Related papers: Ringworlds and Dyson spheres can be stable
We summarize the general formalism describing surface flows in three-dimensional space in a form which is suitable for various astrophysical applications. We then apply the formalism to the analysis of non-radial perturbations of…
After their initial formation, disk galaxies are observed to be rotationally stable over periods of >6 Gyr, implying that any large velocity disturbances of stars and gas clouds are damped rapidly on the timescale of their rotation.…
Ring galaxies are amazing objects exemplified by the famous case of the Hoag's Object. Here the mass of the central galaxy may be comparable to the mass of the ring, making it a difficult case to model mechanically. In a previous paper, it…
All four giant planets and several minor bodies in the Solar System host rings. However, rings around moons have yet to be observed. A host planet can produce magnetic fields that affect its moons, adding a wealth of dynamical phenomena…
As it has already done for Earth, the sun, and the stars, seismology has the potential to radically change the way the interiors of giant planets are studied. In a sequence of events foreseen by only a few, observations of Saturn's rings by…
Loosely inspired by the somewhat fanciful notion of detecting an arbitrarily advanced alien civilization, we consider a general-relativistic thin-shell Dyson mega-sphere completely enclosing a central star-like object, and perform a full…
We study static, spherically symmetric, self-gravitating systems minimally coupled to a scalar field with U(1) gauge symmetry: charged boson stars. We find numerical solutions to the EinsteinMaxwell equations coupled to the relativistic…
Low-energy thermal equilibrium states of strongly coupled ${\cal N}=4$ supersymmetric Yang-Mills (SYM) theory on a three-sphere are unstable with respect to fluctuations breaking the global $SO(6)$ R-symmetry. Using the gauge theory/gravity…
Goal of the presented research is to construct simplified model of the core-halo structures in binary systems. Examples are provided by Thorne-Zytkov objects, hot Jupiters, protoplanets with large moons, red supergiants in binaries and…
We show rational homological stability for the homotopy automorphisms and block diffeomorphims of iterated connected sums of products of spheres. The spheres can have different dimension, but need to satisfy a certain connectivity…
The dynamical stability of tightly packed exoplanetary systems remains poorly understood. While for a two-planet system a sharp stability boundary exists, numerical simulations of three and more planet systems show that they can experience…
MacKey constructed a set of induced representation character formulas to calculate the sum of different powers of the eigenvalues of a matrix with finite group symmetry. We show that these results of MacKey can be used to derive the…
We investigate the dynamical behavior of rings around bodies whose shapes depart considerably from that of a sphere. To this end, we have developed a new self-gravitating discrete element N-body code, and employed a local simulation method…
A nontopological soliton solution of dilaton-Maxwell theory describes a domain wall-like solution which confines magnetic flux in its core [G.W. Gibbons and C.G. Wells, Class. Quant. Grav. 11, 2499 (1994)]. Since the solution is not…
The evolution of closed gravitational systems is studied by means of $N$-body simulations. This, as well as being interesting in its own right, provides insight into the dynamical and statistical mechanical properties of gravitational…
D0-branes are unstable in the presence of an R-R field strength background. A fuzzy two-sphere is classically stable under such a background, this phenomenon being called the Myers effect. We analyze this effect from the viewpoint of…
The hypothesis of a recent origin of Saturn's rings and its mid-sized moons is actively debated. It was suggested that a proto-Rhea and a proto-Dione might have collided recently, giving birth to the modern system of mid-sized moons. It is…
We examine the dynamics of neutral black rings, and identify and analyze a selection of possible instabilities. We find the dominating forces of very thin black rings to be a Newtonian competition between a string-like tension and a…
We analyze the physical properties of boson stars, which possess counterparts in flat space-time, Q-balls. Applying a stability analysis via catastrophe theory, we show that the families of rotating and non-rotating boson stars exhibit two…
Stationary stellar systems with radially elongated orbits are subject to radial orbit instability -- an important phenomenon that structures galaxies. Antonov (1973) presented a formal proof of the instability for spherical systems in the…