Fundamental physics with laser interferometry

This thesis discusses the use of laser interferometers to detect quantum gravity phenomena, dark matter, and gravitational waves. In the first chapter, the laser interferometry experiment known as QUEST is discussed, which consists of twin co-located table-top interferometers. In the second chapter, the detection of quantum space-time fluctuations with laser interferometers is treated. Contemporary literature on holographic quantum space- time fluctuations is reviewed. A basic model for computing interferometric signals from quantum space-time fluctuations is formulated, and prospects of detecting a signal with QUEST are analysed. In the third chapter, we demonstrate the use of laser interferometry to search for scalar field dark matter. Analysis of the data from the GEO600 gravitational-wave detector and the Fermilab Holometer for the presence of dark matter signals was performed; no signals were detected, and constraints are placed on dark matter coupling strengths that exceed previous constraints by orders of magnitude. A polarimetric experiment to search for scalar and pseudoscalar dark matter is proposed, and we discuss prospective dark matter searches with QUEST. In the fourth chapter, we present a new approach for detecting gravitational waves using existing and future detectors that exploits the mixing, or heterodyning, of gravitational waves. We show that this method could allow gravitational-wave detectors such as LISA to detect low-frequency gravitational waves outside of their designed bandwidth using the same infrastructure. We also comment on the prospects of detecting high-frequency (MHz) gravitational waves with QUEST

Observing supermassive black holes with deci-Hz gravitational-wave detectors

The most massive black holes in our Universe form binaries at the centre of merging galaxies. The recent evidence for a gravitational-wave (GW) background from pulsar timing may constitute the first observation that these supermassive black hole binaries (SMBHBs) merge. Yet, the most massive SMBHBs are out of reach of interferometric detectors and are exceedingly difficult to resolve individually with pulsar timing. These limitations call for unexplored strategies to detect individual SMBHBs in the uncharted frequency band $\lesssim10^{-5}\,\rm Hz$ in order to establish their abundance and decipher the coevolution with their host galaxies. Here we show that SMBHBs imprint detectable long-term modulations on GWs from stellar-mass binaries residing in the same galaxy. We determine that proposed deci-Hz GW interferometers sensitive to numerous stellar-mass binaries will uncover modulations from $\sim\mathcal{O}(10^{-1}$ - $10^4)$ SMBHBs with masses $\sim\mathcal{O}(10^7$ - $10^9)\,\rm M_\odot$ out to redshift $z\sim3.5$. This offers a unique opportunity to map the population of SMBHBs through cosmic time, which might remain inaccessible otherwise.Comment: 16 pages, 4 figures, comments welcom

Probing dark matter with polarimetry techniques

In this work, we propose polarimetry experiments to search for low-mass (sub-eV) bosonic field dark matter, including axions and axion-like particles. We show that a polarimetry configuration consisting of a thick birefringent solid inside a Fabry-P\'erot cavity is exceptionally sensitive to scalar field dark matter, which may cause oscillatory variations in the solid's thickness and refractive index. In addition, we show that a reconfiguration of this polarimetry experiment, in which two quarter-wave plates are placed inside the Fabry-P\'erot cavity instead of a thick birefringent solid, is very sensitive to axion-like particles. We investigate the possibility of using cross-correlation of twin polarimeters to increase the sensitivity of the experiment, which in turn could allow us to explore unexplored parts of the parameter space and potentially detect a signal in either dark matter scenario

Extracting electromagnetic signatures of spacetime fluctuations

We present a formalism to discern the effects of fluctuations of the spacetime metric on electromagnetic radiation. The formalism works via the measurement of electromagnetic field correlations, while allowing a clear assessment of the assumptions involved. As an application of the formalism, we present a model of spacetime fluctuations that appear as random fluctuations of the refractive index of the vacuum in single, and two co-located Michelson interferometers. We compare an interferometric signal predicted using this model to experimental data from the Holometer and aLIGO. We show that if the signal manifests at a frequency at which the interferometers are sensitive, the strength and scale of possible spacetime fluctuations can be constrained. The bounds, thus obtained, on the strength and scale of the spacetime fluctuations, are also shown to be more stringent than the bounds obtained previously using astronomical observation at optical frequencies. The formalism enables us to evaluate proposed experiments such as QUEST for constraining quantum spacetime fluctuations and to design new ones

Improving Patient Activity Schedules by Multi-agent Pareto Appointment Exchanging

textabstractWe present a dynamic and distributed approach to the hospital patient scheduling problem: the multi-agent Pareto-improvement appointment exchanging algorithm, MPAEX. It respects the decentralization of scheduling authorities and is capable of continuously adjusting the different patient schedules in response to the dynamic environment. We present models of the hospital patient scheduling problem in terms of th

Adaptive resource allocation for efficient patient scheduling

Objective Efficient scheduling of patient appointments on expensive resources is a complex and dynamic task. A resource is typically used by several patient groups. To service these groups, resource capacity is often allocated per group, explicitly or implicitly. Importantly, due to fluctuations in demand, for the most efficient use of resources this allocation must be flexible. Methods We present an adaptive approach to automatic optimization of resource calendars. In our approach, the allocation of capacity to different patient groups is flexible and adaptive to the current and expected future situation. We additionally present an approach to determine optimal resource openings hours on a larger time frame. Our model and its parameter values are based on extensive case analysis at the Academic Medical Hospital Amsterdam. Results and conclusion We have implemented a comprehensive computer simulation of the application case. Simulation experiments show that our approach of adaptive capacity allocation improves the performance of scheduling patients groups with different attributes and makes efficient use of resource capacity