3,728 research outputs found
Resolving the observer reference class problem in cosmology
The assumption that we are typical observers plays a core role in attempts to
make multiverse theories empirically testable. A widely shared worry about this
assumption is that it suffers from systematic ambiguity concerning the
reference class of observers with respect to which typicality is assumed. As a
way out, Srednicki and Hartle recommend that we empirically test typicality
with respect to different candidate reference classes in analogy to how we test
physical theories. Unfortunately, as this paper argues, this idea fails because
typicality is not the kind of assumption that can be subjected to empirical
tests. As an alternative, a background information constraint on observer
reference class choice is suggested according to which the observer reference
class should be chosen such that it includes precisely those observers who one
could possibly be, given one's assumed background information.Comment: 15 pages, no figure
Gauge symmetry breaking in gauge theories---In search of clarification
The paper investigates the spontaneous breaking of gauge symmetries in gauge
theories from a philosophical angle, taking into account the fact that the
notion of a spontaneously broken local gauge symmetry, though widely employed
in textbook expositions of the Higgs mechanism, is not supported by our leading
theoretical frameworks of gauge quantum theories. In the context of lattice
gauge theory, the statement that local gauge symmetry cannot be spontaneously
broken can even be made rigorous in the form of Elitzur's theorem.
Nevertheless, gauge symmetry breaking does occur in gauge quantum field
theories in the form of the breaking of remnant subgroups of the original local
gauge group under which the theories typically remain invariant after gauge
fixing. The paper discusses the relation between these instances of symmetry
breaking and phase transitions and draws some more general conclusions for the
philosophical interpretation of gauge symmetries and their breaking.Comment: 30 pages, penultimate version, forthcoming with minor changes in
"European Journal for Philosophy of Science
An Easy-to-Construct Automated Winkler Titration System
The instrument described in this report is an updated version of the high precision, automated Winkler titration system described by Friederich et al.(1984). The original instrument was based on the work of Bryan et al. (1976) who developed a colorimetric endpoint
detector and on the work of Williams and Jenkinson (1982) who produced an automated system that used this detector.
The goals of our updated version of the device described by Friederich et al. (1984) were as follows:
1) Move control of the system to the MS-DOS environment because HP-85 computers are no longer in production and because more user-friendly programs could be written using the IBM XT or AT computers that control the new device.
2) Use more "off the shelf" components and reduce the parts count in the new system so that it could be easily constructed and maintained.
This report describes how to construct and use the new automated Winkler titration device. It also includes information on the chemistry of the Winkler titration, and detailed instructions on how to prepare reagents, collect samples, standardize and perform the titrations (Appendix I: Codispoti, L.A. 1991 On the determination of dissolved oxygen in sea water, 15pp.). A disk containing the program needed to operate the new device is also included. (pdf contains 33 pages
The Little Brook
https://digitalcommons.library.umaine.edu/mmb-ps/1134/thumbnail.jp
A new fine-tuning argument for the multiverse
This paper has two aims. First, it points out a crucial difference between the standard argument from fine-tuning for the multiverse and paradigmatic instances of anthropic reasoning. The former treats the life-friendliness of our universe as the evidence whose impact is assessed, whereas the latter treat the life-friendliness of our universe as background information. Second, the paper develops a new fine-tuning argument for the multiverse which, unlike the old one, parallels the structure of paradigmatic instances of anthropic reasoning. The main advantage of the new argument is that it is not susceptible to the inverse gamblerâs fallacy charge
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