Dennis Philipp
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Chronometric assessment of relativistic degrees of freedom of the gravity field Open
The relativistic gravity field has many more degrees of freedom than the Newtonian one. A single scalar potential, sourced by the mass density of matter only, is replaced by a metric - a symmetric and non-degenrate tensor field of rank two…
Simulating spaceborne high-precision optical clocks and their potential for measuring relativistic gravity Open
Highly precise optical clocks are advancing rapidly and hold the promise of enabling gravity measurements with unprecedented accuracy, particularly through the deployment of spaceborne clocks on satellites. Satellite mission simulations ne…
Differentiable Cosimulator for Electrically Reconfigurable Structures Open
This paper introduces a novel CUDA-enabled PyTorch-based framework designed for the gradient-based optimization of such reconfigurable electromagnetic structures with electrically tunable parameters. Traditional optimization techniques for…
General relativity and geodesy Open
Mass redistribution on Earth due to dynamic processes such as ice melting and sea-level rise leads to a changing gravitational field, observable by geodetic techniques. Monitoring this change over time allows us to learn more about our pla…
The scalar angular Teukolsky equation and its solution for the Taub-NUT spacetime Open
The Taub-NUT spacetime offers many curious insights into the solutions of Einstein's electrovacuum equation. In the Bonnor interpretation, this spacetime possesses so-called Misner strings, which induce phenomena strikingly analogous to Di…
Realization of a clock-based global height system: A simulation study for Europe and Brazil Open
Chronometric levelling is a novel technique for the realisation of the International Height Reference System (IHRS). A detailed study of this technique is carried out through closed-loop simulations, aiming to unify regional/local height s…
Gravitational field recovery via inter-satellite redshift measurements Open
Satellite gravimetry is a common tool to monitor global changes in the Earth system, generally utilising accelerometers aboard satellites to measure acting forces along the orbits. In contrast, high-precision atomic clocks are used in firs…
General Relativistic Chronometry from Ground and in Space Open
Geodesy's primary objective lies in the determination of Earth's gravity field through ground and space-based measurements. General relativity and, thus, relativistic geodesy, introduce a novel perspective, leveraging high-precision clock …
View article: Gravitomagnetic Clock Effect: Using GALILEO to explore General Relativity
Gravitomagnetic Clock Effect: Using GALILEO to explore General Relativity Open
All experiments to date are in remarkable agreement with the predictions of Einstein's theory of gravity, General Relativity. Besides the classical tests, involving light deflection, orbit precession, signal delay, and the gravitational re…
Exact wave-optical imaging of a Kerr-de Sitter black hole using Heun's equation Open
Spacetime perturbations due to scalar, vector, and tensor fields on a fixed background geometry can be described in the framework of Teukolsky's equation. In this work, wave scattering is treated analytically, using the Green's function me…
General Relativistic Chronometry with Clocks on Ground and in Space Open
One of geodesy's main tasks is to determine the gravity field of the Earth. High precision clocks have the potential to provide a new tool in a global determination of the Earth's gravitational potential based on the gravitational redshift…
Simulation of relativistic and environmental influences on laser signals used for gravity field recovery with spaceborne optical clocks Open
One major objective of Geodesy is the observation of the Earth, its gravity field and climate. To study subtle but impactful changes in the gravitational field, novel paradigms and high-precision measurement schemes are emerging.According …
Chronometry: On the redshift and relativistic gravity potential determination in GR Open
We derive exact expressions for the relativistic redshift and timing between observers in various configurations in stationary spacetimes for the purpose of chronometry, i.e., relativistic gravimetry based on clocks. These observers are as…
The Framework of Relativistic Geodesy: What do we know? Open
Conventional geodesy builds on (the concepts of) Newtonian gravity. Thus, at the level of a relativistic theory of gravity, the underlying framework needs to be extended and basic notions need to be generalized. This opens an entirely new …
Chronometric Height: a relativistic height definition by generalizing geopotential numbers Open
A height definition in terms of geopotential numbers offers a variety of advantages. Moreover, from the theoretical point of view, such a definition is considered more fundamental.We know, however, that relativistic gravity (here General R…
View article: Performance Assessment of a Single-Layer Metasurface Resonator for 3 T MRI
Performance Assessment of a Single-Layer Metasurface Resonator for 3 T MRI Open
Metamaterials, in particular 2D metasurfaces, offer great potential to advance measurement efficiency in magnetic resonance imaging (MRI) and to overcome some limitations due to physiological restrictions that hamper technically feasible d…
Relativistic geoid: Gravity potential and relativistic effects Open
The Earth's geoid is one of the most essential and fundamental concepts to\nprovide a gravity field-related height reference in geodesy and associated\nsciences. To keep up with the ever-increasing experimental capabilities and to\nconsist…
Fundamental Notions in Relativistic Geodesy - physics of a timelike Killing vector field Open
The Earths geoid is one of the most important fundamental concepts to provide a gravity field- related height reference in geodesy and associated sciences. To keep up with the ever-increasing experimental capabilities and to consistently i…
Theoretical Aspects of Relativistic Geodesy Open
In this thesis, I show how fundamental geodetic notions can be defined within a general relativistic framework. Among the concepts that are analyzed there are the relativistic gravity potential, the geoid, the normal gravity field and its …
Redshift and frequency comparison in Schwarzschild spacetime Open
We derive exact expressions for the relativistic redshift between an Earth-bound observer, that is meant to model a standard clock on the Earth's surface, and various (geodesic) observers in the Schwarzschild spacetime. We assume that the …
Definition of the relativistic geoid in terms of isochronometric surfaces Open
We present a definition of the geoid that is based on the formalism of\ngeneral relativity without approximations; i.e. it allows for arbitrarily\nstrong gravitational fields. For this reason, it applies not only to the Earth\nand other pl…