Effect of Spin Current on Uniform Ferromagnetism: Domain Nucleation

Large spin current applied to a uniform ferromagnet leads to a spin-wave instability as pointed out recently. In this paper, it is shown that such spin-wave instability is absent in a state containing a domain wall, which indicates that nucleation of magnetic domains occurs above a certain critical spin current. This scenario is supported also by an explicit energy comparison of the two states under spin current.Comment: 4 pages, 1 figure, REVTeX, rivised version, to appear in Physical Review Letter

Unified First Law and Thermodynamics of Apparent Horizon in FRW Universe

In this paper we revisit the relation between the Friedmann equations and the first law of thermodynamics. We find that the unified first law firstly proposed by Hayward to treat the "outer"trapping horizon of dynamical black hole can be used to the apparent horizon (a kind of "inner" trapping horizon in the context of the FRW cosmology) of the FRW universe. We discuss three kinds of gravity theorties: Einstein theory, Lovelock thoery and scalar-tensor theory. In Einstein theory, the first law of thermodynamics is always satisfied on the apparent horizon. In Lovelock theory, treating the higher derivative terms as an effective energy-momentum tensor, we find that this method can give the same entropy formula for the apparent horizon as that of black hole horizon. This implies that the Clausius relation holds for the Lovelock theory. In scalar-tensor gravity, we find, by using the same procedure, the Clausius relation no longer holds. This indicates that the apparent horizon of FRW universe in the scalar-tensor gravity corresponds to a system of non-equilibrium thermodynamics. We show this point by using the method developed recently by Eling {\it et al.} for dealing with the $f(R)$ gravity.Comment: v2: revtex, 23 pages, references added, minor changes, to appear in PR

Constraint Propagation of C2C^2-adjusted Formulation - Another Recipe for Robust ADM Evolution System

With a purpose of constructing a robust evolution system against numerical instability for integrating the Einstein equations, we propose a new formulation by adjusting the ADM evolution equations with constraints. We apply an adjusting method proposed by Fiske (2004) which uses the norm of the constraints, C2. One of the advantages of this method is that the effective signature of adjusted terms (Lagrange multipliers) for constraint-damping evolution is pre-determined. We demonstrate this fact by showing the eigenvalues of constraint propagation equations. We also perform numerical tests of this adjusted evolution system using polarized Gowdy-wave propagation, which show robust evolutions against the violation of the constraints than that of the standard ADM formulation.Comment: 11 pages, 5 figures. To be published in Phys. Rev.

Notes on Entropy Force in General Spherically Symmetric Spacetimes

In a recent paper [arXiv:1001.0785], Verlinde has shown that the Newton gravity appears as an entropy force. In this paper we show how gravity appears as entropy force in Einstein's equation of gravitational field in a general spherically symmetric spacetime. We mainly focus on the trapping horizon of the spacetime. We find that when matter fields are absent, the change of entropy associated with the trapping horizon indeed can be identified with an entropy force. When matter fields are present, we see that heat flux of matter fields also leads to the change of entropy. Applying arguments made by Verlinde and Smolin, respectively, to the trapping horizon, we find that the entropy force is given by the surface gravity of the horizon. The cases in the untrapped region of the spacetime are also discussed.Comment: revtex4, 21 pages, no figures, one reference added, published version, to appear in Phys.Rev.

Holographic Superconductors with Ho\v{r}ava-Lifshitz Black Holes

We discuss the phase transition of planar black holes in Ho\v{r}ava-Lifshitz gravity by introducing a Maxwell field and a complex scalar field. We calculate the condensates of the charged operators in the dual CFTs when the mass square of the complex scalar filed is $m^2=-2/L^2$ and $m^2=0$, respectively. We compute the electrical conductivity of the \hl superconductor in the probe approximation. In particular, it is found that there exists a spike in the conductivity for the case of the operator with scaling dimension one. These results are quite similar to those in the case of Schwarzschild-AdS black holes, which demonstrates that the holographic superconductivity is a robust phenomenon associated with asymptotic AdS black holes.Comment: 12 pages, 7 figures,refs adde

