No unitary definition of terrorism exists in international law and it is unlikely that States will agree upon one in the future. Chapter 1 describes how and why definitions differ in peacetime and in armed conflict and between international terrorism and domestic terrorism. Each of these scenarios evinces particularities in the contours of terrorism under international law. The chapter also explains why the United Nations Comprehensive Convention against International Terrorism has not been successfully concluded.

Structure matters for understanding behavior. This chapters introduces the main theme of the book, provides a number of stories about the importance of structure, and outlines the main structure of the book.

Rubel was only eight or nine when he came to Dhaka. He took a train alone from the north, arrived at a station in the centre of the city and walked to a nearby bazaar where he has worked ever since. Memories of his family and village have blurred over the years, and today he is married with two children and stays in a basti (slum) elsewhere in the city. For people who have grown up on the streets of Dhaka, such stories are common. Some recall odd details of their home but have forgotten the name of their village and even family. Some ran away from poverty and cruelty, and described a widowed mother, a resentful stepparent, a neglectful father, mental illness, abuse at school or the madrasah. For some, the story of their arrival is bound up with a precise moment of fear, such as losing a prized asset and not daring to return home or a particularly brutal argument. For others, the streets have always been their home, growing up in makeshift shacks formed from tarpaulin sheets that dot stretches of pavement, and where even today some babies are born.

Dhaka, the capital of Bangladesh, is one of the most densely populated cities on earth. People here live in a sprawling mix of apartment blocks, a few upmarket neighbourhoods and large bastis. Others skirt the edges of these in bazaars, transport terminals and pavements. Despite being one of the most populous cities on earth, it is little known in the so-called Global North, so much so that foreigners often pronounce it ‘Dakar’ after the Senegalese capital. As a city it is rarely deemed beautiful by outside eyes, unlike its iconic cousin Kolkata, nor does it boast obvious distinctions to draw tourists or wider interest. When Dhaka does appear in the world's media, it is sometimes in reference to its violent politics, the garment factories which sit at its edges or its frequent designation as one of the least liveable cities in the world. The only Western film to feature Dhaka – a recent Netflix production concerning the abduction of an Indian drug lord's son and a white mercenary hero – was filmed in India and Thailand, and its earlier title of ‘Dhaka’ scrapped for the more marketable Extraction.

There are a number of microphysics and transport processes that can be extremely important to suppress or enhance the growth of these instabilities. I will provide a detailed description of how the hydrodynamic instability evolutions can be modified by incorporating the viscosity, surface tension, diffuse interface, and compressibility of the flows into the governing equations and growth rates.

Arguably, the Mahabharata is India's most influential political text. Kautilya's Arthashastra may seem a close contender, but it never attained the epic's social depth and was, in any case, forgotten for a millennium before its rediscovery in 1905. The Constitution of India certainly plays a more important role in shaping the modern Indian state, but, as a text, it hardly permeates popular consciousness in the way the Mahabharata does. For over two millennia, the Mahabharata has shaped Indian politics. It has nourished the statecraft of Hindu rajas and Mughal emperors, stirred anti-colonial nationalism and peasant rebellion, moulded Dalit–Bahujan and feminist activism. Beyond India, it has profoundly shaped political cultures across Southeast Asia, inspired pan-Asian thinking in China and Japan, activated the philosophical imagination of European and Arab thinkers, and conversed with Iranian nationalism.

Like one of its protagonists, the divine statesman Krishna, the Mahabharata exists in multiple avatars. The Sanskrit text, ascribed to Vyasa, coexists with versions in several Indian and extra-Indian languages. For many decades now, scholars have written about these textual traditions as well as about the popular appeal of Mahabharata stories. Historians, anthropologists, religious studies scholars, and philosophers have all written about the epic. Admittedly, much more has been said about the pre-modern lives of the Mahabharata than about its modern incarnations – but even on the latter the scholarship is rich and growing.

In this milieu, why is a new book needed about the epic? We offer two compelling reasons. First, there exists no single volume that engages with the Mahabharata's role in shaping modern social, political, and religious thought.

Degree is the simplest of the node-level measures, but its simplicity often hides its power. Here we will apply degree to the problem of mental structure. Specifically, what is the structure of the relationships between information in the mind? George Kingsley Zipf observed that word frequencies in natural language tend to a follow a scale-free distribution: The most frequent words are few, while the less frequent words are many with a specific linear relationship on a log-log plot. It has also been suggested that this power-law distribution applies to the relationships between words as well as to their meanings. Some words share meanings with many other words while others share few. This is a hypothesis based on the structural distribution of shared meanings, or polysemy (words with multiple meanings). This chapter will explain the theory underlying Zipf’s law of meaning and power laws. It will also show how we can combine these ideas with the most basic node-level network measure: degree.

Despite the intensive efforts to develop increased computational capabilities, mix models remain the most viable approach for the solution of many applications. These are an approximation to the true solution of the Navier-Stokes equations. The reason for this state of affairs becomes abundantly clear when one considers the difficulties of achieving the desired turnaround time for applied fluid dynamics calculations. In this chapter, we focus on some of the methodologies currently utilized to tackle the practical problem of simulating hydrodynamic instabilities in engineering designs.

