On Multiparticle Entanglement via Resonant Interaction between Light and atomic Ensembles

Multiparticle entangled states generated via interaction between narrow-band light and an ensemble of identical two-level atoms are considered. Depending on the initial photon statistics, correlation between atoms and photons can give rise to entangled states of these systems. It is found that the state of any pair of atoms interacting with weak single-mode squeezed light is inseparable and robust against decay. Optical schemes for preparing entangled states of atomic ensembles by projective measurement are described.Comment: 11 pages, 1 figure, revtex

Wavelet Methods in Steganography

This paper is devoted to graphic information protection by means of computer steganography using wavelet techniques. The methods of the image processing using digital watermarking are classified. Some research of the structure of the digital image is investigated. In the first solution the steganographic system, which usesa discrete wavelet transform for embedding of grayscale watermark into wavelet coefficients of grayscale container is mоdeled and realized. Stego image is achieved by the inverse discrete wavelet transform. Binarization using halftoning algorithm is considered as a kind of powerful attack to stego image. After binarization attack the extracted watermark was found to have acceptable visual quality. The degradation ofthe embedded digital watermark after binarization is estimated using human visual system. Corresponding conclusions on steganographic system stability are drawn. In the second solution we propose the steganographic scheme which uses the proposed wavelet basis images

On Gauge Equivalence of Tachyon Solutions in Cubic Neveu-Schwarz String Field Theory

Simple analytic solution to cubic Neveu-Schwarz String Field Theory including the $GSO(-)$ sector is presented. This solution is an analog of the Erler-Schnabl solution for bosonic case and one of the authors solution for the pure $GSO(+)$ case. Gauge transformations of the new solution to others known solutions for the $NS$ string tachyon condensation are constructed explicitly. This gauge equivalence manifestly supports the early observed fact that these solutions have the same value of the action density.Comment: 8 pages, LaTe

Descent Relations and Oscillator Level Truncation Method

We reexamine the oscillator level truncation method in the bosonic String Field Theory (SFT) by calculation the descent relation =Z_3<V_2|. For the ghost sector we use the fermionic vertices in the standard oscillator basis. We propose two new schemes for calculations. In the first one we assume that the insertion satisfies the overlap equation for the vertices and in the second one we use the direct calculations. In both schemes we get the correct structures of the exponent and pre-exponent of the vertex <V_2|, but we find out different normalization factors Z_3.Comment: 21 pages, 10 figures, Late

Generating Erler-Schnabl-type Solution for Tachyon Vacuum in Cubic Superstring Field Theory

We study a new set of identity-based solutions to analyze the problem of tachyon condensation in open bosonic string field theory and cubic superstring field theory. Even though these identity-based solutions seem to be trivial, it turns out that after performing a suitable gauge transformation, we are left with the known Erler-Schnabl-type solutions which correctly reproduce the value of the D-brane tension. This result shows explicitly that how a seemingly trivial solution can generate a non-trivial configuration which precisely represents to the tachyon vacuum.Comment: 22 pages, references added, appendix added, 2 subsections adde

Coexistence of electron and hole transport in graphene

When sweeping the carrier concentration in monolayer graphene through the charge neutrality point, the experimentally measured Hall resistivity shows a smooth zero crossing. Using a two- component model of coexisting electrons and holes around the charge neutrality point, we unambiguously show that both types of carriers are simultaneously present. For high magnetic fields up to 30 T the electron and hole concentrations at the charge neutrality point increase with the degeneracy of the zero-energy Landau level which implies a quantum Hall metal state at \nu=0 made up by both electrons and holes.Comment: 5 pages, 6 figure