Blackfolds in (Anti)-de Sitter Backgrounds

We construct different neutral blackfold solutions in Anti-de Sitter and de Sitter background spacetimes in the limit where the cosmological scale is taken to be much larger than the transverse horizon size. This includes a class of blackfolds with horizons that are products of odd-spheres times a transverse sphere, for which the thermodynamic stability is also studied. Moreover, we exhibit a specific case in which the same blackfold solution can describe different limiting black hole spacetimes therefore illustrating the geometric character of the blackfold approach. Furthermore, we show that the higher-dimensional Kerr-(Anti)-de Sitter black hole allows for ultra-spinning regimes in the relevant limit of large cosmological scale, and demonstrate that this is correctly described by a pancaked blackfold geometry. We also give evidence for the possibility of saturating the rigidity theorem in these backgrounds.Comment: v1: 1+29 pages, latex. v2: cosmetic changes. v3: .pdf file correcte

The X-ray spectral properties of very-faint persistent neutron star X-ray binaries

AX J1754.2-2754, 1RXS J171824.2-402934 and 1RXH J173523.7-354013 are three persistent neutron star low-mass X-ray binaries that display a 2--10 keV accretion luminosity Lx of only (1-10)x1E34 erg s-1 (i.e., only ~0.005-0.05 % of the Eddington limit). The phenomenology of accreting neutron stars which accrete at such low accretion rates is not yet well known and the reason why they have such low accretion rates is also not clear. Therefore, we have obtained XMM-Newton data of these three sources and here we report our analysis of the high-quality X-ray spectra we have obtained for them. We find that AX J1754.2-2754 has Lx~1E35 erg s-1, while the other two have X-ray luminosities about an order of magnitude lower. However, all sources have a similar, relatively soft, spectrum with a photon index of 2.3-2.5, when the spectrum is fitted with an absorbed power-law model. This model fits the data of AX J1754.2-2754 adequately, but it cannot fit the data obtained for 1RXS J171824.2-402934 and 1RXH J173523.7-354013. For those sources a clear soft thermal component is needed to fit their spectra. This soft component contributes 40% - 50% to the 0.5-10 keV flux of the sources. When including this additional spectral component, the power-law photon indices are significantly lower. It can be excluded that a similar component with similar contributions to the 2-10 keV X-ray flux is present for AX J1754.2-2754, indicating that the soft spectrum of this source is mostly due to the fact that the power-law component itself is not hard. We note that we cannot excluded that weaker soft component is present in the spectrum of this source which only contributes up to ~25% to the 0.5-10 keV X-ray flux. We discuss our results in the context of what is known of accreting neutron stars at very low accretion rate.Comment: 9 pages, 2 tables, 1 figure. Aceppted for publication in MNRA

XMM-Newton and Swift spectroscopy of the newly discovered very-faint X-ray transient IGR J17494-3030

A growing group of low-mass X-ray binaries are found to be accreting at very-faint X-ray luminosities of <1E36 erg/s (2-10 keV). Once such system is the new X-ray transient IGR J17494-3030. We present Swift and XMM-Newton observations obtained during its 2012 discovery outburst. The Swift observations trace the peak of the outburst, which reached a luminosity of ~7 E35 (D/8 kpc)^2 erg/s (2-10 keV). The XMM-Newton data were obtained when the outburst had decayed to an intensity of ~ 8 E34 (D/8 kpc)^2 erg/s. The spectrum can be described by a power-law with an index of ~1.7 and requires an additional soft component with a black-body temperature of ~0.37 keV (contributing ~20% to the total unabsorbed flux in the 0.5-10 keV band). Given the similarities with high-quality spectra of very-faint neutron star low-mass X-ray binaries, we suggest that the compact primary in IGR J17494-3030 is a neutron star. Interestingly, the source intensity decreased rapidly during the ~12 hr XMM-Newton observation, which was accompanied by a decrease in inferred temperature. We interpret the soft spectral component as arising from the neutron star surface due to low-level accretion, and propose that the observed decline in intensity was the result of a decrease in the mass-accretion rate onto the neutron star.Comment: 3 figures, 2 tables, accepted in MNRAS letter, in pres

Swift J1357.2-0933: the faintest black hole?

