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Classical causal models for Bell and Kochen-Specker inequality violations require fine-tuning
Nonlocality and contextuality are at the root of conceptual puzzles in
quantum mechanics, and are key resources for quantum advantage in
information-processing tasks. Bell nonlocality is best understood as the
incompatibility between quantum correlations and the classical theory of
causality, applied to relativistic causal structure. Contextuality, on the
other hand, is on a more controversial foundation. In this work, I provide a
common conceptual ground between nonlocality and contextuality as violations of
classical causality. First, I show that Bell inequalities can be derived solely
from the assumptions of no-signalling and no-fine-tuning of the causal model.
This removes two extra assumptions from a recent result from Wood and Spekkens,
and remarkably, does not require any assumption related to independence of
measurement settings -- unlike all other derivations of Bell inequalities. I
then introduce a formalism to represent contextuality scenarios within causal
models and show that all classical causal models for violations of a
Kochen-Specker inequality require fine-tuning. Thus the quantum violation of
classical causality goes beyond the case of space-like separated systems, and
manifests already in scenarios involving single systems.Comment: 9 pages, 14 figures. Modified title, discussion and presentatio
Temporal naturalism
Two people may claim both to be naturalists, but have divergent conceptions
of basic elements of the natural world which lead them to mean different things
when they talk about laws of nature, or states, or the role of mathematics in
physics. These disagreements do not much affect the ordinary practice of
science which is about small subsystems of the universe, described or explained
against a background, idealized to be fixed. But these issues become crucial
when we consider including the whole universe within our system, for then there
is no fixed background to reference observables to. I argue here that the key
issue responsible for divergent versions of naturalism and divergent approaches
to cosmology is the conception of time. One version, which I call temporal
naturalism, holds that time, in the sense of the succession of present moments,
is real, and that laws of nature evolve in that time. This is contrasted with
timeless naturalism, which holds that laws are immutable and the present moment
and its passage are illusions. I argue that temporal naturalism is empirically
more adequate than the alternatives, because it offers testable explanations
for puzzles its rivals cannot address, and is likely a better basis for solving
major puzzles that presently face cosmology and physics.
This essay also addresses the problem of qualia and experience within
naturalism and argues that only temporal naturalism can make a place for qualia
as intrinsic qualities of matter
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