths of cyclic transformations of the computational space that generate a specific gate. Then, as a corollary, we derive a nonadiabatic execution time estimate for holonomic gates. In addition, we demonstrate that under certain dimensional conditions, the isoholonomic inequality is tight in the sense that every gate on the computational space can be implemented holonomically and unitarily in a time-optimal way. We illustrate the results by showing that the procedures for implementing a universal set of holonomic gates proposed in a pioneering paper on nonadiabatic holonomic quantum computation saturate the isoholonomic inequality and are thus time optimal.

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) have been used to investigate the nonlinear optical (NLO) properties of phenolic N-pyrimidinyl stilbazolium cationic chromophore in its corresponding noncentrosymmetric crystals. Such a cationic chromophore, the OPR (4-(4-hydroxystyryl)-1-(pyrimidin-2-yl)pyridinium), consists of a strong electron donor, the 4-hydroxyphenyl group, and a strong electron acceptor, the N-pyrimidinylpyridinium group based on two electron-withdrawing groups. The in-crystal NLO properties were determined by applying a supermolecule approach in combination with an iterative electrostatic scheme, in which the surrounding molecules of a unit cell are represented by point charges. With CAM-B3LYP, our absolute estimates for the largest diagonal component of the second-order nonlinear susceptibility tensor of OPR-based crystals range from 64.00 to 80.34 pm/V in the static regime and from 162.09 to 175.52 pm/V at 1907 nm. These values are significant when compared to those of benchmark stilbazolium-based crystals. Furthermore, the third-order susceptibility, which is related to the nonlinear optical process of the intensity-dependent refractive index, is also significant compared to the results for other organic crystals, such as chalcone derivatives. With TD-CAM-B3LYP, the two-state model effectively explains the similarity in the first hyperpolarizability values in the crystalline phase. This similarity arises from the combination of the oscillator strength and the charge transfer of the crucial transition. Therefore, phenolic organic salt crystals show great promise for various nonlinear optical applications.

We construct a candidate tree-level gravitational Compton amplitude for a rotating Kerr black hole, for any quantum spin s 1/4 0, 1/2, 1, ..., infinity, from which we extract the corresponding classical amplitude to all orders in the spin vector S'`. We use multiple insights from massive higher-spin quantum field theory, such as massive gauge invariance and improved behavior in the massless limit. A chiral-field approach is particularly helpful in ensuring correct degrees of freedom, and for writing down compact off-shell interactions for general spin. The simplicity of the interactions is echoed in the structure of the spin-s Compton amplitude, for which we use homogeneous symmetric polynomials of the spin variables. Where possible, we compare to the general-relativity results in the literature, available up to eighth order in spin.

This contribution studies the effect of ordered vacancy compounds (OVCs) on the minority carrier collection in wide-gap (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells. For this purpose, three samples with different ([Ag]+[Cu])/([In]+[Ga]) (I/III) values were processed: 1) a very off-stoichiometric absorber (I/III = 0.31), consisting of isolated chalcopyrite patches embedded in a major OVC bulk phase, 2) a moderately off-stoichiometric absorber (I/III = 0.77) with OVC patches at the front and back interfaces and 3) a close-stoichiometric absorber (I/III = 0.94) with only very few, isolated OVC patches. For each of these samples, synchrotron-based X-ray fluorescence (XRF) was measured on a nanoscale (55 nm resolution), while simultaneously recording the X-ray beam induced current (XBIC). The results, complemented by transmission electron microscopy and electron-beam induced current analyses, clearly indicate that the presence of the OVC phase reduces the carrier collection and thus the short-circuit current density of off-stoichiometric wide-gap ACIGS solar cells.

The way in which a social network is generated, in terms of how individuals attach to each other, determines the properties of the resulting network. Here, we study an intuitively appealing ‘friend of a friend’ model, where a network is formed by each newly added individual attaching first to a randomly chosen target and then to randomly chosen friends of the target, each with probability ⁠. We revisit the master equation of the expected degree distribution for this model, providing an exact solution for the case when nq allows for attachment to all of the chosen target’s friends [a case previously studied by Bhat et al. (2016, Phys. Rev. E, 94, 062302)], and demonstrating why such a solution is hard to obtain when nq is fixed [a case previously studied by Levens et al. (2022, R. Soc. Open Sci., 9, 221200)]. In the case where attachment to all friends is allowed, we also show that when ⁠, the expected degree distribution of the model is stationary as the network size tends to infinity. We go on to look at the clustering behaviour and the triangle count, focusing on the cases where nq is fixed.

