Perturbative calculation of quasi-normal modes of Schwarzschild black holes

We discuss a systematic method of analytically calculating the asymptotic form of quasi-normal frequencies of a four-dimensional Schwarzschild black hole by expanding around the zeroth-order approximation to the wave equation proposed by Motl and Neitzke. We obtain an explicit expression for the first-order correction and arbitrary spin. Our results are in agreement with the results from WKB and numerical analyses in the case of gravitational waves.Comment: 11 pages; references added and a sign error corrected; to appear in CQ

The Plausibility of Policy: Case studies from the social domain

__Abstract__ The social domain has seen a growing debate on the effectiveness of public measures. The realisation is taking shape that the legitimacy of social policies – such as the socialisation of vulnerable groups, anti-radicalisation programs or regeneration projects in deprived neighbourhoods – has to go beyond the intuition that they ‘should’ work. But unlike methods in spheres such as medicine and healthcare, social programs typically have no sharp demarcation in time, intensity or target group and are implemented in a rich context of unforeseen and unknown variables. This makes it difficult (if not impossible) to assess their impact with research methods that centralise a monocausal effect. In The Plausibility of Policy, Vasco Lub presents alternative approaches for assessing the likelihood to which social policy measures achieve their intended effects. One of his main lines of argument is to confront policy assumptions with existing scientific data. In doing so, he sheds light on how such measures can be assessed and to what degree claims about those intended effects can be substantiated

Dekonstruksi Paradigma Radikal dalam Al-Quran

This paper aims to change the radical paradigm based on the verses of the Quran. Religion or verses of Quran often becomes a tool of legitimacy or justification of acts of violence. This research uses the methods of library research. From this research it is achieved that religious radicalism caused by the first war verses, often made up of legitimacy of violence and terrorism in Islam, the second, understanding the Jihad verses translated the war against the enemies of Islam, so that acts of violence against everything that was considered an enemy of Islam is the glorious JihadKeywords: radicalism, religion, violent ideological verses Abstrak Tulisan ini bertujuan untuk merubah paradigma radikal berdasarkan ayat-ayat Al-Quran. Agama atau ayat-ayat al-Qur’an sering menjadi alat legitimasi atau pembenaran atas tindakan kekerasan. Penelitian ini menggunakan metode library research. Dari penelitian ini didapatkan bahwa muculnya radikalisme agama disebabkan oleh pertama, ayat-ayat perang sering dijadikan legitimasi atas pro-kekerasan dan aksi terorisme dalam Islam., kedua, memahami  ayat-ayat Jihad diartikan perang melawan musuh Islam, sehingga tindakan kekerasan terhadap segala sesuatu yang dianggap musuh Islam merupakan Jihad yang mulia Kata kunci: Radikalisme, Agama, Ayat-ayat Ideologi kekerasa

Spectral energy distributions of classical cepheids in the Magellanic Clouds

(abridged) In this study, we constructed spectral energy distributions (SEDs) for a sample of 142 LMC and 77 SMC fundamental-mode classical Cepheids (CCs) using photometric data from the literature. When possible, the data were taken to be representative of mean light or averaged over the light curve. The sample was built from stars that either have a metallicity determination from high-resolution (HR) spectroscopy or have been used in Baade-Wesselink types of analyses, or have a radial velocity curve published in Gaia DR3 or have Walraven photometry, or have their light- and radial-velocity curves modelled by pulsation codes. The SEDs were fitted with stellar photosphere models to derive the best-fitting luminosity and effective temperature. Only one star with a significant infrared excess was found in the LMC and none in the SMC, suggesting that IR excess may be more prominent in MW cepheids than in the Magellanic Clouds. For the large majority of stars, the position in the Hertzsprung-Russell diagram is consistent with theoretical instability strips. Period-luminosity (PL) and period-radius relations were derived and compared to these relations in the MW. For a fixed slope, the zero point of the bolometric PL relation does not depend on metallicity, contrary to recent findings of a significant metallicity term when considering the PL relation in different photometric bands. An intriguing result concerns the flux-weighted gravity (FWG, a quantity derived from gravity and Teff) and its relation to period and luminosity. Both relations agree with theory, with the results for the MW, and with the independent estimates from the six known LMC eclipsing binaries that contain CCs. However, the FWG (as determined from dedicated HR spectroscopy for the sample) is too low by about 0.8 dex in 90 percent of the cases.Comment: accepted by A&