Constraints and Reality Conditions in the Ashtekar Formulation of General Relativity

We show how to treat the constraints and reality conditions in the $SO(3)$-ADM (Ashtekar) formulation of general relativity, for the case of a vacuum spacetime with a cosmological constant. We clarify the difference between the reality conditions on the metric and on the triad. Assuming the triad reality condition, we find a new variable, allowing us to solve the gauge constraint equations and the reality conditions simultaneously.Comment: LaTeX file, 12 pages, no figures; to appear in Classical and Quantum Gravit

Does the mass of a black hole decrease due to the accretion of phantom energy

According to Babichev et al., the accretion of a phantom test fluid onto a Schwarzschild black hole will induce the mass of the black hole to decrease, however the backreaction was ignored in their calculation. Using new exact solutions describing black holes in a background Friedmann-Robertson-Walker universe, we find that the physical black hole mass may instead increase due to the accretion of phantom energy. If this is the case, and the future universe is dominated by phantom dark energy, the black hole apparent horizon and the cosmic apparent horizon will eventually coincide and, after that, the black hole singularity will become naked in finite comoving time before the Big Rip occurs, violating the Cosmic Censorship Conjecture.Comment: 12 pages, 5 figures. PRD accepte

Analisis Konsep Nilai Hasil Pada Proyek Ruko 3 Tingkat Di Jalan Ampera Pontianak Dengan Menggunakan Program Primavera 6.0

Manajemen konstruksi adalah perencanaan, penjadwalan dan pengendalian proyek untuk mencapai tujuan proyek tanpa ada penyimpangan. Proyek konstruksi dapat dikelola dengan baik dan mudah apabila menggunakan Konsep Nilai Hasil (Earned Value Analysis). Konsep Nilai Hasil (Earned Value Analysis) mampu mengendalikan penjadwalan secara efektif dan efisien, karena konsep ini dapat meramalkan hasil pelaporan akhir proyek, sehingga manajemen proyek dapat sesegera mungkin meluruskan kegiatan proyek agar berjalan sesuai rencana jika terjadi penyimpangan. Konsep nilai hasil dapat dikelola dengan bantuan program Primavera 6.0. Pada penelitian ini, data dilakukan dengan menginputkan data ke program Primavera 6.0 maka secara otomatis hasil analisis dapat keluar berdasarkan rumus-rumus kalkulasi yang ada program ini. Sehingga hasil yang dihasilkan dari konsep nilai hasil ini lebih cepat dan akurat. Hasil analisis data yang dilakukan pada Proyek Ruko 3 Tingkat di Jalan Ampera Pontianak menunjukkan bahwa besarnya biaya pelaksanaan (Actual Cost) hingga minggu ke-5 adalah Rp. 258.564.774. Prakiraan biaya akhir proyek (Estimate At Completion) adalah Rp. 1.295.990.982 dan prakiraan waktu akhir proyek (Estimate All Schedule) adalah 273 hari yaitu selesai pada tanggal 26 Oktober 2014. Jika tidak ada evaluasi kinerja, maka kontraktor akan mengalami kerugian (Variance At Completion) sebesar Rp. 139.482.439

High-energy effective theory for matter on close Randall Sundrum branes

Extending the analysis of hep-th/0504128, we obtain a formal expression for the coupling between brane matter and the radion in a Randall-Sundrum braneworld. This effective theory is correct to all orders in derivatives of the radion in the limit of small brane separation, and, in particular, contains no higher than second derivatives. In the case of cosmological symmetry the theory can be obtained in closed form and reproduces the five-dimensional behaviour. Perturbations in the tensor and scalar sectors are then studied. When the branes are moving, the effective Newtonian constant on the brane is shown to depend both on the distance between the branes and on their velocity. In the small distance limit, we compute the exact dependence between the four-dimensional and the five-dimensional Newtonian constants.Comment: Updated version as published in PR