The vibrational properties of monoclinic dirutile-type CoTeO4 (space group P21/c) were investigated by means of Raman and infrared (IR) spectroscopy on stoichiometric single crystals and theoretical density-functional theory (DFT) calculations. Experimental in situ investigations under pressure and temperature variations up to 10.1 GPa and 750 K confirmed the singular phase stability of the monoclinic lattice and the absence of any structural transition. The IR spectra exhibit modes that are not observed in the Raman spectra, thus offering a comprehensive understanding of the vibrational behavior of the title compound. The symmetry and degeneracy of modes and their contributions to the overall vibrational spectrum of CoTeO4 were analyzed using group theory. DFT calculations were performed both on a cluster level and based on the crystal structure of monoclinic CoTeO4 in order to gain further insights into the vibrational properties. The calculated vibrational frequencies and modes were compared with the experimental data, allowing for a detailed investigation of the lattice dynamics and the nature of the vibrational modes in CoTeO4, and are corroborated with the analytical Wilson's F-G matrix method. These findings provide fundamental insights into the crystal symmetry and lattice dynamics of CoTeO4. The results are discussed and compared to those of isoformular systems.

In this proof-of-concept paper, we propose a specific kind of pedagogical use of ChatGPT—to help teachers practice their Socratic dialogue skills. We follow up on the previously published paper 'ChatGPT and the frustrated Socrates' by re-examining ChatGPT's ability to engage in Socratic dialogue in the role of a physics student. While in late 2022 its ability to engage in such dialogue was poor, we see significant advancements in the chatbot's ability to respond to leading questions asked by a human teacher. We suggest that ChatGPT now has the potential to be used in teacher training to help pre- or in-service physics teachers hone their Socratic dialogue skills. In the paper and its supplemental material, we provide illustrative examples of Socratic dialogues with ChatGPT and present a report on a pilot activity involving pre-service physics and mathematics teachers conversing with it in a Socratic fashion.

We settle a longstanding question about the hypermultiplet moduli spaces of the heterotic strings on asymptotically locally Euclidean singularities. These heterotic backgrounds are specified by the singularity type, an instanton number, and a (nontrivial) flat connection at infinity. Building on their interpretation as six-dimensional theories, we determine a class of three-dimensional N = 4 quiver gauge theories whose quantum corrected Coulomb branch coincides with the exact heterotic hypermultiplet moduli space.

Van der Waals (vdW) magnets are promising, because of their tunable magnetic properties with doping or alloy composition, where the strength of magnetic interactions, their symmetry, and magnetic anisotropy can be tuned according to the desired application. However, so far, most of the vdW magnet-based spintronic devices have been limited to cryogenic temperatures with magnetic anisotropies favoring out-of-plane or canted orientation of the magnetization. Here, we report beyond room-temperature lateral spin-valve devices with strong in-plane magnetization and spin polarization of the vdW ferromagnet (Co0.15Fe0.85)5GeTe2 (CFGT) in heterostructures with graphene. Density functional theory (DFT) calculations show that the magnitude of the anisotropy depends on the Co concentration and is caused by the substitution of Co in the outermost Fe layer. Magnetization measurements reveal the above room-temperature ferromagnetism in CFGT and clear remanence at room temperature. Heterostructures consisting of CFGT nanolayers and graphene were used to experimentally realize basic building blocks for spin valve devices, such as efficient spin injection and detection. Further analysis of spin transport and Hanle spin precession measurements reveals a strong in-plane magnetization with negative spin polarization at the interface with graphene, which is supported by the calculated spin-polarized density of states of CFGT. The in-plane magnetization of CFGT at room temperature proves its usefulness in graphene lateral spin-valve devices, thus revealing its potential application in spintronic technologies.

Modern computational techniques that use a combination of electronic structure calculations, adaptive genetic algorithms, and machine learning data analysis have been recently predicting many new unknown structures that may exhibit desired physical properties. Yet, most of these theoretically discovered structures belong to the realm of virtual phase space, and the great challenge to experimentally observe them still remains. Based on the example of the C36 Laves phase in a Co-Fe-Ta system, we demonstrate a practical route to design and produce a material with desired properties.

