Bouncing Palatini cosmologies and their perturbations

Nonsingular cosmologies are investigated in the framework of f(R) gravity within the first order formalism. General conditions for bounces in isotropic and homogeneous cosmology are presented. It is shown that only a quadratic curvature correction is needed to predict a bounce in a flat or to describe cyclic evolution in a curved dust-filled universe. Formalism for perturbations in these models is set up. In the simplest cases, the perturbations diverge at the turnover. Conditions to obtain smooth evolution are derived.Comment: 7 pages, 1 figure. v2: added references

The post-Newtonian limit in C-theories of gravitation

C-theory provides a unified framework to study metric, metric-affine and more general theories of gravity. In the vacuum weak-field limit of these theories, the parameterized post-Newtonian (PPN) parameters $\beta$ and $\gamma$ can differ from their general relativistic values. However, there are several classes of models featuring long-distance modifications of gravity but nevertheless passing the Solar system tests. Here it is shown how to compute the PPN parameters in C-theories and also in nonminimally coupled curvature theories, correcting previous results in the literature for the latter.Comment: 5 pages, no figures; To appear in PRD as a rapid communicatio

Unifying Einstein and Palatini gravities

We consider a novel class of $f(\R)$ gravity theories where the connection is related to the conformally scaled metric $\hat g_{\mu\nu}=C(\R)g_{\mu\nu}$ with a scaling that depends on the scalar curvature $\R$ only. We call them C-theories and show that the Einstein and Palatini gravities can be obtained as special limits. In addition, C-theories include completely new physically distinct gravity theories even when $f(\R)=\R$. With nonlinear $f(\R)$, C-theories interpolate and extrapolate the Einstein and Palatini cases and may avoid some of their conceptual and observational problems. We further show that C-theories have a scalar-tensor formulation, which in some special cases reduces to simple Brans-Dicke-type gravity. If matter fields couple to the connection, the conservation laws in C-theories are modified. The stability of perturbations about flat space is determined by a simple condition on the lagrangian.Comment: 17 pages, no figure

PENGARUH KOMITMEN PRIVASI DAN KEPERCAYAAN AKAN TEKNOLOGI TERHADAP NILAI YANG DIRASAKAN NASABAH DIMODERASIKAN OLEH INFORMASI PRIVASI PADA INTERNET BANKING (STUDI KASUS PADA NASABAH BANK BCA DI BANDA ACEH)

ABSTRAKTujuan yang ingin dicapai pada penelitian ini adalah untuk mengetahui apakah informasi privasi memoderasi pengaruh antara komitmen privasi dan kepercayaan akan teknologi terhadap nilai yang dirasakan nasabah. Dengan menggunakan metode non probability sampling, terdapat 120 responden yang dijadikan sebagai sampel pada penelitian ini yaitu nasabah Bank BCA yang menggunakan internet banking.Jenis data yang digunakan pada penelitian ini adalah data primer. Teknik pengumpulan data dilakukan dengan menyebarkan kuesioner kepada sampel penelitian. Moderated Regression Analysis (MRA) digunakan untuk menguji hipotesis dalam penelitian ini.Hasil penelitian menunjukkan bahwa (1) Komitmen privasi berpengaruh signifikan terhadap nilai yang dirasakan nasabah (2) Kepercayaan akan teknologi berpengaruh signifikan terhadap nilai yang dirasakan nasabah (3) Informasi privasi memoderasi komitmen privasi berpengaruh signifikan terhadap nilai yang dirasakan nasabah Bank BCA Cabang Banda Aceh (4) Informasi privasi memoderasi kepercayaan akan teknologi berpengaruh signifikan terhadap nilai yang dirasakan nasabah Bank BCA Cabang Banda Aceh. Kata Kunci: nilai yang dirasakan, komitmen privasi, kepercayaan akan teknologi, informasi privasiABSTRACTThe aim of this research was to determine whether information privacy moderating influence between privacy commitment and belief in the technology to the customer perceived value. By using non-probability sampling, there were 120 respondents were used as a sample in this research that BCA Bank customers who use Internet banking.Data used in this study are primary data. Techniques of data collection is done by distributing questionnaires to sample. Moderated Regression Analysis (MRA) was used to test the hypothesis in this study.The results showed that (1) Commitment to privacy significantly have effect on the perceived value of customers (2) Belief in the technology significant have effect on the perceived value of customers (3) Information Privacy moderate the commitment privacy significantly have effect on customers' perceived value of Bank BCA Branch Banda Aceh (4) Information technology privacy moderate confidence will significantly have effect on the perceived value of customers of Bank BCA Branch of Banda Aceh.Keywords: perceived value, commitment to privacy, trust in technology, information privac

