Abstract The study of open systems is a cornerstone of many scientific disciplines outside physics. Across the biological, social, and cognitive sciences, systems are commonly understood in terms of their interactions with an environment. This is because, at a fundamental level, the entities studied in these disciplines are rarely, if ever, isolated. While openness is often taken as a given in the special sciences, physics has historically developed with a strong emphasis on closed-system modelling. The success of Newtonian mechanics, classical thermodynamics, and quantum mechanics has to a large extent relied on the ability to isolate and describe systems in terms of well-defined boundary conditions. However, recent developments suggest that the importance of open systems is gaining increasing recognition even within physics. In this introduction we introduce the general topic of open systems in physics and the open systems view, and we summarise each of the other chapters of the volume.
Abstract The study of open systems is a cornerstone of many scientific disciplines outside physics. Across the biological, social, and cognitive sciences, systems are commonly understood in terms of their interactions with an environment. This is because, at a fundamental level, the entities studied in these disciplines are rarely, if ever, isolated. While openness is often taken as a given in the special sciences, physics has historically developed with a strong emphasis on closed-system modelling. The success of Newtonian mechanics, classical thermodynamics, and quantum mechanics has to a large extent relied on the ability to isolate and describe systems in terms of well-defined boundary conditions. However, recent developments suggest that the importance of open systems is gaining increasing recognition even within physics. In this introduction we introduce the general topic of open systems in physics and the open systems view, and we summarise each of the other chapters of the volume.
Abstract Open Systems: Physics, Metaphysics, and Methodology argues that many of the most illuminating questions in contemporary science are best approached by treating systems as inherently embedded in, and interacting with, their environments. While closed-system modelling has long dominated physics, recent advances—from non-equilibrium thermodynamics and open-system quantum dynamics to complex systems science and quantum causal modelling—show that environmental coupling is often not a dispensable complication but a defining feature. Bringing together leading scholars across physics and philosophy, this volume develops the “open systems view” and probes its limits. Part I sets out the view within quantum theory and clarifies its relations to alternative frameworks. Part II traces open/closed concepts across the history and practice of physics, from Newtonian celestial mechanics to blackbody radiation, gravity with boundaries, and biological emergence. Part III turns to the largest scales, examining cosmology, many worlds, and realism about the universal quantum state. Throughout, contributors connect formal tools—density matrices, Lindblad dynamics, interventionist causation—with methodological and metaphysical stakes, including autonomy, reduction, and fundamentality. The result is a unified guide to modelling, explanation, and ontology when closure is an idealisation rather than a premise.
There is a deeply entrenched view in philosophy and physics, the closed systems view, according to which isolated systems are conceived of as fundamental. On this view, when a system is under the influence of its environment this is always described in terms of a coupling between it and a separate system, which taken together are isolated. There is an alternative, the open systems view, according to which systems interacting with their environment are conceived of as fundamental, and the environment’s influence is represented via the dynamical equations that govern the system of interest’s evolution. In this paper we propose (although the formalism is not original to us) a theoretical framework which we call the general quantum theory of open systems (GT), within which one can make sense of the dynamics of open quantum systems in fundamental terms, and we argue that the open systems view, as formalized in GT, is fundamental in quantum theory.
There is a deeply entrenched view in philosophy and physics, the closed systems view, according to which isolated systems are conceived of as fundamental. On this view, when a system is under the influence of its environment this is always described in terms of a coupling between it and a separate system, which taken together are isolated. There is an alternative, the open systems view, according to which systems interacting with their environment are conceived of as fundamental, and the environment’s influence is represented via the dynamical equations that govern the system of interest’s evolution. In this paper we propose (although the formalism is not original to us) a theoretical framework which we call the general quantum theory of open systems (GT), within which one can make sense of the dynamics of open quantum systems in fundamental terms, and we argue that the open systems view, as formalized in GT, is fundamental in quantum theory.
Abstract Since Galileo, physics has traditionally adopted a closed-system view, framed in the more generic strategy of describing highly idealized and generally non-existent situations. However, in the field of quantum mechanics—and also in other fields of physics—an open-system view has been gaining strength in recent decades, maybe under the influence of the practical success of the environment-induced decoherence (EID) developments. This trend is at odds with the perspective of the MHI, which openly adopts a closed-system view. The aim of this chapter is to discuss several aspects of quantum mechanics that reveal the difficulties faced by an open-systems approach. On this basis, a case is made for a closed-system approach that leads to a top-down view of quantum mechanics. This top-down view is in agreement with the ontology of properties introduced in Chapter 4, which will be developed in detail in the following Chapters 9, 10, and 11.
Open quantum systems describe quantum systems that interact unavoidably with their environments. These notes introduce the physical origins of decoherence and dissipation in realistic settings, developing the theoretical framework of reduced dynamics and quantum master equations within the connection to thermodynamics in the quantum regime. Additionally, a set of relevant exercises are proposed to reinforce the acquisition of knowledge. The text equips readers with the tools to model and analyze open quantum dynamics.
Quantum mechanics is traditionally associated with microscopic systems; however, quantum concepts have also been successfully applied to a diverse range of macroscopic systems both within and outside of physics. This book describes how complex systems from a variety of fields can be modelled using quantum mechanical principles; from biology and ecology, to sociology and decision-making. The mathematical basis of these models is covered in detail, furnishing a self-contained and consistent approach. This book provides unique insight into the dynamics of these macroscopic systems and opens new interdisciplinary research frontiers. It will be an essential resource for students and researchers in applied mathematics or theoretical physics who are interested in applying quantum mechanics to dynamical systems in the social, biological or ecological sciences.