Cosmological perturbations in generalized theories of gravity

The first part of the thesis concerns the study of inflation in the context of a theory of gravity called "Induced Gravity" in which the gravitational coupling varies in time according to the dynamics of the very same scalar field (the "inflaton") driving inflation, while taking on the value measured today since the end of inflation. Through the analytical and numerical analysis of scalar and tensor cosmological perturbations we show that the model leads to consistent predictions for a broad variety of symmetry-breaking inflaton's potentials, once that a dimensionless parameter entering into the action is properly constrained. We also discuss the average expansion of the Universe after inflation (when the inflaton undergoes coherent oscillations about the minimum of its potential) and determine the effective equation of state. Finally, we analyze the resonant and perturbative decay of the inflaton during (p)reheating. The second part is devoted to the study of a proposal for a quantum theory of gravity dubbed "Horava-Lifshitz (HL) Gravity" which relies on power-counting renormalizability while explicitly breaking Lorentz invariance. We test a pair of variants of the theory ("projectable" and "non-projectable") on a cosmological background and with the inclusion of scalar field matter. By inspecting the quadratic action for the linear scalar cosmological perturbations we determine the actual number of propagating degrees of freedom and realize that the theory, being endowed with less symmetries than General Relativity, does admit an extra gravitational degree of freedom which is potentially unstable. More specifically, we conclude that in the case of projectable HL Gravity the extra mode is either a ghost or a tachyon, whereas in the case of non-projectable HL Gravity the extra mode can be made well-behaved for suitable choices of a pair of free dimensionless parameters and, moreover, turns out to decouple from the low-energy Physics.

Plato and Frankfurt: Two Theories of the Relations Between Love and Living Well

This thesis provides a comparison of the ideas of caring and love as they appear in the works of Plato and Frankfurt. Frankfurt, a contemporary philosopher, maintains that an individual arrives at the most meaningful life through understanding what it is that heor she cares about the most. Interestingly, the instances of eros in Plato's Symposium and Phaedrus resonate with this idea. We see throughout these erotic dialogues similarities to Frankfurt's notions of care and love.Throughout his many works, Frankfurt provides us with several distinct features of care and love. This thesis offers an in depth discussion of each of these features andalso provides commentary from other contemporary philosophers who are familiar with Frankfurt's work. In addition, this thesis applies these features of care and love to Plato's erotic dialogues, and emphasizes areas in which Plato and Frankfurt agree and those inwhich they disagree. In essence, it becomes apparent that while there are many similarities between the ideas of these two prominent thinkers, Plato and Frankfurt do not agree about what constitutes the best human life. Plato maintains that the best life is onespent dedicated to philosophy and in pursuit of the 'good'. Frankfurt, on the other hand,imposes no such limitations on what we should consider the best life because people are likely to have different life experiences that lead them to care about and love different things. Instead he suggests that the best or most meaningful human life is one in which a person spends his or her life caring about the things he or she does, indeed, care aboutand loving those things he or she does, indeed, love.

Theories of Militancy in Practice: Explanations of Muslim Terrorism in India

This article analyzes the interaction between theories of radicalization and state responses to militancy in India. Focusing on the interpretation of the increased frequency of terrorist attacks in Indian metropolises in the last decade, the article examines the narratives surrounding those classified as terrorists in the context of rising Muslim militancy in the country. Different state agencies operate with different theories about the links between processes of radicalization and terrorist violence. The scenarios of radicalization underlying legislative efforts to prevent terrorism, the construction of motives by the police, and the interpretation of violence by the judiciary all rely on assumptions about radicalization and violence. Such narratives are used to explain terrorism both to security agencies and to the public; they inform the categories and scenarios of prevention. Prevention relies on detection of future deeds, planning, intentions, and even potential intentions. "Detection" of potential intentions relies on assumptions about specific dispositions. Identification of such dispositions in turn relies on the context-specific theories of the causes of militancy. These determine what "characteristics" of individuals or groups indicate potential threats and form the basis for their categorization as "potentially dangerous." The article explores the cultural contexts of theories of radicalization, focusing on how they are framed by societal understandings of the causes of deviance and the relation between the individual and society emerging in contemporary India. It examines the shift in the perception of threat and the categories of "dangerous others" from a focus on role to a focus on ascriptive identity.