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Time's Arrow and De Se Probabilities

Chen, Eddy Keming (2020) Time's Arrow and De Se Probabilities. [Preprint]

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Abstract

One of the most difficult problems in the foundations of physics is what gives rise to the arrow of time. Since the fundamental dynamical laws of physics are (essentially) symmetric in time, the explanation for time's arrow must come from elsewhere. A promising explanation introduces a special cosmological initial condition, now called the Past Hypothesis: the universe started in a low-entropy state. In this paper, I argue that, in a universe where there are many copies of us (in the distant past or the distant future), the Past Hypothesis needs to be supplemented with de se (self-locating) probabilities. However, letting in de se probabilities also helps its rival---the Fluctuation Hypothesis, leading to a kind of empirical underdetermination and radical epistemological skepticism. The skeptical problem is exacerbated by the possibility of ``Boltzmann bubbles.'' Hence, it seems that explaining time's arrow is more complicated than we have realized, and that its explanation may depend on how we resolve philosophical issues about de se probabilities. Thus, we need to carefully examine the epistemological and probabilistic principles underlying our explanation of time's arrow. The task is especially urgent for theories that invoke the Past Hypothesis. The philosophical analysis offered in the paper aims at preparing the conceptual foundation for such a task.


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Item Type: Preprint
Creators:
CreatorsEmailORCID
Chen, Eddy Kemingeddykemingchen@ucsd.edu0000-0001-5144-0952
Keywords: Past Hypothesis, Principle of Indifference, Principal Principle, de se probabilities, time's arrow, entropy, Bayesian epistemology, confirmation, empirical underdetermination, skepticism
Subjects: General Issues > Confirmation/Induction
General Issues > Evidence
General Issues > Laws of Nature
Specific Sciences > Physics
Specific Sciences > Probability/Statistics
Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Depositing User: Keming Chen
Date Deposited: 17 Jan 2020 00:35
Last Modified: 17 Jan 2020 00:35
Item ID: 16824
Subjects: General Issues > Confirmation/Induction
General Issues > Evidence
General Issues > Laws of Nature
Specific Sciences > Physics
Specific Sciences > Probability/Statistics
Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Date: January 2020
URI: http://philsci-archive.pitt.edu/id/eprint/16824

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