Letter from Reginald J. B. Page to Senator Langer Regarding Federal Funding for Road Construction, December 17, 1952

This letter, dated December 17, 1952, from Lt. Col. Reginald J. B. Page of the United States (US) Army Corp of Engineers, Garrison District, to US Senator William Langer, makes reference to Langer\u27s letter of December 10, in which Langer enclosed a copy of a resolution prepared by the McKenzie Country, ND Board of Commissioners, in which the Commissioners asked that a proposed road connecting the Fort Berthold Reservation to Highway no. 23 be constructed at federal expense. In his reply, Page explains that, because the proposed road lies outside the boundaries of the reservation, he has no funding or authority to include such a road in the Fort Berthold road construction project. See also: Letter from Senator Langer to Reginald J. B. Page Regarding Federal Funding for Road Construction, December 10, 1952https://commons.und.edu/langer-papers/1786/thumbnail.jp

Notice of Public Hearing from R. J. B. Page Regarding the Proposed Recreational Developments from the Garrison Reservoir, May 12, 1953

This notice of public hearing, dated May 12, 1953, from Colonel R. J. B. Page of the United State (US) Corps of Engineers declares that under the authority of the Flood Control Act, a “Master Plan of Reservoir Development and management is being prepared which will consider recreational developments in connection with the Garrison Reservoir Project on the Missouri River in North Dakota.” The notice states that the proposed plan is being developed in cooperation with interested Federal and State Agencies, and that the public hearings will take place on May 26, 1953, at 2:00 p.m. in the City Auditorium of Garrison, North Dakota, along with additional hearings in Beulah, North Dakota, and New Town, North Dakota (no dates given). The notice also states that information is “particularly desired” in regard to how state and local governments will finance public parks, recreational facilities, and highways to access these recreational areas “proposed for development on Government-owned lands.” The notice concludes by stating that oral arguments will be heard but important facts and arguments should be submitted in writing.” See also: Letter from Senator Langer to R. J. B. Page Regarding the Proposed Recreational Developments from the Garrison Reservoir, May 18, 1953https://commons.und.edu/langer-papers/1753/thumbnail.jp

Dynamic coherent backscattering of ultrasound in three-dimensional strongly-scattering media

We present measurements of the diffusion coefficient of ultrasound in strongly scattering three-dimensional (3D) disordered media using the dynamic coherent backscattering (CBS) effect. Our experiments measure the CBS of ultrasonic waves using a transducer array placed in the far-field of a 3D slab sample of brazed aluminum beads surrounded by vacuum. We extend to 3D media the general microscopic theory of CBS that was developed initially for acoustic waves in 2D. This theory is valid in the strong scattering, but still diffuse, regime that is realized in our sample, and is evaluated in the diffuse far field limit encountered in our experiments. By comparing our theory with the experimental data, we obtain an accurate measurement of the diffusion coefficient of ultrasound in our sample. We find that the value of $D$ is quite small, $0.74 \pm 0.03$ mm$^2/\mu$s, and comment on the implications of this slow transport for the energy velocity

No Time Asymmetry from Quantum Mechanics

With CPT-invariant initial conditions that commute with CPT-invariant final conditions, the respective probabilities (when defined) of a set of histories and its CPT reverse are equal, giving a CPT-symmetric universe. This leads me to question whether the asymmetry of the Gell-Mann--Hartle decoherence functional for ordinary quantum mechanics should be interpreted as an asymmetry of {\it time} .Comment: 14 pages, Alberta-Thy-11-9