Quantum transport properties of two-dimensional systems in disordered magnetic fields with a fixed sign

Quantum transport in disordered magnetic fields is investigated numerically in two-dimensional systems. In particular, the case where the mean and the fluctuation of disordered magnetic fields are of the same order is considered. It is found that in the limit of weak disorder the conductivity exhibits a qualitatively different behavior from that in the conventional random magnetic fields with zero mean. The conductivity is estimated by the equation of motion method and by the two-terminal Landauer formula. It is demonstrated that the conductance stays on the order of $e^2/h$ even in the weak disorder limit. The present behavior can be interpreted in terms of the Drude formula. The Shubnikov-de Haas oscillation is also observed in the weak disorder regime.Comment: 6 pages, 7 figures, to appear in Phys. Rev.

Shot noise and conductivity at high bias in bilayer graphene: Signatures of electron-optical phonon coupling

We have studied electronic conductivity and shot noise of bilayer graphene (BLG) sheets at high bias voltages and low bath temperature $T_0=4.2$ K. As a function of bias, we find initially an increase of the differential conductivity, which we attribute to self-heating. At higher bias, the conductivity saturates and even decreases due to backscattering from optical phonons. The electron-phonon interactions are also responsible for the decay of the Fano factor at bias voltages $V>0.1$ V. The high bias electronic temperature has been calculated from shot noise measurements, and it goes up to $\sim1200$ K at $V=0.75$ V. Using the theoretical temperature dependence of BLG conductivity, we extract an effective electron-optical phonon scattering time $\tau_{e-op}$. In a 230 nm long BLG sample of mobility $\mu=3600$ cm$^2$V$^{-1}$s$^{-1}$, we find that $\tau_{e-op}$ decreases with increasing voltage and is close to the charged impurity scattering time $\tau_{imp}=60$ fs at $V=0.6$ V.Comment: 7 pages, 7 figures. Extended version of the high bias part of version 1. The low bias part is discussed in arXiv:1102.065

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PENGEMBANGAN MODEL PERMAINAN GERAK DASAR LEMPAR UNTUK SISWA KELAS V SDN TAWANGARGO 4 KARANGPLOSO MALANG

Penelitian ini bertujuan mengembangkan permainan gerak dasar lempar bagi siswa kelas V di SDN Tawangargo 4 Karangploso Kabupaten Malang Jawa Timur. Metode penelitian yang digunakan adalah penelitian dan pengembangan dengan model konseptual. Prosedur  penelitian meliputi: analisis kebutuhan, pengembangan produk, dan uji coba produk. Teknik analisis data yang digunakan adalah analisis data kualitatif dan kuantitatif. Hasil penelitian menunjukkan bahwa produk ini valid digunakan siswa kelas V di SDN Tawangargo 4 Karangploso Kabupaten Malang. Hasil uji coba kelompok kecil dan kelompok besar mendapat rata-rata persentase 89,26%. Angka tersebut menunjukkan bahwa model permainan ini praktis digunakan oleh siswa kelas V di SD dan efektif meningkatkan gerak dasar lempar kelas V SD. Kata Kunci: model permainan, gerak dasar lempar, siswa SD

Non-metric chaotic inflation

We consider inflation within the context of what is arguably the simplest non-metric extension of Einstein gravity. There non-metricity is described by a single graviscalar field with a non-minimal kinetic coupling to the inflaton field $\Psi$, parameterized by a single parameter $\gamma$. We discuss the implications of non-metricity for chaotic inflation and find that it significantly alters the inflaton dynamics for field values $\Psi \gtrsim M_P/\gamma$, dramatically changing the qualitative behaviour in this regime. For potentials with a positive slope non-metricity imposes an upper bound on the possible number of e-folds. For chaotic inflation with a monomial potential, the spectral index and the tensor-to-scalar ratio receive small corrections dependent on the non-metricity parameter. We also argue that significant post-inflationary non-metricity may be generated.Comment: 7 pages, 1 figur

Shot Noise in Ballistic Graphene

We have investigated shot noise in graphene field effect devices in the temperature range of 4.2--30 K at low frequency ($f$ = 600--850 MHz). We find that for our graphene samples with large width over length ratio $W/L$, the Fano factor $\mathfrak{F}$ reaches a maximum $\mathfrak{F} \sim$ 1/3 at the Dirac point and that it decreases strongly with increasing charge density. For smaller $W/L$, the Fano factor at Dirac point is significantly lower. Our results are in good agreement with the theory describing that transport at the Dirac point in clean graphene arises from evanescent electronic states.Comment: Phys. Rev. Lett. 100, 196802 (2008