We show how flux vacua that differ from each other in flux quanta can be seen as different vacua in a single scalar potential of an enlarged field space, which resolves the separation by thin domain walls. This observation, which is motivated by the anti–de Sitter distance conjecture, allows one to compute distances between different vacua using the usual field-space metric. We verify for explicit examples such as scale-separated IIA flux vacua and the IIB Freund-Rubin vacua that the distance conjecture (for scalar fields) is satisfied and that the asymptotic directions in the enlarged field space are indeed hyperbolic. This enlarged field space contains the tachyon fields on the unstable ˜Dp-branes of type II string theory, which can induce the brane charges of the stable D-branes. We suggest that requiring continuous interpolations refines the cobordism conjecture and postdicts the existence of unstable ˜Dp-branes.

In this paper, we study rotating horizonless black shells as an alternative to Kerr black holes. We make use of Ernst’s potential to solve the Einstein equations perturbatively in the angular momentum a. Calculating to order a6, we find accurate predictions up to about a = 0.45, where the quadrupole moment is predicted to be around 1% higher than its Kerr value; higher multipole moments show deviation of the order of ∼ 10%. Our analysis takes into account deformations of the black shells, and we propose that it can be used for numerical simulations comparing gravitational waves emitted by orbiting black shells with those emitted by orbiting black holes. We find that matter on the rotating shell takes the form of a viscous fluid. We make extensive use of relativistic hydrodynamics, and discover an intricate structure of circulating flows of this fluid and heat on the black shell, sustained by the Unruh effect.

In the context of the 21st century and the fourth industrial revolution, the substantial proliferation of data has established it as a valuable resource, fostering enhanced computational capabilities across scientific disciplines, including physics. The integration of Machine Learning stands as a prominent solution to unravel the intricacies inherent to scientific data. While diverse machine learning algorithms find utility in various branches of physics, there exists a need for a systematic framework for the application of Machine Learning to the field. This review offers a comprehensive exploration of the fundamental principles and algorithms of Machine Learning, with a focus on their implementation within distinct domains of physics. The review delves into the contemporary trends of Machine Learning application in condensed matter physics, biophysics, astrophysics, material science, and addresses emerging challenges. The potential for Machine Learning to revolutionize the comprehension of intricate physical phenomena is underscored. Nevertheless, persisting challenges in the form of more efficient and precise algorithm development are acknowledged within this review.

Although higher-order interactions are known to affect the typical state of dynamical processes giving rise to new collective behavior, how they drive the emergence of rare events and fluctuations is still an open problem. We investigate how fluctuations of a dynamical quantity of a random walk exploring a higher-order network arise over time. In the quenched case, where the hypergraph structure is fixed, through large deviation theory we show that the appearance of rare events is hampered in nodes with many higher-order interactions, and promoted elsewhere. Dynamical fluctuations are further boosted in an annealed scenario, where both the diffusion process and higher-order interactions evolve in time. Here, extreme fluctuations generated by optimal higher-order configurations can be predicted in the limit of a saddle-point approximation. Our study lays the groundwork for a wide and general theory of fluctuations and rare events in higher-order networks., QC 20240925

Generation of Runaway Electrons (REs) during plasma disruptions is of great concern for ITER and future reactors based on the tokamak concept. Unmitigated RE generation in the current STEP (Spherical Tokamak for Energy Production) concept design is modelled using the code DREAM, with hot-tail generation found to be the dominant primary generation mechanism and avalanche multiplication of REs found to be extremely high. Varying assumptions for the prescribed thermal quench (TQ) phase (duration, final electron temperature) as well as the wall time, the plasma-wall distance, and shaping effects, all STEP full-power and full-current unmitigated disruptions generate large RE beams (from 10 MA up to full conversion). RE mitigation is first studied by modelling idealised mixed impurity injections, with ad-hoc particle transport arising from the stochasticity of the magnetic field during the TQ, but no combination of argon and deuterium quantities allows runaways to be avoided while respecting the other constraints of disruption mitigation. Initial concept of STEP disruption mitigation system is then tested with DREAM, assuming two-stage shattered pellet injections (SPI) of pure D 2 followed by Ar+ D 2 . Such a scheme is found to reduce the generation of REs by the hot-tail mechanism, but still generates a RE beam of about 13 MA. Options for further optimising the SPI scheme, for mitigating a large RE beam in STEP (benign termination scheme), as well as estimations of required RE losses during the current quench (from a potential passive RE mitigation coil) will also be discussed., QC 20240927