Swift J1357.2-0933 is the first confirmed very faint black hole X-ray transient and has a short estimated orbital period of 2.8 hr. We observed Swift J1357.2-0933 for ~50 ks with XMM-Newton in 2013 July during its quiescent state. The source is clearly detected at a 0.5-10 keV unabsorbed flux of ~3x10^-15 erg cm-2 s-1. If the source is located at a distance of 1.5 kpc (as suggested in the literature), this would imply a luminosity of ~8x10^29 erg s-1, making it the faintest detected quiescent black hole LMXB. This would also imply that there is no indication of a reversal in the quiescence X-ray luminosity versus orbital period diagram down to 2.8 hr, as has been predicted theoretically and recently supported by the detection of the 2.4 hr orbital period black hole MAXI J1659-152 at a 0.5-10 keV X-ray luminosity of ~ 1.2 x 10^31 erg s-1. However, there is considerable uncertainty in the distance of Swift J1357.2-0933 and it may be as distant as 6 kpc. In this case, its quiescent luminosity would be Lx ~ 1.3 x 10^31 erg s-1, i.e., similar to MAXI J1659-152 and hence it would support the existence of such a bifurcation period. We also detected the source in optical at r' ~22.3 mag with the Liverpool telescope, simultaneously to our X-ray observation. The X-ray/optical luminosity ratio of Swift J1357.2-0933 agrees with the expected value for a black hole at this range of quiescent X-ray luminosities.Comment: 5 pages, 3 figures, Accepted for publication in MNRA

Derivation of the blackfold effective theory

We study fluctuations and deformations of black branes over length scales larger than the horizon radius. We prove that the Einstein equations for the perturbed p-brane yield, as constraints, the equations of the effective blackfold theory. We solve the Einstein equations for the perturbed geometry and show that it remains regular on and outside the black brane horizon. This study provides an ab initio derivation of the blackfold effective theory and gives explicit expressions for the metrics near the new black holes and black branes that result from it, to leading order in a derivative expansion.Comment: 20 pages. v4: Typo corrected in eq. (6.11) -- erratum in the published versio

Analisis Penyebab Kesulitan Belajar Komputer Akuntansi pada Siswa Kelas XI Akuntansi Smk Nurul Falah Pekanbaru

Abstrac : This study aimed to determine what factors are the cause of accounting computer learning difficulties in class XI Accounting student of SMK Nurul Falah Pekanbaru. The study lasted from July to December 2015. The population in this study were all students of class XI Accounting SMK Nurul Falah Pekanbaru totaling 58 students. The sampling technique is purposive sampling sample selection based on consideration of the particular destination where consideration is the student who can not do the work according to the schedule at least 3 times totaling 35 students. Data collection instruments used were questionnaires were processed using semantic differential scale with variable depender: learning difficulties (Y); independent variables: internal factors (X1) and external factors (X2). From the results it can be concluded that based on the results of descriptive analysis 89.98% of the students agreed to external factors and 73.16% agree to internal factors so that external factors more influential in causing learning difficulties accounting computer in class XI student of SMK Nurul Falah Accounting Pekanbaru. The same is indicated by the results of the t test where t test result of external factors 2.907> 2.78 t internal factors

An X-ray view of the very faint black hole X-ray transient Swift J1357.2-0933 during its 2011 outburst

