from PRA – fundamentalconcepts by Pablo L. SaldanhaFri Dec 22 2023 18:00:00 (16 hours)# 1.
Author(s): Pablo L. Saldanha
We propose an electrodynamic Aharonov-Bohm (AB) scheme where a nonzero AB phase difference appears even if the interferometer paths do not enclose a magnetic flux and are subjected to negligible scalar potential differences during the propagation of the quantum charged particle. In the proposal, the…
[Phys. Rev. A 108, 062218] Published Fri Dec 22, 2023
from quant-ph by Andrei KhrennikovFri Dec 22 2023 12:25:55 (22 hours)# 2.
We develop the contextual measurement model (CMM) which is used for clarification of the quantum foundations. This model matches with Bohr’s views on the role of experimental contexts. CMM is based on contextual probability theory which is connected with generalized probability theory. CMM covers measurements in classical, quantum, and semi-classical physics. The CMM formalism is illustrated by a few examples. We consider CMM framing of classical probability, the von Neumann measurement theory, the quantum instrument theory. CMM can also be applied outside of physics, in cognition, decision making, and psychology, so called quantum-like modeling.
from gr-qc by Elliott Tammaro, Hunter Angle, Edmund MbaduFri Dec 22 2023 12:25:44 (22 hours)# 3.
A ubiquitous feature of quantum mechanical theories is the existence of states of superposition. This is expected to be no different for a quantum gravity theory. Guided by this consideration and others we consider a framework in which classical reference frames may be in superposition relative to one another. Mirroring standard quantum mechanics we introduce a complex-valued wavefunctional, which takes as input the transformations between the coordinates, $\Psi[x(x’)]$, with the interpretation that an interaction between the reference frames may select a particular transformation with probability distribution given by the Born rule – $P[x(x’)] = \text{probability distribution functional} \equiv \vert \Psi[x(x’)] \vert^2$. The cases of two and three reference frames in superposition are considered explicitly. It is shown that the set of transformations is closed. A rule for transforming wavefunctions from one system to another system in superposition is proposed and consistency with the Schrodinger equation is demonstrated.
from quant-ph by Michael Ridley, Emily AdlamFri Dec 22 2023 12:25:36 (22 hours)# 4.
We investigate two types of temporal symmetry in quantum mechanics. The first type, time symmetry, refers to the inclusion of opposite time orientations on an equivalent physical footing. The second, event symmetry, refers to the inclusion of all time instants in a history sequence on an equivalent physical footing. We find that recent time symmetric interpretations of quantum mechanics fail to respect event symmetry. Building on the recent fixed-point formulation (FPF) of quantum theory, we formulate the notion of an event precisely as a fixed point constraint on the Keldysh time contour. Then, considering a sequence of measurement events in time, we show that both time and event symmetry can be retained in this multiple-time formulation of quantum theory. We then use this model to resolve conceptual paradoxes with time symmetric quantum mechanics within an `all-at-once’, atemporal picture.
from physics.hist-ph by Gabriel M.Carral, Iñaki Garay, Francesca VidottoFri Dec 22 2023 12:24:34 (22 hours)# 5.
The definition of a quantum system requires a Hilbert space, a way to define the dynamics, and an algebra of observables. The structure of the observable algebra is related to a tensor product decomposition of the Hilbert space and represents the composition of the system by subsystems. It has been remarked that the Hamiltonian may determine this tensor product structure. Here we observe that this fact may lead to questionable consequences in some cases, and does extend to the more general background-independent case, where the Hamiltonian is replaced by a Hamiltonian constraint. These observations reinforces the idea that specifying the observables and the way they interplay with the dynamics, is essential to define a quantum theory. We also reflect on the general role that system decomposition has in the quantum theory.
from gr-qc by Gabriel M.Carral, Iñaki Garay, Francesca VidottoFri Dec 22 2023 12:24:34 (22 hours)# 6.
