Aristotelian powers at work: reciprocity without symmetry in causation

This paper puts powers to work by developing a broadly Aristotelian account of causation, built on the fundamental idea (which Aristotle found in Plato, attributed by him to Heraclitus) that causation is a mutual interaction between powers. On this Aristotelian view, causal powers manifest them-selves in dependence on the manifestation of their mutual partners. (See also Heil, this volume; Mumford, this volume; and Martin 2008.) The manifestations of two causal power partners are co-determined, co-varying, and co-extensive in time. (See Marmodoro 2006.) Yet, causation has a direction and is thus asymmetric. This asymmetry is what underpins metaphysically the distinction between causal agent and patient. The proposed Aristotelian analysis of the interaction between mutually manifesting causal powers is distinctive, in that it pays justice to the intuition that there is agency in causation. That is, agency is not a metaphorical way of describing what causal powers do. For some powers, it is a way of being that instantiates the non-anthropomorphic sense in which powers are causal agents. This point is brought out in the paper in relation to the explanation of the concept of change. In an Aristotelian fashion, the paper argues that the distinction be-tween agent and patient in causation is pivotal to offering a realist account of causation that does not reify the interaction of the reciprocal causal partners into a relation. On the proposed view, the interaction between mutually manifesting causal partners consists in the power of one substance being realized in another substance. Specifically, the agent’s causal powers metaphysically belong to the agent, but come to be realized in the patient. The significance of this is that the interaction of the agent’s and the patient’s powers is not a relation; rather, it is an ex-tension of the constitution of the agent onto the patient, which occurs when agent and patient interact and their powers are mutually manifested. Thus the proposed Aristotelian account of causation explains the mutual interaction between manifestation partners—potentiality, agency, and change—as irreducible to one another, but interconnected

Why studying the history of philosophy matters

The debate over whether and how philosophers of today may usefully engage with philosophers of the past is nearly as old as the history of philosophy itself. Does the study of the history of philosophy train or corrupt the budding philosopher's mind? Why study the history of philosophy? And, how to study the history of philosophy? I discuss some mainstream approaches to the study of the history of philosophy (with special focus on ancient philosophy), before explicating the one I adopt and commend

Exchange interaction and its tuning in magnetic binary chalcogenides

Using a first-principles Green's function approach we study magnetic properties of the magnetic binary chalcogenides Bi2Te3, Bi2Se3, and Sb2Te3. The magnetic coupling between transition-metal impurities is long-range, extends beyond a quintuple layer, and decreases with increasing number of d electrons per 3d atom. We find two main mechanisms for the magnetic interaction in these materials: the indirect exchange interaction mediated by free carriers and the indirect interaction between magnetic moments via chalcogen atoms. The calculated Curie temperatures of these systems are in good agreement with available experimental data. Our results provide deep insight into magnetic interactions in magnetic binary chalcogenides and open a way to design new materials for promising applications

Two in nature - one in substratum: an Aristotelian metaphysical model for ontologically dependent entities

My research topic is the ontology of causation in Aristotle, with a view to also making a contribution to contemporary philosophy. I offer a new interpretation of Aristotle's account of causation and perception. I argue that Aristotle understands the causal link in terms of a single complex entity which involves essentially two interdependent natures (e.g. an activity that grounds teaching and learning). Internally, such an entity has the same metaphysical structure as a line that grounds two vectors with opposite directions. But the causal entity, as opposed to the line and vectors, is itself ontologically dependent on the two substances that are in causal interaction. This is because the entity's two natures are the realisation of two interdependent potentialities of the two substances (e.g. for teaching and learning). Aristotle builds a causal bridge between substances out of mutually realised potentialities of the two substances. Their mutual realisation binds them together into a net of ontological dependencies which delineates the boundary of the causal entity. In my thesis I describe the multifarious ontological dependencies and argue that Aristotle has made a unique contribution to the history of the analysis of causation by offering an ontological account of it in terms of potentiality -actuality and ontological dependence. Furthermore, Aristotle puts to use his theory of causation to account for the metaphysical status of what we call after Locke secondary properties, e.g. colours, sounds etc. I reconstruct Aristotle's theory of secondary properties in the light of my understanding of his two -in -one metaphysical model. I put Aristotle's theory of causation as applied to his theory of perception to the test of whether it gives philosophical gains in contemporary philosophy in the field of the philosophy of mind. I engage with David Chalmers' arguments against Primitivism - which is a new contemporary account of the metaphysics of colours. Primitivism is the account of colours philosophically most alike to Aristotle's own one. I put forward my own original position on the metaphysics of colours inspired by Aristotle's theory of causation, arguing for the core Primitivist assumptions, while avoiding Chalmers' criticisms

Probing the Fermi surface by positron annihilation and Compton scattering

Positron annihilation and Compton scattering are important probes of the Fermi surface. Relying on conservation of energy and momentum, being bulk sensitive and not limited by short electronic mean-free-paths, they can provide unique information in circumstances when other methods fail. Using a variety of examples, their contribution to knowledge about the electronic structure of a wide range of materials is demonstrated

Atomistic spin dynamics simulations of magnonic spin Seebeck and spin Nernst effects in altermagnets

Magnon band structures in altermagnets are characterized by an energy splitting of modes with opposite chirality, even in the absence of applied external fields and relativistic effects, due to an anisotropy in the Heisenberg exchange interactions. We perform quantitative atomistic spin dynamics simulations based on ab initio electronic structure calculations on rutile RuO$_2$, a prototypical "d-wave" altermagnet, to study magnon currents generated by thermal gradients. We report substantial spin Seebeck and spin Nernst effects, i.e., longitudinal or transverse spin currents, depending on the propagation direction of the magnons with respect to the crystal, together with a finite spin accumulation associated with non-linearities in the temperature profile. Our findings are consistent with the altermagnetic spin-group symmetry, as well as predictions from linear spin wave theory and semiclassical Boltzmann transport theory

Atomistic spin dynamics simulations of magnonic spin Seebeck and spin Nernst effects in altermagnets

Magnon band structures in altermagnets are characterized by an energy splitting of modes with opposite chirality, even in the absence of applied external fields and relativistic effects, because of an anisotropy in the Heisenberg exchange interactions. We perform quantitative atomistic spin dynamics simulations based on ab initio electronic structure calculations on rutile RuO2, a prototypical “d-wave” altermagnet, to study magnon currents generated by thermal gradients. We report substantial spin Seebeck and spin Nernst effects, i.e., longitudinal or transverse spin currents, depending on the propagation direction of the magnons with respect to the crystal, together with a finite spin accumulation associated with nonlinearities in the temperature profile. Our findings are consistent with the altermagnetic spin-group symmetry, as well as predictions from linear spin-wave theory and semiclassical Boltzmann transport theory