The landscape and the multiverse: What’s the problem?

As a candidate theory of quantum gravity, the popularity of string theory has waxed and waned over the past four decades. One current source of scepticism is that the theory can be used to derive, depending upon the input geometrical assumptions that one makes, a vast range of different quantum field theories, giving rise to the so-called landscape problem. One apparent way to address the landscape problem is to posit the existence of a multiverse; this, however, has in turn drawn heightened attention to questions regarding the empirical testability and predictivity of string theory. We argue first that the landscape problem relies on dubious assumptions and does not motivate a multiverse hypothesis. Nevertheless, we then show that the multiverse hypothesis is scientifically legitimate and could be coupled to string theory for other empirical reasons. Looking at various cosmological approaches, we offer an empirical criterion to assess the scientific status of multiverse hypotheses.

Storm-induced deformations of barred beach slope

It is shown that behavior of the multiple-bar system during a storm can be described in frameworks of the model assuming that bars move toward the sea with almost the same mean speed, while the over-bar depths increase in accordance with the local bed slope. Analysis of suspended-sediment balance over the bar crest leads to expression for the bar movement speed, which demonstrates very strong dependence on ratio of wave height to the over-bar depth. Using empirical criterion of bar activity the model suggested is capable assess the bar displacement during a storm action and predict the post-storm bed profile. Comparison with the published field data leads to conclusion that the computed and observed storm-induced deformations of barred beach slopes are in satisfactorily agreement.

Coded Language Among Muslim Activists: Salafīs and the Prophet’s Sermon of Necessity

This article examines how use of the Prophet Muḥammad’s Khuṭbat al-ḥāja (Sermon of Necessity) became a distinguishing marker of Salafism. To understand the Sermon’s role, the article draws on the notion of “coded language,” messages that communities use to communicate with insiders while excluding outsiders. The article analyzes the content of the Sermon and describes its spread among Salafīs. The Sermon was championed by Muḥammad Nāṣir al-Dīn al-Albānī (1914-99), who played a pivotal role in shaping Salafī practice. Relating the Sermon’s spread to methodological debates about studying Salafism, the article suggests that the Sermon furnishes one empirical criterion that can be used to date Salafism’s crystallization to the mid-twentieth century. The article closes by examining how jihādīs selectively use the Sermon to “Salafize” their speech, and by discussing how instances of opposition to the Sermon’s use were connected to debates over the validity of Salafism and the status of al-Albānī.

Hume über kausale Kräfte und Sätze

This paper takes a new approach to understanding Hume’s view on causality, taking ontological as well as semantic issues into account. It attempts to attain three different goals. In the first place, it dismisses the main arguments that were put forward by the New Humeans in order to show that Hume must be regarded as a sceptical realist with respect to causality. Secondly, by employing a genetic reading of Hume’s two definitions of causality, the paper argues for an interpretation of Hume that takes his empirical criterion of meaning as seriously as possible. And thirdly, it presents a proposal to analyse the meaning of causal sentences from a Humean perspective. According to this approach, the meaning of causal sentences divides into a descriptive and a projective component. By taking advantage of Hume’s general view on meaning, we can underpin the projectivist interpretation of Hume’s theory of causality with exegetical evidence.

Study on the Adiabatic Temperature of Al-Ti-C Grain Refiner Synthesized by SHS Technique

SHS technique and conventional melting and casting technology were combined and used for the preparation of Al-Ti-C grain refiner alloy. Experimental results show that when SHS reaction occurs to the Al, Ti and C powder reactant in Al melt and the composition proportion factor, n , is between 4 and 10, the effect of composition on the initial temperature of SHS reaction is small and its initial temperature ranges from 810 to 815°C. However, the highest temperature of the melt increases with increasing n values and increases gradually from 845 to 1370°C. In the meantime, when the composition proportion factor for Al, Ti and C powder reactant, n, is greater than 5.95, its adiabatic temperature Td>1800K which conforms to the empirical criterion proposed by Merzhanov et al. The SHS reaction of reactant can accomplish by self-maintenance.