# 2023.05.11 - New Perspectives on the Philosophy of Quantum Physics

**Date**: 11.05.2023

**Venue**: Warsaw University of Technology, room 206 GG

**Format**: Hybrid (to receive the Zoom link, please register here)

**Organizers**: Philosophy of Physics Group (WAiNS) and Center for Advanced Studies

**Contact**: antonio.vassallo@pw.edu.pl

**Program**:

- 15:00-15:15 Welcome address by the Dean of the Faculty of Administration and Social Sciences
- 15:15-16:30 Davide Romano (Lisbon): "A decoherence-based approach to the classical limit in Bohm’s theory"
- 16:30-17:45 Tomasz Bigaj (UW): "On the identity and persistence of quantum objects"
- 17:45-18:15 Coffee break
- 18:15-19:30 Antonio Vassallo (PW): "A Machian framework for quantum physics"
- 20:00 Social dinner

**Abstracts**:

*A decoherence-based approach to the classical limit in Bohm’s theory*

I present an account of the quantum-to-classical transition in Bohm’s theory based on the following three steps: (i) the interaction with the environment produces effectively factorized states, leading to the formation of effective wave functions and hence decoherence; (ii) the effective wave functions selected by the environment–the pointer states of decoherence theory–will be well-localized wave packets, typically Gaussian states; (iii) the quantum potential of a Gaussian state becomes negligible under standard classicality conditions; therefore, the system will move according to Newtonian mechanics in the correct classical limit. As a result, a Bohmian system in interaction with the environment is described by an effective Gaussian state and–when the system is macroscopic–it moves approximately according to Newtonian mechanics.

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*On the identity and persistence of quantum objects*

This talk will broadly evaluate the problem of the identity, discernibility, individuality and persistence of quantum particles, taking into account the ubiquitous symmetrization postulate with respect to the states of same-type particles. Several interpretative options will be considered, compared and contrasted, ranging from the total indiscernibility and non-individuality of quantum objects to their qualitative absolute discernibility. I will pay particular attention to the problem of the reidentification of quantum objects over time, taking into consideration a recent proposal by Philip Goyal of how to derive the symmetrization postulate from some postulates regarding the transition amplitudes for the systems of same-type particles.

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*A Machian framework for quantum physics*

The talk presents an extension of the metaphysics of self-subsisting structures to the realm of non-relativistic quantum physics. The discussion is centered around a Pure Shape Dynamics model representing a relational implementation of a De Broglie-Bohm N-body system. An interpretation of this model in terms of self-subsisting structures is proposed and assessed against the background of the debate on the metaphysics of quantum physics, with a particular emphasis on the nature of the wave function. The analysis shows that elaborating an appropriate Leibnizian/Machian metaphysics of the quantum world requires a substantial revision of the notion of world-building relation. [Based on joint work with Tim Koslowski and Pedro Naranjo]