Related papers: Dyson Spheres
Radiation by the atoms of a resonant medium is a cooperative process in which the medium participates as a whole. In two previous papers \cite{PG00,GP00}, we treated this problem for the case of a medium having slab geometry, which, under…
Freeman Dyson has questioned whether any conceivable experiment in the real universe can detect a single graviton. If not, is it meaningful to talk about gravitons as physical entities? We attempt to answer Dyson's question and find it is…
A model of static boson-fermion star with spherical symmetry based on the scalar-tensor theory of gravity with massive dilaton field is investigated numerically. Since the radius of star is \textit{a priori} an unknown quantity, the…
Optically thin dusty disks around Main Sequence stars consist of debris from catastrophic collisions or from low erosion of long-lived planetesimals. Resolved observations of dusty disks have systematically evidenced asymmetries and annular…
A static, spherically symmetric, asymptotically flat spacetime may allow for circular, closed null-geodesics which are said to belong to a photon sphere. In the context of gravitational lensing in the strong deflection regime, the presence…
Galactic dynamo models have generally relied on input parameters that are very challenging to constrain. We address this problem by developing a model that uses observable quantities as input: the galaxy rotation curve, the surface…
The discovery of a 2 Msun neutron star provided a robust constraint for the theory of exotic dense matter, bringing into question the existence of strange baryons in the interiors of neutron stars. Although many theories fail to reproduce…
We study solutions for boson stars in multiscalar theory. We start with simple models with N scalar theories. Our purpose is to study the models in which the mass matrix of scalars and the scalar couplings are given by an extended method of…
We complete our previous investigation concerning the structure and the stability of "isothermal" spheres in general relativity. This concerns objects that are described by a linear equation of state $P=q\epsilon$ so that the pressure is…
The most important features of the proposed spherical gravitational wave detectors are closely linked with their symmetry. Hollow spheres share this property with solid ones, considered in the literature so far, and constitute an…
Spinning neutron stars, when observed as pulsars, are seen to undergo occasional spin-up events known as glitches. Despite several decades of study, the physical mechanisms responsible for glitches are still not well understood, but…
This work explores the dynamic properties of test particles surrounding a distorted, deformed compact object. The astrophysical motivation was to choose such background, which could constitute a more reasonable model of a real situation…
Compact objects occupy a pivotal role in the exploration of Nature. The interest spans from the role of compact objects in astrophysics to their detection through various methods (gravitational waves interferometry, microlensing, imaging).…
Batygin and Brown (2016) have suggested the existence of a new Solar System planet supposed to be responsible for the perturbation of eccentric orbits of small outer bodies. The main challenge is now to detect and characterize this putative…
The effects of nonlinear oscillations in compact stars are attracting considerable current interest. In order to study such phenomena in the framework of fully nonlinear general relativity, highly accurate numerical studies are required. We…
We study the optimal packing of hard spheres in an infinitely long cylinder, using simulated annealing, and compare our results with the analogous problem of packing disks on the unrolled surface of a cylinder. The densest structures are…
Topical problems in the physics of and basic facts about neutron stars are reviewed. The observational manifestations of neutron stars, their core and envelope structure, magnetic fields, thermal evolution, and masses and radii are briefly…
We explore the dynamics of boson stars in the presence of axionic couplings through nonlinear evolutions of Einstein's field equations. We show that, for large axionic couplings, isolated boson stars become unstable, and decay via a large…
The main goal of the paper is to solve some problems about shadow for the sphere generalized on the case of the ellipsoid. Here, the essence of the problem is to find the the minimal number of non-overlapping balls with centers on the…
We develop a model to describe the properties of random assemblies of polydisperse hard spheres. We show that the key features to describe the system are (i) the dependence between the free volume of a sphere and the various coordination…