We discuss various aspects of D-branes in string theory and holography in string theory and loop quantum gravity. One way to study D-branes is from a microscopic perspective, using conformal field theory techniques. For example, we investigate the question of how D-branes can be introduced into orbifolded theories. Another way to study D-branes is from a space-time perspective. An example is provided by unstable D-branes, where we compute an effective action describing the decay of a bosonic D-brane. The holographic principle is a proposed duality which suggests that a theory in any region has a dual description on the boundary. We explore two examples: (1) The area law for the entropy of a black hole in the framework of loop quantum gravity, related to particular regularizations of the area operator. (2) The AdS/CFT correspondence proposal, where we investigate a string pulsating on AdS using spin chains.

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The idea of holography [1, 2] finds a concrete realization in form of the AdS/CFT correspondence [3, 4]. This duality relates a field theory with conformal symmetries to quantum gravity living in one higher dimension. In this thesis we study aspects of black hole quasinormal modes, higher spin theories and entanglement entropy in the context of this duality. In almost all cases we have been able to subject the duality to some precision tests. Quasinormal modes encode the spectrum of black holes and the time-scale of pertur- bations therein [5]. From the dual CFT viewpoint they are the poles of retarded Green's function (or peaks in the spectral function) [6]. Quasinormal modes were previously studied for scalar, gauge field and fermion fluctuations [7]. We solve for these quasinormal modes of higher spin (s _ 2) fields in the background of the BTZ black hole [8, 9]. We obtain an exact solution for a field of arbitrary spin s (integer or half-integer) in the BTZ background. This implies that the BTZ is perhaps the only known black hole background where such an analysis can be done analytically for all bosonic and fermionic fields. The quasinormal modes are shown to match precisely with the poles of the corresponding Green's function in the CFT living on the boundary. Furthermore, we show that one-loop determinants of higher spin fields can also be written as a product form [10] in terms of these quasinormal modes and this agrees with the same obtained by integrating the heat-kernel [11]. We then turn our attention to dualities relating higher-spin gravity to CFTs with W algebra symmetries. Since higher spin gravity does go beyond diffeomorphism invariance, one needs re_ned notions of the usual concepts in differential geometry. For example, in general relativity black holes are defined by the presence of the horizon. However, higher spin gravity has an enlarged group of symmetries of which the diffeomorphisms form a subgroup. The appropriate way of thinking of solutions in higher spin gravity is via characterizations which are gauge invariant [12, 13]. We study classical solutions embedded in N = 2 higher spin supergravity. We obtain a general gauge-invariant condition { in terms of the odd roots of the superalgebra and the eigenvalues of the holonomy matrix of the background { for the existence of a Killing spinor such that these solutions are supersymmetric [14]. We also study black holes in higher spin supergravity and show that the partition function of these black holes match exactly with that obtained from a CFT with the same asymptotic symmetry algebra [15]. This involved studying the asymptotic symmetries of the black hole and thereby developing the holographic dictionary for the bulk charges and chemical potentials with the corresponding quantities of the CFT. We finally investigate entanglement entropy in the AdS3/CFT2 context. Entanglement entropy is an useful non-local probe in QFT and many-body physics [16]. We analytically evaluate the entanglement entropy of the free boson CFT on a circle at finite temperature (i.e. on a torus) [17]. This is one of the simplest and well-studied CFTs. The entanglement entropy is calculated via the replica trick using correlation functions of bosonic twist operators on the torus [18]. We have then set up a systematic high temperature expansion of the Renyi entropies and determined their finite size corrections. These _nite size corrections both for the free boson CFT and the free fermion CFT were then compared with the one-loop corrections obtained from bulk three dimensional handlebody spacetimes which have higher genus Riemann surfaces (replica geometry) as its boundary [19]. One-loop corrections in these geometries are entirely determined by the spectrum of the excitations present in the bulk. It is shown that the leading _nite size corrections obtained by evaluating the one-loop determinants on these handlebody geometries exactly match with those from the free fermion/boson CFTs. This provides a test for holographic methods to calculate one-loop corrections to entanglement entropy. We also study conformal field theories in 1+1 dimensions with W-algebra symmetries at _nite temperature and deformed by a chemical potential (_) for a higher spin current. Using OPEs and uniformization techniques, we show that the order _2 correction to the Renyi and entanglement entropies (EE) of a single interval in the deformed theory is universal [20]. This universal feature is also supported by explicit computations for the free fermion and free boson CFTs { for which the EE was calculated by using the replica trick in conformal perturbation theory by evaluating correlators of twist fields with higher spin operators [21]. Furthermore, this serves as a verification of the holographic EE proposal constructed from Wilson lines in higher spin gravity [22, 23]. We also examine relative entropy [24] in the context of higher-spin holography [25]. Relative entropy is a measure of distinguishability between two quantum states. We confirm the expected short-distance behaviour of relative entropy from holography. This is done by showing that the difference in the modular Hamiltonian between a high-temperature state and the vacuum matches with the difference in the entanglement entropy in the short-subsystem regime.

