arXiv subjects

Michael Florian Wondrak

Publications and source records attributed to Michael Florian Wondrak.

6 recordsLinked to original sources

arXiv2021

Modeling (anti)deuteron formation at RHIC with a geometric coalescence model

We study (anti)deuteron formation rates in heavy-ion collisions in the framework of a wave-function based coalescence model. The main feature of our model is that nucleons are emitted from the whole spherically symmetric fireball volume, while antinucleons are emitted only from a spherical shell close to the surface. In this way, the model accounts for nucleon-antinucleon annihilations in the center of the reaction at lower beam energies. Comparison with experimental data on the coalescence parameter in the range $\sqrt{s_{NN}}= 4.7-200$ GeV allows us to extract radii of the respective source geometries. Our results are qualitatively supported by data from the UrQMD transport model which shows a comparable trend in the geometric radii as a function of beam energy. In line with our expectations, we find that at lower energies, the central region of the fireball experiences stronger annihilation than at higher energies.

hep-ph↗

arXiv2020

Deuteron and Antideuteron Coalescence in Heavy-Ion Collisions: Energy Dependence of the Formation Geometry

We investigate the collision energy dependence of deuteron and antideuteron emission in the RHIC-BES low- to mid-energy range $\sqrt{s_{NN}} = 4.6-200$ GeV where the formation rate of antinuclei compared to nuclei is strongly suppressed. In the coalescence picture, this can be understood as bulk emission for nuclei in contrast to surface emission for antinuclei. By comparison with experimental data on the coalescence parameter $B_2$, we are able to extract the respective source geometries. This interpretation is further supported by results from the UrQMD transport model, and establishes the following picture: At low energies, nucleons freeze out over the total fireball volume, while antinucleons are annihilated inside the nucleon-rich fireball and can only freeze out on its surface. Towards higher energies, this annihilation effect becomes irrelevant (due to the decreasing baryochemical potential) and the system's freeze-out is driven by the mesons. Thus, the nucleon and antinucleon freeze-out distributions become similar with increasing energy.

hep-ph↗

arXiv2017

Black Holes and High Energy Physics: From Astrophysics to Large Extra Dimensions

Up to now, Einstein's general theory of relativity has passed all experimental tests. But yet we know that it is not a fundamental theory and that it is incompatible with quantum theory. While several extended and improved gravitational theories on classical and quantum level are nowadays available, it is a great challenge to find experimental setups to check their signatures. We discuss recent developments in direct observation of black holes comprising gravitational waves from black hole mergers, radio interferometry images of black hole shadows, and Hawking radiation of black holes in particle accelerators. These investigations cover the full black hole mass range from microscopic to stellar and supermassive black holes. We comment on the associated strong-field tests of Einstein's general theory of relativity and implications for quantum gravity. Special emphasis lies upon the physics of large extra dimensions and black hole evaporation, the existence of a minimal black hole mass, and the cross sections of higher-dimensional black holes. We complete this short review with the latest experimental constraints at the Large Hadron Collider.

gr-qc↗

arXiv2017

AdS/CFT far from equilibrium in a Vaidya setup

In this paper we apply the AdS/CFT correspondence to study a strongly coupled plasma far from equilibrium with a strong emphasis on the shear behavior. The plasma serves as a model for an electrically charged quark-gluon plasma. On the gravitational side, we use an ingoing Vaidya black brane spacetime. The highest rate of mass infall is confined to a short time interval.

hep-th↗

arXiv2017

Planck scale black holes - Theory vs. observations

In this paper we present the status of the physics of Planck scale black holes with particular reference to their conjectured production in particle accelerator experiments at the terascale. After reviewing some open issues of fundamental interactions and introducing the physics in the large extra-dimensional scenario, we present the expected signatures left by a microscopic black hole in a particle detector. The final part of the paper is devoted to the latest experimental bounds on the sought black hole signals.

hep-ph↗

arXiv2017

The Cosmological Constant and its Problems: A Review of Gravitational Aether

In this essay we offer a comprehensible overview of the gravitational aether scenario. This is a possible extension of Einstein's theory of relativity to the quantum regime via an effective approach. Quantization of gravity usually faces several issues including an unexpected high vacuum energy density caused by quantum fluctuations. The model presented in this paper offers a solution to the so-called cosmological constant problems. As its name suggests, the gravitational aether introduces preferred reference frames, while it remains compatible with the general theory of relativity. As a rare feature among quantum gravity inspired theories, it can predict measurable astronomical and cosmological effects. Observational data disfavor the gravitational aether scenario at $2.6\text{-}5\,σ$. This experimental feedback gives rise to possible refinements of the theory.

gr-qc↗