In this work, we propose a method to implement a quantum version of the physics informed neural network (QPINN) to solve differential equations. We use quantum circuits that can be modelled as Fourier series approximation of the desired function to encode the solution of a differential equation. We resort to parameter shift rules to compute the exact derivatives of this quantum circuit and hence to define a physics loss. Further we enforce the boundary conditions of our differential equations in the loss function of the QPINN to obtain a unique solution to the given differential equation. We present our preliminary results for two instances of 1D Poisson equation., Part of ISBN: 9798400718021QC 20240924

Red blood cells (RBCs) are more deformable than most other cells in the body, and any change in the deformability of RBCs can have major physiological effects. Here, we report a high-throughput micro- fluidic device to determine the Young's modulus of single RBCs. Our device consists of a single channel opening into a funnel, with a semi-circular obstacle placed at the mouth of the funnel. As an RBC passes the obstacle, it deflects from its original path. Using populations of artificially stiffened RBCs, we show that the stiffer RBCs deflect more compared to the healthy RBCs. We then generate a calibration curve that maps each RBC trajectory to its Young's modulus, obtained using an atomic force microscope. Finally, we sort a mixed population of RBCs based on their deformability alone. Our device could potentially be further miniaturized to sort and obtain the elastic constants of nanoscale objects, such as exosomes, whose shape change is difficult to monitor by optical microscopy., QC 20240912

We show that rotating two-dimensional Fermi gases possess a nonrelativistic scale and conformal invariance at weak but nonzero interactions, where the scale invariance of universal short-range interactions is not yet broken by quantum effects. We demonstrate the symmetry in the excitation spectrum of few-fermion ensembles in a harmonic trap obtained by exact diagonalization. The excitation spectrum is shown to split in a set of primary states and derived excited states that consist of breathing modes as well as two different center-of-mass excitations, which describe cyclotron and guiding-center excitations of the total particle cloud. Furthermore, the conformal symmetry is manifest in the many-body wave function, where it dictates the form of the hyperradial component, which we demonstrate using Monte Carlo sampling of few-body wave functions., QC 20240701

QC 20240827

Polarization-entangled photons are indispensable to numerous quantum technologies and fundamental studies. In this paper, we propose and demonstrate what we believe to be a novel source that generates collinear polarization-entangled photons by simultaneously achieving two distinct types of phase-matching conditions (noncritically birefringent and quasi phase matching) in a periodically poled nonlinear crystal with a large poling period of 2 mm. The photon pairs are generated in a polarization-entangled state with a fidelity and concurrence of 0.998 and 0.935, respectively, and violate the Clauser-Horne-Shimony-Holt inequality by 84 standard deviations. The compact source does not require interferometer, delicate domain structures, or post selection, and is advantageous for scalable quantum computing and communication, where many replicas or chip-scale devices are needed., QC 20240906

In this work, we present a modeling methodology to solve the eigenvalue problem for periodic structures with a hexagonal lattice. The method is based on the previously proposed multi-modal transfer matrix method, which is a hybrid method that takes into account the coupling between the multiple modes of the ports surrounding the single unit cell. Commercial software can be used to obtain the generalized scattering parameters which are subsequently applied to set up and solve the eigenvalue problem of the periodic structure. This approach has the ability to obtain complex solutions and thus makes it possible to analyze the attenuation in the stopbands. Here, we extend the multimodal transfer matrix method to the efficient solution of the resulting eigenvalue problem for the case of a hexagonal lattice, detailing the selection of the appropriate supercells and the appropriate irreducible Brillouin zones. Two types of structures are analyzed: a mirror-symmetric structure and a glide-symmetric structure. Very good agreement is obtained with commercial software, limited to the real part of the dispersion diagrams., Part of proceedings ISBN: 978-88-31299-09-1QC 20240517

An original solution with 5% efficiency and 0.3 nm linewidth for spontaneous-parametric down-conversion in 2 mm long semiconductor waveguides is proposed. The simultaneous amplitude and phase-matching in the transverse and propagation directions, respectively results in the efficient utilisation of the entire nonlinear volume., Part of ISBN 9798350393873QC 20240829