Implementing object detection methods for runway detection during landing approaches is limited in the safety-critical aircraft domain. This limitation is due to the difficulty that comes with verification of the design and the ability to understand how the object detection behaves during operation. During operation, object detection needs to consider the aircraft's position, environmental factors, different runways and aircraft attitudes. Training such an object detection model requires a comprehensive dataset that defines the features mentioned above. The feature's impact on the detection capabilities needs to be analysed to ensure the correct distribution of images in the dataset. Gathering images for these scenarios would be costly and needed due to the aviation industry's safety standards. Synthetic data can be used to limit the cost and time required to create a dataset where all features occur. By using synthesised data in the form of generating datasets in a simulated environment, these features could be applied to the dataset directly. The features could also be implemented separately in different datasets and compared to each other to analyse their impact on the object detections capabilities. By utilising this method for the features mentioned above, the following results could be determined. For object detection to consider most landing cases and different runways, the dataset needs to replicate real flight data and generate additional extreme landing cases. The dataset also needs to consider landings at different altitudes, which can differ at a different airport. Environmental conditions such as clouds and time of day reduce detection capabilities far from the runway, while attitude and runway appearance reduce it at close range. Runway appearance did also affect the runway at long ranges but only for darker runways.

<p dir="ltr">In holographic quantum field theories, a bulk geometric semiclassical spacetime emerges from strongly coupled interacting conformal field theories in one less spatial dimension. This is the celebrated AdS/CFT correspondence. The entanglement entropy of a boundary spatial subregion can be calculated as the area of a codimension two bulk surface homologous to the boundary subregion known as the RT surface. The bulk region contained within the RT surface is known as the entanglement wedge and bulk reconstruction tells us that any operator in the entanglement wedge can be reconstructed as a non-local operator on the corresponding boundary subregion. This notion that entanglement creates geometry is dubbed "ER=EPR'' and has been the driving force behind recent progress in quantum gravity research. In this thesis, we put together two results that use Tomita-Takesaki modular theory and quantum ergodic theory to make progress on contemporary problems in quantum gravity.</p><p dir="ltr">A version of the black hole information loss paradox is the inconsistency between the decay of two-point functions of probe operators in large AdS black holes and the dual boundary CFT calculation where it is an almost periodic function of time. We show that any von Neumann algebra in a faithful normal state that is quantum strong mixing (two-point functions decay) with respect to its modular flow is a type III₁ factor and the state has a trivial centralizer. In particular, for Generalized Free Fields (GFF) in a thermofield double (KMS) state, we show that if the two-point functions are strong mixing, then the entire algebra is strong mixing and a type III₁ factor settling a recent conjecture of Liu and Leutheusser.</p><p dir="ltr">The semiclassical bulk geometry that emerges in the holographic description is a pseudo-Riemannian manifold and we expect a local approximate Poincaré algebra. Near a bifurcate Killing horizon, such a local two-dimensional Poincaré algebra is generated by the Killing flow and the outward null translations along the horizon. We show the emergence of such a Poincaré algebra in any quantum system with modular future and past subalgebras in a limit analogous to the near-horizon limit. These are known as quantum K-systems and they saturate the modular chaos bound. We also prove that the existence of (modular) future/past von Neumann subalgebras also implies a second law of (modular) thermodynamics.</p>

