News Release

Physics tip sheet #7 – April 3, 2002

Peer-Reviewed Publication

American Physical Society

1) Bubble fusion refutation
S.J. Putterman, L.A. Crum, K. Suslick
arXiv preprint server

An analysis of the experimental method employed by Taleyarkhan, et al. in their Science publication is discussed. The authors write that the study “neither proves nor disproves” the possibility of fusion in acoustic cavitation but that “the possibility of a major discovery has been obscured by substandard experimental techniques”.

Preprint: http://www.arxiv.org/abs/cond-mat/0204065

2) A model of terrorism
S. Galam
arXiv preprint server

A model of terrorism is developed based on the concept of passive supporters who may not be actively engaged in terrorism but will not prevent terrorist acts from occurring. An analysis shows that once a sufficient proportion of randomly distributed passive supporters exist, the society undergoes a transition to a state that makes global terrorist acts possible. Furthermore, these networks do not require coordination, are almost undetectable and can exist within communities that oppose terrorism as a group. The author comments on implications for intelligence and military actions.

Preprint: http://www.arxiv.org/abs/cond-mat/0204052

3) River meandering dynamics
B. F. Edwards and D. H. Smith
Physical Review E (Print issue: April 2002)

Rivers are not generally set in stone, so to speak. Some, such as the Mississippi, move sideways up to 20 meters each year. A model of river dynamics predicts the behavior of river movements including how bends move upstream or downstream depending on how tight they are and when oxbow lakes (former river bends cut off from the main flow) appear.

Journal article: http://link.aps.org/abstract/PRE/v65/e046303

4) A rough slide
B. N. J. Persson and A. I. Volokitin
Physical Review B (Print issue: April 1, 2002)

Understanding how friction is generated when rubber slides against other objects in important from the design of tires to wiper blades and in the cosmetics industry. This paper presents a model of friction for rubber that shows how a rough surface causes oscillations in sliding rubber that dissipate energy through internal friction in the rubber. The area of real contact and the friction force depend on the nature of the surface roughness and on the history of the sliding motion.

Journal article: http://link.aps.org/abstract/PRB/v65/e134106

5) Weighing the Milky Way
M. Karim, A. Tartaglia, A. H. Bokhari
ArXiv preprint server

Some suggested experiments might be able to measure the mass of the Milky Way galaxy using a table-top device. The experiment is based on a Michelson-Morley interferometer, as used in early tests of Einstein’s theory of special relativity.

Preprint: http://www.arxiv.org/list/gr-qc/0203

6) Did you hear the one about the rumor?
D. H. Zanette
Physical Review E (Print issue: April 2002)

A model of rumor propagation is developed, similar to epidemiological models of disease spreading, but modified to take into account “small-world” social structures. Depending on various properties of the social network, a rumor may die out after being constrained to a relatively small population or could spread throughout the network, reaching a significant proportion of the entire population.

Journal article: http://link.aps.org/abstract/PRE/v65/e041908

7) Observing the Earthshine
N. J. Woolf, P. S. Smith, W. A. Traub, K. W. Jucks
arXiv preprint server

Amid the interest in observation of planets in far-off systems, one has to ask: “What would a habitable planet look like from outside its system?” To answer this question, researchers have measured the spectrum of Earthshine – the characteristic colors given off by the Earth and an indicator of what it would look like from far away. The measurement was made by looking at the dark side of the moon. Although no sunlight hits that part of the moon, some light that has been reflected from the Earth does illuminate it slightly and that light can be measured as it bounces back to the Earth.

Preprint: http://www.arxiv.org/abs/astro-ph/0203465

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