Hybrid organic-inorganic perovskites (HOIPs) are promising candidates for next-generation photovoltaic materials. However, there is a debate regarding the impact of interactions between the organic center and the surrounding inorganic cage on the solar cell's high diffusion lengths. It remains unclear whether the diffusion mechanism is consistent across various halide perovskite families and how light illumination affects carrier lifetimes. The focus is on ion kinetics of (CH3NH3)PbX3 (X = Br, Cl) perovskite halide single crystals. Muon spectroscopy (mu+SR)is employed to investigate the fluctuations and diffusion of ions via the relaxation of muon spins in local nuclear field environments. Within a temperature range of 30-340 K, ion kinetics are studied with and without white-light illumination. The results show a temperature shift of the tetragonal-orthorhombic phase transition on the illuminated samples, as an effect of increased organic molecule fluctuations. This relation is supported by density functional theory (DFT) calculations along the reduction of the nuclear field distribution width between the phase transitions. The analysis shows that, depending on the halide ion, the motional narrowing from H and N nuclear moments represents the molecular fluctuations. The results demonstrate the importance of the halide ion and the effect of illumination on the compound's structural stability and electronic properties., QC 20240828

Different computational techniques for cosmological phase transition parameters can impact the gravitational wave (GW) spectra predicted in a given particle physics model. To scrutinize the importance of this effect, we perform large-scale parameter scans of the dynamical real-singlet extended Standard Model using three perturbative approximations for the effective potential; the MS¯ and on shell schemes at leading order, and three-dimensional thermal effective theory (3D EFT) at next-to-leading order. While predictions of GW amplitudes are typically unreliable in the absence of higher-order corrections, we show that the reconstructed model parameter spaces are robust up to a few percent in uncertainty. While 3D EFT is accurate from one-loop order, theoretical uncertainties of reconstructed model parameters, using four-dimensional standard techniques, remain dominant over the experimental ones even for signals merely strong enough to claim a detection by LISA., QC 20240820

This chapter is an integrated overview of organic solid-state tunable laser oscillators that adds an additional and complimentary perspective to the material covered in chapters 5 to 9. Emphases are on miniaturized tunable organic lasers using DFB, VECSOL, and waveguide architectures. Furthermore, the use of dye-doped transparent wood, as an all-organic solid-state gain medium, is described and discussed., Part of ISBN 9780750355490, 9780750355452QC 20240725

We analytically derive universal bounds that describe the tradeoff between thermodynamic cost and precision in a sequence of events related to some internal changes of an otherwise hidden physical system. The precision is quantified by the fluctuations in either the number of events counted over time or the waiting times between successive events. Our results are valid for the same broad class of nonequilibrium driven systems considered by the thermodynamic uncertainty relation, but they extend to both time-symmetric and asymmetric observables. We show how optimal precision saturating the bounds can be achieved. For waiting-time fluctuations of asymmetric observables, a phase transition in the optimal configuration arises, where higher precision can be achieved by combining several signals., QC 20240704

Transportation of fresh fuel assemblies requires the utilization of transport casks to ensure the internal radioactive material does not affect the environment. In this work, we introduce an innovative design of a transport cask for the fresh fuel assembly of a Small Module Reactor (SMR). The cask is constituted by two containers, supports and various energy-absorbing structures welded at the outer container. The structural integrity of the transport cask under variant scenarios determined by the International Atomic Energy Agency (IAEA) and domestic regulations was numerically evaluated. The detailed 3D model of the cask was created, and the simulations were performed via the Finite Element Method (FEM) using commercial software ABAQUS. Simulation results obtained from static and dynamic analyses indicated that the integrity of the designed transport cask can be assured during normal and accident conditions. The most severe damage during the 9 m drop tests was caused by a horizontal oblique condition and this configuration is recommended to be tested in future experiments., QC 20240708

