116970526
Dynamics of Rotating Cylindrical Shells in General Relativity
Cylindrical spacetimes with rotation are studied using the Newmann–Penrose formulas. By studying null geodesic deviations, the physical meaning of each component of the Riemann tensor is given. These spacetimes are further extended to include rotating dynamic shells, and the general expression of the surface energy-momentum tensor of the shells is given in terms of the discontinuity of the first derivatives of the metric coefficients. As an application of the developed formulas, a stationary shell that generates the Lewis solutions, which represent the most general vacuum cylindrical solutions of the Einstein field equations with rotation, is studied by assuming that the spacetime inside the shell is flat. It is shown that the shell can satisfy all the energy conditions by properly choosing the parameters appearing in the model, provided that 0 ≤ σ ≤ 1, where σ is related to the mass per unit length of the shell. PACS numbers: 04.20Cv, 04.30.+x, 97.60.Sm, 97.60.Lf.
10393301
On the sources of static plane symmetric vacuum space-times
Abstract The sources of static vacuum plane space-times with reflection symmetry are considered. It is argued that the counterpart of the Einstein theory to the gravitational field of a massive Newtonian plane should be described by the Rindler solution, which represents also a uniform gravitational field, and the test particles moving in which have constant accelerations.
109935503
No-Go theorem in spacetimes with two commuting spacelike killing vectors
Four-dimensional Riemannian spacetimes with two commuting spacelike Killing vectors are studied in Einstein's theory of gravity, and found that no outer apparent horizons exist, provided that the dominant energy condition holds.
2444705
Gravitational and particle radiation from long cosmic strings
Gravitational and massless particle radiation from infinitely long cosmic strings with finite thickness is studied by constructing analytic solutions to the Einstein field equations with certain forms of energy - momentum tensor. Using Thorne's -energy arguments, it is shown that the radiation always carries away energy. As a result, the angle defect outside the string is less than that in the non-radiation case. Since the solutions are exact, the back reaction of the radiation is automatically taken into account. In fact, it is shown that because of this back reaction the spacetime is always singular on the symmetry axis. The singularity is a scalar one and not removable.
119227824
Cosmological constant and late transient acceleration of the universe in the Horava-Witten Heterotic M-Theory on S^{1}/Z_{2}
Abstract Orbifold branes are studied in the framework of the 11-dimensional Horava–Witten heterotic M-theory. It is found that the effective cosmological constant can be easily lowered to its current observational value by the mechanism of large extra dimensions. The domination of this constant over the evolution of the universe is only temporary. Due to the interaction of the bulk and the branes, the universe will be in its decelerating expansion phase again in the future, whereby all problems connected with a far future de Sitter universe are resolved.
119168760
Homothetic self-similar solutions of three-dimensional Brans-Dicke gravity
All homothetic self-similar solutions of the Brans-Dicke scalar field in three-dimensional spacetime with circular symmetry are found in closed form.
81234
Levi-Civita solutions coupled with electromagnetic fields
The local and global properties of the Levi-Civita (LC) solutions coupled with an electromagnetic field are studied and some limits to the vacuum LC solutions are given, from which the physical and geometrical interpretations of the free parameters involved in the solutions are made clear. Sources for both the LC vacuum solutions and the LC solutions coupled with an electromagnetic field are studied, and in particular it is found that all the LC vacuum solutions with σ ≥ 0 can be produced by cylindrically symmetric thin shells that satisfy all the energy conditions, weak, dominant and strong. When the electromagnetic field is present, the situation changes dramatically. In the case of a purely magnetic field, all the solutions can be produced by physically acceptable cylindrical thin shells, while in the case of a purely electric field, no such shells are found for any choice of the free parameters involved in the solutions.
5973680
Shear-free radiating collapse and conformal flatness
Here we study some general properties of spherical shear-free collapse. Its general solution when imposing conformal atness is re-obtained (Refs. 1 and 2) and matched to the outgoing Vaidya spacetime. We propose a simple model satisfying these conditions and study its physical consequences. Special attention deserve, the role played by relaxational processes and the conspicuous link betweeen dissipation and density inhomogeneity.
118411966
Elastic Scattering of Positive Kaons on Polarized Deuterons at 1.5 Gev/c.
120345656
Evidence for the noneikonal effects in the tensor and vector analyzing powers in p-d elastic scattering at 800 MeV☆
Abstract Deuteron tensor and vector analyzing powers have been measured for the first time in p- d elastic scattering at 800 MeV proton laboratory energy for a - t range between 0.032 and 1.038 (GeV/ c ) 2 . The data provide a very sensitive test of the multiple scattering theory at intermediate energies. The inclusion of the noneikonal correction in the Glauber diffraction theory is essential in the description of the data, especially for -t ⪆0.2 (GeV/ c 2 ), where discrepancies of up to 150% are observed with the theory based on the eikonal approximation.
18340591
Direct Detection of a CME-Associated Shock in LASCO White Light Images
The LASCO C2 and C3 coronagraphs recorded a unique coronal mass ejection on April 2, 1999. The event did not have the typical three-part CME structure and involved a small filament eruption without any visibile overlying streamer ejecta. The event exhibited an unusually clear signature of a wave propagating at the CME flanks. The speed and density of the CME front and flanks were consistent with the existence of a shock. To better establish the nature of the white light wave signature, we employed a simple MHD simulation using the LASCO measurements as constraints. Both the measurements and the simulation strongly suggest that the white light feature is the density enhancement from a fast-mode MHD shock. In addition, the LASCO images clearly show streamers being deflected when the shock impinges on them. It is the first direct imaging of this interaction.