Olimpia Lombardi

El propósito del presente trabajo consiste en abordar la pregunta por la ontología de la química cuántica. Para ello nos concentraremos en el concepto de enlace químico desde la perspectiva de los dos enfoques a través de los cuales la ecuación de Schrödinger se aplica a los sistemas químicos moleculares: la teoría del enlace de valencia (EV) y la teoría del orbital molecular (OM). Sobre la base de la presentación de ambos enfoques y su comparación, señalaremos que, a pesar de su denominación tradicional, no pueden considerarse estrictamente como teorías científicas, sino que se ajustan mejor a la noción de modelo; en particular, son modelos que incorporan conceptos y leyes tanto del ámbito de la mecánica cuántica como del de la química estructural. Estas consideraciones nos permitirán argumentar que la química cuántica no posee un referente ontológico autónomo, sino que se trata de un ámbito científico cuya vigencia descansa sobre su éxito práctico en el cálculo y la predicción. Finalmente, indicaremos de qué modo los enfoques EV y OM del enlace químico abren una nueva perspectiva respecto de la noción misma de modelo en ciencias empíricas

Prigogine afirma que, en presencia de alta inestabilidad (caos), los estados puntuales y las trayectorias lineales en el espacio de las fases se convierten en una falsa idealización. En el presente trabajo se sostiene que: (i) los argumentos de Prigogine en favor de tal tesis no son concluyentes, y (ii) hay buenas razones para retener la postulacion de estados puntuales y trayectorias lineales, en tanto conceptos teóricos legítimos en mecánica estadística.Prigogine asserts that the existence of radical instability (chaos) makes the postulation of pointlike states and linelike trajectories in phase space a false idealization. In this paper we argue that (i) Prigogine’s arguments for this claim are not conclusive, and (ii) there are good reasons for retain the positing of pointlike states and linelike trajectories as a legitimate theoretical posit in statistical mechanics

Prigogine afirma que, en presencia de alta inestabilidad (caos), los estados puntuales y las trayectorias lineales en el espacio de las fases se convierten en una falsa idealización. En el presente trabajo se sostiene que: (i) los argumentos de Prigogine en favor de tal tesis no son concluyentes, y (ii) hay buenas razones para retener la postulacion de estados puntuales y trayectorias lineales, en tanto conceptos teóricos legítimos en mecánica estadística.Prigogine asserts that the existence of radical instability (chaos) makes the postulation of pointlike states and linelike trajectories in phase space a false idealization. In this paper we argue that (i) Prigogine’s arguments for this claim are not conclusive, and (ii) there are good reasons for retain the positing of pointlike states and linelike trajectories as a legitimate theoretical posit in statistical mechanics.

The aim of this paper is to introduce a new member of the family of the modal interpretations of quantum mechanics. In this modal-Hamiltonian interpretation, the Hamiltonian of the quantum system plays a decisive role in the property-ascription rule that selects the definite-valued observables whose possible values become actual. We show that this interpretation is effective for solving the measurement problem, both in its ideal and its non-ideal versions, and we argue for the physical relevance of the property-ascription rule by applying it to well-known physical situations. Moreover, we explain how this interpretation supplies a description of the elemental categories of the ontology referred to by the theory, where quantum systems turn out to be bundles of possible properties.

The general question to be considered in this paper points to the nature of the world described by chemistry: what is macro-chemical ontology like? In particular, we want to identify the ontological categories that underlie chemical discourse and chemical practice. This is not an easy task, because modern Western metaphysics was strongly modeled by theoretical physics. For this reason, we attempt to answer our question by contrasting macro-chemical ontology with the mainstream ontology of physics and of traditional metaphysics. In particular, we introduce the distinction between stuff-ontology, proper of chemistry, and individual-ontology, proper of physics. These two ontologies differ from each other in the basic categories of their own structures. On this basis, we characterize individual-ontology in such a way that the features of stuff-ontology will arise by contrast with it

In this paper we will address the problem of the existence of orbitals by analyzing the relationship between molecular chemistry and quantum mechanics. In particular, we will consider the concept of orbital in the light of the arguments that deny its referring character. On this basis, we will conclude that the claim that orbitals do not exist relies on a metaphysical reductionism which, if consistently sustained, would lead to consequences clashing with the effective practice of science in its different branches.

En el presente artículo abordaremos la cuestión del determinismo ontológico en física. Proponemos una elucidación del concepto de posibilidad que resulte útil para tratar el problema del determinismo ontológico en física, y mediante la cual pueda interpretarse el concepto de probabilidad de un modo signifi cativo para la práctica de la física teórica. Finalmente, los conceptos previamente elucidados se aplican a un caso paradigmático de la física, el de los sistemas altamente inestables, argumentando que en este ámbito determinismo e indeterminismo ontológicos pueden coexistir en un único sistema clásico.

The aim of the present paper is to analyze the problem of the relationship between chemistry and physics, by focusing on the widely discussed case of the atomic orbitals. We will begin by remembering the difference between the physical and the chemical interpretation of the concept of orbital. Then, we will refer to the claim made in 1999 that atomic orbitals have been directly imaged for the first time. On this basis, we will analyze the problem from a new approach, by comparing the concept of orbital used in physics with the concept of orbital used in chemistry. Such an analysis will allow us to argue for an ontological pluralism that admits the coexistence of different ontologies without priorities or metaphysical privileges. From this philosophical framework, the concepts of chemical orbital and physical orbital correspond to two different ontologies. As a consequence, chemical orbitals are real entities belonging to the ontology of molecular chemistry, and can be observed like any other entity not belonging to the quantum mechanical ontology.

