4,351 research outputs found
Geometric scalar theory of gravity
We present a geometric scalar theory of gravity. Our proposal will be
described using the "background field method" introduced by Gupta, Feynman and
others as a field theory formulation of general relativity. We analyze previous
criticisms against scalar gravity and show how the present proposal avoids
these difficulties. This concerns not only the theoretical complaints but also
those related to observations. In particular, we show that the widespread
belief of the conjecture that the source of scalar gravity must be the trace of
the energy-momentum tensor - which is one of the main difficulties to couple
gravity with electromagnetic phenomenon in previous models - does not apply to
our geometric scalar theory. Some consequences of the new scalar theory are
explored.Comment: We did some modifications which do not change the content of the tex
Optical Properties of Organometallic Perovskite: An ab initio Study using Relativistic GW Correction and Bethe-Salpeter Equation
In the development of highly efficient photovoltaic cells, solid perovskite
systems have demonstrated unprecedented promise, with the figure of merit
exceeding nineteen percent of efficiency. In this paper, we investigate the
optical and vibrational properties of organometallic cubic perovskite
CH3NH3PbI3 using first-principles calculations. For accurate theoretical
description, we go beyond conventional density functional theory (DFT), and
calculated optical conductivity using relativist quasi-particle (GW)
correction. Incorporating these many-body effects, we further solve
Bethe-Salpeter equations (BSE) for excitons, and found enhanced optical
conductivity near the gap edge. Due to the presence of organic methylammonium
cations near the center of the perovskite cell, the system is sensitive to low
energy vibrational modes. We estimate the phonon modes of CH3NH3PbI3 using
small displacement approach, and further calculate the infrared absorption (IR)
spectra. Qualitatively, our calculations of low-energy phonon frequencies are
in good agreement with our terahertz measurements. Therefore, for both energy
scales (around 2 eV and 0-20 meV), our calculations reveal the importance of
many-body effects and their contributions to the desirable optical properties
in the cubic organometallic perovskites system.Comment: 5 pages, 4 figure
Pengaruh Kebijakan Pemerintah Tentang Kredit Usaha Rakyat (KUR) terhadap Laba Perusahaan Umum Jaminan Kredit Indonesia Kantor Cabang Jayapura
Penelitian ini bertujuan untuk mengetahui pengaruh kebijakan Pemerintah tentang kredit USAha rakyat (KUR) terhadap laba Perusahaan Umum (Perum) Jaminan Kredit Indonesia (Jamkrindo) Kantor Cabang Jayapura. Rumusan masalah penelitian adalah apakah kebijakan pemerintah tentang Kredit USAha rakyat mempunyai pengaruh yang signifikan terhadap Laba Perusahaan Umum (Perum) Jaminan Kredit Indonesia (Jamkrindo) Kantor Cabang Jayapura. Populasi dalam penelitian ini adalah Laporan Keuangan Perusahaan Umum (Perum) Jaminan Kredit Indonesia (Jamkrindo) Kantor Cabang Jayapura, sehingga sampel yang digunakan dalam penelitian ini adalah Laporan Keuangan Perusahaan Umum (Perum) Jaminan Kredit Indonesia (Jamkrindo) Kantor Cabang Jayapura secara berturut-turut untuk periode 2010-2012.Hasil analisis dengan menggunakan uji regresi. Hasil uji regresi menunjukkan bahwa terdapat hubungan yang positif antara kebijakan pemerintah dengan laba Perum Jamkrindo dengan nilai konstanta sebesar 996.501, artinya bahwa jika variabel yang dianalisis adalah nol atau tidak adanya kebijakan penambahan KUR maka laba Perum Jamkrindo akan mengalami penurunan sebesar Rp 996.501,- setiap triwulannya. Hal ini karena yang dijadikan parameter adalah data tiap triwulan sejak Tahun 2010–2012. Namun hasil ini ditandai dengan nilai tidak signifikan dari hasil olah statistic yaitu 0,143,nilainya lebih besar dari pada nilai α (alpha) yang ditetapkan sebesar 0,05.Dengan demikian,Ha ditolak yaitu kebijakan kredit USAha rakyat (X)secara simultan tidak mempunyai pengaruh yang signifikan terhadap laba Perusahaan (Y) Perum Jamkrindo Kantor Cabang Jayapura. Kata Kunci : pengaruh kebijakan kredit USAha rakyat terhadap laba Perusahaan
Cosmological Effects of Nonlinear Electrodynamics
It will be shown that a given realization of nonlinear electrodynamics, used
as source of Einstein's equations, generates a cosmological model with
interesting features, namely a phase of current cosmic acceleration, and the
absence of an initial singularity, thus pointing to a way to solve two
important problems in cosmology
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