Compton Heating of the Intergalactic Medium by the Hard X-ray Background

High-resolution hydrodynamics simulations of the Ly-alpha forest in cold dark matter dominated cosmologies appear to predict line widths that are substantially narrower than those observed. Here we point out that Compton heating of the intergalactic gas by the hard X-ray background (XRB), an effect neglected in all previous investigations, may help to resolve this discrepancy. The rate of gain in thermal energy by Compton scattering will dominate over the energy input from hydrogen photoionization if the XRB energy density is 0.2x/ times higher than the energy density of the UV background at a given epoch, where x is the hydrogen neutral fraction in units of 1e-6 and is the mean X-ray photon energy in units of m_ec^2. The numerical integration of the time-dependent rate equations shows that the intergalactic medium approaches a temperature of about 1.5e4 K at z>3 in popular models for the redshift evolution of the extragalactic background radiation. The importance of Compton heating can be tested experimentally by measuring the Ly-alpha line-width distribution as a function of redshift, thus the Lyman-alpha forest may provide a useful probe of the evolution of the XRB at high redshifts.Comment: LaTeX, 10 pages, 2 figures, final version to be published in the Ap

Transient Observers and Variable Constants, or Repelling the Invasion of the Boltzmann's Brains

If the universe expands exponentially without end, ``ordinary observers'' like ourselves may be vastly outnumbered by ``Boltzmann's brains,'' transient observers who briefly flicker into existence as a result of quantum or thermal fluctuations. One might then wonder why we are so atypical. I show that tiny changes in physics--for instance, extremely slow variations of fundamental constants--can drastically change this result, and argue that one should be wary of conclusions that rely on exact knowledge of the laws of physics in the very distant future.Comment: 4 pages, LaTeX; v2: added references; v3: more discussion of setting, alternative approaches, now 5 pages; v4: added discussion of the effect of quantum fluctuations on varying constants, appendix added, now 7 pages; v5: new reference, minor correctio

Towards operational measures of computer security

Ideally, a measure of the security of a system should capture quantitatively the intuitive notion of ‘the ability of the system to resist attack’. That is, it should be operational, reflecting the degree to which the system can be expected to remain free of security breaches under particular conditions of operation (including attack). Instead, current security levels at best merely reflect the extensiveness of safeguards introduced during the design and development of a system. Whilst we might expect a system developed to a higher level than another to exhibit ‘more secure behaviour’ in operation, this cannot be guaranteed; more particularly, we cannot infer what the actual security behaviour will be from knowledge of such a level. In the paper we discuss similarities between reliability and security with the intention of working towards measures of ‘operational security’ similar to those that we have for reliability of systems. Very informally, these measures could involve expressions such as the rate of occurrence of security breaches (cf rate of occurrence of failures in reliability), or the probability that a specified ‘mission’ can be accomplished without a security breach (cf reliability function). This new approach is based on the analogy between system failure and security breach. A number of other analogies to support this view are introduced. We examine this duality critically, and have identified a number of important open questions that need to be answered before this quantitative approach can be taken further. The work described here is therefore somewhat tentative, and one of our major intentions is to invite discussion about the plausibility and feasibility of this new approach

Intergenerational justice of what: welfare, resources or capabilities?

An important aspect of intergenerational justice concerns the specification of a 'currency of advantage' that can be used to evaluate distributive outcomes across time. Environmental theorists have introduced several innovative currencies of justice in recent years, such as ecological space and critical natural capital. However they have often downplayed the application of established currencies (such as welfare, resources or capabilities) to issues of futurity. After exploring the merits of a number of rival currencies, it is argued that the currency of 'capabilities to function' provides a promising basis for a theory of justice that takes seriously the rights and duties of intergenerational justice

Agnesi Weighting for the Measure Problem of Cosmology

The measure problem of cosmology is how to assign normalized probabilities to observations in a universe so large that it may have many observations occurring at many different spacetime locations. I have previously shown how the Boltzmann brain problem (that observations arising from thermal or quantum fluctuations may dominate over ordinary observations if the universe expands sufficiently and/or lasts long enough) may be ameliorated by volume averaging, but that still leaves problems if the universe lasts too long. Here a solution is proposed for that residual problem by a simple weighting factor 1/(1+t^2) to make the time integral convergent. The resulting Agnesi measure appears to avoid problems other measures may have with vacua of zero or negative cosmological constant.Comment: 26 pages, LaTeX; discussion is added of how Agnesi weighting appears better than other recent measure