This article focuses on the relationship between microevolution and macroevolution. The main purpose is to argue that up to the present time in the consolidation of the evolutionary synthesis macroevolution has been always conceived as dependent on microevolution. Such dependence was very clear in the synthesis, but seems to have been left aside by later authors. Nevertheless, we show that the criticisms of the synthesis since the decade of the 1970s did not modify that general trend: the new perspectives reproduced the dependence of macroevolution on microevolution by means of strategies different than those appealed to by the traditional synthesis.

Traditional discussions about the arrow of time in general involve the concept of entropy. In the cosmological context, the direction past-to-future is usually related to the direction of the gradient of the entropy function of the universe. But the definition of the entropy of the universe is a very controversial matter. Moreover, thermodynamics is a phenomenological theory. Geometrical properties of space-time provide a more fundamental and less controversial way of defining an arrow of time for the universe as a whole. We will call the arrow defined only on the basis of the geometrical properties of space-time, independently of any entropic considerations, “the global arrow of time.” In this paper we will argue that: (i) if certain conditions are satisfied, it is possible to define a global arrow of time for the universe as a whole, and (ii) the standard models of contemporary cosmology satisfy these conditions.

The aim of this paper is to consider in what sense the modal-Hamiltonian interpretation of quantum mechanics satisfies the physical constraints imposed by the Galilean group. In particular, we show that the only apparent conflict, which follows from boost-transformations, can be overcome when the definition of quantum systems and subsystems is taken into account. On this basis, we apply the interpretation to different well-known models, in order to obtain concrete examples of the previous conceptual conclusions. Finally, we consider the role played by the Casimir operators of the Galilean group in the interpretation.

In several previous papers we have argued for a global and non-entropic approach to the problem of the arrow of time, according to which the “arrow” is only a metaphorical way of expressing the geometrical time-asymmetry of the universe. We have also shown that, under definite conditions, this global time-asymmetry can be transferred to local contexts as an energy flow that points to the same temporal direction all over the spacetime. The aim of this paper is to complete the global and non-entropic program by showing that our approach is able to account for irreversible local phenomena, which have been traditionally considered as the physical origin of the arrow of time.

Scientific cosmology is an empirical discipline whose objects of study are the large-scale properties of the universe. In this context, it is usual to call the direction of the expansion of the universe the "cosmological arrow of time". However, there is no reason for privileging the ‘radius’ of the universe for defining the arrow of time over other geometrical properties of the space-time. Traditional discussions about the arrow of time in general involve the concept of entropy. In the cosmological context, the direction past-to-future is usually related to the direction of the gradient of the entropy function of the universe. But entropy is a thermodynamic magnitude that is typically associated with subsystems of the universe: the entropy of the universe as a whole is a very controversial matter. Moreover, thermodynamics is a phenomenological theory. Geometrical properties of space-time provide a more fundamental and less controversial way of defining an arrow of time for the universe as a whole. We will call the arrow defined only on the basis of the geometrical properties of space-time, independently of any entropic considerations, the "cosmological arrow of time". In this paper we will argue that: (i) it is possible to define a cosmological arrow of time for the universe as a whole, if certain conditions are satisfied, and (ii) the standard models of contemporary cosmology satisfy these conditions.

According to Zurek, decoherence is a process resulting from the interaction between a quantum system and its environment; this process singles out a preferred set of states, usually called “pointer basis”, that determines which observables will receive definite values. This means that decoherence leads to a sort of selection which precludes all except a small subset of the states in the Hilbert space of the system from behaving in a classical manner: environment-induced-superselection (einselection) is a consequence of the process of decoherence. The aim of this paper is to present a new approach to decoherence, different from the mainstream approach of Zurek and his collaborators. We will argue that this approach offers conceptual advantages over the traditional one when problems of foundations are considered; in particular, from the new perspective, decoherence in closed quantum systems becomes possible and the preferred basis acquires a well founded definition.

In this paper we argue that the formalisms for decoherence originally devised to deal just with closed or open systems can be subsumed under a general conceptual framework, in such a way that they cooperate in the understanding of the same physical phenomenon. This new perspective dissolves certain conceptual difficulties of the einselection program but, at the same time, shows that the openness of the quantum system is not the essential ingredient for decoherence. †To contact the authors, please write to: Mario Castagnino, CONICET-IAFE, Universidad Nacional de Buenos Aires, Casilla de Correos 67, Sucursal 28, 1428 Buenos Aires, Argentina; Roberto Laura, IFIR-Universidad Nacional de Rosario, Av. Pellegrini 250, 2000 Rosario, Argentina; Olimpia Lombardi, CONICET-Universidad Nacional de Buenos Aires, C. Larralde 3440, 6°D, 1430, Buenos Aires; e-mail: [email protected].

According to Zurek, decoherence is a process resulting from the interaction between a quantum system and its environment; this process singles out a preferred set of states, usually called “pointer basis”, that determines which observables will receive definite values. This means that decoherence leads to a sort of selection which precludes all except a small subset of the states in the Hilbert space of the system from behaving in a classical manner: environment-induced-superselection—einselection —is a consequence of the process of decoherence. The aim of this paper is to present a new approach to decoherence, different from the mainstream approach of Zurek and his collaborators. We will argue that this approach offers conceptual advantages over the traditional one when problems of foundations are considered; in particular, from the new perspective, decoherence in closed quantum systems becomes possible and the preferred basis acquires a well founded definition.