Conformal Transformations with Multiple Scalar Fields

Many interesting models incorporate scalar fields with non-minimal couplings to the spacetime Ricci curvature scalar. As is well known, if only one scalar field is non-minimally coupled, then one may perform a conformal transformation to a new frame in which both the gravitational portion of the Lagrangian and the kinetic term for the (rescaled) scalar field assume canonical form. We examine under what conditions the gravitational and kinetic terms in the Lagrangian may be brought into canonical form when more than one scalar field has non-minimal coupling. A particular class of two-field models admits such a transformation, but models with more than two non-minimally coupled fields in general do not.Comment: 17 pages, no figures. References added to match published version

Reduction

This is a contribution to the encyclopedia of systems biology on reduction

The Components and Boundaries of Mechanisms

Mechanisms are said to consist of two kinds of components, entities and activities. In the first half of this chapter, I examine what entities and activities are, how they relate to well-known ontological categories, such as processes or dispositions, and how entities and activities relate to each other (e.g., can one be reduced to the other or are they mutually dependent?). The second part of this chapter analyzes different criteria for individuating the components of mechanisms and discusses how real the boundaries of mechanisms are

Disposition

This is a contribution to the encyclopedia of systems biology on dispositions

Multifield Inflation after Planck: Isocurvature Modes from Nonminimal Couplings

Recent measurements by the {\it Planck} experiment of the power spectrum of temperature anisotropies in the cosmic microwave background radiation (CMB) reveal a deficit of power in low multipoles compared to the predictions from best-fit $\Lambda$CDM cosmology. The low-$\ell$ anomaly may be explained by the presence of primordial isocurvature perturbations in addition to the usual adiabatic spectrum, and hence may provide the first robust evidence that early-universe inflation involved more than one scalar field. In this paper we explore the production of isocurvature perturbations in nonminimally coupled two-field inflation. We find that this class of models readily produces enough power in the isocurvature modes to account for the \emph{Planck} low-$\ell$ anomaly, while also providing excellent agreement with the other {\it Planck} results.Comment: 19 pages, 15 figures. Minor edits to match published versio

Primordial Perturbations from Multifield Inflation with Nonminimal Couplings

Realistic models of particle physics include many scalar fields. These fields generically have nonminimal couplings to the Ricci curvature scalar, either as part of a generalized Einstein theory or as necessary counterterms for renormalization in curved background spacetimes. We develop a gauge-invariant formalism for calculating primordial perturbations in models with multiple nonminimally coupled fields. We work in the Jordan frame (in which the nonminimal couplings remain explicit) and identify two distinct sources of entropy perturbations for such models. One set of entropy perturbations arises from interactions among the multiple fields. The second set arises from the presence of nonminimal couplings. Neither of these varieties of entropy perturbations will necessarily be suppressed in the long-wavelength limit, and hence they can amplify the curvature perturbation, $\zeta$, even for modes that have crossed outside the Hubble radius. Models that overproduce long-wavelength entropy perturbations endanger the close fit between predicted inflationary spectra and empirical observations.Comment: 16 pages, no figures. References added to match published versio

Well-Ordered Philosophy? Reflections on Kitcher's Proposal for a Renewal of Philosophy.

In his recent article Philosophy Inside Out, Philip Kitcher presents a metaphilosophical outlook that aims at nothing less than a renewal of philosophy. His idea is to draw philosophers’ attention away from “timeless questions” in the so-called “core areas” of philosophy. Instead, philosophers should address questions that matter to human lives. The aim of this paper is twofold: first, to reconstruct Kitcher’s view of how philosophy should be renewed; second, to point out some difficulties relating to his position. These difficulties concern the integration of his naturalism into the pragmatic vision of philosophy, the role of putative philosophical experts, and the ideal status of the program of well-ordered inquiry

Modification of primordial ices by cosmic rays as simulated by cyclotron irradiation

Frozen CH4 and CH4/Ar mixtures closed into metal cuvettes and open to the vacuum were irradiated at 15 and 77 K with 10 - 20 MeV p and He-3(2+) ions in order to simulate the effect of cosmic rays on solid organic matter in space. Ices exposed to vacuum represent surfaces of icy systems whereas closed systems stand for bulk ices. The products were analyzed by MS, SEM, RBS, ERDA, H-1-NMR, HPLC, GC-MS, NEXAFS, and FT-IR. Volatile products consisted of a mixture of low molecular species, e.g., C2H2, C2H4, C2H6, and long linear aliphatic and olefinic compounds. The formation of polycyclic aromatic hydrocarbons (PAH's) and related species in solid CH4 is due to a multi-center reaction within one collision cascade and is governed by energy density effects with critical linear energy transfer values L(sub T) between 2 and 10 keV/micron. Open ices exhibit preferential hydrogen release resulting in an increased carbonization as compared to more hydrogen rich molecules protected inside large icy bodies

Problems and Prospects of Interdisciplinarity: The Case of Philosophy of Science

In this paper, we discuss some problems and prospects of interdisciplinary encounters by focusing on philosophy of science as a case study. After introducing the case, we give an overview about the various ways in which philosophy of science can be interdisciplinary in Section 2. In Section 3, we name some general problems concerning the possible points of interaction between philosophy of science and the sciences studied. In Section 4 we compare the advantages and risks of interdisciplinarity for individual researchers and institutions. In Section 5, we discuss interdisciplinary PhD programs, in particular concerning two main problems: increased workload and the quality of supervision. In the final Section 6, we look at interdisciplinary careers beyond the PhD