Race, Gender, Sexuality, Ability, Identity and Cycling, Blog 3

Student blog posts from the Great VCU Bike Race Book

Laws, Symmetry, and Symmetry Breaking; Invariance, Conservation Principles, and Objectivity

Given its importance in modern physics, philosophers of science have paid surprisingly little attention to the subject of symmetries and invariances, and they have largely neglected the subtopic of symmetry breaking. I illustrate how the topic of laws and symmetries brings into fruitful interaction technical issues in physics and mathematics with both methodological issues in philosophy of science, such as the status of laws of physics, and metaphysical issues, such as the nature of objectivity

The impact of nonpoint source pollution from mining wastes on water quality, Elko County, Nevada

A study was performed at a mine site in Elko County, Nevada to determine the effects on water quality resulting from waste rock at the site. Statistically significant (alpha less than or equal to 0.05) increases of several constituents, including sulfate (272 mg/L), calcium (46 mg/L), and magnesium (39 mg/L), were found to occur in the North Fork of the Humboldt River as it flows through the mine site. Geochemical modeling and historical data suggested that waste rock from the mine is primarily responsible for the increase in dissolved solids concentration. Electrical conductivity of the water exhibits seasonal fluctuations, with high values occurring in association with both snowmelt in the spring, and increased precipitation in the fall. Mass loading of dissolved constituents was found to be controlled by river discharge. Many of the deleterious impacts commonly associated with mine wastes, such as acidification and increases in suspended sediment concentrations were not found to be occurring at the site, due to factors such as carbonate buffering of acidity and the presence of sediment control structures at the site

The Role of Idealizations in the Aharonov-Bom Effect

On standard accounts of scientific theorizing, the role of idealizations is to facilitate the analysis of some real world system by employing a simplified representation of the target system, raising the obvious worry about how reliable knowledge can be obtained from inaccurate descriptions. The idealizations involved in the Aharonov-Bohm (AB) effect do not, it is claimed, fit this paradigm; rather the target system is a fictional system characterized by features that, though physically possible, are not realized in the actual world. The point of studying such a fictional system is to understand the foundations of quantum mechanics and how its predictions depart from those of classical mechanics. The original worry about the use of idealizations is replaced by a new one; namely, how can actual world experiments serve to confirm the AB effect if it concerns the behavior of a fictional system? Struggle with this issue helps to account for the fact that almost three decades elapsed before a consensus emerged that the predicted AB effect had received solid experimental support. Standard accounts of idealizations tout the role they play in making tractable the analysis of the target system; by contrast, the idealizations involved in the AB effect make its analysis both conceptually and mathematically challenging. The idealizations required for the AB effect are also responsible for the existence of unitarily inequivalent representations of the canonical commutation relations and of the current algebra, representations which an observer confined to the electron's configuration space could invoke to `explain' AB-type effect without the need to posit a hidden magnetic field. The goal of this paper is to bring to the attention of the philosophers of science these and other aspects of the AB effect which are neglected or inadequately treated in literature

Some Puzzles and Unresolved Issues About Quantum Entanglement

Schrödinger (1935) averred that entanglement is the characteristic trait of quantum mechanics. The first part of this paper is simultaneously an exploration of Schrödinger's claim and an investigation into the distinction between mere entanglement and genuine quantum entanglement. The typical discussion of these matters in the philosophical literature neglects the structure of the algebra of observables, implicitly assuming a tensor product structure of the simple Type I factor algebras used in ordinary QM. This limitation is overcome by adopting the algebraic approach to quantum physics, which allows a uniform treatment of ordinary QM, relativistic QFT, and quantum statistical mechanics. The algebraic apparatus helps to distinguish several different criteria of quantum entanglement and to prove results about the relation of quantum entanglement to two additional ways of characterizing the classical vs. quantum divide, viz. abelian vs. non-abelian algebras of observables, and the ability vs. inability to interrogate the system without disturbing it. Schrödinger's claim is reassessed in the light of this discussion. The second part of the paper deals with the relativity-to-ambiguity threat: the entanglement of a state on a system algebra is entanglement of the state relative to a decomposition of the system algebra into subsystem algebras; a state may be entangled with respect to one decomposition but not another; hence, unless there is some principled way to choose a decomposition, entanglement is a radically ambiguous notion. The problem is illustrated in terms a Realist vs. Pragmatist debate, the former claiming that the decomposition must correspond to real as opposed to virtual subsystems, while the latter claims that the real vs. virtual distinction is bogus and that practical considerations can steer the choice of decomposition. This debate is applied to the fraught problem of measuring entanglement for indistinguishable particles. The paper ends with some (intentionally inflammatory) remarks about claims in the philosophical literature that entanglement undermines the separability or independence of subsystems while promoting holism

Laws, Symmetry, and Symmetry Breaking; Invariance, Conservation Principles, and Objectivity

Given its importance in modern physics, philosophers of science have paid surprisingly little attention to the subject of symmetries and invariances, and they have largely neglected the subtopic of symmetry breaking. I illustrate how the topic of laws and symmetries brings into fruitful interaction technical issues in physics and mathematics with both methodological issues in philosophy of science, such as the status of laws of physics, and metaphysical issues, such as the nature of objectivity

Additivity Requirements in Classical and Quantum Probability

The discussion of different principles of additivity (finite vs. countable vs. complete additivity) for probability functions has been largely focused on the personalist interpretation of probability. Very little attention has been given to additivity principles for physical probabilities. The form of additivity for quantum probabilities is determined by the algebra of observables that characterize a physical system and the type of quantum state that is realizable and preparable for that system. We assess arguments designed to show that only normal quantum states are realizable and preparable and, therefore, quantum probabilities satisfy the principle of complete additivity. We underscore the little remarked fact that unless the dimension of the Hilbert space is incredibly large, complete additivity in ordinary non-relativistic quantum mechanics (but not in relativistic quantum field theory) reduces to countable additivity. We then turn to ways in which knowledge of quantum probabilities may constrain rational credence about quantum events and, thereby, constrain the additivity principle satisfied by rational credence functions

“The Experience of Left and Right” Meets the Physics of Left and Right

I consider an argument, due to Geoffrey Lee, that we can know  a priori   from the left‐right asymmetrical character of experience that our brains are left‐right asymmetrical. Lee's argument assumes a premise he calls  relationism , which I show is well‐supported by the best philosophical picture of spacetime. I explain why Lee's relationism is compatible with left‐right asymmetrical laws. I then show that the conclusion of Lee's argument is not as strong or surprising as he makes it out to be.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93584/1/j.1468-0068.2010.00814.x.pd

Bayes, Hume, and Miracles

Recent attempts to cast Hume’s argument against miracles in a Bayesian form are examined. It is shown how the Bayesian apparatus does serve to clarify the structure and substance of Hume’s argument. But the apparatus does not underwrite Hume’s various claims, such as that no testimony serves to establish the credibility of a miracle; indeed, the Bayesian analysis reveals various conditions under which it would be reasonable to reject the more interesting of Hume’s claims

Time in quantum gravity

Quantum gravity--the marriage of quantum physics with general relativity--is bound to contain deep and important lessons for the nature of physical time. Some of these lessons shall be canvassed here, particularly as they arise from quantum general relativity and string theory and related approaches. Of particular interest is the question of which of the intuitive aspects of time will turn out to be fundamental, and which 'emergent' in some sense.Comment: 18 pages, 1 figur