Recently, it was argued that the spacetime dynamics can be understood by calculating the difference between the degrees of freedom on the boundary and in the bulk in a region of space. In this Letter, we apply this new idea to braneworld scenarios and extract the corresponding Friedmann equations of (n − 1)-dimensional brane embedded in the (n + 1)-dimensional bulk with any spacial curvature. We will also extend our study to the more general Gauss-Bonnet braneworld with curvature correction terms on the brane and in the bulk, and derive the dynamical equation in a nonflat Universe.
A very interesting new proposal on the origin of the cosmic expansion was recently suggested by Padmanabhan [arXiv:1206.4916]. He argued that the difference between the surface degrees of freedom and the bulk degrees of freedom in a region of space drives the accelerated expansion of the universe, as well as the standard Friedmann equation through relation △V = △t(N sur −N bulk ). In this paper, we first present the general expression for the number of degrees of freedom on the holographic surface, N sur , using the general entropy corrected formula S = A 4L 2 p + s(A). Then, as two example, by applying the Padmanabhan's idea we extract the corresponding Friedmann equations in the presence of power-law and logarithmic correction terms in the entropy. We also extend the study to RS II and DGP branworld models and derive successfully the correct form of the Friedmann equations in these theories.Our study further supports the viability of Padmanabhan's proposal.
Pattern synthesize of conformal array antennas is often a challenging problem. Various optimization algorithms such as genetic, particle swarm optimization (PSO), and invasive weed optimization have already been used for pattern synthesizing of conformal arrays. In this paper, a focused beam is synthesized for a quarter cylindrical conformal array antenna using the PSO algorithm with small computations. The desired pattern is a focused beam at
θ = 90° and
ϕ = 45° with 10° beamwidth in elevation and 15° beamwidth in azimuth with −20 dB side‐lobe level. This method can be used in general for synthesizing arbitrary desired patterns and array geometries.
Abstract-We propose and theoretically and experimentally demonstrate a novel tunable spurious-free single-loop optoelectronic oscillator (OEO) with low drift and low-phase noise. In the proposed transposed-frequency OEO (TF-OEO), a nonreciprocal bias unit and an optical phase modulator in a fiber Sagnac interferometer function jointly as an intrinsically drift-free intensity modulator, which improves the long-term drift. Besides, a transposed-frequency low-noise filtered amplifier is used which replaces the conventional radio frequency (
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