A universal basic income is widely endorsed as a critical feature of effective governance. It is also growing in popularity in an era of substantial collective wealth alongside growing inequality. But how could it work? Current economic policies necessarily influence wealth distributions, but they are often sufficiently complicated that they hide their inefficiencies. Simplifications based on network science can offer plausible solutions and even offer ways to base universal basic income on merit. Here we will examine a case study based on a universal basic income for researchers. This is an important case because numerous funding agencies currently require costly proposal processes with high administrative costs. These are costly for the proposal writers, their evaluators, and the progress of science itself. Moreover, the outcomes are known to be biased and inefficiently managed. Network science can help us redesign funding allocations in a less costly and potentially more equitable way.

The way networks grow and change over time is called network evolution. Numerous off-the-shelf algorithms have been developed to study network evolution. These can give us insight into the way systems grow and change over time. However, what off-the-shelf algorithms often lack are knowledge of the behavioral details surrounding a specific problem. Here we will develop a simple case that we will revisit over the next few chapters: How do children learn words from exposure to a sea of language? One possibility is that the words children learn first influence the words they learn next. Another possibility is that the structure of language itself facilitates the learning of some words over others. Indeed, we know that adults speak differently to children in ways that facilitate language learning, with semantically informative words tending to appear more often around words that children learn earliest. This invites the question: To what extent does the semantic structure of language predict word learning? This chapter will provide a general framework for building and competing models against one another with a specific application to the network evolution of child vocabularies.

A valuable feature of networks is their ability to quantify structural relationships. Much like a chemist who, having purified their sample, can bring to bear a wide range of tools for understanding their sample by transforming data into a network, a network scientist can leverage a range of tools that provide precise measurements of their data’s structure. This includes node-level measures like degree and centrality, meso-scale measures like community formation, and macro-scale measures like density and modularity. This chapter introduces these measures and gives a brief guide to their use.

Words, like biological species, are born and then, someday, they die. The half-life of a word is roughly 2,000 years, meaning that in that interval about half of all words are replaced with an unrelated (noncognate) word. Where do the new words come from? There are numerous dimensions along which new words could vary from old words, so it may not be easy to see how to enter this problem. However, extending our small worlds metaphor and the observation of clusters in language, we tell a simple story that mirrors biological theories about the origin of species. Language has urban centers with well-populated and well-connected meanings (like *food* and *red*). It also has rural fringes, where words live more isolated lives as hermits with limited connections to other words (like *twang* and *ohm*). Are new words more likely to be born in urban centers or in the rural fringes?

Introduction

The Bhagavadgita is an 18-chapter philosophical dialogue between Arjuna, the despondent warrior hero reluctant to raise arms against his kin, and his divine charioteer, Krishna, who exhorts him to wage war with detachment as an instrument of divine will. It is set on the battlefield in the Sanskrit epic, the Mahabharata, moments before the beginning of a war. The Bhagavadgita (henceforth Gita), as Richard H. Davis elucidates in his ‘short biography’ of the text, intrigued scholars with its ‘doubleness’ – ‘its historical specificity and its continuing, even eternal, life’. Its ambiguities and accommodation of multiple theological currents made it possible (and continues to do so) for the text to appeal to diverse groups of readers and commentators in medieval, pre-colonial, and colonial India and beyond. It gained a transnational community of readers in Europe and America, as colonial commentators, Christian missionaries, Romantic philosophers, and Indologists popularized it as a Hindu philosophical text at par with the Quran and the Bible. By the early twentieth century, it came to provide a wide range of Indian political thinkers, from Aurobindo Ghose to Bal Gangadhar Tilak, who were occupied in anti-colonial struggle with an opportunity to ‘rethink politics in a novel language of action without consequence’. Among such engagements, M. K. Gandhi's approach to the Gita as a guide to moral action in the realm of politics has attracted maximum scholarly attention. Such works have accorded due focus to the genealogies of (mostly Western) political and religious thought that informed his readings and the innovative agency of Gandhi himself.

This chapter, however, shifts the optic from Gandhi to the Gandhian(s) to draw attention to the hermeneutics of reading the Gita through the prism of non-violence (ahimsa) that Gandhi introduces in Indian sociopolitical thought and constructs an intellectual history of such hermeneutical exercises. Through this, I wish to move beyond the individual centricity that has characterized the global intellectual history of Gandhian thought.

The multi-mode instability is the simultaneous growth across many wavelengths. This is closer to the reality of many applications. We provide a detailed treatment of the various stages of development. It is widely believed that many turbulent flows, such as RTI, RMI, and KHI mixing layers, evolve toward self-similarity. Here, the RTI grows quadratically with time, and the suitable proportionality constant is the subject of ongoing research. The growth exponent for RMI is also the subject of ongoing research. I also discuss measurements of these parameters in experiments and simulations arising from multimodal initial perturbations.

I will describe the earlier efforts in both hydrodynamic instability and turbulence mixing research and provide a broad non-mathematical overview of the significance of turbulence mixing on scientific and engineering applications. I will briefly explain several varied applications in which hydrodynamic instability plays a critical role, namely, inertial confinement fusion (ICF), supernova explosions, solar prominences, paintings, and combustions and detonations, among others, to provide the reader with an idea of what will be discussed later in the book.