Center for Theoretical Physics

About: Center for Theoretical Physics is a facility organization based out in Warsaw, Poland. It is known for research contribution in the topics: Gamma-ray burst & Accretion (astrophysics). The organization has 68 authors who have published 112 publications receiving 1086 citations. The organization is also known as: Centrum Fizyki Teoretycznej PAN & Centrum Fizyki Teoretycznej Polskiej Akademii Nauk.

Canonical quantization, twistors and relativistic wave equations

Abstract: A formulation of relativistic quantum mechanics in twistor space is studied. The phase-space description of the classical theory leads (via canonical quantization) to all known wave equations describing massless particles. A natural link between the classical and the quantum description is provided by the Wigner function defined on the space of twistors.

Narrow Line Seyfert 1 galaxies in the context of Quasar Main Sequence

Abstract: Narrow-line Seyfert 1 galaxies are defined on the basis of their line widths, and they are generally considered to be high Eddington ratio sources. But in the context of the Quasar Main Sequence, high Eddington rate sources are those which have weak [O III] lines and strong Fe II lines. There is an overlap between the two populations, but they are not identical. Thus these two selection criteria give a different view on which objects are actually high Eddington ratio sources. We discuss this issue in the context of the broad band spectral energy density, emission line shape modeling, Fe II pseudo-continuum strength, and the level of X-ray variability. We also discuss the issue of the viewing angle and the insight one can gain from spectropolarimetric observations. We conclude that there is no single driver behind the Quasar Main Sequence, and the Eddington ratio of the source cannot be determined from the source location on the optical plane alone. On the other hand, an expected range of AGN parameters combined with a simple model of the Fe II production represent well the observed coverage pattern of the plane, with not much effect needed from the dispersion due to the viewing angle.

Bipartite entanglement, spherical actions and geometry of local unitary orbits

Abstract: We use the geometry of the moment map to investigate properties of pure entangled states of composite quantum systems. The orbits of equally entangled states are mapped by the moment map on coadjoint orbits of local transformations (unitary transformations which do not change entanglement), thus the geometry of coadjoint orbits provides a partial classification of different entanglement classes. To achieve the full classification a further study of fibers of the moment map is needed. We show how this can be done effectively in the case of the bipartite entanglement by employing Brion's theorem. In particular, we presented the exact description of the partial symplectic structure of all local orbits for two bosons, fermions and distinguishable particles.

On the Existence of Rigid Spheres in Four-Dimensional Spacetime Manifolds

Abstract: This paper deals with the generalization of usual round spheres in the flat Minkowski spacetime to the case of a generic four-dimensional spacetime manifold M. We consider geometric properties of sphere-like submanifolds in M and impose conditions on its extrinsic geometry, which lead to a definition of a rigid sphere. The main result is a local existence theorem concerning such spheres. For this purpose, we apply the surjective implicit function theorem. The proof is based on a detailed analysis of the linearized problem and leads to an eight-parameter family of solutions in case when the metric tensor g of M is from a certain neighborhood of the flat Minkowski metric. This contribution continues the study of rigid spheres in (Class. Quantum Grav. 30: 175010, 2013).