Testing, verification and validation of sensors, components and systems is vital in the early-stage development of new cars with computer-in-the-car architecture. This can be done with the help of the existing technique, hardware-in-the-loop (HIL) testing which, in the close loop testing case, consists of four main parts: Real-Time Simulation Platform, Sensor Simulation PC, Interface Unit (IU), and unit under test which is, for instance, a Vehicle Computing Unit (VCU). The purpose of this degree project is to research and develop a proof of concept for in-house development of an image injection solution (IIS) on the IU in the HIL testing environment. A proof of concept could confirm that editing, customizing, and having full control of the IU is a possibility. This project was initiated by Volvo Cars to optimize the use of the HIL testing environment currently available, making the environment more changeable and controllable while the IIS remains a static system. The IU is an MPSoC/FPGA based design that uses primarily Xilinx hardware and software (Vivado/Vitis) to achieve the necessary requirements for image injection in the HIL testing environment. It consists of three stages in series: input, image processing, and output. The whole project was divided in three parts based on the three stages and carried out at Volvo Cars in cooperation by three students, respectively. The author of this thesis was responsible for the output stage, where the main goal was to find a solution for converting, preferably, AXI4 RAW12 image data into data on CSI2 format. This CSI2 data can then be used as input to serializers, which in turn transmit the data via fiber-optic cable on GMSL2 format to the VCU. Associated with the output stage, extensive simulations and hardware tests have been done on a preliminary solution that partially worked on the hardware, producing signals in parts of the design that could be read and analyzed. However, a final definite solution that fully functions on the hardware has not been found, because the work is at the initial phase of an advanced and very complex project. Presented in this thesis is: important theory regarding, for example, protocols CSI2, AXI4, GMSL2, etc., appropriate hardware selection for an IIS in HIL (FPGA, MPSoC, FMC, etc.), simulations of AXI4 and CSI2 signals, comparisons of those simulations with the hardware signals of an implemented design, and more. The outcome was heavily dependent on getting a certain hardware (TEF0010) to transmit the GMSL2 data. Since the wrong card was provided, this was the main problem that hindered the thesis from reaching a fully functioning implementation. However, these results provide a solid foundation for future work related to image injection in a HIL environment.

<p dir="ltr">We now live in a world where we can reach people directly through social media, without relying on traditional media such as television and radio. The landscape of social media is highly distributed, as users generate and consume a variety of content. On the other hand, social media platforms collect vast amounts of data and create very specific profiles of different users through targeted advertising. Various interest groups, politicians, advertisers, and stakeholders utilize these platforms to target potential users to advance their interests by adapting their messaging.  A significant challenge lies in understanding this messaging and how it changes depending on the targeted user groups. Another challenge arises when we do not know who the users are and what their motivations are for engaging with content. The initial phase of our research focuses on comprehensively understanding users and their underlying motivations, whether practitioner-based or promotional. Gaining this understanding is crucial in reshaping our perspective on the content disseminated by these users. Step beyond that, assuming the identification of the involved parties, this study aims to characterize the messaging and explore how it adapts based on various targeted demographic groups. This thesis addresses these challenges by developing computational approaches and frameworks for (1) characterizing user types and their motivations, (2) analyzing the messaging based on topics relevant to the users and their responses to it, and (3) delving into the deeper understanding of the themes and arguments involved in the messaging.</p>