Anatomy of three-body decay I. Schematic models

Sequential three-body decay proceeds via spatially confined quasi-stationary two-body configurations. Direct three-body decay populates the three-body continuum without intermediate steps. The relative importance of these decay modes is discussed in a schematic model employing only Coulomb or centrifugal barrier potentials. Decisive dimensionless charge, mass and energy ratios are derived. Sequential decay is usually favored for charged particles. Small charge and small mass of high energy is preferably emitted first. Without Coulomb potential the sequential decay is favored except when both resonance energy and intermediate two-body energy are large.Comment: To be published in Nuclear Physics

Recent developments in radioactive charged-particle emissions and related phenomena

The advent and intensive use of new detector technologies as well as radioactive ion beam facilities have opened up possibilities to investigate alpha, proton and cluster decays of highly unstable nuclei. This article provides a review of the current status of our understanding of clustering and the corresponding radioactive particle decay process in atomic nuclei. We put alpha decay in the context of charged-particle emissions which also include one- and two-proton emissions as well as heavy cluster decay. The experimental as well as the theoretical advances achieved recently in these fields are presented. Emphasis is given to the recent discoveries of charged-particle decays from proton-rich nuclei around the proton drip line. Those decay measurements have shown to provide an important probe for studying the structure of the nuclei involved. Developments on the theoretical side in nuclear many-body theories and supercomputing facilities have also made substantial progress, enabling one to study the nuclear clusterization and decays within a microscopic and consistent framework. We report on properties induced by the nuclear interaction acting in the nuclear medium, like the pairing interaction, which have been uncovered by studying the microscopic structure of clusters. The competition between cluster formations as compared to the corresponding alpha-particle formation are included. In the review we also describe the search for super-heavy nuclei connected by chains of alpha and other radioactive particle decays.Comment: 58 pages, submitted to Prog. Part. Nucl. Phy

Epigenesis of Pure Reason and the Source of Pure Cognitions

Kant describes logic as “the science that exhaustively presents and strictly proves nothing but the formal rules of all thinking”. (Bviii-ix) But what is the source of our cognition of such rules (“logical cognition” for short)? He makes no concerted effort to address this question. It will nonetheless become clear that the question is a philosophically significant one for him, to which he can see three possible answers: those representations are innate, derived from experience, or originally acquired a priori. Although he gives no explicit argument for the third answer, he seems committed to it—especially given his views on the source of pure concepts of the understanding and on the nature of logic. It takes careful preparatory work to gather all the essential materials for motivating and reconstructing Kant’s “original acquisition” account of logical cognition. I shall proceed in two sections. In section 1, I analyze Kant’s argument that pure concepts of the understanding (or intellectual concepts)—as one kind of pure cognition—must be acquired originally and a priori. My analysis partly concerns his varied attitudes toward Crusius’s and Leibniz’s versions of the nativist account of such concepts. I give special attention to how Kant characterizes the nativist account and his own “original acquisition” account in terms of “preformation” and “epigenesis”. My goal is, firstly, to tease out the sense in which Kant grants that there must be an innate ground (or preformation) for the derivation of pure concepts and, secondly, to introduce—and pave the way for answering—the question about the source of logical cognition. In section 2, in light of Kant’s reference to Locke and Leibniz as the greatest reformers of philosophy (including logic) in their times (Log, AA 9: 32), I examine the Lockean and Leibnizian approaches to logic, respectively. Both approaches are “physiological” by Kant’s standard and are directly opposed to his own strictly critical method. I explain how this methodological move shapes Kant’s view that representations of logical rules must be originally acquired a priori. This acquisition involves a kind of radical epigenesis of pure reason: unlike the acquisition of pure concepts, it presupposes no further innate ground (or preformation). This view will have important consequences for issues such as the ground of the normativity of logical rules and the boundaries of their rightful use