The definition of a quantum system requires a Hilbert space, a way to define the dynamics, and an algebra of observables. The structure of the observable algebra is related to a tensor product decomposition of the Hilbert space and represents the composition of the system by subsystems. It has been remarked that the Hamiltonian may determine this tensor product structure. Here we observe that this fact may lead to questionable consequences in some cases, and does extend to the more general background-independent case, where the Hamiltonian is replaced by a Hamiltonian constraint. These observations reinforces the idea that specifying the observables and the way they interplay with the dynamics, is essential to define a quantum theory. We also reflect on the general role that system decomposition has in the quantum theory.
from physics.hist-ph by Marcello PolettiFri Dec 22 2023 12:24:33 (22 hours)# 7.
Quantum mechanics is a theory that is as effective as it is counterintuitive. While quantum practices operate impeccably, they compel us to embrace enigmatic phenomena like the collapse of the state vector and non-locality, thereby pushing us towards untenable “hypotheses non fingo” stances. However, a century after its inception, we are presented with a promising interpretive key, intimated by Wheeler as early as 1974. The interpretative paradoxes of this theory might be resolved if we discern the relationship between logical undecidability and quantum undecidability. It will be demonstrated how both are intricately linked to an observer/observed relational issue, and how the idiosyncratic behaviours of quantum physics can be reconciled with the normative, following this path.
from APS selected papers by Katherine WrightTue Dec 19 2023 18:00:00 (3 days)# 8.
Author(s): Katherine Wright
A new model reproduces both the dynamical and steady-state behavior of a group of living organisms, a first for such systems.
[Physics 16, s180] Published Tue Dec 19, 2023
from philsciMon Dec 18 2023 12:49:44 (4 days)# 9.
Koberinski, Adam (2023) Phase transitions and the birth of early universe particle physics. [Preprint]
from physics.hist-ph by Christopher M. GraneyMon Dec 18 2023 11:06:21 (4 days)# 10.
This paper argues that Tycho Brahe’s “principal argument against Copernicus” (as the astronomer Christiaan Huygens called it) likely derived from a much older argument regarding the sizes of the “two great lights” described in the first chapter of the book of Genesis. Brahe’s argument, that in the Copernican system stars would have to be absurdly large, played an important role in opposition to the Copernican system in the seventeenth century. Brahe presented the argument in an exchange of letters with Christoph Rothmann in 1588-89. Within that exchange Rothmann and Brahe touched both on the question of the two great lights of Genesis and on theologians such as Augustine of Hippo who treated that question. The fundamentals of Brahe’s important line of argument against Copernicus thus well pre-dated Copernicus and Brahe.
from physics.hist-ph by Maria Papageorgiou, Doreen FraserMon Dec 18 2023 11:06:20 (4 days)# 11.
Arguments by Sorkin arXiv:gr-qc/9302018 and Borsten, Jubb, and Kells arXiv:1912.06141 establish that a natural extension of quantum measurement theory from non-relativistic quantum mechanics to relativistic quantum theory leads to the unacceptable consequence that expectation values in one region depend on which unitary operation is performed in a spacelike separated region. Sorkin labels such scenarios “impossible measurements”. We explicitly present these arguments as a no-go result with the logical form of a reductio argument and investigate the consequences for measurement in quantum field theory (QFT). Sorkin-type impossible measurement scenarios clearly illustrate the moral that Microcausality is not by itself sufficient to rule out superluminal signalling in relativistic quantum theories that use L\”uders’ rule. We review three different approaches to formulating an account of measurement for QFT and analyze their responses to the “impossible measurements” problem. Two of the approaches are: a measurement theory based on detector models proposed in Polo-G\’omez, Garay, and Mart\’in-Mart\’Inez arXiv:2108.02793 and a measurement framework for algebraic QFT proposed in Fewster and Verch arXiv:1810.06512. Of particular interest for foundations of QFT is that they share common features that may hold general morals about how to represent measurement in QFT. These morals are about the role that dynamics plays in eliminating “impossible measurements”, the abandonment of the operational interpretation of local algebras as representing possible operations carried out in a region, and the interpretation of state update rules. Finally, we examine the form that the “impossible measurements” problem takes in histories-based approaches and we discuss the remaining challenges.
from philsciSun Dec 17 2023 07:58:53 (6 days)# 12.
Driessen, Alfred (2020) Aristotle and the Foundation of Quantum Mechanics.
