Conoscopic holography

A new method for recording holograms using incoherent light is described. The method is based on optical propagation through birefringent crystals. Optical methods for the reconstruction of such a hologram are also presented

A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair Theorem

According to the no-hair theorem, astrophysical black holes are uniquely characterized by their masses and spins and are described by the Kerr metric. Several parametric deviations from the Kerr metric have been suggested to study observational signatures in both the electromagnetic and gravitational-wave spectra that differ from the expected Kerr signals. Due to the no-hair theorem, however, such spacetimes cannot be regular everywhere outside the event horizons, if they are solutions to the Einstein field equations; they are often characterized by naked singularities or closed time-like loops in the regions of the spacetime that are accessible to an external observer. For observational tests of the no-hair theorem that involve phenomena in the vicinity of the circular photon orbit or the innermost stable circular orbit around a black hole, these pathologies limit the applicability of the metrics only to compact objects that do not spin rapidly. In this paper, we construct a Kerr-like metric which depends on a set of free parameters in addition to its mass and spin and which is regular everywhere outside of the event horizon. We derive expressions for the energy and angular momentum of a particle on a circular equatorial orbit around the black hole and compute the locations of the innermost stable circular orbit and the circular photon orbit. We demonstrate that these orbits change significantly for even moderate deviations from the Kerr metric. The properties of our metric make it an ideally suited spacetime to carry out strong-field tests of the no-hair theorem in the electromagnetic spectrum using the properties of accretion flows around astrophysical black holes of arbitrary spin.Comment: 11 pages, 7 figures, accepted for publication in PR

Characterization of the DuPont photopolymer for three-dimensional holographic storage

DuPont's HRF-150 photopolymer film is investigated for use in three-dimensional holographic memories. Measurements of sensitivity, hologram persistence, the lateral spread of the photoinitiated reaction, and the variation of diffraction efficiency with modulation depth, spatial frequency and tilt angle, and intensity are reported. We observed that the diffraction efficiency of the HRF-150 photopolymer for a given exposure decreases with increases in intensity and grating tilt angle. The holograms were nondestructively reconstructed for long periods of time at room temperature. The photoinitiated reaction spread less than 100 µm over a period of 16 h

Pixel size limit in holographic memories

The bandwidth of holographic recording in LiNbO3 (Fe doped) in the 90° geometry is studied theoretically and experimentally. The wide holographic bandwidth of LiNbO3 makes it possible to record submicrometer pixels and reconstruct them by phase conjugation in a holographic memory system. This approach reduces the system cost and increases the system storage density. We demonstrate the recording and the phase-conjugate reconstruction of various pixel sizes down to 1 μm × 1 μm . The signal–noise ratio and the bit-error rate are examined

Slowly Rotating Relativistic Stars in Tensor-Vector-Scalar Theory

In order to examine the rotational effect around neutron star in tensor-vector-scalar (TeVeS) theory, we consider the slowly rotating relativistic stars with a uniform angular velocity. As a result, we find that similar to the case in general relativity (GR), the angular momentum is proportional to the angular velocity. Additionally, as the value of coupling constant $K$ becomes higher, the frame dragging in TeVeS becomes quite different distribution from that in GR, where we can also see the deviation even in the interior of star. While with smaller value of $K$, although the frame dragging approaches to that expected in GR, the induced vector field due to the rotation does not vanish and still exists. Thus, through the observations associated with relativistic object, one could be possible to distinguish the gravitational theory in strong field regime even in the case that the value of coupling constant $K$ is quite small.Comment: Accepted in Phys.Rev.