Superconducting nanowire single-photon detectors (SNSPDs) have become a mainstream photon-counting technology that has been widely applied in various scenarios. So far, most multi-channel SNSPD systems, either reported in literature or commercially available, are polarization sensitive, that is, the system detection efficiency (SDE) of each channel is dependent on the state of polarization of the to-be-detected photons. Here, we reported an eight-channel system with fractal SNSPDs working in the wavelength range of 930 to 940 nm, which are all featured with low polarization sensitivity. In a close-cycled Gifford-McMahon cryocooler system with the base temperature of 2.2 K, we installed and compared the performance of two types of devices: (1) SNSPD, composed of a single, continuous nanowire and (2) superconducting nanowire avalanche photodetector (SNAP), composed of 16 cascaded units of two nanowires electrically connected in parallel. The highest SDE among the eight channels reaches 96−5+4%, with the polarization sensitivity of 1.02 and a dark-count rate of 13 counts per second. The average SDE for eight channels for all states of polarization is estimated to be 90 ± 5%. It is concluded that both the SNSPDs and the SNAPs can reach saturated, high SDE at the wavelength of interest, and the SNSPDs show lower dark-count (false-count) rates, whereas the SNAPs show better properties in the time domain. With the adoption of this system, we showcased the measurements of the second-order photon-correlation functions of light emission from a single-photon source based on a semiconductor quantum dot and from a pulsed laser. It is believed that this work will provide new choices of systems with single-photon detectors combining the merits of high SDE, low polarization sensitivity, and low noise that can be tailored for different applications., QC 20240528

Unparalleled specificity and high sensitivity have made fluorescence microscopy an indispensable tool for life sciences. Both these aspects come from the use of light-emitting fluorophores, labeled to molecules and structures of interest. The diffraction-limited, maximum achievable resolution of traditional microscopes roughly corresponds to half the wavelength of the light used for observation. In the last decades, however, super-resolution microscopy (SRM) has been developed, which provide spatial information far beyond this diffraction limit. While different SRM techniques use different principles to achieve super resolution, most of these techniques rely on selectively switching the fluorophore emission on and off, within a diffraction-limited volume. Upon excitation, fluorophores can undergo transitions into transient dark states or become permanently photobleached. While reversible transitions may be used to achieve super resolution, they also reduce the overall emission. Characterization and modeling of photophysical dark state transitions are thus important, since they can both provide a basis for, as well as negatively affect the performance of SRM. Nevertheless, SRM has already proven valuable in biological and biomedical research, where the enhanced resolution allows for improved understanding of basic molecular mechanisms in cells and opens for future diagnostic opportunities. This thesis presents two applications of SRM. In paper I, we used STED (stimulated emission depletion) SRM to image the disruption of beta-actin filaments in neurons infected with Streptococcus pneumoniae, suggesting a possible mechanism for neuronal death in bacterial meningitis. In paper II, the nanoscale distribution patterns of six different platelet proteins were imaged with STED to find activation-specific protein rearrangements upon co-incubation of the platelets with cancer cells. Streamlined image acquisition, analysis and classification methods were also developed, openin, Oöverträffad specificitet och hög känslighet har gjort fluorescensmikroskopi till ett oumbärligt verktyg inom livsvetenskaperna. Dessa egenskaper härrör från användandet av ljusemitterande fluoroforer, inmärkta till de molekyler och strukturer man vill studera. Den diffraktionsbegränsade, maximalt uppnåeliga upplösningen hos traditionella mikroskop motsvarar grovt sett hälften av våglängden hos det ljus som används för observation. Under de senaste decennierna har emellertid superupplösningsmikroskopi (SRM) utvecklats, vilket möjliggjort att spatiell information kan erhållas långt bortom denna diffraktionsbegränsning. Även om olika SRM-tekniker använder olika principer för att uppnå superupplösning, förlitar sig de flesta av dem på att selektivt kunna slå på och av fluoroforemissionen inom en diffraktionsbegränsad volym. Vid excitation kan fluoroforer övergå till mörka, transienta tillstånd eller permanent fotoblekas. Även om reversibla övergångar kan användas för att uppnå superupplösning minskar de också den totala emissionen. Karakterisering och modellering av fotofysikaliska övergångar till mörka tillstånd är således mycket viktigt, eftersom de både kan ge en grund för och negativt påverka prestanda hos SRM. SRM har dock redan visat sig vara värdefullt inom biologisk och biomedicinsk forskning, där den förbättrade upplösningen ger en bättre förståelse av grundläggande molekylära mekanismer i celler samt öppnar för framtida diagnostiska möjligheter. Denna avhandling presenterar två tillämpningar av SRM. I arbete I använde vi STED (stimulated emission depletion) SRM för att avbilda påverkan på beta-aktinfilament i neuroner infekterade med Streptococcus pneumoniae, vilket ledde oss till att föreslå en möjlig mekanism för neuronal död vid bakteriell meningit. I arbete II avbildades de nanoskaliga distributionsmönstren hos sex olika trombocyterproteiner med STED för att hitta aktiveringsspecifika distributionsförändringar hos proteinerna vid samtidig inkubering av tr, QC-2024-05-20