We report on the X-ray spectral (using XMM-Newton data) and timing behavior (using XMM-Newton and Rossi X-ray Timing Explorer [RXTE] data) of the very faint X-ray transient and black hole system Swift J1357.2-0933 during its 2011 outburst. The XMM-Newton X-ray spectrum of this source can be adequately fitted with a soft thermal component with a temperature of ~0.22 keV (using a disc model) and a hard, non-thermal component with a photon index of ~1.6 when using a simple power-law model. In addition, an edge at ~ 0.73 keV is needed likely due to interstellar absorption. During the first RXTE observation we find a 6 mHz quasi-periodic oscillation (QPO) which is not present during any of the later RXTE observations or during the XMM-Newton observation which was taken 3 days after the first RXTE observation. The nature of this QPO is not clear but it could be related to a similar QPO seen in the black hole system H 1743-322 and to the so-called 1 Hz QPO seen in the dipping neutron-star X-ray binaries (although this later identification is quite speculative). The observed QPO has similar frequencies as the optical dips seen previously in this source during its 2011 outburst but we cannot conclusively determine that they are due to the same underlying physical mechanism. Besides the QPO, we detect strong band-limited noise in the power-density spectra of the source (as calculated from both the RXTE and the XMM-Newton data) with characteristic frequencies and strengths very similar to other black hole X-ray transients when they are at low X-ray luminosities. We discuss the spectral and timing properties of the source in the context of the proposed very high inclination of this source. We conclude that all the phenomena seen from the source cannot, as yet, be straightforwardly explained neither by an edge-on configuration nor by any other inclination configuration of the orbit.Comment: 9 pages, 4 figures, 1 table. Accepted for publication in MNRA

Pengaruh Sektor Ekonomi terhadap Pendapatan Asli Daerah Provinsi Riau

Salah satu indikator kemajuan perekonomian suatu daerah dapat dilihat dariperkembangan Produk Domestik Regional Bruto (PDRB). PDRB memperlihatkanbesarnya produksi yang telah diciptakan oleh masing-masing sektor ekonomi padatahun tertentu. Semakin tinggi PDRB yang dihasilkan pada masing – masing sektor,maka akan semakin besar pula kontribusi sektor tersebut terhadap perekonomiandaerah. Oleh karena itu, penelitian ini bertujuan untuk mengetahui pengaruh sektorekonomi (migas dan non migas) terhadap Pendapatan Asli Daerah (PAD) ProvinsiRiau dari tahun 1990 hingga 2011. Jenis data yang digunakan dalam penelitian iniadalah data sekunder berupa data PDRB sektor ekonomi dan laporan realisasipendapatan asli daerahProvinsi Riau yang terdapat pada Badan Pusat Statistik(BPS) Provinsi Riau. Metode statistik yang digunakan untuk menguji hipotesispenelitian adalah regresi linear berganda. Hasil penelitian ini menunjukkan bahwasektor ekonomi tanpa migas berpengaruh signifikan terhadap Pendapatan AsliDaerah (PAD) Provinsi Riau, meskipun tidak setinggi pada pertumbuhan ekonomimigas. Terutama dari sektor pertambangan, sektor bangunan, sektor pengangkutandan sektor jasa –jasa. Hasil penelitian ini juga menunjukkan bahwa sektor ekonomimigas berpengaruh signifikan terhadap Pendapatan Asli Daerah (PAD) ProvinsiRiau, terutama pada sektor pertambangan, sektor industri pengolahan, sektorperdagangan, hotel dan restoran, dan sektor pengangkutan dan komunikasi

Thermal Giant Gravitons

We study the giant graviton solution as the AdS_5 X S^5 background is heated up to finite temperature. The analysis employs the thermal brane probe technique based on the blackfold approach. We focus mainly on the thermal giant graviton corresponding to a thermal D3-brane probe wrapped on an S^3 moving on the S^5 of the background at finite temperature. We find several interesting new effects, including that the thermal giant graviton has a minimal possible value for the angular momentum and correspondingly also a minimal possible radius of the S^3. We compute the free energy of the thermal giant graviton in the low temperature regime, which potentially could be compared to that of a thermal state on the gauge theory side. Moreover, we analyze the space of solutions and stability of the thermal giant graviton and find that, in parallel with the extremal case, there are two available solutions for a given temperature and angular momentum, one stable and one unstable. In order to write down the equations of motion, action and conserved charges for the thermal giant graviton we present a slight generalization of the blackfold formalism for charged black branes. Finally, we also briefly consider the thermal giant graviton moving in the AdS_5 part.Comment: v1: 32 pages + 11 pages appendices, 13 figures, v2: typos fixed in Sec.2 and other misprints, references adde