A New Nonlinear Liquid Drop Model. Clusters as Solitons on The Nuclear Surface

By introducing in the hydrodynamic model, i.e. in the hydrodynamic equations and the corresponding boundary conditions, the higher order terms in the deviation of the shape, we obtain in the second order the Korteweg de Vries equation (KdV). The same equation is obtained by introducing in the liquid drop model (LDM), i.e. in the kinetic, surface and Coulomb terms, the higher terms in the second order. The KdV equation has the cnoidal waves as steady-state solutions. These waves could describe the small anharmonic vibrations of spherical nuclei up to the solitary waves. The solitons could describe the preformation of clusters on the nuclear surface. We apply this nonlinear liquid drop model to the alpha formation in heavy nuclei. We find an additional minimum in the total energy of such systems, corresponding to the solitons as clusters on the nuclear surface. By introducing the shell effects we choose this minimum to be degenerated with the ground state. The spectroscopic factor is given by the ratio of the square amplitudes in the two minima.Comment: 27 pages, LateX, 8 figures, Submitted J. Phys. G: Nucl. Part. Phys., PACS: 23.60.+e, 21.60.Gx, 24.30.-v, 25.70.e

Systematic Low-Energy Effective Theory for Magnons and Charge Carriers in an Antiferromagnet

By electron or hole doping quantum antiferromagnets may turn into high-temperature superconductors. The low-energy dynamics of antiferromagnets are governed by their Nambu-Goldstone bosons -- the magnons -- and are described by an effective field theory analogous to chiral perturbation theory for the pions in strong interaction physics. In analogy to baryon chiral perturbation theory -- the effective theory for pions and nucleons -- we construct a systematic low-energy effective theory for magnons and electrons or holes in an antiferromagnet. The effective theory is universal and makes model-independent predictions for the entire class of antiferromagnetic cuprates. We present a detailed analysis of the symmetries of the Hubbard model and discuss how these symmetries manifest themselves in the effective theory. A complete set of linearly independent leading contributions to the effective action is constructed. The coupling to external electromagnetic fields is also investigated.Comment: 53 pages, no figures, added references, extended the introductio

Bargaining in the Photonics Industry

This paper investigates how path dependence may come about in inter- organizational networks. To do so, we focus our analysis on one particular type of network management practices – bargaining practices – and ask whether and how they can become path-dependent. Bargaining practices are recurrent activities through which network partners agree to identify and distribute their cooperative surplus. Targeting these practices, we first operationalize the core concepts of path dependence theory by deriving empirical indicators. We then use a ‘pattern matching’ approach to analyze whether these empirical indicators can be found in real bargaining practices. Empirically, we conduct three case studies of regional networks in the photonics industry. We use qualitative interviews and content analysis to reconstruct the development dynamics of their bargaining practices. A major finding is that network bargaining practices can indeed exhibit inter-organizational path dependencies. This paper contributes not only by operationalizing the theory of organizational path dependence but also by extending this theory to the network level of analysis

Virtuous interactions in removing exclusion

We devise a retrospective panel data approach to evaluate the effects of fair trade affiliation on the schooling decisions of a sample of Thai organic rice producers across the past 20 years. We find that the probability of school enrolment in families with more than two children is significantly affected by affiliation years. The finding is robust when dealing with endogeneity and heterogeneity issues in the estimate. The nonpositive preaffiliation performance documents that our result is not affected by selection bias and that fair trade affiliation generates a significant break in the schooling decisions of affiliated households.child schooling; market access; fair trade

Virtuous interactions in removing exclusion: The link between foreign market access and access to education

We devise a retrospective panel data approach to evaluate the effects of fair trade affiliation on the schooling decisions of a sample of Thai organic rice producers across the past 20 years. We find that the probability of school enrolment in families with more than two children is significantly affected by affiliation years. The finding is robust when dealing with endogeneity and heterogeneity issues in the estimate. The non-positive preaffiliation performance documents that our result is not affected by selection bias and that fair trade affiliation generates a significant break in the schooling decisions of affiliated households.child schooling, market access, fair trade.