This thesis is composed of three essays on the perdurantist approach to persistence and identity over time. In Chapter 1, I discuss how the following papers are to be understood as parts of a unified perdurantist account of persistence over time. This chapter also outlines some of my philosophical assumptions and provides some background information about the metaphysics of persistence. In Chapter 2, I respond to the objection that the worm theory is unable to account for our intuitions about ordinary (...) counting sentences. I do this by invoking the standard linguistic phenomenon of covert quantifier domain restriction and supplementing the worm theory with situation semantics. My version of the worm theory makes our intuitive judgements come out true, and it does so well enough that there is no need to adopt the stage theory or revisionary theories of counting. Furthermore, my version of the worm theory offers a unified account of event- and object-related counting. Chapter 3 focuses on a commonly neglected difference between different kinds of perdurantism, which are differences in mereological priority. I discuss three different views: parts-first perdurantism, no-priority perdurantism, and wholes-first perdurantism. I briefly outline all three views and some of the motivations for each of them. I fend off objections from and motivations for no-priority perdurantism. I also contend that intraperdurantist debates about phenomenology ought not to be framed with respect to these forms of perdurantism. Instead, I suggest that the relativity of simultaneity presents an interesting scenario for parts-first and wholes-first perdurantists. I respond to Thomas Pashby’s arguments against the doctrine of temporal parts in Chapter 3. Pashby argues that metaphysicians ought to give an account of how quantum systems persist over time and that nonrelativistic quantum mechanics is incompatible with perdurantism. I contend that his arguments rely on controversial, non-standard assumptions about the existence and importance of time observables. I demonstrate that perdurantists have no problem giving an account of how quantum systems persist over time in reference to an external time parameter. Finally, I conclude with a summary of my arguments and some thoughts about directions for future research. (shrink)

In early 1927, Pascual Jordan published his version of what came to be known as the Dirac-Jordan statistical transformation theory. Later that year and partly in response to Jordan, John von Neumann published the modern Hilbert space formalism of quantum mechanics. Central to both formalisms are expressions for conditional probabilities of finding some value for one quantity given the value of another. Beyond that Jordan and von Neumann had very different views about the appropriate formulation of problems in the new (...) theory. For Jordan, unable to let go of the analogy to classical mechanics, the solution of such problems required the identification of sets of canonically conjugate variables, i.e., p’s and q’s. Jordan ran into serious difficulties when he tried to extend his approach from quantities with fully continuous spectra to those with wholly or partly discrete spectra. For von Neumann, not constrained by the analogy to classical physics and aware of the daunting mathematical difficulties facing the approach of Jordan ), the solution of a problem in the new quantum mechanics required only the identification of a maximal set of commuting operators with simultaneous eigenstates. He had no need for p’s and q’s. Related to their disagreement about the appropriate general formalism for the new theory, Jordan and von Neumann stated the characteristic new rules for probabilities in quantum mechanics somewhat differently. Jordan was the first to state those rules in full generality, von Neumann rephrased them and then sought to derive them from more basic considerations. In this paper we reconstruct the central arguments of these 1927 papers by Jordan and von Neumann and of a paper on Jordan’s approach by Hilbert, von Neumann, and Nordheim. We highlight those elements in these papers that bring out the gradual loosening of the ties between the new quantum formalism and classical mechanics. (shrink)

PhD dissertation addressing what can be called conceptual-mathematical anomalies in quantum electrodynamics. This work can be seen as following the line of philosophy of physics studies of quantum field theory that started to emerge in a systematic way in the early eighties of last century. One example is Teller’s work on standard quantum electrodynamics.In this work, by following a historical approach, I will return to the standard version of quantum electrodynamics, which is the only one available when we want to (...) get numbers out to compare with experimental results. This work spins around two main vectors. One is the divergence of the S-matrix series expansion, the other is the spatio-temporal description of physical processes in the theory. (shrink)

Time, along with concepts as space and matter, is bound to be a central concept of any physical theory. The chapter first discusses how time is treated similarly in quantum and classical theories. It then provides a few references on time‐reversal. The chapter discusses three chosen authors' (Paul Busch, Jan Hilgevoord and Jos Uffink) clarifications of uncertainty principles in general. Next, the chapter follows Busch in distinguishing three roles for time in quantum physics. They are external time, intrinsic time and (...) observable time. It also provides a brief discussion on time operators, in particular Pauli's influential proof. Finally, the chapter talks about time‐energy uncertainty principles with intrinsic times. (shrink)

We consider the classical concept of time of permanence and observe that its quantum equivalent is described by a bona fide self-adjoint operator. Its interpretation, by means of the spectral theorem, reveals that we have to abandon not only the idea that quantum entities would be characterizable in terms of spatial trajectories but, more generally, that they would possess the very attribute of spatiality. Consequently, a permanence time shouldn’t be interpreted as a “time” in quantum mechanics, but as a measure (...) of the total availability of a quantum entity in participating to a process of creation of a spatial localization. (shrink)

These preprints were automatically compiled into a PDF from the collection of preprints deposited on PhilSci-Archive in conjunction with the Workshop on Cosmology and Time at at Penn State.