5,535 research outputs found
Does von Neumann Entropy Correspond to Thermodynamic Entropy?
Conventional wisdom holds that the von Neumann entropy corresponds to thermodynamic entropy, but Hemmo and Shenker (2006) have recently argued against this view by attacking von Neumann's (1955) argument. I argue that Hemmo and Shenker's arguments fail due to several misunderstandings: about statistical-mechanical and thermodynamic domains of applicability, about the nature of mixed states, and about the role of approximations in physics. As a result, their arguments fail in all cases: in the single-particle case, the finite particles case, and the infinite particles case
Does von Neumann Entropy Correspond to Thermodynamic Entropy?
Conventional wisdom holds that the von Neumann entropy corresponds to
thermodynamic entropy, but Hemmo and Shenker (2006) have recently argued
against this view by attacking von Neumann (1955) and his argument. I argue
that Hemmo and Shenker's arguments fail due to several misunderstandings: about
statistical-mechanical and thermodynamic domains of applicability, about the
nature of mixed states, and about the role of approximations in physics. As a
result, their arguments fail in all cases: in the single-particle case, the
finite particles case, and the infinite particles case
Does Von Neumann's Entropy Correspond to Thermodynamic Entropy?
Conventional wisdom holds that the von Neumann entropy corresponds to thermodynamic entropy, but Hemmo and Shenker (2006) have recently argued against this view by attacking von Neumann's (1955) argument. I argue that Hemmo and Shenker's arguments fail due to several misunderstandings: about statistical mechanical and thermodynamic domains of applicability, about the nature of mixed states, and about the role of approximations in physics. As a result, their arguments fail in all cases: in the single-particle case, the finite particles case, and the infinite particles case
T Falls Apart: On the Status of Classical Temperature in Relativity
Taking the formal analogies between black holes and classical thermodynamics
seriously seems to first require that classical thermodynamics applies to
relativistic regimes. Yet, by scrutinizing how classical temperature is
extended into special relativity, I argue that it falls apart. I examine four
consilient procedures for establishing classical temperature - the Carnot
process, the thermometer, kinetic theory, and black-body radiation. I show how
their relativistic counterparts demonstrate no such consilience in defining
relativistic temperature. Hence, classical temperature does not appear to
survive a relativistic extension. I suggest two interpretations for this
situation - eliminativism akin to simultaneity, or pluralism akin to rotation.Comment: Presented at the Philosophy of Science Association 2022 meeting.
Forthcoming at Philosophy of Scienc
Effective fair pricing of international mutual funds
We propose a new methodology to provide fair prices of international mutual funds by adjusting prices at the individual security level using a comprehensive and economically relevant information set. Stepwise regressions are used to endogenously determine the stock-specific optimal set of factors. Using 16 synthetic funds whose characteristics are extracted from 16 corresponding actual US-based Japanese mutual funds, we demonstrate that our method estimates fund prices significantly more accurately than existing methods. Although existing fair-pricing methods provide an improvement over the current practice of simply using Japanese market closing prices, they are still highly vulnerable to exploitation by market-timers. By contrast, our method is the most successful in preventing such strategic exploitation since no competing method can profit from our stated prices. © 2008 Elsevier B.V. All rights reserved.preprin
No Time for Time from No-Time
Programs in quantum gravity often claim that time emerges from fundamentally
timeless physics. In the semiclassical time program time arises only after
approximations are taken. Here we ask what justifies taking these
approximations and show that time seems to sneak in when answering this
question. This raises the worry that the approach is either unjustified or
circular in deriving time from no-time.Comment: Presented at Philosophy of Science Association 2021 meetin
Decoherence, Branching, and the Born Rule in a Mixed-State Everettian Multiverse
In Everettian quantum mechanics, justifications for the Born rule appeal to
self-locating uncertainty or decision theory. Such justifications have focused
exclusively on a pure-state Everettian multiverse, represented by a wave
function. Recent works in quantum foundations suggest that it is viable to
consider a mixed-state Everettian multiverse, represented by a (mixed-state)
density matrix. Here, we develop the conceptual foundations for decoherence and
branching in a mixed-state multiverse, and extend the standard Everettian
justifications for the Born rule to this setting. This extended framework
provides a unification of 'classical' and 'quantum' probabilities, and
additional theoretical benefits, for the Everettian picture.Comment: 29 page
The Time in Thermal Time
Preparing general relativity for quantization in the Hamiltonian approach leads to the `problem of time,' rendering the world fundamentally timeless. One proposed solution is the `thermal time hypothesis,' which defines time in terms of states representing systems in thermal equilibrium. On this view, time is supposed to emerge thermodynamically even in a fundamentally timeless context. Here, I develop the worry that the thermal time hypothesis requires dynamics -- and hence time -- to get off the ground, thereby running into worries of circularity
The Time in Thermal Time
Preparing general relativity for quantization in the Hamiltonian approach leads to the `problem of time,' rendering the world fundamentally timeless. One proposed solution is the `thermal time hypothesis,' which defines time in terms of states representing systems in thermal equilibrium. On this view, time is supposed to emerge thermodynamically even in a fundamentally timeless context. Here, I develop the worry that the thermal time hypothesis requires dynamics -- and hence time -- to get off the ground, thereby running into worries of circularity
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