This book presents an overview of state-of-the-art approaches to determine thermal safety margins in nuclear reactors. It presents both the deterministic aspects of thermal safety margins of nuclear reactors and a comprehensive treatment of aleatory and epistemic uncertainties to facilitate the understanding of these two difficult topics at various academic levels, from undergraduates to researchers in nuclear engineering. It first sets out the theoretical background before exploring how to determine thermal safety margins in nuclear reactors, through examples, problems and advanced state-of-the-art approaches. This will help undergraduate students better understand the most fundamental aspects of nuclear reactor safety. For researchers and practitioners, this book provides a comprehensive overview of the most recent achievements in the field, offering an excellent starting point to develop new methods for the assessment of the thermal safety margins. This book is written to bridge the gap between deterministic methods and appropriate treatment of uncertainties to assess safety margins in nuclear reactors, presenting these approaches as complementary to each other. Even though these two approaches are frequently used in parallel in real-world applications, there has been a lack of a consistent teaching approach in this area. This book is suitable for readers with a background in calculus, thermodynamics, fluid mechanics, and heat transfer. It is assumed that readers have previous exposure to such concepts as laws of thermodynamics, enthalpy, entropy, and conservation equations used in fluid mechanics and heat transfer. Key Features: • Covers the theory, principles, and assessment methods of thermal safety margins in nuclear reactors whilst presenting state-of-the-art technology in the field • Combines the deterministic thermal safety considerations with a comprehensive treatment of uncertainties, offering a framework that is applicable to all current and future comm, QC 20240522Part of ISBN 978-104003495-8, 978-103217105-0

The interplay between quantum theory and general relativity remains one of the main challenges of modern physics. A renewed interest in the low -energy limit is driven by the prospect of new experiments that could probe this interface. Here we develop a covariant framework for expressing post -Newtonian corrections to Schr & ouml;dinger's equation on arbitrary gravitational backgrounds based on a 1/c2 expansion of Lorentzian geometry, where c is the speed of light. Our framework provides a generic coupling prescription of quantum systems to gravity that is valid in the intermediate regime between Newtonian gravity and General Relativity, and that retains the focus on geometry. At each order in 1/c2 this produces a nonrelativistic geometry to which quantum systems at that order couple. By considering the gauge symmetries of both the nonrelativistic geometries and the 1/c2 expansion of the complex Klein-Gordon field, we devise a prescription that allows us to derive the Schr & ouml;dinger equation and its post -Newtonian corrections on a gravitational background order -by -order in 1/c2. We also demonstrate that these results can be obtained from a 1/c2 expansion of the complex Klein-Gordon Lagrangian. We illustrate our methods by performing the 1/c2 expansion of the Kerr metric up to O(c-2), which leads to a special case of the Hartle-Thorne metric. The associated Schr & ouml;dinger equation captures novel and potentially measurable effects., QC 20240503

Idealized models are a natural part of physics research and education. In upper-division physics courses, which tend to be more abstract and sophisticated than the introductory courses, such simplified toy models often serve as pedagogical tools to illustrate concepts and calculations. In the topic of statistical mechanics, we have studied the challenges faced by small problem-solving groups of upper-division students. Our findings indicate that students struggle to recognize the underlying structure of commonly used toy models. Students faced various pitfalls as they tended to rely on surface features of the tasks, in combination with loosely connected ideas about key concepts. Based on our findings, we discuss recommendations for teachers in statistical mechanics and other advanced courses that resort to simplified models to explain complex concepts.

Intuition has been reported as being pivotal in guiding students' problem solving. In this ongoing project, we employ a grounded approach to investigate how students use intuition during problem solving in beyond-intro chemistry and physics courses. We adopt a dynamic perspective on intuition, recognizing its context-dependency, to examine how students respond to their intuitions. In a case study, we inductively analyze existing video data of problem-solving sessions, and show that students' responses to intuition can be productive or unproductive, regardless of the intuition's "correctness". This highlights the need to equip students with strategies to manage their intuitions productively. Based on our findings, we recommend teachers to: adopt a flexible stance toward intuition; explicitly incorporate the topic of intuition in classroom discussions; and encourage students to actively reflect on their intuitions. Future studies should consider the processes governing the development of intuition and expand research on students' epistemological views on intuition.

