2025
A pipeline for megahertz X-ray photon correlation spectroscopy on soft matter samples at the MID instrument of European XFEL
Aliaksandr Leonau · Et al.
In this article, we present the experimental protocol and data-processing framework for megahertz X-ray Photon Correlation Spectroscopy (MHz-XPCS) experiments on soft matter samples implemented at the Materials Imaging and Dynamics (MID) instrument of the European X-ray Free-Electron Laser (EuXFEL). Due to the introduction of a standard configuration and the implementation of a highly automated data-processing pipeline, MHz-XPCS measurements can now be conducted and analyzed with minimal user intervention. A key challenge lies in managing the extremely large data volumes generated by the Adaptive Gain Integrating Pixel Detector (AGIPD) – often reaching several petabytes within a single experiment. We describe the technical implementation, discuss the hardware requirements related to effective parallel data processing and propose strategies to enhance data quality, in particular related to data reduction strategies and an improvement of the signal-to-noise ratio. Finally, we address strategies for making the processed data FAIR (Findable, Accessible, Interoperable, Reusable), in alignment with the goals of the DAPHNE4NFDI project.
2023
Magnetized thick disks around boson stars
Kristian Gjorgjieski · Jutta Kunz · Matheus C. Teodoro · Lucas G. Collodel · Petya Nedkova
The effects of magnetic fields on accretion disks around compact objects are of high importance in the study of their general properties and dynamics. Here we analyze the influence of magnetic fields on thick accretion disks around rotating boson stars. We assume a uniform constant specific angular momentum distribution and a polytropic equation of state. The purely hydrodynamical thick disk solutions are extended to magnetized solutions by adding a toroidal magnetic field and then analyzed in terms of a magnetization parameter. We consider one-centered solutions as well as two-centered solutions and focus on retrograde tori, since they are more distinctive due to their unique properties. Our computed solutions indicate that strong magnetic fields influence the characteristics of thick disks around rotating boson stars and possibly affect their unique features.
2021
Thick toroidal configurations around scalarized Kerr black holes
Matheus C. Teodoro · Lucas G. Collodel · Jutta Kunz · Daniela Doneva · Petya Nedkova · Stoytcho Yazadjiev
In this work we aim to investigate thick tori configurations around Kerr black holes with scalar hair (KBHsSH). For that goal, we provide a first approach using constant specific angular momentum non-self-gravitating Polish doughnuts. Through a series of examples, we show the feasibility of new topologies, such as double-centered tori with two cusps as well as similar structures as the ones found for rotating boson stars (BSs), namely, tori endowed with two centers and a single cusp. These KBHsSH solutions are also shown to possibly house static surfaces, associated with the static rings present in these spacetimes. Through this paper we highlight the differences between these fluid configurations when housed by some KBHsSH examples, standard Kerr black holes and rotating BSs.
2021
Retrograde Polish Doughnuts around Boson Stars
Matheus C. Teodoro · Lucas G. Collodel · Jutta Kunz
We investigate polish doughnuts with a uniform constant specific angular momentum distribution in the space-times of rotating boson stars. In such space-times thick tori can exhibit unique features not present in Kerr space-times. For instance, in the context of retrograde tori, they may possess two centers connected or not by a cusp. Rotating boson stars also feature a static ring, neither present in Kerr space-times. This static ring consists of static orbits, where particles are at rest with respect to a zero angular momentum observer at infinity. Here we show that the presence of a static ring allows for an associated static surface of a retrograde thick torus, where inside the static surface the fluid moves in prograde direction. We classify the retrograde Polish doughnuts and present several specific examples.
2021
Tidal effects in the motion of gas clouds around boson stars
Matheus C. Teodoro · Lucas G. Collodel · Jutta Kunz
We study the motion of gas clouds in the vicinity of boson stars, performing simulations with the black hole accretion code. We compare the motion of the gas clouds with particle motion along geodesics and analyze the tidal effects on the gas clouds, which leads to the disruption of the clouds. First we consider small and dense clouds associated with three different types of bound orbits close to the boson star and analyze the mechanisms of debris formation for these. We infer from the simulations that the lifetimes of these nearby clouds are longer for initially circularly orbiting clouds than for clouds on initially eccentric orbits. Next we compare the evolution of more extended and less dense clouds on initially circular orbits around a boson star and a Schwarzschild black hole and compare the motion in these two spacetimes. In particular, we observe the formation of a ringlike structure around the boson star endowed with a spiralling shock structure and a constant thermal bremsstrahlung total luminosity. This final configuration contrasts strongly with the black hole scenario where the gas is totally captured behind the event horizon.
2019
Perturbations of black holes pierced by cosmic strings
Matheus C. Teodoro
The present-day interest in gravitational waves, justified by the recent direct detections made by LIGO, is opening the exciting possibility to answer many questions regarding General Relativity in extreme situations. One of these questions is whether black hole are – indeed – described totally by their mass, charge and angular momentum or whether they can have additional long-range hair. This project is concerned with this question. We aim at studying the influence of additional structure on the black hole horizon in the form of long-range hair by studying linearized Einstein equation the solutions when perturbed. More precisely, we will study the Schwarzschild solution, pierced by an infinitely long and thin cosmic string such that the space-time possesses a global deficit angle. Quasi-normal modes are believed to dominate the gravitational wave emission during the ring down phase of an excited black hole that would e.g. be the result of a merger of two ultra-compact objects, therefore linearized perturbations can be considered. With the advent of gravitational wave astronomy the proposed study will be very important when reconstructing the source of the detected gravitational wave signals.