Non-perturbative aspects of quantum field theories are notoriously hard to explore. In this thesis we study applications of two different techniques that give non-perturbative results for supersymmetric quantum field theories. The first exact technique we use is supersymmetric localization which allows for the exact computation of partition functions on compact manifolds and squashed spheres of various dimensions are the manifolds of our choice. In three dimensions we use the squashed sphere partition functions to test dualities of N=4 gauge theories. For a squashed sphere preserving six supercharges we lift analytic results from the round sphere. On a squashed sphere preserving 4 supercharges we numerically evaluate the ABJM and N=8 super Yang-Mills (SYM) partition functions at low rank and find equality within estimated error margins. In four dimensions we present a framework to obtain partially integrated correlators of 4d N=2 gauge theories from their localized partition functions. Moreover we discuss the general form of the free energy of N=2 superconformal field theories on deformed four-dimensional spheres and use localization in N=4 SYM for an explicit example. In seven dimensions we study the super Yang-Mills on a sphere and propose a contribution of three-dimensional membrane instantons to its localized partition function. We then outline an approach to study the weak negative coupling limit of the SYM theory on the seven-sphere. As the second approach to exact results we use the integrability of N=4 SYM and ABJM theory in the planar limit. Using the quantum spectral curve we compute the Hagedorn temperature for finite coupling both in N=4 SYM and ABJM theory. On the dual AdS side we use an effective model to compute subleading terms in the curvature expansion of the Hagedorn temperature. We use the numeric CFT calculation to conjecture the analytic form of an unfixed coefficient in the effective model.

In the Swedish academic system, the doctoral defence marks the PhD student's final hurdle before potentially earning the title of doctor. This period is typically marked by stress and intense preparation. Unlike a conference presentation, where a student discusses only one study or a part of it, the doctoral defence encompasses the entire spectrum of research conducted over the last four years. This breadth necessitates readiness to address a wide range of questions. However, research on effective defence preparation strategies for PhD students is limited. Common preparation methods include reviewing the thesis, crafting the presentation, and participating in mock defences (Lantsoght, 2022). Our study explores the use of generative AI to generate defence questions based on the student's thesis. We input the thesis into a generative AI model, which then simulates a defence committee member by posing three challenging questions to the student. Participating students anonymously evaluate these questions through a survey, using a 5-point Likert scale to assess four aspects: intelligibility, difficulty, relevance, and novelty. Preliminary findings indicate that students generally find the AI-generated questions relevant and understandable. However, they often perceive them as insufficiently challenging and note that they had considered similar questions previously. While a doctoral thesis includes segments not directly pertinent to the defence, these are crucial for comprehending the overall research work. Interestingly, our results suggest that the AI-generated questions are highly relevant for defence preparation. Yet, the low perceived difficulty and prior consideration, i.e., implying low novelty, of these questions by students suggest limitations in their effectiveness for defence preparation. In the presentation, we will discuss the results and potential improvements and alternatives for enhancing the quality of the questions.

Gravitational scattering processes involving black holes as asymptotic states can provide insight into the classical dynamics of binary black hole systems. The observed gravitational waves emitted during mergers need to be compared to high-precision theoretical predictions. By modelling black holes as massive point particles in an effective quantum field theory, one can take advantage of the advanced computational tools originally designed for collider physics. For Schwarzschild black holes the natural objects to study are scattering amplitudes involving massive scalar fields with interactions mediated by gravitons. The classical physics is extracted by considering limits of the kinematics. Extending this effective description to rotating Kerr black holes introduces subtleties. To leading order in the post-Minkowskian perturbation scheme, there now exists candidate three-point scattering amplitudes for massive higher-spin particles that in the classical limit reproduce the Kerr metric. For small quantum spins, these are given by familiar theories of interacting massive fields which have a well-behaved massless limit. These theories are sufficient to capture the first few spin-multipole orders for the classical observables; however, to capture more orders one is required to use input from higher-spin theories. The three-point higher-spin amplitudes were originally introduced without reference to an underlying Lagrangian description. Lagrangians for interacting higher-spin fields are notoriously complicated as they necessarily describe composite fields in an effective higher-derivative theory. This thesis explores the underlying higher-spin effective theories suitable for describing rotating black holes, and proposes a new spin-s family of Compton scattering amplitudes. We present two complementary constructions for consistent interacting higher-spin Lagrangians: the first relies on massive higher-spin gauge symmetry to remove unwanted states, and the second one manif